Thursday, December 31, 2009

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"I think we're in trouble..."
- Lyrics to a 70's song whose title escapes me just now

6:00 AM Thursday, 12-31-09On this last day of the decade's final year, our weather decided to have one more round for Auld Lang Syne. As you can tell by looking out the window, snowfall is heavier than NWS anticipated. The forecast team is raising it's totals accordingly. Latest NWS advisories : Baltimore | Philadelphia

I-95 Corridor: Up to 3" possible by noon before changeover to rain.
Towson, MD north and west: 4" + before a mid-afternoon change.
Central/Southern PA: Up to 5" possible then sleet mixes in PM.

Please post your location in the comments with your observations, and the forecast team will respond as time permits. A second update posted by noon today.

Collaborators: Mr. Foot, PasadenaMatt, Winterman, Mr. B, Andy.

Monday, December 28, 2009

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 Snowy & Wet For Auld Lang Syne

10:30 PM 12-30 Update # 2: As the Stormcast Team surmised from a variety of nowcast data, including radar and upper level charts, the situation is trending colder than anticipated by NWS and Accuweather.  The surface low is producing snow in the NC and VA foothills, and the coastal surface high is drifting eastward too slowly, permitting precip has already begun to over-run at upper levels. This suggests much of the I-95 corridor from Washington to Philadelphia and their metro interior area may see more snow than sleet or freezing rain, due in part to evaporative cooling as precip falls into air with low dewpoints. Snowfall totals below were adjusted slightly to reflect this.

2:30 PM 12-30 Update # 1: Winter Weather Advisories from 4AM - 1PM for western Virginia, central and western Maryland into south-central Pennsylvania

11:00 AM WEDNESDAY 12-30-09  Stormcasters Mr. B and PasadenaMatt with an update on the New Year's Storm: A "play in three acts" from Thursday to Saturday for Mid-Atlantic/Northeast

ACT 1 ~ THE SNOW: By 6AM Thu, light snow is accumulating.
8 AM Becomes steady along I-95 corridor, central/western MD and PA. 3" or more from Towson, MD north / west into southern PA. Up to 2" in Baltimore/Washington metro areas toward Philadelphia in the morning hours (snow & sleet combined).
12 PM Mixes with sleet and freezing rain in the Baltimore-Washington region. Higher elevations of southern / eastern PA may see 4" or more before changeover.
4 PM to Ball Drop All precip over to rain for New Year's Eve celebrations along I-95. Areas west of I-81 should remain snow or occasionally mix with rain/sleet.

ACT 2 ~ THE SWITCH: New Year's Day, rain changes back to snow as the secondary low moves off the New England coast. Some wind-driven "wrap-around" snow is possible across eastern Mid-Atlantic ; Western MD and Shenandoah Valley may see a prolonged period of snow into the weekend enhanced by lake-effect. 

ACT 3 ~ THE SECONDARY Saturday into Sunday, cold northwest winds arrive as the low departs. Coastal New Jersey, Long Island, and coastal southern New England stay rain the longest, ending as snow Saturday morning. Blizzard conditions are possible along Downeast Maine and the Interior Friday night into Sunday. Surrounding states may also receive heavy snowfall rates well into Saturday.

SUMMARY: Unless you are heading to the ski resorts, it is not shaping up to be a rockin' New Year's Eve for "First Night" celebrations across the Eastern U.S. If you want a winter wonderland while pounding the glades up yonder, then pack today and leave tonight. We would if we were you.  Stormcasters: Mr. B, PasadenaMatt | Editor: Mr. Foot | Advisor: Mr. Andy of Southern York Co., PA

Saturday, December 26, 2009

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Big Kahuna Forecast: 1st & 10

4:30 PM SUNDAY 12-27  This is gametime update to let you know that our weekly storm analysis is in development, and will be posted after the games are over. As in past storm preparation research, we post an outline and synopsis of ideas, then add details and supporting links. 

What is the basic thinking for this storm? More snow than rain, arriving in the Mid-Atlantic by Thursday and continuing into Friday or longer. As for Times Square ratings, this could be Ryan Secrest's moment. For quick sense of what is brewing, the Baltimore/Washington NWS office has a Hazardous Weather Outlook posted. The HPC is spot on in their discussions, and Hazard Assessments. Using BWI airport as an example, the GFS computer model is vacillating between "Day After Tomorrow" storm and flurries. Being that we're "inside five days" before the storm, various projections such as 3.0" of liquid for New York City probably have have emergency managers already taking notes.

Computer trends and climate indicators are being co-analyzed. When we know more, you'll know - and you can check our facebook page for a heads up during the day. The previous post follows:

"We're riding in a wonderland of snow..."
- lyrics from the classic holiday orchestral piece Sleigh Ride,
first recorded in 1949 by Arthur Fiedler and the Boston Pops.

6:00 AM FRIDAY, DECEMBER 26   Though today's rain will remove most of the snow we didn't, the Winter Stormcast Team expects that you will be surrounded by a wintry fairyland again in short order. The current pattern over North America, identified by our student climate collaborative as -NAO, -AO, +PNA* may yield one or two more significant winter storms by January 6. That would be just in time for Ephihany's Arrival of the Magi (you know...when the Wise Men came to Bethlehem). Powderhounds who remember great storms of the 1950's and 60's can attest to non-stop multi-year sleigh rides through wonderlands of snows.
(cue for readers: insert memorable snow tale here.)
* "alignment" of these three atmospheric indicators often precedes east coast snowstorms.

Many thanks go out to Winterman for keeping a close eye on the Christmas Day event, as noted in the official facebook page. Mr. Foot, Mr. B and Snowlover are immersed in activites with their families. Stormcaster PasadenaMatt and Team advisor Mr. Andy of Southern York County, PA are already monitoring NWS reports and atmospheric signals for the next event. They have good company, even the 6- to 10-day outlook by NOAA's Climate Prediction Center suggests conditions will be ripe for snow in the Dec 31 - Jan 4 period. The Global Forecast System is one of several models indicating sleighs in the Northeast may stop by a woods on a snowy evening as we ring in the New Year.

Those with travel or party plans for 2010 weekend celebrations are encouraged to check in daily for latest developments. To remain appropriate in our use of scientific data, we won't release a preliminary timeline until the event is "inside 5 days." Until then, rest awhile with your cup of mint holiday tea and permit those bones a chance to regroup, they'll be pressed back into service before long.

Friday, December 25, 2009

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Yes, Virginia - there is a snow flake
(and a Santa Claus, too!)

DECEMBER 25, 2009: The Winter Stormcast Team wishes the happiest of holiday greetings to you and your family. Some of us in the Mid-Atlantic might receive an extra treat today, so glance out the window occasionally. It might not be won't last long, but it will be something we don't usually see on this day. Enjoy!

Editor's note: If you're not sure about the meaning behind today's headline, (there was snow in Virginia this morning), it is derived from a precious letter sent by an 8-year old to the New York Sun in September 1897. You can read the article here and enjoy an image of the original newspaper. This story reminds us that despite how many years young we become, "the bell still rings...for all who truly believe."

Thursday, December 24, 2009

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"I--ce COULD be home for Christmas..."
- The third little known variation of Bing Crosby's timeless song

UPDATE # 3 - 8:30 PM THURSDAY 12-24  
Warm Holiday Wishes to all our readers! The potential ice situation may be trending toward mostly rain for the immediate Baltimore area, but not elsewhere. Details on why the forecast has changed:

SYNOPSIS: A large and powerful winter storm moving into the Midwest today will produce MOSTLY RAIN with SOME LIGHT FREEZING RAIN across much of the Mid-Atlantic on Christmas Day into the evening.
* Areas at risk for ice accretion to .20" from 4 am - 6 pm Christmas night remain central and western Pennsylvania and western Maryland.
* Areas at risk of ice accretion to .10"  from 6 am - 12 pm Christmas before changing to rain are along and west of a line from Charlottsville, VA to Washington, DC to Bel Air, MD.
The Sterling, VA NWS has posted a Winter Weather Advisory for much of this region.

WHY DID OUR FORECAST CHANGE? We elected to follow that simple rule taught in the Penn State Meteorology Department: "Predict the high and you predict the storm."  The Stormcast Team, upon analyzing most recent computer model projections, realized the game-changer was a weak surface high which appeared over central Maryland yesterday.

Although this "Jack Frost" high, at 1028 mb or less, caused the frigid temperatures this morning, once it drifts east, return flow on backside of the high will interact with southerly flow ahead of the midwestern storm. It came down to simple physics: Development of a weak "double-barrel" southerly flow between the distant low and local high. This will permit surface temperatures east of the Blue Ridge to range from upper 20's to near 30 once precip arrives Friday morning, limiting ice build-up before changing to rain.

SO WHAT ABOUT THE ICING POTENTIAL?  There will definitely pockets of ice across many in cold valleys of central and western Maryland. The good news is that any significant icing (> .25") may now be confined just to the roof of Grandmother's gingerbread house.

The Foot girls enjoying their first gingerbread house.
It has long since been consumed.

REVISED STORM TIMELINE (as of 4:00 PM 12-24)

THIS EVENING Residents of the Mid-Atlantic attending Christmas Eve services or holiday gatherings should not encounter any travel problems. Even lighting the lumineres tonight will be problem-free, if a bit chilly. At least the candles will stay lit!

Overnight, one particular traveler making his rounds may encounter some light freezing rain and freezing drizzle. This should not delay delivery of important packages. Parents are no longer advised to make arrangements - and can prepare children to reach the appointed bedtime accordingly. All residents not involved in package delivery are encouraged to clear chimneys, sidewalks, bus stops, rooftops and parking lots in an effort to provide children with the opportunity for this visitor to make deliveries unimpeded. Parents of the Howard County Public Schools appreciate your help.

CHRISTMAS DAY Residents across the Mid-Atlantic west of I-95 will awaken to a calm and foggy landscape, with a thin glaze of ice bespeckling the windshields and trees. Surface cold air will erode throughout the day, permitting any precip falling by afternoon to be mostly rain with some sleet mixed.

THE CHANGEOVER Occuring east to west, starting along I-95 by late morning 12-25, progressing across Maryland and Pennsylvania to a line from Centre County, PA to Carroll County, MD. West of this line, freezing rain may continue to accrete past .10 inch into Christmas night. In some areas, there is risk of falling tree branches weakened by heavy snow. Residents west of Carroll County, MD would be wise not to permit children to venture outside. Let's not have sad breaking news on Christmas Day that a branch fell on a child taking the new family dog for it's first walk.

Juuustt in case things change back (and we've all seen that before) text of our earlier ideas is left below for comparison. Many thanks to the team for taking a step back and looking at the big picture! But...given widespread cold surface, it seems prudent to remain cautious when traveling to evening slip on the church sidewalk can make for a less than pleasant Christmas Eve. Earlier forecast revised at 7:30 AM 12-24 :

--> Eastern boundary: I-95 corridor ~ Washington to Philadelphia,
including Philly suburbs of Chester County northwest to Centre County
--> Northern boundary: State College area/Centre County, PA
--> Western boundary: Northern VA across the MD/VA Blue Ridge
to the WV Panhandle and north to Bedford and Centre County, PA


(we may go back to this!)
Approx .10 inch = Along I-95 including Baltimore-Washington metro, and extending north into the western Philadephia suburbs of Chester County
Approx .20 inch = Western DC suburbs through northern Virginia to Carroll County and into south-central Pennsylvania including Harrisburg and Lancaster.
More than .25 inch = The Stormcast Team believes Frederick, MD will be the "dividing line" between significant icing above .25 an inch. Areas west of that line are at risk of a dangerous ice storm, including Western Virginia north through the WV panhandle into west central PA to all MD counties west of Frederick. The Sterling, VA NWS has issued Winter Storm Watches for these regions effective late Thursday through Friday afternoon.

NWS CURRENT: Hazardous Wx Outlook | HPC Winter Wx

DISCUSSIONS Sterling, VA | State College, PA | HPC Snow/Ice 
EXAMPLES: Westminster, MD | West Chester, PA | Lancaster, PA 
ANALYSIS: US Hazards  | 12-36 Hour Short Range | 5-day Precip 

And now, for a little holiday fun and video memorabilia...

Wednesday, December 23, 2009

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"Do, or do not...there is no 'try' "
- Yoda in Star Wars: The Empire Strikes Back

3:00 pm Wednesday 12.23.09 Now that we're all heading into "the most wonderful time of the year" according to Andy Williams, you need a heads-up on the incoming chunks of ice-covered coal headed to your stocking. Links below include the Christmas storm, a recap of the forecasts, and our Storm Grade Report.

Christmas Ice Storm  Summary | Analysis 
Our blizzard forecast ~ first call posted 6:00 AM Thu 12-17
Student analysis ~ second call posted 6:00 AM Fri 12-18 
How we predicted 24" ~ Crossroads students figured out final snowfall amounts by 3:30 PM Fri 12-18, the Stormcast Team verified it 10:00 PM Friday night and then, it happened.

What does 2010 have in stock? Good news and bad news! If you are a powderhound, make arrangements to be safely nestled at your favorite ski resort by New Years. If you are a teacher or student, be ready to roll quickly into instruction the week of 1/4 - the atmosphere has more "plans" for us. If you are an HSA planner in Maryland, we hypothesize conditions in mid-January will turn around and warm up - just in time to get state testing completed. After that? Let's just say the Empire Strikes Back - as in the empire of Old Man Winter. The January 20 to February 15 period might be a time that tries men's souls (and ladies too of course!)

Please take a moment to meet our Winter Stormcast Team and Climate Collaboration Teams in the report below. They deserve credit for the forecasts many followed so fervently on this site, well before before their work was featured in the Baltimore Sun on Saturday by Weather & Science Reporter Frank Roylance. For one last look at this historic moment, the image below is from NASA's Earth Observatory, showing extent of Mid-Atlantic snowcover following the storm:

Data assembled by PasadenaMatt, Public Safety Nowcaster
Sources: 12/22/09 Public Information Statements  by NWS offices:
Wakefield, VA | Sterling, VA | Mount Holly, NJ | State College, PA
NWS draft summary of December 2009 Storm, State College, PA

Since last Saturday (that's December 12) these fine young men devoted several hours per day of their own time, well into the evening, without any formal recognition or byline, to successfully forecast this storm. The discussion roundtables were lively but tiring, as we collectively corralled multiple maps and data sources into a succinct and clear message for the readership. With another significant pattern change looming around the New Year, it seemed timely to formally introduce the "faces behind the place." If these gentlemen scholars are any indication of what America's future holds, it is looking bright and promising indeed.

Mr. B, a junior at Penn State University, is also a student meteorologist and shift manager at the PSU Campus Weather Service. He has been a frequent contributor to this site since the Winter of 2006-07, providing early insight into pattern changes, model analyses and valuable “nowcast” data. When Mr. B is not comparing the GFS, NAM and European models late at night, you can find him playing hockey or building igloos.

Winterman, a junior at North Carroll High School in Carroll County, MD has been a frequent contributor to the site since Winter 2007-08. An avid fan of big snow, he has been able to peg trends leading to development of major storms, and closely monitors local forecasts for any hint of a “bust.” Upon joining the Winter Stormcast Team, winterman quickly established our new Facebook page. When not checking the forecast or tracking a storm, you can find him out for a run (year-round, mind you) or playing # 2 singles for the North Carroll Panthers. Beyond that, he's considering a college program in Environmental Science or Meteorology.

PasadenaMatt, a Senior at Archbishop Spalding High School in Anne Arundel County, MD became a regular contributor in 2008. Always "spot on" with local observations, he has a keen eye for details that get lost in the multi-tasking of weather predictions. Following the storm, PasadenaMatt quickly setup our Photobucket page. When team analyses are in progress, he readily provides "nowcast" data and public safety reports. When not following a Winter Storm or Hurricane, PasadenaMatt is active with local Emergency Management agencies, hopes to pursue a career in that field.

Equally as deserving of recognition are our intrepid bands of climate data explorers. Polar-sized kudos go out to Ms. Gerst's 5th grade students at Baltimore County's Perry Hall Elementary for their diligent tracking of extensive climate data tracing back to early November. Ms. Abrahms' 9th grade students at Mount Saint Joseph's High deserve a hearty round of applause, as they were the first group to begin tracking atmospheric signals along with Mr. Foot's 9th grade students at the BCPS Crossroads Center. The robust and weekly research these three classes generated is why the Winter Stormcast team was confident in presenting what seemed to many a bold forecast at the time.

We saw the potential for a significant winter pattern as early as August 2009, and refined those ideas in October. On 10/19/09 the following projection was made: "A rapid onset of persistent and disruptive winter weather is expected by December 5. If this unstable pattern continues, as was observed in October-December of 2002, areas of the Mid-Atlantic region could experience widespread school closings for 2 or more days this December. This may equal or exceed the cold and snowy period observed in the Baltimore region from December 4-11, 2002."

Just think, we're only two days past the actual winter solstice! What a ride there will be going forward, and we hope you'll continue with us in this grand adventure known as "Winter 2009-2010."  As the Carpenters singing group would say, "We've only just begun."

Tuesday, December 22, 2009

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It's about to be...
"The Most Wonderful Time of the Year!"
(for SOME students, parents, teachers and even central offices)

lyrics and music of this quintessential Andy Williams song.

12:15 PM TUESDAY 12-22-09. We interrupt this stormcast on the first full day of winter to bid Happy Holidays to all our loyal and effervescent readers. With some Baltimore & DC metro area schools closing for Wednesday 12-23, the forecast team also bids happy trails to those heading over the river and through the woods to Grandmother's house.  If you're just going to settle down for a long winter's nap, we know it is a well-earned break. We all have a lot of winter ahead of us, so rest now friends, you will need it.

This post will remain until after the evening news, at which time our stormcasting will resume.

Monday, December 21, 2009

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Christmas 2009 Ice Storm Analysis

THE SITUATION: This will be a highly complex system (aren't they all?) involving a long "front end" period of freezing rain on Christmas Eve Night extending into Christmas Day. Early indications are that areas mosts affected Christmas Eve are likely to be west of a line extending from Carroll County, MD  to Northern and Western Virginia as well as portions of the WV panhandle. Although surface cold air will be marginal (~32 F) across the I-95 corridor, computer model projections and convention wisdom both suggest that low-level cold air will not erode as quickly as anticipated.

A SAMPLE MAP: Shown below is the 7AM computer model projection from today by the GFS for 2 meter temperatures, 10 meter winds and precip by 7PM Christmas Eve. This link will take you to a larger map that's easier to read. A key feature to notice include the 0 C line- which is nearly to Raleigh, NC. That means one thing: Any precip that reaches the ground Thursday evening across the Mid-Atlantic is likely to be sleet or freezing rain, and may last into the early morning hours.

THE EVOLUTIONThis NWS forecast map loop provides a quick glance of the timeline. We expect a sprawling 1035 millibar high pressure system, currently near the James Bay, will relocate to southern Ontario by Thursday 12/24. This will be the source region for extensive cold air to funnel south ahead of a  very strong developing surface low in the mid-Mississippi Valley. Moisture feeding northeast ahead of this storm will over-ride cold air at the surface east of the Blue Ridge mountains. Our major concern centers on these indications of "cold air damming" and the potential exists for this to become a dangerous-to-crippling ice event for some during a crucial travel period.

THE PREPARATION:  It would be advisable for homeowners to clear snow away from nearby street storm drains, home downspouts and sump pump outlets. When a big rainstorm follows a snowstorm (as it did in January 1996), the biggest threat to all residents and property is often flooding caused by blocked storm drains. The daily refreezing of snow around storm drains this week, followed by significant icing, followed by heavy rain will create significant urban flooding. The water will have nowhere to go but your basement, parking lot or backyard. School systems need to factor the potential of this storm into their planning decisions regarding re-opening.

THE ACKNOWLEDGEMENTS: Members of our forecast team, the advisory board, and readers in the comments all pegged the potential of this storm starting Sunday afternoon. Special mention goes out to Mr. B of Greencastle, PA; PasadenaMatt, Andy of Southern York County, and Mr. Harris of Glen Burnie, MD. In addition, Snowlover and Winterman were on board in gathering data and observations. All these fine gentlemen were spot on in detection of changes in the computer models that led our team to prepare the current storm statement. We look forward to continued collaboration in the weeks ahead for it is rumored Mother Nature has quite a playbook of acts ready to show.

Saturday, December 19, 2009

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The Most Wonderful Time Of The Year...?

7:30 AM 12-21 COMMENT  We are mindful of the many people whom have to brave the icy conditions today regardless of schools being closed. It was a welcome relief that systems across many states announced their decisions early enough for parents to make care arrangement.  For the school kids, Andy William's famed holiday song "The Most Wonderful Time Of The Year" is most apt right about now, but maybe not for their parents!

A morning update is in progress to briefly discuss the roadway & school situation for Tuesday, and what may be placed in your stocking over Christmas Weekend. Later today, we'll post the storm grade report, and take a glimpse at the pattern ahead as well as add our new facebook page info. As The Carpenters (a late 60's - early 70's group) might say, "We've only just begun." That applies whether we are talking about the website, or the winter which officially begins at 12:47 PM today.

Be A Forecast Friend

9:00 PM 12-20 UPDATE: Share your storm pics in our photobucket created by PasadenaMatt. To receive permission for image posting, make a request in the comments, your email address is visible only to site administrators. All approved pictures added in the "Blizzard of December 2009" gallery, automatically appear in the slideshow.

If posting in the main gallery, please limit photos to your 5 best per participant. You are welcome to create your own album and place all pics there and provide a few classic shots for the main gallery. All images will be moderated, are expected to be appropriate, in good taste and related to the storm.  The forecast team retains admin control over all images in the album.

Thanks for joining, now go share in the fun of this historic event where many locations across the Mid-Atlantic received 20" or more throughout the weekend. So much for the "flurries" some reported The Weather Channel's local forecast had for Baltimore on Saturday.

So I Heard You're Having A White Christmas?

7:15 am Sunday 12-19-09   Although astronomical winter has yet to officially arrive, Enya's White in the Winter Night I believe captures the essense and beauty of the  season to come. A pre-Christmas Blizzard in Baltimore was fun albeit a bit shocking, but it did require one thing some don't often do prior to the holidays: Spend time with our immediate family.  Despite the feeling  that  we're smack dab in the middle of February, having our scripted Saturday routine whisked away in a rush of snowy wind was for some,  a welcome relief.  Yet we must not overlook this reality: Thousands of people who would rather spend time with their families are instead working on your behalf to clear our roads, schools and businesses for re-opening.

Instead of jamming the day full with shopping, many stayed home to simply enjoy the snow, shovel a piece, sip the hot choc afterwards or juuusstt take a break. I am mindful that many many other people unfortunately suffered terribly  in this storm. But times like these bring people together in ways unlike any other.

Enya's delightful winter melody is a lyric that conveys the thrill of being a child in a snowstorm: "Have you heard their sweet heart's cry for all this time they're waiting..."  From the joyous sounds I've already heard emanating at a "Who-ville" in Virginia, it appears the waiting for many will soon be over.

Our storm grade report will be based on the spotter and official reports in public information statements at NWS offices in Wakefield, VA  Sterling, VA and Mount Holly, NJ Members of the forecast team will revisit our snowfall predictions and confirm the final accumulation. We can given you an early glimpse based on the observation data from BWI. Mr. Roylance of the Baltimore Sun has a detailed data summary of the records.

Predicted 3:30 PM Friday 12-17  Amount 24.7"  Liquid 2.06"
Forecaster Grade 9 BCPS Crossroads student, Mr. Foot's Period 4
Location BWI Thurgood Marshall Airport
Actual 21.1 as reported by the Sterling, VA NWS office
BWI storm grade: 21.1 / 24.7 = 87.5 B+ or a 3.50 GPA.
Pretty darn good for a 9th grade "student" meteorologist wouldn't you say?

If you are new to the site, we warmly welcome your participation and input. We hope you find the comments to be a pleasantly respectful place of robust discussion, especially when winter storms threated the Mid-Atlantic. I am grateful for the diligent work of all our student climate collaborators, and snow-filled kudos to our four county/two-state forecast team. Special acknowledgement goes out to Mr. Roylance of the Baltimore Sun, for his detailed report on the student project as featured on Saturday's 12-19 front page (even above the fold!)

Check back before the 4:15 PM Ravens game for some refreshing improvements that will include a separate Facebook page, a Photobucket sharing site and perhaps even Twitter. Our team is moving these projects forward quickly, because if this winter resembles that of 1957-58 in any way, it won't be long before we're back together all over again! Enjoy the snow.

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6:45 PM UPDATE 12-19  Blizzard warnings, which were in effect across the entire Baltimore-Washington metro area have been discontinued by the Sterling, VA NWS. The Winter Storm Warning remains in effect until 6 AM Sunday. Regarding final snow totals, for my long time friends and colleagues in Dundalk, MD where this site began-- I ran the final numbers for our town as a sampling of the outcome. At 7AM I observed 4" at my house. The period 7AM Saturday to 12AM Sunday may produce a total of 1.50 liquid x 16.7 ratio (provided by Terpguy) = 25.05 + 4 = 29.05" for Dundalk, MD. Stay on top of the shoveling tonight if you can!

The forecast team believes a third and final shortwave will cross central Maryland  later this evening, extending the duration of accumulating snowfall into the early morning hours. This may add an additional 2-5" depending on your location. Higher totals near the Bay, lesser near the Blue Ridge.

Bursts of heavy, thunder-laden snow, falling at 2-3" per hour across much of Maryland today resulted in part from several upper level shortwaves. Mr. Snowlover in western Baltimore County has tracked this upper level system since Wednesday night on NOAA charts. The original shortwave energy engaged a nearby upper level low in the Midwest. Upon the low's arrival in this area, it enhanced pre-existing conditions further, and contributed to the heavy snow and the thunder today. Note that the forecast team on Friday morning 12-18 predicted thundersnow and rates of 2-3" per hour for this afternoon, 30 hours in advance. Photo: Dundalk, MD at arrival time of 850 mb shortwave.

STORM GRADE TOTALS by 12 PM Sunday 12-20
For new readers, the "StormGrade" refers to a percent accuracy grade assigned to these counts based on deviation of actual from predicted at end of storm. We use NWS data and/or NWS spotter reports only. Since this effort is also a student research project, we do not adjust the numbers once they are confirmed. Then we use a simple accountability system to determine accuracy. Key: total liquid x predicted ratio = final accumulation.
Source of liquid equivalent data for our calculations.

PENNSYLVANIA locations added 1:00 PM 12-19
Philadelphia 1.77 x 12 = 21" | Allentown 1.25 x 14 = 17.5" 
Lancaster = 18" | Harrisburg 1.2 x 15 = 11" | State College = 6.5" | Altoona  = 7"

DELAWARE: Wilmington (pending) | Dover 2.62 x 10 = 26"

MARYLAND locations added 1:00 PM 12-19
Hagerstown 1.75 x 15 = 26" | Frederick (tbd) | Reisterstown (tbd)
Parkville (tbd) | Baltimore 2.37 x 12 = 28" | Dundalk 1.50 x 16 = 29"
Belair (tbd) | Salisbury 1.7 x 8 = 14"

VIRGINIA: Washington 2.08 x 14 = 29" | Richmond 2.22 x 10 = 22"

STUDENT SNOWFALL REPORT: 9:30 AM UPDATE 12-19 The snowcast kudos go to 9th grade science students at the Baltimore County Public School's Crossroads Center. (Baltimore Sun article) On Thursday 12-17, Mr. Foot's students conducted similar calculations as noted above, and reached a preliminary estimate that storm totals could exceed 12 inches. On Friday 12-18 their analysis was refined to  24.72" by Sunday 12 PM for BWI airport as a representative location for the Mid-Atlantic. Below: a photo of 9th grader J.E.'s TI-84 calculator and his liquid equiv. calculations.

However, these forecasts would not be possible without the extensive research on climate data conducted by our intrepid band of student climate collaborators. The climate team consists of Ms. Gerst's inquisitive 5th grade students at Perry Hall Elementary AND the multi-tasking 9th grade science students of Ms. Abrahm's at Mount Saint Joseph's High School in southwest Baltimore. Since early November, those two teams closely tracked  atmospheric and oceanic data to pinpoint a trigger event which led our collaborative effort to conclude a major storm would develop.

5:30 AM 12-19 UPDATE: Northeast base reflectivity radar from the National Weather Service shows heavy bands of snow continue to move north across Virginia, Maryland and well into Pennsylvania. The National perspective shows why there may be occasional lulls in the snow this morning. Heavier snowfall rates are likely as the second set of shortwaves and upper level lows in the midwest move through the Mid-Atlantic. Our intrepid team of winter storm forecasters will iron out those details this morning, and post our report by 11AM if possible. The totals reflect our projection of the storm potential as of 11:00 PM Friday 12-18-09.   

Regional coverage of our snowfall totals will be expanded to include other key locations where many loyal readers reside. Spotter reports from the Sterling, VA NWS Office continue to show accumulations climbing throughout the night, although we were stunned just by how much had fallen in places like Charlottesville, VA (11") by midnight Saturday. Spotter reports from the surrounding NWS offices will be added once the links can be located. Check back often, additional media and content will be made available including Facebook, Twitter and photo sharing space for use  during non-instructional time. The objective is to provide meaningful scientific analysis and enrich your experience on this site as we all collectively share in this historic moment.

Link to this morning's Baltimore Sun article on our student climate and weather project. And, as you can see, we in the Foot household are getting out to enjoy the storm.

Friday, December 18, 2009

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NWS Current Spotter Reports: Sterling, VA  | Mount Holly, NJ | State College, PA
The snowcast team completed an analysis of the storm situation and identified the current and future position of upper level lows at 5,000 feet. The location and speed of these lows as they move from the Carolinas tonight to near Richmond by daybreak will impact the duration of heavy snow periods and hourly snowfall rates.  Additional disturbing news about latest computer model trends for the Mid-Atlantic is supported by the local storm reports posted above. The 00z (7pm) NAM (North American Mesoscale) was analyzed at 10:30 PM and showed a much higher liquid equivalent for BWI, as did several other models.  Research from earlier this evening as noted below shows the daytime Sat temp may remain in the mid to upper 20's across the region, producing ratios of 13:1 or 14:1 possible. This may increase the already high totals below.

PA: Philadelphia 1.77 x 12 = 21 | Harrisburg (MDT) 1.2x 15 = 11
PA: Allentown 1.25 x 14 = 17.5 |
DE: Dover 2.62 x 10 = 26 |
MD: Baltimore 2.37 x 12 = 28  | Hagerstown 1.75 x 15 = 26
MD: Salisbury 1.7 x 8 = 14
VA: Washington (IAD) 2.08 x 14 = 29  | Richmond 2.22 x 10 = 22 

Other locations in the Mid-Atlantic to be added Saturday morning, including central/western Maryland, Northern Virginia, the WV Panhandle and Central PA.

6:00 PM FRIDAY 12-18-09 BRIEF UPDATE  The forecast team has projected an initial snowfall total for BWI : 24.72” This is based upon analysis of  the 12z (7am) precipitation data from the North American Mesoscale model. Students at the BCPS Crossroads Center at 3:30 PM today calculated the liquid equivalent expected for the storm period. Their totals were 2.06” and used a liquid-to-snow ratio of 12:1 based on an expected daytime temperature on Saturday of approximately 30 F in Baltimore. Thus, the calculation is 2.06 x 12 ratio = 24.72” as prepared by Mr. Foot's Period 4 students at Crossroads and verified as a valid call by our Central PA Snowcaster and PSU student meteorologist Mr.B.

He also reported at 6:10 PM that when using the National Weather Service’s “BUFKIT” precipitation analysis tool, the data output shows a liquid equivalent of 2.37”. Utilizing the same ratio of 12 results in a total accumulation of 29” for BWI.

However, entering the same 2.37” but using 18z NAM surface temperature projection for Saturday in Baltimore points to a mid-day temp of 24 F. This would result in a much higer snow ratio of 15:1 than our original 12:1, producing 35.5” for BWI by Sunday 12 noon.

The forecast team will report results as they become available this evening, but not before 10:00 PM. Our report will Include final snowfall amounts for major metro areas in the Mid-Atlantic as well as West Virginia, Virginia and Central Pennsylvania. There is strong evidence in the upper air data suggesting thundersnow will occur between 8AM and 1PM Saturday in the region including Southeast Baltimore County to Annapolis, as well as western Baltimore County to Carroll and parts of eastern Frederick County down to Montgomery. Embedded in these thunderstorm-like cells will be snowfall rates that could exceed 3” per hour. Our source is the RUC (Rapid Update Cycle) model which updates every 3 hours.

Final comment before our team returns to research: Mr. B reports that NOAA has dispatched one of the hurricane hunter aircraft from Mississippi, and as of this writing it was dropping radiosondes into and ahead of the storm. That alone should be an indication to you we have a serious and life-threatening situation. Mother Nature is ready to rumble. Are you?

Thursday, December 17, 2009

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Y'all ready for this?"
- by 2 Unlimited in their 1991 single Get Ready For This


* NWS Winter Storm Watches & Warnings  12AM Sat to 6AM Sun for:
* Prelim snowfall for BWI airport by Sunday 6PM: 8.9 to 14.4
(calculated by 9th grade Pacific Community students at the BCPS Crossroads Center)
* Student data based on Thu 12-17-09 1 PM NAM model data
(liquid equiv. range of .70" - 1.2" x snow ratio of 12:1)
* Current precip projection for BWI airport (multiply by 12 = amt.)

FORECAST TEAM ROUNDTABLE: The winter storm analysis team collaborated last night at 8:30 PM on the developing situation. Answers to your questions include:

1. IS THIS REALLY GOING TO HAPPEN? There appears to be "no escape" route for the storm, now quickly developing across the Gulf coast (IR satellite loop) The current surface map reveals a set of high pressure systems settled in across New York and Ontario. Cold dry air is firmly in place ahead of the storm. This will provide the textbook setup for an historic Mid-Atlantic winter storm which resulting snow amounts at BWI airport may rival that of January 1996, January 2000 or even February 2003. Widespread school cancellations are possible for Monday 12-21 or beyond from Virginia to Maryland to Southern PA, the DelMarVa and New Jersey. 

2. WHEN WILL IT START? The first Big Kahuna of the 2009-2010 season will get underway between 9PM and midnight Friday across Maryland and Virginia, if not sooner. Saturday morning will afford powderhounds young and old alike the chance to walk in a winter wonderland until 20-25 mph winds and heavy snow bands arrive mid-day and continue overnight. The Harrisburg-Lancaster-Philadelphia metro region will see snow begin before sunrise Saturday.

3. HOW BAD COULD IT BE? Saturday night, near-blizzard conditions are possible along the Chesapeake Bay and along the Baltimore-Washington-Richmond corridor. Winds may reach or exceed 35 mph at height of the storm, reducing visibility to 1/4 mile or less. As the coastal low deepens off the Virginia capes, snowfall rates overnight may exceed 2 inches per hour at times. Strong upward motion off the Chesapeake Bay may produce brief periods of "thundersnow" and lightning along the I-97 corridor. Significant tidal flooding along the western Bay will occur due to an easterly fetch of 20 mph+ winds over a 12-24 hour period. Extensive beach erosion along Delmarva coastal communities is likely. 

4. HOW MUCH SNOW? Ensemble computer model output, the map shown above, are averages of multiple projections. These maps continue to show a minimum of 1.25" liquid equivalent for most of the Chesapeake Bay & associated metro regions. For those who value not having a sore back for weeks, this is a disturbing development. If the average, basic trend is 1.25" that means the actual precip amount could be 2.0" or greater. This map is for the 24 hour period ending 1AM Sunday, please view the source. By using our standard storm grade calculation, and selecting BWI as a baseline location, this still delivers a minimum of 12" if using the liquid-to-snow ratio of 10:1 (1.25" x 10 = 12.5"). A map showing how we calculate the totals:

More recent computer model runs have shown a possible 2.48" liquid for BWI. Even at the low end ratio of 6:1 for a sloppy wet snow, that is still 14.88 inches (2.48" x 6 = 14.88). The latest GFS computer model (00z 12-18-09) run shows a fairly extensive hit of 12"+ from Western North Carolina to New York City by 7AM Sunday morning.

5. WHAT HAPPENS NEXT? We surmise someone at NWS may be contemplating Blizzard Watches based on the wind speed and duration. You may see additional posts today provided by our Central PA Nowcaster Mr. B. Our forecast team will have another roundtable tonight and release our final storm grade amounts by 10:00 PM. Special thanks to the hard work last night by Snowlover, Winterman, Mr. B and PasadenaMatt for hammering out all the details our readers rely upon.

PREVIOUS UPDATE 7:00 PM 12-17-09

* NWS WINTER STORM WATCHES are in effect for all of Maryland until Saturday night. Watches are likely to be raised to Warnings by Thursday evening or Friday morning.
* Our team retains this morning's call that amounts in the Baltimore-Washington metro area, central and western Maryland MAY EXCEED 12 inches by Sunday night.
* Respected meteorologists whom the forecast team follow as part of their research are indicating potential for blizzard-like conditions in the I-95 corridor from DC to PHL.
* Parents, teachers and school administrators should be aware this situation could negatively impact the school calendar for all of next week.

The Stormcast Team is currently having dinner in their respective homes and reloading for the gathering gale ahead. Our evening roundtable between 8:00 and 9:00 will establish the storm timeline, impacts and preliminary accumulation ideas. In preparation for the storm grade amounts, Mr. Foot's 9th grade science students at the Baltimore County School's Crossroads Center today conducted their "liquid equivalent/snow ratio calculations" for BWI airport as a baseline.

OUR FINAL WORDS: Is your vehicle fueled up? Homeowners, do you have a stake to post near the sump pump outlet or storm drains, in case you need to find them later? Are your gutters clear of debris? Got that shovel with the long handle that bends in the middle? What are the daycare plans for next week if school is closed? Yes, we hear you, as if there wasn't alreeady enough to do this time of year!