Wednesday, January 30, 2008

12 comments:
HOW HAPPY WILL YOUR FRIDAY BE?

Uncertainty abounds in the latest round of winter weather set to affect the Mid-Atlantic Thursday night into Friday. High pressure settling into place for the next 2 days will allow overnight temperatures to refreeze the ground and make all surfaces quite cold as the next storm system approaches from the Tennessee Valley. Overnight Thursday into Friday it seems likely that west of I-95 in Maryland will see several hours of freezing rain. Rapid arrival of the storm will allow low level cold air to hang tough into the early morning Friday, and will take until well after sunrise for the southeast and easterly flow to scour out that cold air. However, low dewpoints also mean the potential for a delayed start of precip, which for those hoping to get school delayed, could be a "mixed" blessing, no weather puns intended.


Since many of you come to this site for the "inside scoop" on weather events like this one, here's the breakdown: A tricky call for school districts in central Maryland. Baltimore County especially will face a challenging decision for several reasons:
- There will be ice accretion in roughly two-thirds of the county, north and west of a line from Fork to Towson to Catonsville, enough to disrupt morning traffic only. South and west of a line from White Marsh to Glen Burnie, expect a brief period of freezing rain overnight turning to all rain. If your commute keeps you along or east of 95, icing will be minimal.
- All frozen precip will change over to rain by 10 AM, with exception of far N and W, such as Hereford Zone and obviously into the more rural counties like Carroll and Frederick.
- Despite this changeover likelihood, the issue becomes... will it occur quickly enough (say by 8AM) so as to let a 2 hour delay stand. We all know that if a school system announces the call at 5:30, they can't wait until 8AM to change it, because by then buses would already be rolling to pickup high school students.

- My theory on the logistics of this (based on witnessing similar situations in Feb 2005), is that any decision to upgrade a 2 hour delay to a closing really has to be made by 6:30-7:00 AM. While it may still be icing throughout the area (except for east of 95)...I fully expect temperatures to warm above 32 by mid morning SO THAT were buses to start rolling at 8AM...things theoretically would be fine.
- The problem with this whole setup is the call to stick with a 2 hour delay will have to be made on a HOPE that the forecast pans out as projected. The danger is that if warming to well above 32 has not occured by 8AM, the whole area remains a disastrously treacherous commute right at the critical time of 8 to 9 AM, only to clear up perfectly at 10.


For simplicity sake, let's hope that:
1. In eastern areas (the immediate Baltimore Metro area) Any freezing rain/sleet quickly turns to rain just in time to let school systems feel confident the 2 hour delay call was a good one.
2. in central and western areas (Carroll County on west)...the weather forecast at least makes it easy for schools to make a sensible call that won't cause political or parental consternation.


What do I think will happen?
Honestly, I can see Baltimore County closing the Hereford Zone, (or perhaps allowing them a 2 hour delay) and leaving everyone else with a 1 hour delay. I say this because I sense we'll have a later start time, (5AM instead of after midnight) limiting how much can fall and freeze. The city may not even have a delay. Carroll, Frederick and west-ward are facing a significant ice storm that could result in .25" or greater, and strong winds behind the storm are going to knock down trees and powerlines. They're going to heed the call and close outright in my opinion. From Howard County on south, expect mostly rain and nothing in the way of delays or closings, sorry Anne Arundel, PG and Montco, you'll have to sit out this one. Harford County likely ends up with a 2 hour delay. Will be interesting to see what the morning brings, so goodnight all!

Friday, January 25, 2008

8 comments:
IN MARKING PERIOD GRADE MODE UNTIL MONDAY

Sorry for not being able to post recently, what little brainpower is left in the evenings this week has been diverted to preparing quarterly grades. Sometime during the weekend, I hope to post an overview of what's lurking for February. I see the potential for a little surprise snow Saturday, and some computer models are having trouble resolving the development of a possible rogue coastal on Sunday. At least there wasn't much Mid-Atlantic weather to talk about this past week. But as we head into February, I foresee some "weather whiplash" coming up, with wild swings in temperature and storm types. Feel free to post any questions you have about the upcoming pattern and I will answer this weekend as time permits.

Tuesday, January 22, 2008

3 comments:
WILL THE TREND BE YOUR FRIEND?

Tuesday 1/22 thoughts on the clipper: Think over the trend of the past 2 storms that approached us from the west/south...both ended up as "overperformers" due to more dynamic development once in the Mid-Atlantic. The Dec 5 and Jan 17 events produced more snowfall than was anticipated by NWS and Accuweather. I believe today's event will continue that trend, for 2 reasons:

1) While dewpoints are again low presently, southwest winds ahead of the storm will raise temperatures a few degrees faster than normal, and moistent the atmosphere quickly ahead of arrival. This will enable snow to once again start suddenly as it did in the Jan 17 storm.
2) This system is slower moving, and while moisture content is low, the surface and boundary layer temperarures will below freezing until late in the day, allowing whatever falls to freeze on contact. This will create instant and widespread slippery conditions.

WHAT ABOUT SCHOOL? Easy call there...another round of parental pandemonium.
MOST LIKELY: 1 HOUR EARLY DISMISSAL IF the precip arrives sometime after 10 am in the Baltimore/DC Metro areas, and is generally light but persistent for several hours. A changeover at or after 3 PM won't help high and middle schools which let out in the 2:15 to 2:45 period.
LESS LIKELY: 2 or 3 hour dismissal. The mess that resulted from the 2 hour call recently I don't think will be reattempted again for sometime. There is not enough heavy precip potential to warrant a big call for that. THEN AGAIN... do you think there's a chance that backlash from last week might have some districts running scared and they'll over-react, going with a 3 hour when a 1 hour would be sufficient? Regardless of the call, I can forecast widespread parental pandemonium if the trend turns out to be our friend and this event becomes another over-performer.

Monday, January 21, 2008

12 comments:
WILL THE FUN BE LASTING?

This forecast graphic just made me smile this morning, and for powderhounds in the area, I'm sure it'll have the same effect. If this pans out, look for a highly disrupted week considering the overnight temperatures. Keep in mind now I use places like downtown Baltimore or Dundalk as my bellweathers... because if warming influences of the urban heat island/bay are not enough to overcome frozen precip potential, then it's a sure bet outlying areas north and west are going to see more. If not "more" they'll at least see generally frozen precip.
Will The Fun Be Lasting
Right on schedule, the Baltimore/DC NWS is coming around to the ideas I originally posted late last week: 3 snow events on tap for the Mid-Atlantic over the next 7-8 days. Now Saturday's Vlizzard could have been counted as one of those 3, so that leaves Tuesday and Wed-Thu as candidates. There is still potential for a weekend system, and if the timing/amounts are right, is there a chance this might deliver TEACHERS as well as students in some school systems (namely Baltimore County) a shot at a 3 day weekend? The answer is: I suspect region-wide accumulations next Sunday would have to be 5"+, or at least fall very late overnight into Monday. Obviously that is too far distant right now for any solid projections, but the potential is there and I'll be watching it carefully.


Final note: Very busy today trying to get grades, paperwork done along with attempts to resurrect the "forecast computer." I may have spilled some water into the laptop's wireless port (of all the dumbest places!) and now, the laptop just sits on my lap and hums. It is not a pretty tune, so I'm hoping our President will deliver on his promise to send us all bonus money borrowed from China that I can use ot help stimulate the economy. (Just don't tell my wife!)Anyway, will try to respond to your comments as time and family permit.

Sunday, January 20, 2008

5 comments:
IT WAS FUN WHILE IT LASTED

1/20/2008: Until we get to the next round of winter weather (first minor shot Tuesday, next major shot Saturday-Sunday), I wanted to share with everyone these delightful images sent to me by 2 of our readers..they're white-blooded powderhounds, and teachers in Baltimore County. If you're looking for a wintery screen saver to tide you over until next time, these are worthy candidates:

Frostry branches adorning the Hereford Zone of northern Baltimore County, MD
frosty branches
I think it's Par for course that no one will be hitting any birdies here.
golf course
Robert Frost would have been proud: "Stopping by a woods on a snowy evening..."

Julee's bench

In case no one noticed yesterday, you went about you day underneath one of the longest-duration "vlizzards" I have ever seen. (That's a virga blizzard). I mean it snowed like mad for at least 9 hours straight, giant invisible flakes coating everything in a blanket of vapor. Actually, it was a virga storm. All that beautiful white and blue on the radar yesterday was snow falling but evaporating before reaching the ground. Whodunit? Dewpoint depression. Boundary layer moisture content was too low to be overcome, and the dryness prevented any of that snow from reaching the ground. Had it reached the surface, we could have called it a "flizzard."


Also of note is one of my personal first accomplishments with this website. After 4 years of blogging, I finally figured out ...totally by accident mind you... how to embed animation in the post. I've been wanting to show radar and satellite loops for the longest time, and as long as I can remember how I figured it out, there'll be more internet weather fun like that for you in the next storm. I'll stake out some time today to revisit our still-on-the-table Rumble Storms..the Tuesday quick shot and the Saturday-Sunday big shot.

Saturday, January 19, 2008

5 comments:
DE JA VU ALL OVER AGAIN?
Twice in the past 7 years, I've heard the famous words:
"No need for concern, the storm is going to stay mostly south of DC."

Results:
(1) January 25, 2000. Initial forecast for Baltimore: 1.5" Actual: 17"
(2) February 16, 2003: Initial forecast for Baltimore: Light rain/snow mixed. Actual: 24"

The map below was a projection by the GFS on conditional snowfall for Saturday evening. Of course no one bought this solution, because it was (and still is) believed the approaching cold front in the mid-west would kick the Southeast storm out to sea before affecting the Mid-Atlantic and Northeast. Now scroll down to see the current radar and compare. Call me a wishcaster, but it seems that the western edge of precipitation is a tad bit west of DC.
Saturday Surprise 1

Saturday Surprise 2

Thursday, January 17, 2008

9 comments:
"LLLLLET'S GET READY TO RUMBLLLLLLLE..."

-The catch phrase popularized by Wrestling announcer Michael Buffer
The Middle Atlantic States may experience two or possibly three snow events over the next 7-8 day period, combined with very cold Arctic air this weekend with another round of cold later next week. One point to make clear is that by Saturday morning, sidestreets and parking lots will likely be slick and "cruncy" as Justin Berk of ABC2 News noted. This may impact school activities and events planned for tomorrow.


ON THE WEEK AHEAD: (I'ved moved graphics to bottom of the post, as they are blocked by some school servers.) The Saturday storm has potential to deliver anywhere from a glancing blow to a similar amount of snow as occured on Thursday. The second event next Tuesday will feature some winter precipitation but does not appear to be significant. Next Thursday into Friday could very possibly contain the necessary ingredients for a major coastal snowstorm. The setup for this third and final storm of the month looks similar in orientation to that which we saw prior to the February 2003 Blizzard. I know that sounds like a hypecast statement, but bear with me on the explanation as to why I am seeing this.


The meteorologists whom read this site are going to chuckle and say, "Yes, but that's the GFS 7 days from now. Come on, you know a lot can change between now and then." I must agree that they would be right. To the contrary, they would also agree that the GFS has sometimes shows a big storm in the long range, then loses it for a few days. We've looked back at model verification to see that the final solution occasionally ended up looking a lot like the initial projection. With that precedent in mind, allow me to explain the dynamics of a Mid-Atlantic Big Kahuna # 1.

If you're not able to view the graphic below, I'll summarize the main features:
1. The next two events are going to orient the upper atmospheric flow in such a way as to leave behind a "piece of energy" or a closed 500mb Low in the Southwest, as alluded to in HPC discussions of late.
2. Between Monday and Wednesday, this upper level feature will begin to rotate east and eventually eject into the Gulf of Mexico. An active southern stream will provide the impetus for a surface low to develop.
3. High pressure in northern Canada should settle to Ontario and expand over the Northeast and Great Lakes by Thursday morning.
4. Easterly and southerly flow off the Gulf and Atlantic will allow precipitation to break out over the Lower Mississippi valley Wednesday into Thursday as the developing storm moves northeast. A slightly neutral to postive NAO and generally slightly positive PNA should allow for any Southeast Canadian High Pressure to remain in place as the surface low travels through the Tennessee Valley and toward the Carolina coast by Friday morning.


IN CONCLUSION FOR NOW: While I'm not saying the map that some of you can't see will exactly verify, what I am saying is it represents the general trend of pressure systems over the next week. One of the most important features necessary for a solid East Coast snow event is a strong, stationary High Pressure in SE Canada. I think the climate teleconnectors are indicating the environment becomes most favorable for this arrangement by middle to late next week. How much snow is too early to tell, but the potential is there for a large scale winter weather event across much of the Mid-Atlantic and Northeast.

Thu 1-24 Banana High

28 comments:
BE CAREFUL WHAT YOU WISH FOR

THU 1/17 - 4:45 PM. SO...ABOUT THAT "CHANGEOVER" IF ANYONE OUT THERE ACTUALLY WITNESSING ACTUAL RAIN? In Dundalk, it was all snow until about 4:30. Preliminary snow reports from across MD are interesting, and considering that Anne Arundel has some of the highest totals in the Metro area, and they weren't even part of the original advisory package. My temp has dropped 2 degrees, now back to 32, when we were supposed to be rising by now. The rain/snow line according to the AccuWx Radar has been firmly established along and east of the Bay all day, and it's only now begun to move west. Could this turn into the "Big Storm That Would?" I think it's becoming clear to most of you that even light rain for a few hours won't be enough to wash away all the slush, and with temps holding near 32 overnight, delays tomorrow I think are IN THE BAG.

THU 1/17 - 1:30 PM As I write this, snow is softly falling outside my classroom window while I enjoy the peace and quiet of seeing our school's front yard glistened over with white. I am sorry to all of you who have to commute and face snarled traffic instead of a tranquil ride home. So in honor of all those commuters out there, I will walk the grueling, downhill trek of my endless 400 yards home, and think of you among the winter wonderland.

FOLLOWUP OBSERVATIONS ON TODAY'S EVENT:

1. My start time was much earlier than news and weather outlets, and I can see why it took until mid morning (at least in southeast Baltimore County). I would surmise the immediate boundary layer was still quite dry, and several hours of virga (when precip is falling but evaporating before reaching the surface), delayed the onset.

2. However, the very nature of what "virga" does is what I believe enabled the snow to reach greater intensity once it began. The atmosphere became sufficiently chilled and moistened to the point that snowfall rates were very high from the start. Combined with the fast moving shield of snow that overspread the area, I knew that once it got started, the snow would make up for lost time by accumulating more quickly.

3. I wore a special tie I reserve for these occasions.. the dark blue one featuring my 2 skiing snowmen. My wife asked what the tie meant this time, and I told her that the 2 snowmen on the tie indicated schools (at least the ones that have some sense to make the right call ...Frederick County...ahem.. Bueller...anyone?) would close 2 hours early. To this she remarked: "Of course, when I bought this tie for you 4 years ago, I had this exact date in mind, January 17, 2008. Riiiight."

HAVE WE LEARNED OUR LESSON FROM PREVIOUS STORMS?

It's obvious now this storm is turning out to mimick it's December 5 cousin, aptly named "The Little Storm That Could" by faithful powderhound Mr. Ligner, the Athletic Director at Sparrows Point High School. That means the 2-4" could end up closer to 5" in some parts of northern and western Baltimore County. I suspect Carroll and out-in-left-field-they-must-have-hired-their-transportation-folks-from-Buffalo-
Frederick County will see amounts on the high end of their Warning criteria... with widespread 6-7-8" likely. Of course I adore my job, my students, my employer and the nice summer 2-month bonus I get every year, so you can be sure that MY COUNTY will always make the right call, no matter what. ;-) I leave all the bad weather related decision making to other places, like Howard and Anne Arundel Counties, for starters. No offense and kudos to my Ho Co colleagues who quickly pointed out they are on an exam schedule this week..so they were scheduled to get out early ANYWAY!

There have been several times in the past 5 years that school systems were burned for making a call based on the BELIEF that dire predictions of weather agencies would come to fruition, and didn't. The one that sticks out in my mind most recently is late February 2005, when NWS had posted a Heavy Snow Warning for most of Maryland. You might have thought it was going to be "Day After Tomorrow, Part 2." Everyone closed from bow to stern. The snow started... at 10 AM. Oh it was heavy all right, and started to stick on the parking lot here in southern Balto County, around 3 PM. I know because I was working in the school greenhouse that day, watching the heavy white clumps land on the grass and MELT. It was so unfortunate how that that storm turned out, because in reality we could have squeezed a full school day out of that. The ground was too warm to support accumulate UNTIL the sun angle decreased, once it did, snow started to stick like glue, but roads were still just slushy and not frozen over by any means.

Since that time, I believe school systems have been following a Revolutionary Era to making the call. You've heard the old saying from the Battle of Bunker Hill in 1775.. "Don't fire until you see the whites of their eyes!" I think we are seeing proof of that proverb here in Maryland. We can identify 3 storms tied to the dubious distinction of being a "Whites of their Eyes" Storm:
- Feb 12-14 Valentine's Day Massacre of 2007
- December 5, 2007 Little Storm That Could
- January 17, 2008 Frederick Co. Honorable Mention "What's a Winter Storm Warning?" Storm

GET TO THE POINT WILL YOU?

Oh sorry, got carried away with reminiscing about climatology. Okay, the point is for tomorrow:

If two-thirds of your geographical scope of authority receive at or above the projected snow amounts, and a changeover to rain is delayed or denied, the likelihood of your school system calling for a delay or closing is inversely porportional to the decision made the day before and the parent reaction to that decision. Without delving too far into the political gooeyness (sp?) of this, let's break it down like such:

IF YOUR SCHOOL SYSTEM WAS.. TODAY YOU RECEIVED... TOMORROW YOU WILL BE..
a Winter Storm Warning area... No early dismissal... Closed, for various reasons.
a Winter Weather Advisory area... A 2 hour early dismissal... 1-2 hour late opening
a Winter Weather Advisory area... No early dismissal... On time, No late opening
Not in any warning or advisory area... Snow but no dismissal... 1-2 hour late opening

WHEN'S THE NEXT STORM?

There is potential for a coastal system to surprise the Mid-Atlantic yet again on Saturday. With cold air in place and models continuing to back the shield of precip more westward with each run, I could see a Special Weather Statement coming out on Friday for the Saturday system which has the potential to deliver the same amount or greater than what the Mid-Atlantic saw Thursday.


And then there's Kahuna potential lurking in the near future, as early as Tuesday and perhaps again on Friday. I will endeavor to stay on top of these developing winter weather events and bring you the latest scoops of truth as time and family permit. As I said in the heading, those of you who were honking for snow, be careful what you wish for, because Mother Nature is about to make up for lost time.

As always, please post your observations in the comments, and feel free to send me a snow pic that I can use to beautify the site: rdfoot@comcast.net. Enjoy the snow while it lasts!

Sincerely,
Forecaster Foot

4 comments:
AFTERNOON HEADACHES ON TAP

With precip not starting as early as I expected, it's obvious why all area Baltimore and DC Metro schools are heading in on time. I'm sure they're grumbling out in Frederick and Carroll Counties, being under a Winter Storm Warning and yet in school. Once snow and sleet begin this morning, roads will become slick since whatever falls is going to freeze on contact. I envision widespread early dismissals being announced in the mid-morning, making for a very headache filled day. In fact, it seems as though this might even turn out similar to the Dec 5 "Little Storm That Could" which brought many area schools an early dismissal followed by delays the next day.

Wednesday, January 16, 2008

10 comments:
WILL POWDERHOUNDS BE PLEASANTLY SURPRISED?

WED 1/16 - 10:00 PM UPDATE: I am now expecting an earlier start time, based on rising dewpoints and faster than anticipated movement of the southern system. I believe you'll see snow and sleet mixed outside your window at 5 AM in the Baltimore/DC area. If I'm right and you see precip before daybreak, this will be the field goal that nets you that day off you've been hoping for so long (if you're in Baltimore County or City, Harford, Carroll, Frederick and yes even lil' ole' stodgy Howard County too, believe it or not.) The map below is the 10:30 PM Radar, and you can see precipitation is already intruding southwest Virginia. Even though much of that may not be reaching the ground, the speed of arrival tells me that it should overspread the area between 4:00 and 5:00 AM. Late-breaking addition...NWS Sterling, VA has upped the amounts on your Winter Weather Advisory, and upgraded large swaths of Virginia to Winter Storm Warnings. If that all comes to pass, the school forecast is, as George Tenet might say, a SLAM DUNK.

Thursday Surprise 3

Now compare how hugely different this map has become from just one hour previously. Didn't your grandfather always used to say "the biggest storms always came from the south." Here's a another weather rule that never fails: If it's snowing in Atlanta, it'll be snowing in Baltimore.

Thursday Surprise 2

WED 1/16 - 7:00 PM UPDATE: This projection from the GFS model indicates snow and/or frozen precip may still be falling even at 1 PM Thursday across most of central and western Maryland.

Thursday Surprise 1


WED 1/16 - 6:00 PM: I figured you'd be back here before long. Perhaps you were wondering if I would ever be back, but since the weather has provided us a new topic, as Captain Kirk might say: "Well, now you have something new to talk about." As many of you already know, the Baltimore/DC NWS issued a Winter Weather Advisory for the most of Maryland west of the Chesapeake Bay, including the DC and Baltimore Metro areas. I've been watching their discussions, the observations, satellite, and of course our old friend, the computer models, for several days now in anticipation this storm was going to deliver some sort of winter precipitation on Thursday. Those in this region whom follow winter weather are beginning to suspect that this system is not turning out as expected, and I anticipate a diversity of surprise closings and delays throughout the DC-Baltimore Metro areas are on tap Thursday morning. Low level cold air appears entrenched into the deep South, as evidenced by the extent of NWS winter weather advisories from here to Georgia.

This fast-moving system will display unique impacts across the Mid-Atlantic area (specifically in Maryland west of I-95, south central Pennsylvania, Northern Virginia, the West Virginia Panhandle, and of course the Shenandoah region):

1. Persisent high pressure "centers" in the Mid-Atlantic will allow temperatures overnight to drop below freezing. By daybreak, whatever precip that begins to fall will freeze on contact, allowing slippery travel conditions to develop quickly, and catch unsuspecting motorists/walkers off guard.
2. A rapid onset of precipitation from southwest to northeast in the pre-dawn hours.
3. The timing of snow and sleet is such that it will disrupt and delay traffic in the critical hours from 5 to 9 AM, and a changeover to "liquid precip" may not occur until afternoon.
4. Changing and unresolved precipitation timing concerns that may disrupt school schedules.
5. A fast moving system that WOULD become a major snowstorm were it not for lack of access to an Arctic high in Southeast Canada. (actually there is one there, but the timing and orientation are not right this round)

The biggest concern which prompted NWS to hoist advisories for the Maryland region is that computer models do not see to be handling the presence of low level cold air across the region. Secondly, the eventual intrusion of warm air aloft may be delayed such that frozen precip is now more likely over a wider area than originally thought, and for a longer period of time. Accuweather, on the other hand has been downplaying the potential for ice or mixed precip. As I remind my students in situations like this, the amounts sometimes does not matter if we have a mixture of frozen precip, because even one tenth of an inch of ice as you all know can wreak far greater havoc than just one inch of snow. The movement of this storm can be seen in a computer model animation from a site I've recently discovered: coolwx.com


For those who have wanted to know what's been going on: The lack of activity on this site is due mainly to the challenge of managing young children, on going winter illness and teaching high school. Those of you with children, or who teach children, or even just know how to spell children understand how rewardingly drained one feels at the end of the day sometimes. Hence there has been little energy left over to post on our recent weather events. I am grateful for the ongoing support of the many loyal readers out there, and feel bad I could not deliver more frequent updates the past month. Especially for my Pennsylvania, New Jersey and New England colleagues who must think we're no longer on speaking terms, as I stopped forecasting altogether even for Boston's recent snows, sorry guys! I will make it up to you. There are big things in the offing for next week and I have a special post in preparation for the announcement that "something is brewing out there...and it's not just the coffee."


Overnight and tomorrow morning: Please post your observations and location in the comments if you are able and willing.