A trick for some, a treat for others

11:00 AM EDT 10/29/11 | FINAL STORM GRADE FORECAST AMOUNTS 
The image below contains our final storm projections for this event. Once all Local Storm Reports have been submitted to the respective NWS office, we a member of our team outside the Mid-Atlantic will conduct an independent verification of our results and grade the storm, based on the departure between predicted and actual.  

INTERACT WITH YOUR LOCAL TEAM IN FACEBOOK

If you want to take part in recording this historic event, you are welcome to post imagery and observations in the comment feature on this page, or to your local team in facebook as linked below. Many readers in Maryland and Virginia are already reporting snow on secondary roads, cars and grassy surfaces.

WINTER STORMCAST ZONES Mid-Atlantic | Northeast 

VIRGINIA Central | Northern | Tidewater

WEST VIRGINIA Potomac Ridge & Valley 
MARYLAND   Capital Region | Central |  Northern Bayshore 
PENNSYLVANIA   Southeast | Central | Three Rivers
NEW YORK  Central NY State | New York Metro


8:50 AM EDT 10/29/11 A SIGHT YOU'VE NEVER SEEN The image above from the NWS Eastern Regional Headquarters depicts the current extent of Winter Storm Warnings and related Winter advisories along the Mid-Atlantic and Northeast. If this were December or after, we would all be saying, "well after all it is December you know." In October 2009 an early season snow brought up to six inches in State College, PA along with the subsequent power outages. It led to a post we titled "December in October?" That event gave our team an indication of what the winter would bring: Unexpected high impact events generated by a resurgent El Nino. 

Mr. Foot, Devon PA, Oct 1972

Now we are faced with a new wild card: A La Nina pattern producing a significant winter storm occuring very far outside the climatological norm. The only comparison we could find was back to October 1972 for so much snow this early. Thanks to Mr. Foot's Mother, we were able to dig up photo proof of the last time there was measurable snow at this time of year: October 18 and 19, 1972 as reported by Pennsylvania  Lehigh Valley's Morning Call in this article. Like Charleton Heston said in his gravelly voice at the opening of the 1998 film Armageddon, "It happened before, it will happen again. It's just a question of... when." 


             Winter Stormcast Zone returns


12:10 AM EDT 10/29/11 | WELCOME BACK TO THE WINTER STORMCAST ZONE. In advance of this significant early season storm, we have relaunched the most popular zone on this page from the previous two winters, found at this link. For those in schools or at work and unable to access facebook during the business day, this new tab will provide you with a wide-angle heads up on the next storm, as posted on the regional facebook page. 


6:15 PM EDT 10/28/11 | STORM UPDATE & ANALYSIS | While once-strong Hurricane Rina has drifted into weak Tropical Depression status, her parting gift may be an injection of moisture into the expected Mid-Atlantic and Northeast U.S. snowstorm. We have conducted extensive analysis of the situation throughout the day and are very concerned about several key  issues:


* POWER OUTAGES: While 8 or more inches may fall in places like Lancaster or Harrisburg in PA, and Westminster, Frederick MD-- perhaps just 4 inches will reach the ground due to the sun evaporating away the snow as it falls. However those 4 inches might actually contain 1 full inch of water. The weight of this water-laden snow on full foliage may produce extremely disruptive and complicated outages.


*DYNAMICAL COOLING: We are observing evidence that a high pressure system in Canada is starting to orient in the classic, but troubling "sweet spot" of southern Ontario. At 1025 mb, the cold air within this High is likely to be tapped by the developing ~1000mb low. The interaction of these two opposing pressure systems over a relatively small geographical area (the eastern mid Atlantic) could easily produce strong upward motion and in turn, dynamical cooling. This has the effect of allowing the storm to generate additional cold air, feeding on the decreasing temperatures as snow falls, and squeezing more snow out of the same amount of atmospheric moisture.  


*HEAVY SNOW BANDS: We believe some areas of central Maryland, central Virginia and central Pennsylvania may experience extremely high snowfall rates in a short period of time which could eclipse current NWS projections for those areas, especially if the snow becomes convective in nature as suggested by modeled data from the North American Mesoscale.


(Advisors Mr. Foot and Dr. Winstead, Forecasters Jason M., and Greg J.)


11:30 AM EDT 10/28/11 | SIGNIFICANT EARLY SEASON SNOWSTORM | The Snowfall Probability Graphic below is derived from the NOAA Winter Weather Product Suite as posted by the National Centers for Environmental Prediction in Camp Springs, MD. Many members of our team have visited this facility and interacted with their meteorologists. 

We have respect for their professional eye on winter weather, and concur with NOAA on this developing situation. By 5 PM this afternoon, the Winter Stormcast Team will be posting preliminary "Storm Grade Amounts" for representative locations in the Mid-Atlantic, as posted in a data graphic on this page. 

We have high confidence this event will be a significant snowfall for many areas east of Interstate 81 along the Mid-Atlantic and into the Northeastern U.S.

STORM SYNOPSIS: The arrival of a cold high pressure system last night across the Mid-Atlantic and Northeast has become the "game changer" of this storm situation. Low pressure in the Gulf of Mexico today will move northeast to off the North Carolina coast by early Saturday, and northward to New England by Sunday. Due to the pressure gradient interaction that is likely to setup between the coastal low and the cold high pressure system, we are in fact looking at a classic winter storm scenario for the populated areas of the I-95 corridor from Washington DC to the Baltimore region to eastern Pennsylvania, most of New Jersey, eastern New York and New England. 

Graphic:  Surface Low Tracks as projected by NOAA NCEP. 

PRIMARY HAZARDS: The multi-state Winter Storm Watches that started this Happy Friday for millions of people may seem like a joke in October, but belie a greater danger: Leaves. With 80% of the foliage still on trees throughout the Mid-Atlantic and Northeast, a heavy snow event, even if 3 or 4 inches, could produce surprisingly disruptive power outages. The moisture content of any snow falling this time of year will be much higher than what would be observed in mid winter. Our main concerns:

* POWER OUTAGES: While 8 inches may fall in places like Lancaster or Harrisburg in PA, and Westminster, Frederick or Rockville, MD-- perhaps just 4 inches will reach the ground due to the sun evaporating away the snow as it falls. However those 4 inches might actually contain 1 full inch of water. The weight of this water-laden snow on full foliage may produce extremely disruptive and complicated outages.

* VISIBILITY: In Pennsylvania, New Jersey and along the I-95 corridor from Philadelphia to Washington, rain on Saturday should mix with and change to snow as the afternoon progresses. However, once snow does fully change over, we expect it to be falling rapidly and in large flakes. The primary risk period is from 4 to 8 PM, as the heaviest snowfall should occur during the busiest commuting time of the day, even for a Saturday. You will probably notice how quickly the ground becomes covered tomorrow afternoon as the sun begins to set, allowing the ground to chill further as the snow falls. 

* LACK OF PUBLIC AWARENESS: A reader from Lancaster PA noted to the team, "how can we be getting 4 to 8 inches tomorrow, it is a gorgeous sunny day right now?" All we can say is that La Nina is known for producing short term, high impact events that catch many people off guard. It is difficult to accept that by noon on Saturday, those seeing blue skies presently may be digging for the snowshovel in the basement.  

WHY IS THIS HAPPENING? We know it is only October, and historically these kinds of winter weather events do not happen this far outside of winter. However, a resurgent La Nina has played a major role in the variability and frequency of both hurricanes and mid-latitude cyclones. As NOAA stated in the recently released Winter Outlook, "“There is a wild card, though. The erratic Arctic Oscillation can generate strong shifts in the climate patterns that could overwhelm or amplify La Niña’s typical impacts.”  It is interesting to note that just over a week after this statement, the Mid-Atlantic faces a wild card storm event that is, ironically, occuring just as the Arctic Oscillation is currently in a negative trend.

NEXT TEAM REPORT: Our Winter Stormcast Team is assembling a new overview presently, and will post this afternoon on this site as well as in our Mid-Atlantic and Northeast Winter Stormcast Zones on facebook.

(Forecasters Foot, Jason and Dakota. Advisors Dr. Pete Winstead, Brad Lear Keith Krichinsky)