Cornell University- Atmospheric Sciences Student; Central PA SKYWARN Storm Spotter; American Meteorological Society Member; PA CoCoRaHS Branch Member
By: Zachary Labe , 4:11 PM GMT on January 20, 2014
Posted: 20 January 2014
A series of clippers and weak shortwaves have continued to parade south out of Canada and around the base of the trough. A strong vortex of energy will move in this similar direction by Monday night. However, it will begin to slow down and amplify as it moves through the Middle Atlantic and up the coast. It will spread a widespread snow shield to the northwest of its center with moderate accumulations of snow expected along the I-95 corridor. Very cold temperatures will assist in high snow ratios for those farther northwest.
Current Surface Plot...
(Courtesy of HPC)
January 21-22 Clipper Redevelopment Discussion and Timeline
Another I-95 snowstorm is expected on Tuesday. The setup is relatively simple. A strong shortwave is sinking south out of Canada into the Dakotas. A very tight H85 temperature gradient will allow this Alberta Clipper to maintain its steam and even strengthen. Meanwhile, over the east an arctic front is moving south out of New England. This boundary will sink into the central Middle Atlantic. Temperatures north of the front will be very cold. Current 2m model prognostics indicate boundary layer temperatures in the low to mid 20s for I-95, with teens to the northwest. The entire column will be well below freezing with the dendritic growth layer at the ideal 700-800mb level. This will allow for excellent snow growth. Keep in mind, snow ratios are not based on temperatures like many are left to believe. Snow ratios are based on ice crystal growth. Unfortunately, there is no simple formula for this calculation. It is left up to a bit of one's interpretation. Maximum snow ratios will be near 20:1. This will be for cities such as York, PA -Trenton, NJ - Worcester, MA.
Surface maps take the 1000mb low off the coast around Norfolk, VA with a widespread stratiform precipitation shield to the north. Current 700mb RH and frontogenic forcing maps suggest impressive mesoscale banding 50 miles or so north of the H8 low. This will focus the 1-2"/hr snow rates across the Mason-Dixon line and then eventually eastern New England. This will also correspond with the best snow growth and therefore snow ratios. SREF individual ensemble packages focus a mean of 10-12" of snow for this region. This is probably a pretty reasonable estimate. Maximum snow totals of 14" or so for a few isolated locations is possible. I particularly like parts of York, Lancaster, and Chester Counties in PA for this localized maximum along with inland, central New Jersey.
I want to note that there is the possibility this entire system shifts a bit to the north. I have been noting this on the latest model trends. Looking at the synoptic setup, the jet stream is still very progressive with limited blocking to the north. This system could easily nudge another 50-75 miles to the north. Most areas would not be affected, but this may introduce the threat of rain for immediate coastal regions. Right now my forecast does not account for this, however it is a distinctive possibility.
Analyzing mid levels show a classic textbook setup with a central axis of heavy snow along I-95. All of the major cities will be in fair game for 6" or more.
Timeline for this system is relatively simple. It will begin across the Middle Atlantic before sunrise on Tuesday. The precipitation shield will spread north and east during the day reaching southern New England by mid morning. The event will last about 12 hours for most areas. The heaviest snow accumulations for Washington DC up through Philadelphia will coincide right with the evening commute from 4-6pm. I expect major transportation impacts from this event given its timing.
(Courtesy of Intellicast)
(Courtesy of NOAA)
1. Widespread and long duration snowstorm with moderate to heavy accumulations across the I-95 corridor. It will also fall during the daytime hours.
2. Cold temperatures in the teens will make for easy and fast accumulations especially for those northwest of I-95.
3. Bitter cold temperatures with wind chills below -10F will move in behind the storm system for all areas.
4. Heaviest accumulations expected along the Mason-Dixon Line up through central New Jersey eventually into eastern Massachusetts.
5. Northwest gradient of the precipitation shield is in question due to dry air to the north.
Current Heavy Snow Line...
Given the cold thermodynamics of this system, rain and/or mixed precipitation will not be a threat for any areas. For once, we will not have to worry about these lines. However, I will outline a line to signify the boundary between a nuisance and plowable snow. I am defining a plowable snow as 3 inches or more. So for areas south and east of my designated line, a plowable snow is expected...
Altoona, PA - Selinsgrove, PA - Mt. Pocono, PA - Poughkeepsie, NY - Pittsfield, MA - Manchester, NH
Current Great Lakes Water Temperatures...
(Courtesy of NOAA)
Selected City Accumulations for the Northeast...
Hagerstown, MD- 5-10" of snow
Baltimore, MD- 4-8" of snow
Salisbury, MD- 4-8" of snow
Washington, DC- 4-8" of snow
Wilmington, DE- 6-12" of snow
Dover, DE- 5-10" of snow
Pittsburgh, PA- 2-5" of snow
State College PA- 1-3" of snow
Williamsport, PA- C-2" of snow
Altoona, PA- 2-5" of snow
Harrisburg, PA- 3-6" of snow
Lancaster, PA- 6-12" of snow
Philadelphia, PA-6-12" of snow
Allentown, PA- 3-6" of snow
Scranton, PA- C-2" of snow
Trenton, NJ- 6-12" of snow
New York City, NY- 6-12" of snow
Poughkeepsie, NY- 1-3" of snow
Binghamton, NY- Cloudy
Ithaca, NY- Cloudy
Albany, NY- Cloudy
Hartford, CT- 5-10" of snow
Concord, NH- 1-3" of snow
Providence, RI- 6-12" of snow
Worcester, MA- 6-10" of snow
Boston, MA- 6-12" of snow
Nantucket, MA- 4-8" of snow, may mix with rain at times
Hyannis, MA- 5-10" of snow, may mix with rain at times
Burlington, VT- Cloudy
Portland, ME- 1-2" of snow
Bangor, ME- Cloudy
"Subject to Change"
Current Northeast Snow Depth and Northeast Wind chills...
(Courtesy of Wunderground)
This snowstorm will definitely come as a surprise for many whom thought the forecast only consisted of a few flurries on Tuesday. Sure, one can blame poor modeling and forecasting as a result, however the pattern is very distinctive in one with too many vortices of energy. Our current computer model algorithms cannot pick up on which vort to focus, and therefore we do not see which one amplifies into a larger scale event until the last 60 hours.
For us modeling gurus, it was definitely clear that this clipper had the best potential out of any so far to amplify and develop off the coast. The primary shortwave was near a tight temperature gradient in the Dakotas increasing its strength as it progressed eastward. As it rounds the base of the trough, it slowed down and amplified. We have remarkable consistency across the modeling board for this event. The only differences remain in the details. Although I should mention the outlier... the ECMWF. Despite many people's beliefs, verification tables prove that the GFS has been equally if not more accurate across the medium and short term. The current ECMWF is significantly drier with QPF due to its southeast and less amplified track. I think though it is playing catch up, and we will see it trend wetter in the coming few runs.
High resolution modeling with 4km and 12km grids are definitely the way too go when forecast this event. They will be able to pick up on mesoscale banding that will occur 25-50 mi north of the H8 low. Currently, as mentioned this will likely be across the Mason-Dixon line with a line stretching into eastern Massachusetts. The latest BUFKIT grids from the SREF suggest snow ratios around 20:1 for areas northwest of I-95 with excellent dendritic growth occurring exactly between 700-800mb. The latest RGEM and NAM prognostics show increasing frontogenesis in this region with snow rates of 1-2" per hour during the height of the event. I can see how a few isolated see a foot of snow due to high ratios and excellent snow growth.
The northwest gradient of the precipitation shield will be a difficult forecast due to a very dry air to the north allowing for significant virga. However, many times modeling does not pick up on the northwest extent of snow in these events. This is something to keep in mind for the storm's forecast. I have seen many times in these clipper amplifiers where snow is a bit farther northwest than many forecasters expected.
It is fun to note that there are several extreme SREF outliers shows 24+ inch accumulations for the favored mesoscale banding regions. This is highly unlikely due to the progressive flow. But anyways, it is just fun to look at. This system has a very low bust potential for most areas. Models are very consistent, and I expect little change over the next 24 hours. HRRR and RAP will have a good handle on this system given their biases and algorithms.
After the Storm
Bitter cold air will move into the region by Wednesday across the Northeast as H85 thermals dip to -25C as far south as the NY/PA border. The flow will be at around a 330-340 trajectory, which is a bit too northerly for widespread lake effect snow. However due to a low dendritic growth layer, any semi-organized cumulus cloud could at least squeeze out a few flurries. I am also watching the potential for some finger lake effect snow, but the conditions may just be too dry. Anyways the bigger story will definitely be the cold. The 2m GFS shows negative digits as far south as the Mason-Dixon line. It seems a bit overdone, although with widespread snow cover I can see how it is possible. A tight pressure gradient for the first half of Wednesday will allow winds to gust around 20-30mph for many areas. This will allow for widespread wind chill advisory criteria wind chills as far south as Washington DC with warning criteria from northern Pennsylvania up through northern New England. The rest of the week will continue a similar arctic blast reload pattern with no relief in sight. In fact, wavelengths favor the coldest period toward early next week behind the next organized clipper on Saturday and Sunday. Current track has it favoring areas across New York state and northern New England, although that track could easily change.
The bottom line is that a continued active pattern of clippers and arctic air will continue through at least the next ten days. While not quite as severe as the early January arctic outbreak, it will be much longer and duration and cause more impacts to the infrastructure. Any snow on the ground will be pretty permanent, especially for the Northeast's standards. Any organized, major snowstorm is unlike during this progressive flow. But like we see for Tuesday, it does not take much for one of these clippers to amplify off coast. Unfortunately, it is difficult to predict until a day or two before the event.
As we close the month and enter February, it is possible a more stormy pattern begins. I am expecting a warm up around February 2-5 or so with another arctic blast around mid month. However, there are signs a west-based negative NAO may be forming. This would slow the jet down and increase the threat for a more widespread heavy snowstorm. While this period remains well in the long term, it may be the best chance we have at seeing a heavy snowstorm this winter.
Please post storm reports in this blog from across the Northeast during the winter storm, and please post location of observation in each report...
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Lower Susquehanna Valley Doppler...
(Courtesy of WGAL)
"10mi northeast of Harrisburg 2013-2014 Winter Statistics"
Monthly Total (October)- 0.0"
Monthly Total (November)- Dusting
Monthly Total (December)- 9.6"
Monthly Total (January)- 10.3"
Seasonal Total- 19.9"
(Snow Storms Stats)
Trace - November 8 - First trace of snow - Lake effect snow shower
Dusting - November 12 - First snow on the ground - Anafront
1.5" - December 8 - First inch of snow - WAA double barrel low
4.3" - December 14 - Miller B - Changed to freezing rain/sleet
1.3" - December 17 - Alberta Clipper
2.0" - December 26 - Surprise squall/clipper
4.8" - January 2-3 - Miller B Coastal
1.5" - January 10 - SWFE all snow
3.1" - January 21 - Redeveloping clipper with heavy snow along I-95
Winter Weather Advisories- 8
Winter Storm Warnings- 1
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 2
Winter Storm Watches- 2
Lowest High Temperature- 9.6F on 1/7/2014
Lowest Low Temperature- -3.1F on 1/7/2014
Wind Chill Advisories- 3
Wind Chill Warnings- 0
(Cornell University (950ft elev.) Snow Stats)
Monthly Total (October)- 0.0"
Monthly Total (November)- 3.7"
Monthly Total (December)- 16.4"
Monthly Total (January)- 16.5"
Seasonal Total- 36.6"
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|Dew Point:||15.2 °F|
|Wind Gust:||9.0 mph|
Updated: 10:37 AM EST on January 18, 2014