Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 1:57 PM GMT on February 28, 2009
Thoughts on February 28-March 2 Storm...
A major coastal storm will be working along the Middle Atlantic coastline during Sunday night through Monday. Early morning water vapor loop shows increasing moisture across the southeastern states with an impressive 500mb cutoff vortex across the extreme deep south almost as far south as the Florida panhandle. This is causing a deep surge of cold air with snow being reported well into the southeast gulf states. Winter weather advisories have been issued for the Atlanta metro area for 1-3inches of snow. Interestingly enough this is the second time this year snow has occurred much farther south than climatologically favored snow locations. Surface maps indicate a gathering low pressure across Georgia. This low will lift northward along a frontal boundary and move northeast along the coastline keeping a favorable track for an all snow scenario. A cold Canadian high will funnel in northwesterly winds to all of Pennsylvania along with dry air which will inhibit widespread moisture, but instead it will provide all snow for all of Pennsylvania. There is no mid-level warming in this storm system for once. Upper trough begins to become negatively tilted as low pulls up the coastline causing the low amplify. There is still some question to what and how much amplification takes place in the early stages of this storm as it will have a result in how far the precipitation gets in the west. Strong frontogenisis occurs in eastern Pennsylvania early Sunday evening as moisture pulls into the region. Deformation axis looks to be across extreme eastern Pennsylvania with the hills of Chester and Bucks County getting the brunt of the banding. Some mid level instability will promote high snow rates of 1-2inches for much of the event in these areas along with the possibility of thundersnow. 700mb RH charts indicate a non-gradual boundary between snow and non-snow which will likely setup near the Harrisburg area up through the northern Poconos. This area is where the highest bust potential exists with the possibility of more or less snow than being forecasted. No snow is expected from a line of Chambersburg-Lewistown-Mansfield and westward. Instead these areas will be seeing just some high cirrus clouds under a cyclonic flow. As the low strengthens to near 1000mb off the coast the tight pressure gradient will promote high winds in many locations causing blizzard conditions especially across far eastern Pennsylvania. The snow will be powdery as snow ratios especially in western areas will be near 15:1. Overall the event favors extreme eastern Pennsylvania for heavy snow with a prominent cutoff zone near the Harrisburg area. Isolated totals of 16inches are possible in a few higher elevations above 700ft in far eastern Pennsylvania.
3-5pm... Clouds will begin to thicken across southern Pennsylvania after any breaks in the clouds early afternoon. Temperatures may be slightly above freezing for most locations, but with colder air funneling in they will drop below freezing as the precipitation moves into the region.
5-9pm... As isentropic lift occurs to our south. Light snow will begin spreading into southern and eastern parts of Pennsylvania. Temperatures during this time will still be right around freezing preventing roads from too much accumulation for the initial light snow. As heavier precipitation moves in travel will become highly discouraged. Snow amounts in this period will range around a coating to up to one inch.
9pm-12am... Heavier precipitation will work into the region along with enhanced banding in many locations across eastern Pennsylvania. Snow rates may approach 1inch per hour in some locations. Roads will quickly become snow covered. Temperatures will fall into the 20s statewide. Snowfall accumulations will be 2-4inches in far eastern areas with 1inch across the west.
12am-4am... This period will feature the heaviest snow with rates approaching 3inches in one hour for a few isolated locations. Thundersnow can also not be ruled out for the I-95 area. Snow accumulations will range from 3-5inches in the east and 1-3inches in the west. Temperatures will fall into the low to mid 20s and winds will begin to become gusty. Blizzard conditions cannot be ruled out for a period in far eastern areas.
4am-8am... The morning commute will feature the main banding pull northeast of the region with additional snow accumulations of 1-3inches statewide. Winds will remain gusty with blowing and drifting snow with limited visability.
8am-12pm... The final burst of snow will approach with an upper level low along the western flank of the storm with a period of light to moderate snow across eastern Pennsylvania. Additional snow accumulations may be 2-4inches for many areas. Temperatures will continue to fall with increasingly windy conditions.
This is my current rain/snow line...
This storm will feature very far south in comparison to storms of the previous few winters. This sleet/snow line is for the period at the height of the storm for these locations. To the north of the line will be snow and to the south will be more of a mix or rain.
My sleet/snow line is... Greenville, SC - Charlotte, NC - Fayetteville, NC - Goldsboro, NC - Wakefield, VA - Salisbury, MD - Lakewood, NJ
*Note these lines are estimates and actual locations may vary.
1. Periods of very heavy snow in mesoscale banding.
2. Snow rates of 1-2inches across far eastern Pennsylvania.
3. Blowing and drifting snow generally after the storm.
4. High impacts to metropolitan areas of eastern Pennsylvania.
5. Sharp-cuff of snow/no snow between Reading and State College.
*Note this does not include snow amounts from the first wave.
Selected City Accumulations for the Northeast...
Hagerstown, MD- C-2inches of snow
Baltimore, MD- 5-9inches of snow
Washington, DC- 5-10inches of snow
Wilmington, DE- 6-12inches of snow
Dover, DE- 5-9inches of snow
Cape May, NJ- 3-7inches of snow
Trenton, NJ- 8-14inches of snow
New York City, NY- 5-10inches of snow
Poughkeepsie, NY- 6-12inches of snow
Binghamton, NY- 2-4inches of snow
Albany, NY- 2-5inches of snow
Hartford, CT- 9-15inches of snow
Concord, NH- 6-12inches of snow
Providence, RI- 8-12inches of snow
Worcester, MA- 9-15inches of snow
Boston, MA- 6-12inches of snow
Nantucket, MA- 3-6inches of snow
Hyannis, MA- 3-7inches of snow
Portland, ME- 6-12inches of snow
Bangor, ME- 8-12inches of snow
"Subject to Change"
Instead of looking at each model, I am going to show maps that helped support my forecast from each model. The low will be forming across the southeast near the coast of the South Carolina coastline. Low pressure will track to the northeast. The GFS seems to have a pretty good hold on the precipitation shield and low strength. Although the low does seem a bit stronger and more amplified looking at infrared satellites and the water vapor loop.
As the low tracks there will be a sharp-cutoff between snow and no snow. 700mb charts indicate the best relative humidity to be across eastern Pennsylvania.
While QPF will be lighter in the western side of the precipitation shield, snow ratios will be better as colder air comes rushing into the system. I was looking at the snow from last night and it is very dry with a low moisture content made up of dendrites. Omega growth and dendritic growth is superb for this event with best dynamics found in the mesoscale bands that are likely to form overnight Sunday. While the best frontogenisis remains to our south it does appear there will be an intense band of snow over eastern Pennsylvania.
500mb charts are classic for the entire event with a sharp negatively tilted trough and a deep 500mb vortex to the south. Jet streak is located in eastern Pennsylvania and that will be associated for where the heaviest snow will fall.
Overall it looks like a classic nor'easter is headed towards the Northeast.
After the storm...
Monday- Coastal low near benchmark will be pulling to the northeast. Deformation band of snow will remain parked across eastern Pennsylvania with heaviest snow likely in extreme eastern portions of the state. For a time Monday morning snow could be quite heavy in far eastern areas. Disturbance with weak associated cold front boundary will move by afternoon pushing the system out of the area and bringing in much colder air. Dewpoints will drop below zero for the mountains with temperatures below freezing statewide. Winds will be quite gusty under tight pressure gradient causing windchills in the single digits. This will likely be the coldest day during the next 9-10 months. Under the week upper air disturbance snow showers will persist across the state with some light snow accumulations possible in the Laurel Highlands and northwest mountains. Monday night will feature lows dropping in the single digits for much of the state under a gusty 20-35mph northwest wind. Wind chills will be near advisory criteria for the mountains. Partly cloudy skies will prevail.
Tuesday- Tuesday will feature partly cloudy skies statewide. A few snow showers will be across the Laurel Highlands during the day with a few coatings of snow possible. A low strato-cumulus deck will prevail across the higher elevations above 2000ft. Downsloping winds will result in sunshine for eastern areas along with a fresh snow pack making air temperatures quite cold. Highs will generally be below freezing statewide with some blowing and drifting of snow in the morning under breezy conditions. Tuesday night will feature clear skies and breezy conditions. A few cirrus and cumulus clouds may work overhead overnight as a weakening disturbance moves to the north. Lows will drop in the teens and single digits statewide.
Wednesday- High pressure remains in control across Pennsylvania with sunshine. Temperatures will be warming up back to the low 40s and upper 30s for most areas which is still slightly below normal. Wednesday night winds will begin to calm combined with low dewpoints which could make for some very cold temperatures in the sheltered valleys. Lows will work down in the teens and single digits once again.
Thursday- Departing high pressure will keep generally sunny skies statewide with some warming of the air temperatures. Melting snow will be occuring statewide. Highs will be near seasonal values with highs in the mid 40s across the south and mid to upper 30s across the north. Thursday night clouds will moves in and thicken from west to east ahead of the next storm system. Some light rain may move into western Pennsylvania after midnight with amounts generally less than .1inches. Lows will be in the mid 30s across the west to around freezing in the east.
Friday- Low pressure moves across the western Great Lakes into Canada with a slow moving cold front with limited moisture. Light rain showers will persist throughout the day with totals less than .25inches for all areas with most areas much less than that even. Stratus deck will lower over the higher elevations with ceilings below 1000ft causing for some IFR conditions at the local airfields. High temperatures will be mild under southwesterly flow across western Pennsylvania in the 50s, but eastern Pennsylvania will still be under easterly flow keeping highs cooler and in the 40s thanks to departing high pressure in the Canadian Maritimes. Friday night will feature cloudy skies and light drizzle and rain showers. Lows will be mild and well above normal generally in the upper 30s statewide.
Please post storm reports in this blog from across the Northeast during the winter storm...
This blog is in progress. Check back soon...
"Here northeast of Harrisburg 2008-2009 winter statistics"
Current Snow Cover- 2inches
Monthly Total- 3.00inches
Seasonal Total- 25.40inches
Winter Weather Advisories- 7
Winter Storm Warnings- 2
Ice Storm Warnings- 1
Blizzard Warnings- 0
Freezing Rain Advisories- 0
Winter Storm Watches- 4
Lowest High Temperature- 14degrees
Lowest Low Temperature- -3degrees
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First Snow - October 29 - Trace
First Snow on Ground - November 18 - Coating
Lake Effect Snow - November 21/22 - 6.00inches
Synoptic Snow - December 16 - 3.50inches
Clipper - January 17-19 - 1.50inches
Synoptic Snow - January 27/28 - 4.00inches
Lake Effect Snow - 2.00inches
Coastal Storm - 2.00inches
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