Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 3:24 PM GMT on January 25, 2009
Thoughts on January 27-29 storm...
A multi-wave, extended, winter storm event is headed across much of the country dumping heavy snow and severe ice in its path. An overrunning disturbance across the Missouri Valley and Ohio Valley will head eastward overnight Monday bringing snows across the Middle Atlantic region generally south of I-80. Increasing 700mb RH values and frontogenisis will promote the development of light snows across the southern portions of Pennsylvania as the main dynamics of the system pass to the south. QPF looks generally light anywhere from .05-.15inches south of I-80. Orographic lift will aid in the highest amounts across the Laurel Highlands. H85s near -10C and ok dendritic growth will aid in some snow ratios near 15:1/20:1 creating snow totals of 1-4inches with the highest amounts south of the turnpike across the Laurel Highland mountains. Locations such as South Mountain and Blue Ridge across Franklin County may due fairly well also from this event. Better dynamics to our south will aid in a snow shield across Maryland, West Virginia, and Virginia giving snow totals of 2-4inches. QPF in this region looks to be .1-.25inches. As this system pulls to the east a growing area of precipitation over the same region will lead to the development of an upper level low will which eventually track towards the Ohio Valley by later in the day Tuesday. A large lull in the precipitation looks looks likely Tuesday afternoon.
*The second storm discussion will be posted Tuesday.
Light snow will generally be across central and northern Pennsylvania as some very weak warm air comma advection snows occur. Snow accumulations will generally be light and most places will only see flurries. A few locations across the northern mountains above 2000ft could see an inch or two of fluffy, fresh snow. A few locations across far southeastern Pennsylvania could see a bit of cloud clearing before a mid level stratus deck works into the region.
A shortwave disturbance moves across the Middle Atlantic south of Pennsylvania. But 700mb frontogenisis will promote light to occasional moderate snow to form across southern areas of Pennsylvania in the predawn hours. Snow amounts will be generally a Coating as far north as I-80 to about a few inches across the southern border counties particularily across the Laurel Highlands where a few locations could see up to 3inches of snow on the favored upslope locations.
Light snow will continue across southern areas accumulating another C-1inch before a temporary lull in precipitation. Eastern areas will likely see less amounts due to some downsloping. Clouds will be thick across the region with MVRF ceilings as low as 2500ft. A few flurries will be found across the northern mountains. Temperatures will range in the upper teens to mid 20s across the state.
A lull in precipitation will occur between systems as a much stronger upper level low forms across the Mississippi Valley and another weaker disturbance pulls out to sea leaving most of Pennsylvania in an area of subsidence resulting in generally cloudy skies and dreary conditions. Temperatures will range from the low to mid 20s across the state to near 30degrees near Philadelphia.
***The timeline for the second system will be issued tomorrow afternoon.
This is my current rain/snow line...
This is a complex storm system with rain/snow lines that gradually move north through the entire event. But the lines I have picked out in particular will be for where the boundaries are for the majority of the precipitation. All areas will see likely all types of precipitation at one point or another so keep this in mind. Although the only plain rain should be seen in the immediant metro of Philadelphia. And it is likely farthern north areas do not see freezing rain.
My rain/sleet line is... Deep Valley (Greene County) - Morgantown, WV - Deep Creek, MD - Ft. Ashby WV - Martinsburg, WV - Frederick, MD - Manchester, MD - Newark, DE - Philadelphia (Philadelphia County)
My sleet/snow line is... Mercer (Mercer County) - Du Bois (Clearfield County) - Renovo (Clinton County) - Wellsboro (Tioga County) - Towanda (Bradford County) - Starlight (Wayne County)
*Note these lines are estimates and actual locations may vary.
Alrighty well here are some of the local snow reports from the region. I tried to include everyone's report here from the blog, but if I missed yours it was only by accident. I am extremely pleased with this forecast and really going back my only difference would have been to extend the .1inch of ice a bit farther north. Also when looking at the map remember the 5-9inches is supposed to be 4-8inches. Finally an event that goes according to plan.
1. Long duration with entirely wintry precipitation.
2. Cold ground temperatures making for plowable snow.
3. Heavy snow across north totaling up to 8inches.
4. Large area of damaging ice in South Central Mountains.
5. Statewide impact with at least one or more inches of snow.
*Note for the snow map. The 5-9inch region is actually 4-8inches for this event. I didn't accurately change the key to 4-8inches.
*Note that totals such as .25inches are maximum. So for example if you are in the .25 range, then you have the possibility to receive between .1 and .25inches of freezing rain. The map is also highly elevation specific therefore the reasoning for the non uniform lines.
Selected City Accumulations for the Northeast...
Hagerstown, MD- 2-4inches of snow with .3inches of ice.
Baltimore, MD- 2-3inches of snow with .2inches of ice.
Washington, DC- 1-3inches of snow with .2inches of ice.
Wilmington, DE- 1-3inches of snow with .1inches of ice.
Dover, DE- 1inch of snow with an icy glaze.
Cape May, NJ- 1inch of snow, .5inches of rain.
Trenton, NJ- 3-5inches of snow, 1inch of sleet, .2inches of ice.
New York City, NY- 3-6inches of snow, 1-2inches of sleet.
Poughkeepsie, NY- 4-8inches of snow with 1-3inches of sleet.
Binghamton, NY- 5-9inches of snow, trace of sleet.
Albany, NY- 5-9inches of snow.
Hartford, CT- 3-7inches of snow, 1inch of sleet, .1inch of ice.
Concord, NH- 6-12inches of snow.
Providence, RI- 3-5inches of snow, .2inches of ice.
Worcester, MA- 4-7inches of snow, .1inch of ice.
Boston, MA- 3-7inches of snow, .1inch of ice.
Nantucket, MA- 1-3inches of snow, .75inches of rain.
Hyannis, MA- 1-4inches of snow, .5inches of rain.
Portland, ME- 6-12inches of snow, trace of sleet.
Bangor, ME- 7-14inches of snow.
"Subject to Change"
So it is the battle of the computer models with the GFS/SREF/GEFS taking the colder route with this system while the EURO/NAM take a warmer route with a more pronounced northern low. My blend looks to be GFS/EURO/NAM. The NAM takes a relatively nice conservative route between the EURO and GFS. This model analysis will take a look at the variables in this event to explain my reasoning. The first wave is part with a warm air advection snow. This will take H85s from nearly -14C up to near -3C by Tuesday night. Warm air advection will likely not result in warmer surface temperatures. The 18z GFS shows the primary area of warm air advection snows looking at the 700mb RH chart...
Note the best forcing is to our south across the Middle Atlantic. But with temperatures aloft near -10C along with some decent Omega and dendritic growth southern areas should be able to squeeze out some snow. Orographic lift will aid in snow development and QPF likely totaling near .1inches south of I-80 and up to .15inches across the Laurel Highlands. Snow ratios should be near 20:1 making for widespread 1-3inches of snow possibly 4inches Somerset County overnight Monday into Tuesday morning. A lull in the precipitation develops as the low gathers to our southeast. Trough from over the Rockies comes in positively tilted and scoots the New England high out sea along with destorying some confluence over southern Canada. 18z NAM notes the jet streak being north of the region creating a lack in snow development as the next wave moves in...
The 850 vortex low generally travels up through Ohio and up through New York State generally supporting the idea of mixing for most locations up through the NY/PA state border. Generally the heaviest snows occur 50-90miles north of the vortices. Here is the placement of the 850 low as the front end precipitation moves into the region as illustrated by the 12z HIRES NMM...
Note the 850 tries to become cutoff, but is not quite able which is good as it limits the warm air aloft advection. The surface low pressure moves across northern Maryland and through the Delmarva. This generally keeps 2m temperatures below freezing. With remnants of the high to the north cold air damming does result for many locations including the Laurel Highlands. As the low moves due south of central Pennsylvania H85s will rise above freezing for the southern half of the state resulting in freezing rain. The best frontogenisis locates itself across northern Pennsylvania as evident by the HIRES WRF 700mb...
As the low moves east and a weak undefined secondary low forms, cold air should move back into the system making for some snows to end the system. Even -10C 850s will make their way into western Pennsylvania. Snow accumulations will remain light but be noticeable. 18z NAM indicates the cold air rushing in quickly...
So that is my general model diagnostic. I usually end up using the high resolution models in short term periods. Foreign models other than the EURO prove to be relatively useless. I do think the EURO is a tad to strong with the wrapping of the low and too warm in thermal layer. But if the EURO does prove true then some forecasts may need to be rewired. Total QPF for this event looks to be 1-1.5inches statewide.
After the storm...
The long term period is looking high volite with patterns and it seems to be difficult to find which pattern will dominate. La Nina continues to being going full swing across equitorial Pacific, but there are signs of some warming anomalies, and from past experience it always seems that ENSO patterns peak during the winter months. The Pacific has definitely ruled this winter with a low negative PDO and I do not see any signs of that changing. The PNA is also heading negative with signs of troughing across the west, but not near as deep as was the case in December with the record cold. During the same time the NAO is heading negative which should help balance out the east coast from getting too mild, but the overall pattern does look warmer than it has been. It seems to me that the beginning of February should start warmer than normal with positive anomalies near 3-5, but colder air should work in as the AO heads negative correlating to eastern colder conditions. The MJO looks to be heading into phases 2 and 3, but impacts will not be too great as the pattern is very progressive with the wave movements. There are also some signs of Greeland blocking forming, but at this point I would not expect any development in the next week or two. Generally guidance supports of warmer than normal pattern especially from Pennsylvania southward with a more active northern jet which should generate wintry mixes. The pattern in my eyes looks identical to the one with went through around mid December so yep that means ice will be more of a threat. Now it does seem cold air will eventually try to work its way in down the road, but overall the coldest air of the winter is likely over. And there are no signs screaming snow, so basically the same pattern of the winter continues.
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- 3.5inches of snow/sleet
Monthly Total- 8.00inches
Seasonal Total- 18.45inches
Winter Weather Advisories- 6
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
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