Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 8:36 PM GMT on November 24, 2008
"Afternoon Thoughts" (Updated 11/24)
Well what a wintry week it has been here in Pennsylvania with some very unusual lake effect snows. So here I will try to summarize what happened with the lake effect snow to make it so far reaching. During the beginning of the week a clipper system caused some light snows across far southern Pennsylvania, but it did not amount to anything. Lake effect machine then fired up with amounts in Warren County near 16inches as some short-fetched bands reached over the region. Elsewhere some other heavy accumulations occured in the Laurel Highlands with 6inches being reported at Mt. Davis in Somerset County. Then a second clipper system bringing the coldest air of the season moved in for Thursday causing a widespread .5-1.5inches of snow across northern Pennsylvania and also creating a light coating of snow as far south as Harrisburg during the morning Thursday. By Thursday late afternoon and evening a long Huron-Erie Connector streamer formed with the northwest flow and was enhanced by a mesovortex over Lake Erie. The streamer went from Erie-Bradford-Lock Haven-Lewisburg-Selinsgrove-Reading-West Chester-Philadelphia. Within that narrow band some very heavy snow accumulations occurred with nearly 11inches falling near St Marys in Elk County and 4.5inches near Lewisburg in Snyder County. Overnight the band remained relatively stationary, but drifted south affecting areas such as Bellefonte in Centre County and Wisconsico in Dauphin County giving those areas 1-2inches. The snow band then weakened by Friday morning and gave way to a shortwave that moved across the Mason-Dixon line enhancing the lake effect snows and drawing them into far southern regions. Areas like Harrisburg-Lebanon-Reading saw a decent 3inches of snow Friday morning with southern areas Gettysburg-York-Lancaster seeing some light snow totals from .5-1.5inches of snow. Areas in the northwestern Philadelphia suburbs also saw some light amounts. A break then occurred midday for southern areas, while snow broke out over snow belts delivering Pittsburgh up to 3inches of snow and parts of the Laurel Highlands an additional 4-7inches of snow. A new Huron-Erie streaming band began to form later in the day, but was broken up and not very organized. Still though intense core cells developed in the snow showers with near 45dbz causing whiteout conditions from the Selinsgrove-Harrisburg-York corridor delivering another 1-3inches of snow for those areas. By later Friday night snow was mainly confined to northern areas with the northwest snow belts seeing quite a bit of snow near 6inches in parts of Warren and McKean Counties. Also the Mercer-Crawford-Erie corridor saw a decent amount of snow. Later that night bands shifted southward in western Pennsylvania dropping 1-2 more inches in Pittsburgh and up to 5inches for counties immediately north of Alleghany County. Saturday rolled around with scattered snow showers, but a definite Huron-Erie streamer once again that then moved across State College-Lewistown-Harrisburg-Hershey, becoming the classic 322 streamer. This band eventually produced up to 3inches in areas just south of I-81 in Dauphin County. Finally by Saturday night the snow ended for all of Pennsylvania and resulted in official record lows for some areas including Williamsport that tied their record of 15degrees. It was quite an unusual wintry November event.
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion" (Updated 11/24)
A complex weather system is headed our way for the beginning of the week followed by a more cyclonic flow bringing down lake effect snow showers across much of the snow belts resulting in major accumulations. Then a storm system approaches the region for the weekend with some leftover stagnant cold air that could cause another wintry mess. Low pressure system currently moving across parts of the Ohio Valley with move across the region, while a secondary low pressure forms off the coast causing the trough to become negatively tilted, but swings back around in New York State as a cut-off low. Ahead of the low pressure in the Ohio Valley warm air advection with southwesterly winds is causing temperatures to warm above freezing across the western part of the state. Meanwhile cold air is hanging tough across central and northern Pennsylvania. Temperatures in the 1000-500 column remain marginal right around freezing from Clearfield to State College to Williamsport on northward. But those thicknesses will be dropping overnight slowly from west to east. 850s will see a slight rise, but should stay at or slightly below 0C for most areas, except extreme southwestern Pennsylvania. Precipitation will break out across all of Pennsylvania with snowfall falling in some areas for the immediant wave as evaporational cooling and marginal temperatures aloft are just cold enough for snow as far south as Harrisburg. But overnight warm air advection should change over most areas to rain, but with past history cold air does like to hang tough and that is why frozen precipitation will remain possible over north-central Pennsylvania mountains and valleys throughout the night changing over to all snow by morning. Ice accumulations from freezing rain could occur in the northern Laurels up to Du Bois. This ice accretion will occur quite a bit for elevations above 2000ft where ice amounts may go up to .25inches. Sleet amounts will be widespread across central Pennsylvania near State College ranging from 1-2inches. Snowfall will be highly elevation specific overnight with up to 5-6inches of snow across the northern tier counties. Parts of the northeast mountains in Wayne County could see up to 7inches of snow as they stay under a strong deformation band. Overnight energy will shift to new coastal low and temperatures aloft and at bounday layer will fall making a changeover from rain to snow from west to east. Looks like a pretty defined deformation band will form across parts of central and northeastern Pennsylvania. If this band is strong enough as trough becomes negatively titled there could be some additional snowfall across the Susquehanna Valley. But by late Tuesday all areas will be in snow showers with additional accumulations from storm system up to 2inches. Low pressure will move across New York State and become a weakening cut-off low creating a cyclonic flow across the state with a west-northwesterly flow for lake effect snow through Thursday morning. High pressure moves in for control for late in week before a generally weak system moves in for weekend. That will need to be monitored later this week. Overall temperatures this week stay below normal with a very wintry feel to the air.
Snow map for Monday through Tuesday evening...
*Note this does not include lake effect snow...
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 11/24)
Tuesday- Tuesday is looking to be a very wintry day across the state as low pressure off the coast begins to move inland keeping the flow west of the low around west-northwest. And with a cold blast of air and decent lapse rates, some pretty significant lake effect snow will start up across the snowbelts particularily in the Laurel Highlands during the day Tuesday. During the morning hours most of the precipitation will have shifted over to snow with a colder blast of air. A deformation band of snow may form on the cold side of the state affecting parts of northeastern and central Pennsylvania, possibily into the Susquehanna Valley with snow accumulations up to 2inches. Meanwhile winds will become gustier at times to near 30mph with moisture coming off the lake. The near westerly flow will bring significant snow bands to much of the state, but particularily the southwestern Laurel Highlands in Fayette and Somerset Counties. Some of the bands will be capable of snow rates up to 2inches per hour across the mountains. Orographic snow will also be ongoing in other parts of the western half of Pennsylvania with snow bands possibility into the Pittsburgh metro by dark. Snow bands may also shift up into the Erie plateau by dark. Highs will be several degrees below normal with them generally under 40degrees, except for eastern Pennsylvania. Snow accumulations across western Pennsylvania will be near 1-3inches relatively widespread with definitely higher amounts. Snow bands will develop further overnight with slightly more west-northwest flow and become quite organized overnight with all snowbelt regions seeing heavy accumulations. Lows will be below normal and below freezing statewide.
Wednesday- Wednesday will be a primary lake effect snow day for the western half of Pennsylvania as a dying low pressure north of the state enhances the lake effect even downwind of the Appalachians at times. The flow generally remains west-northwest throughout most of the day before shifting to the southwest by later in the day. Cloud cover deck will remain over the state for much of the day with stratocumulus. Snow bands look to be favored in the Laurel Highlands in the morning before shifting northward into the northwestern snowbelts. Snow showers and squalls will at times be across other parts of the eastern half of the state with coatings to one inch of snow not being ruled out. Across the snowbelts up to 6inches of snow wll fall with some of the higher elevations above 2000ft picking up nearly 10inches of snow as snow ratios will be at times near 15:1 across some of the mountains. Highs will remain well below normal and generally below freezing for western half of state, while eastern half has highs below 40degrees. Snow bands will shift across extreme northwestern Pennsylvania by dusk as winds turn more to the southwest ahead of the next high pressure for Thanksgiving. An impressive snow band may set up along the lake shore near Erie dumping up to 5inches of snow or potentially more. Overnight cloud cover will be sporadic across the state keeping low temperatures from falling down too much other than in the mid to upper 20s for most locales. Lows may be above freezing for the Philadelphia metro area.
"Current River Ice Reports and Ski Conditions" (Updated 11/23)
Well after this cold spell this discussion will sound like it is late December. Many ski results have opened across the mountains with fresh powder of up to 8inches near Blue Knob in the last couple of days. The base snow packed in generally machined granullar though. Many ski resorts will be picking several more inches of snow up by Wednesday with parts of the Laurel Highlands and northwest mountains seeing up to a foot of snow. Conditions will also be cold enough for elsewhere locations for snow making. Base packs of snow will be rising in the next couple of days making for some unusual seasonable skiing conditions over the Thanksgiving holiday. Many people are looked to be flocking to the slopes due to these unseasonably great conditions. Areas also in the Poconos and northeast mountains will be picking up more snow in the coming days with the storm system and should see up to 5inches of snow pack added on the highest elevations in particular counties such as Wayne County, Carbon County, Monroe County, Lackawanna County, Wyoming County, and Pike County. Looking at ice reports, many ponds and even streams have frozen up quite early this year with some very small farm ponds with an inch or two thickness. But due to the early start to the river ice season, no one should try walking across the ice as it is still too thin in all areas in patches that cannot be seen with the naked eye. Stay tuned in the coming weeks as high thicknesses will be rising and just maybe some of the northern major streams and rivers will be starting to accumulate ice layers on the tops floating down the river as light sheet ice. The link below for river ice reports should come in handy for later in the year. Please still act responsibly throughout the winter.
Alpine Mountain… Open
Big Boulder… Open
Blue Knob… Open
Blue Mountain Ski Area… 12/05
Camelback Ski Area… Open
Eagle Rock… 12/03
Hidden Valley Four Seasons Resort… Open
Mount Pleasant… 12/20
Seven Springs… Open
Shawnee Mountain Ski Area… Open
Ski Big Bear… 12/13
Ski Liberty… 12/05
Ski Round top… 11/28
Ski Sawmill… Open
Spring Mountain Ski Area… 12/13
Tussey Mountain… 12/06
-Link to official reports page from NWS...Link.
-Link to local ski resort snow conditions...Link.
"Current Northeast Snow Depth and Northeast Windchills"
(Courtesy of Wunderground)
"Lake Effect Snow Conditions" (Updated 11/25)
Strong westerly cyclonic flow will favor some signficant snow accumulations for the snowbelts of Pennsylvania, particularily across extreme nortwestern Pennsylvania and the Laurel Highlands. Cut-off low will be generally north of Pennsylvania keeping a west-northwest flow across the lakes. With steep lapse rates and decent Omega values we could see some nice orographic snows for parts of the Laurel Highlands. Temperatures aloft will gradually start to fall in the 850mb level from -2C to nearly -8C with will help crank up the lake effect machine. The column aloft 1000-500mb level will also be below freezing and with decent ice crystal growth, all precipitation should stay in the form of snow. Latest NMM and WRF simulated radars indicate a decent low-level Huron-Erie band across southern Pennsylvania into parts of Mt. Washington in through Fayette County and then Somerset County. For those with interests in western Maryland, this lake effect scenario generally gives them some very heavy snow in parts of Garret County and the Potomic Highlands on southward through West Virginia near Snowshoe. With cold boundary layer temperatures generally in the 20s, this will favor snow ratios near 15:1 and in the higher elevations above 2000ft near 20:1. Western facing slopes in southwestern Pennsylvania will see accumulations up to 10inches of snow in some of the favored western favored ridge tops. Valley locations will primarily see lighter accumulations on the order of 2-5inches. Flow will begin to shift more southwest as mid level vortex moves over region slightly inforcing cold air and this will bring snow bands across northwestern Pennsylvania particularily across Erie, Mercer, and Crawford Counties with heavy snow up to 10inches with the bands. Even lake shores will get in on the action as heaviest bands sit right over the city of Erie for a time period Wednesday. Lake effect generally shifts north of Pennsylvania into New York State by Thursday keeping Thanksgiving only with a few snow showers and or squalls. Throughout the week eastern areas will also see snow showers and squalls occasionally accumulating up to an inch of snow. Lake effect looks farely widespread. Stay tuned for more updates with snow map coming Tuesday.
Snow Map for Tuesday through Thursday Morning...
*Note this all does include some wrap around snows for central Pennsylvania.
"Current Lake Erie Wind Direction and Speed"
(Courtesy of NOAA)
"Current Lake Erie Water Temperature"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 11/24)
A very interesting pattern is setting up for the beginning of December, which could make for some very cold weather and potentially snow. Teleconnections and upstream weather patterns favor a blocking scenario with a non-transiet trough over much of the Midwest through the East. Latest GFS ensemble means show some very impressive troughing across the east with heights well below normal. At times the models have showed a more elongated trough, which would favor below normal temperatures across much of the nation, which I do think is possible. PNA and EPO favor this setup with them favoring a slight trough over the west and the NAO shows a sharp negative drop resulting in a more defined trough over the east. Snow pack developing across many mountain areas over the east, and snow pack developing in the Great Lakes will help favor and keep the cold air over the region. From what I can see it appears the warmest weather for the next several weeks will occur this Thanksgiving Day week. Some of the latest GFS runs have showed H85s dropping to near -20C across parts of the Northeast, which intern probably would result in historically cold air. The unusual thing about this pattern has been the continued cold setup for past several months. May was a very below normal month across the state, June went down warm but only thanks to the heat spell the first half of the month as the rest of the month was cool, July went down around normal to slightly below normal, August was well below normal, September was a near normal month, and October through November have been well below normal. For those keeping tabs on statistics for November the entire warm anomalies for the month have been erased by this cold spell. Most climatology stations are now within +-1degree of normal and that will be dropping to below normal by the end of the month. For example average highs in Harrisburg during this week are around 50degrees, and not once this week will temperatures even get to above 45degrees. Average lows are near 34degrees, and every night this week we will see below freezing lows. Just this Saturday night my low dropped to 14degrees which is 20degrees below normal. Overall the pattern has favored a consistent east coast trough and that is going to continue. Pattern is showing signs of a more blocking scenario with high pressure over the North Atlantic. The problem will be though if the trough is more amplified and confined to the Midwest and Northeast, or will it be more elongated across the entire United States. If more elongated it will be harder for the trough to be negatively tilted across the east for a big east coast storm. Right now for what I am seeing is both options are possible. And right now I think we could be looking at a big storm setup for the first week of December. A few problems we could be running into December for snowfall is suppression, but one thing I am sure on is we will have extremely cold and below normal weather for a majority of the month.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Monthly Outlook" (November)
So hard to believe October has already passed, but it has and we are now entering November. Looking at my October outlook I called for normal to slightly below normal temperatures with normal precipitation. Looking at most official climate stations most areas came in with below normal temperatures around 1-2degrees below normal. I am very pleased with my temperature forecast, but as for precipitation almost all areas were below normal in precipitation and many areas did not see rain until the last few weeks in the month. It seems the Fall season has been pretty dry in consideration to normal. Snowfall was highly above normal in all locations with snowfall totals over a foot in parts of the Poconos and areas in western Pennsylvania saw record monthly snow totals including Pittsburgh which I believe saw the 8th snowiest October on record. Looking at now November there are some better signals for the temperature and precipitation totals than there were last month. Last month there were few signals for the overall pattern.
Temperature- Temperatures look to be near normal across much of Pennsylvania, except southern Pennsylvania which should see below normal temperatures. Across other parts of Pennsylvania I cannot rule out some slightly below normal reports. It seems that the first half of the month will favor above normal temperatures, but clouds from marine layers in an easterly flow will keep temperatures closer to normal in the south. The positive temperature departure should be much higher in the north and west than in the south and east come mid month. By midmonth teleconnective signals are showing a dive-bombing AO along with a positive PNA and a negative NAO. I am thinking the second half of the month will be very cold and that pattern should continue through December. Looking like some nice Greenland Blocking will develop. EURO weeklies and GEFS indicate this pattern switch come midmonth, but the operational GFS is a bit slower to show this pattern change. So overall looking at normal to below normal temperatures statewide.
Precipitation- I think precipitation will be near normal. I am looking at a more active storm track than recent months, but still not anomalous in comparison to normal. Coastal storms look possible along with warm air advection events especially near the pattern switch come midmonth. Snowfall looks to be near normal with almost all areas likely seeing their first accumulating snow before the month’s end. Lake effect snows look possible along with some nuisance clipper type events. Looks like snowfall will be in quite a positive start in comparison to normal for parts of eastern and western Pennsylvania as we head into the start of winter.
"Temperature and Precipitation Outlooks from Climate Prediction Center for next 30 days"
(Courtesy of NOAA)
-Winter 2008-2009 forecast... Link.
-Winter 2008-2009 forecast update... Link.
"Here northeast of Harrisburg 2008-2009 winter statistics"
Current Snow Cover- Trace
Monthly Total- 6.00inches
Seasonal Total- 6.00inches
Winter Weather Advisories- 0
Winter Storm Warnings- 0
Heavy Snow Warnings- 0
Blizzard Warnings- 0
Snow Advisories- 0
Winter Storm Watches- 0
Lowest High Temperature- 31
Lowest Low Temperature- 14
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
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.