Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 9:27 PM GMT en Noviembre 17, 2008
"Afternoon Thoughts" (Updated 11/17)
Extremely exciting weather week resembling a typical winter week in Pennsylvania with clippers and lake effect snow. I will be posting several blogs this week to focus in on each event. This second blog will cover the major lake effect snow outbreak starting Monday night through Tuesday night. It will also cover the weak clipper moving through that may affect some areas. A third blog will be issued Wednesday evening covering the clipper system passage on Thursday and the lake effect snow to follow that through Friday night. And then of course a new blog will be issued Sunday of that weekend to account for next weeks weather and Thanksgiving Weather. So overall a busy weather week is ahead for lots of us resembling a typical northwest flow in late December.
As we all know each NWS has a different threshold for posting winter weather warnings/advisories. For example in the southeast last winter during one of the winter storms in Alabama, Georgia, and Mississippi they had winter storm warnings out for 2-4inches of snow. But here in Pennsylvania they would only issue winter storm warnings for accumulations above 6inches. It all is dependent on how adapt locals are to driving in winter weather. For example nearly 6inches of snow would shut down Atlanta for days, while over a foot and a half of snow would be needed to shut down Northeastern cities. Well doing one of my morning runs through the NWSs, I noticed that Sterling, VA NWS was going to be operating a new system during this winter for Public-Impact Advisories during the winter. For example a winter weather advisory last winter meant snowfall would be greater than 2inches and less than 5inches. Now if winter storms occur during rush hour with as little as 1inch of snow, a winter weather advisory will be issued. It all is dependent on the time of hour the storm hits and the amount of impact on local traffic patterns. Here is a link from their public information statement… Link. Now many other NWSs have been talking about something similar to this such as snow squall warnings during the winter. I believe that is an even better idea to issue snow squall warnings instead of the special weather statements, which no one even takes serious. Many major car accidents every winter are caused by white out conditions during snow squalls. Here is a link to a great case study of implementing warnings during snow squalls… Link. So overall it will be interesting to see how this new system works in the Washington DC. My personal opinion is the public needs to have a basic set of advisories or warnings. If you get to many special warnings then they will not understand the thresholds and not take things seriously. Your comments are also welcome. Have a great day!!!
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion" (Updated 11/17)
This forecast discussion is from Monday night through Wednesday night. Currently a shortwave type clipper system is moving through the Middle Atlantic printing out some 10-15dbz over Maryland and Virginia with mostly it being rain or virga. Undefined cold front attached to clipper is swinging through region shifting the winds from southwesterly to northwesterly and bringing in some even colder temperatures with H85s dropping to near -11C by early Tuesday morning and 1000-500mb thicknesses near 515, which is several deviations below normal for this time of year. Water temperatures in Lake Erie in the upper 40s combined with a cold blast of nortwesterly air will bring widespread lake effect snow activity across much of the state with decent Omega values and dendrite growth. Current clipper will try to reform off the coast and throw some light .1inch QPF back into parts of the coastline maybe into near Philadelphia. Winter weather advisories are out for parts of the Delmarva, but I have a hard time seeing them pick up any accumulations above 1inch on elevated surfaces. Coastal storm will pull away keeping the northwesterly flow around with occasional gusty winds mixing down to the surface up to 30mph. H85s continue to drop to near -14C across northern Pennsylvania with winds veering to the north bringing an end to widespread lake effect as high pressure and a cold ridge approaches from the west. High pressure moves over region Tuesday night to provide some clearing through Wednesday until clouds approach from west ahead of the next clipper system to bring some snow showers starting as early as Wednesday evening. Overall pattern looks very unsettled for western and northern Pennsylvania with temperatures statewide below normal by nearly 10-15degrees.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 11/17)
Tuesday- In the morning widespread lake effect snow shower activity should be around the state with a thick stratocumulus deck. Fog on ridgetops is likely across western Pennsylvania with ceilings below 1000ft. Some impressive snow bands should be into parts of the Laurel Highlands with snow rates of 1-2inches per hour with some areas seeing totals near a foot of snow especially for westward facing ridges with elevations above 2000ft. Snow bands will also be intense in northwestern Pennsylvania near Oil City, Butler, Bradford, Erie, Du Bois, Meadville, and Franklin. Snow accumulations in that area will range from 2-5inches. Snow showers will be widespread across central Pennsylvania with a coating in some areas to maybe an inch. Eastern Pennsylvania will mainly be seeing morning flurries with a few isolated snow showers. Temperatures will be well below normal by a good 10degrees for highs on Tuesday with highs struggling to reach 40degrees in many areas, excluding Philadelphia. Western and northern Pennsylvania will see highs below 32degrees with highs below 30degrees in some mountaineous locations such as Johnstown and Bradford. Winds will be a bit breezy out of the north-westnorth gusting occasionally to 30mph and maybe 40mph on the ridgetops. Winds will gradually be shifting to the north. For Tuesday night lake effect snows will gradually ease with last bands near Erie giving an additional inch. Some clearing may occur Tuesday making for what could be a very cold night. Lows will be in the mid 20s for many areas with some upper teens possible for northern Pennsylvania in areas that have snow pack.
Wednesday- Wednesday will be a cold but sunny day across the state as high pressure dominates the weather. A few flurries may occur in northern Pennsylvania, but other than that partly cloudy to sunshine will prevail. Highs will be the coldest of the week so far struggling to reach the mid 30s even for eastern Pennsylvania. Highs in central Pennsylvania will be near freezing and highs in western Pennsylvania will be in the mid 20s. Winds will be generally light out of the due north. Clouds will begin to move in from the west by afternoon along with some light snow showers by dusk near Pittsburgh. Overnight clouds will move over the entire state with scattered snow showers mainly from Altoona-State College-Lock Haven and westward. Accumulations will generally be less than an inch even for the ridgetops. Lows will be cold near 10degrees below normal generally in the 20s statewide with some low to mid 30s in the Philadelphia metro area. Winds will be turning gradually to the west.
"Current River Ice Reports and Ski Conditions" (Updated 11/15)
Well after this cold spell probably next week we will be talking about some ice reports of small ponds and maybe even a few early ski resorts opened up in the Laurel Highlands such as Blue Knob and Shawnee Mountain Ski Area. Snow pack will be building up out that way and conditions will be cold enough to keep the snow pack around along with even some snowmaking. So for those early skiers here in Pennsylvania, you may be able to get out there by this coming weekend and next week towards Thanksgiving. Very nice start to the season. Also some local ponds may start to be gathering ice on the very tops and should be very thin. But still it could pose some problems as it makes it look deceivingly thick especially for younger local children. Water temperatures right now are dropping relatively steadily already in the upper 40s across the shoreline of Lake Erie. This is cold enough to cause hypothermia if fallen into water for an extended period of time. Water temperatures will be rapidly falling throughout this coming week. Snow pack will also be building up in the Adirondacks and Tug Hill Plateau in New York for skiing next weekend along with the White and Green Mountains. Also mountains into Garret County, Maryland and West Virginia may see up past a foot of snow. Stay tuned for more updates on local ski reports. Here is a list so far of planned openings for ski resorts…
Ski Sawmill... 12/08
Ski Liberty... 12/05
Shawnee Mountain Ski Area... 11/29
Camelback Ski Area... 12/05
Blue Mountain Ski Area... 12/05
-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 11/17)
A nice fetch into the Laurel Highlands will aid into some big time snow totals. For most of Sunday through Sunday night lake effect snow bands were confined in northwestern Pennsylvania with a 300 trajectory fetch. Some very heavy accumulations fell in parts of northwestern Pennsylvania with 16inches of snow reported in Warren County and other heavy reports of over 6inches in Erie County including the downtown region. A shortwave type clipper system is rotating across West Virginia and Maryland currently bringing a return to a northwesterly flow along with colder air. H85s will be dropping below -10C by midnight Monday night with a 310 trajectory becoming more and more northerly as the night progresses. With some decent Omega and ice crystal growth along with relatively non-dry dewpoints and PWATs near .5inches, there should be a pretty widespread lake effect outbreak especially Monday night into early Tuesday morning. This outbreak will favor locations more south of where the first outbreak of lake effect took place. Decent orographic lift in the Laurels will result in heavy snow with western facing valleys receiving even a few inches of snow. Bands look to be setting up with a primary Huron-Erie streamer into Somerset County bring the western facing ridges QPF near .75inches with 15:1 snow ratios resulting in nearly a foot of snow especially for Mt. Davis and Laurel Summit. Lake effect snow bands will also be in other parts of the Laurels in Westmoreland and Fayette Counties where orographic lifting will not be as favorable resulting in snow accumulations near 6inches on the ridge tops. Another decent band is looking to setup as a Huron-Erie Streamer near the classic 322 setup potentially bringing the western ridge and valley region near State College and maybe even Lewistown a nice C-2inches of snow with places like Mt. Nittany and Seven Mountains seeing the higher end of those accumulations. Lastly a final major band should setup as a Georgia Bay-Erie streamer affecting western and northwestern Pennsylvania in the Venango-Forest-Elk-Cameron County type vicinity with some possible accumulations near 3inches or slightly more. Snow showers and flurries though will be statewide with a heavier snow shower bringing some areas a coating of snow to areas in northeastern Pennsylvania, Poconos, and Ridge and Valley region. Flow will begin to turn more northernly and H85s will drop to near -13C bringing a slow end to the lake effect snow on Tuesday with only a few weak bands across the state. The latest guidance shows possibility of a band coming off of Lake Erie into Erie County, so I added a decent 5-9inches in that region. Overall though lake effect for this outbreak will favor the Laurel Highlands.
Additional lake effect snow Monday night through Tuesday night...
"Current Lake Erie Wind Direction and Speed"
(Courtesy of NOAA)
"Current Lake Erie Water Temperature"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 11/15)
So is the cold pattern going to continue through the rest of November past Thanksgiving? Well in this section I will highlight my forecast. Based on past climatology, typically extended cold patterns like this one are not able to last through an extended period of time. There usually has to be a time for the weather pattern to reload up in the Arctic with a relaxation of the jet stream in the United States. Based on what I am seeing I think we keep the cold weather with well below normal temperatures up until Thanksgiving. Between Thanksgiving and December 1 I think we will see a relaxation of the pattern with a Pacific zonal flow. Now something interesting is that the zonal flow may still keep temperatures below normal, as snow pack will have already developed across much of the nation’s northern regions such as the Dakotas and Great Lakes. This will keep the cooler air over the Northeast preventing a real blowtorch of very mild temperatures. During this time the pattern will reload up into the Arctic and northern Canada. Latest GFS does keep the pattern very cold through December 1, but I believe this is an exaggeration of the cold based on a cold-GFS bias. But then the 12z EURO run from Friday afternoon showed extremely cold temperatures around this period, but then this morning’s 0z run showed a more transient weather pattern. So in a way I am sort of going against the grain. I do think by mid to late week of the first week in December we will see an arctic blast that will hold its ground over the region for almost all of December creating a very stormy period. So overall I do not think the pattern is capable of any extreme periods of warmth any time in the foreseeable winter. I do not want to jump the gun, but the pattern is sort of looking eerily similar to December of 95. Remember some meteorologists had the winter of 95-96 as an analog year for this winter. So overall this pattern is quite interesting with many opportunities of snow, and if we can build up an early snow pack here in November across the Lakes, then I think we are in for quite an interesting December. Stay tuned.
"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- Coating
Monthly Total- Coating
Seasonal Total- Coating
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- 43
Lowest Low Temperature- 26
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First Snow - October 29 - Trace
First Snow on Ground - November 18 - Coating
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.