Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 4:31 PM GMT on November 15, 2008
"Afternoon Thoughts" (Updated 11/15)
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 first blog will cover the rain changing to snow deformation band Saturday night, the lake effect snow from Sunday to Sunday night, and the weakening stages of the lake effect snow Monday afternoon. Another blog will be issued Monday evening covering the clipper system Monday night through Tuesday morning, the lake effect snow to follow that clipper through Tuesday night, and the coldest day of the week Wednesday. 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 11/15)
As the 996mb low pressure along the cold front pulls off to the northeast, a deformation band of snow is likely to form early Saturday night. Temperatures will be falling relatively rapidly behind the initial cold front with boundary layers temperatures falling into the low 40s by 8pm in western Pennsylvania. Snowfall will be relatively light and confined to the ridge tops as H85s will only be near –1C and a 538thickness. But as the cold air continues to move into the region northwesterly winds will kick up and 850s will fall near –4C with widespread snow shower activity over the region west of the Altoona-State College-Lock Haven line. Snow accumulations from the deformation band will generally be near 1-2inches and mainly confined to elevations above 1800ft. Band will begin to weaken with the northwesterly flow giving way to a widespread stratocumulus deck over all of Pennsylvania with falling temperatures. Lake effect will dominate the region with a general 300 trajectory. Winds will gust up to 35mph in the valleys and up to 40mph on the ridge tops thanks to some overnight mixing. By Monday morning another relatively undefined cold front will move through the region shifting lake effect snow a bit more from the westerly trajectory. Omega values will favor ice crystal growth and 1000-500mb thickness will drop to near 533. H85s will be near –7C and boundary layer temperatures will generally be in the upper 30s to below freezing for most areas. Winds will generally keep downsloping conditions over eastern Pennsylvania until some additional orographic lift and clipper snows create some moisture for Monday night. Snowfall accumulations will be near 10inches by Monday night in a few favored snow belt locations. Trough continues to pull colder air over region and the “arctic front” approaches for Monday night with winds turning more northerly cutting off quite a bit of lake effect snow. Clipper may be able to produce some light QPF up to .2inches over southern areas and many areas may squeeze out an inch or two. I would not be surprised for even areas east of mountains to see a coating to one inch of snow Monday night. H85s nosedive late Monday night below –10C. Lake effect machine keeps snow showers confined to far northwestern areas by Tuesday. More information on conditions later in the week will be provided with Monday evening’s blog.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 11/15)
Saturday Night- After the front moves through a pretty intense temperature drop should follow with the frontal passage near I-95 by 9pm. A deformation snow band is likely to form in western Pennsylvania with an inch of snow possible on some of the ridge tops especially in the far northwest and Laurel Highlands. Possibly even 2inches of snow for elevations above 2000ft near Bradford and Cherry Springs State Park. Lows will be falling throughout the night into the upper 30s across the mountains and 40s across the eastern half of the state. Winds will be becoming gusty later in the night up to gusts near 30mph at times out of the northwest. Deformation band will not making it any farther east than the Altoona-State College-Lock Haven-Mount Pleasant line. Skies will begin to become partly cloudy late across eastern Pennsylvania.
Sunday- Numerous snow showers will be developing across western Pennsylvania during the morning Sunday with temperatures aloft well below freezing. A bit of rain may mix with the snow in the valleys early on the day, but will turn to all snow by noon. Snow showers across northwestern Pennsylvania will give accumulations from 5-8inches, especially on the favored ridge tops. In the Laurel Highlands snow showers will give many areas a widespread 1-3inches with maybe a 2-4inch-type accumulation near Laurel Summit and Mt. Davis in Somerset County. Snow showers may make it east of the mountains at times during the day Sunday, but no accumulation is likely. The Pittsburgh metro area may see a coating to one inch of snow during the day. Snow showers will also persist across the northeastern mountains especially later in the day giving a coating to one inch in some areas particularly in Wayne County. Temperatures will be falling throughout the day starting in the low 40s across western areas falling below freezing by noon. Eastern areas will start in the mid 40s and be falling into the mid 30s with partly cloudy skies and an occasional flurry or two. Winds will be quite gusty out of the west-northwest sustained at 20-25mph with gusts up to 35mph. A few 40mph gusts on the ridge tops above elevations of 1500ft will be possible. Sunday night the flow turns a bit more westerly ahead of the clipper system keeping snow showers most widespread over the northwest mountains. But due to the widespread moisture aloft snow showers will be possible across the entire state. A decent squall could form across the far northwest just off the lakeshore with another 2-4inches of snow in that region. An additional 1inch is possible in western and northern Pennsylvania before the flow turns more unfavorable towards the west-southwest. Lows will be chilly and in the low 30s across the east and upper 20s across the north.
Monday- Flow turns a bit more west-southwesterly Monday morning prohibiting widespread lake effect snow activity. But the northwestern part of the state should pick up an additional 1inch of snow. A clipper system will be approaching from the west and will help to turn the flow more northwesterly later in the day with widespread snow shower activity. Snowfall accumulations will generally be light up until dusk. Winds will be breezy gusting at times to 25mph making for wind chills in the 20s statewide. Highs will be well below normal Monday by nearly 10degrees with highs not making it to freezing for elevations above 1800ft. Valley locations will be lucky to see highs in the low 40s. The Philadelphia metro area will see highs in the mid 40s. By dusk the clipper will put widespread snow shower activity over the entire state with a chance of widespread 1-3inches of western Pennsylvania and even a possibility of an inch of snow into the Ridge and Valley region. More details on this clipper will be evident in the coming days. Lows will be quite cold in the 20s for almost all regions except the east with lows in the low 30s.
"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 11/15)
Lake effect snowfall conditions will be very favorable this week for some significant outbreaks. This discussion will cover the lake effect snow patterns from Saturday night until late Monday afternoon. As the deformation snow band begins to weaken Saturday night, the northwesterly wind will begin to fire up the lake effect snow machine with a decent 300 trajectory. Decent banding will set up in the Erie-Bradford line with some decent ice crystal growth and decent omega. H85s will be slowly falling from –4C to –7C across northern areas with 1000-500mb temperatures below 540 thickness. Boundary layer temperatures will initially be above freezing but slowly falling below freezing by Sunday morning. Snow ratios will initially be 10:1 but as temperatures cool near Bradford ratios will rise to 15:1. Band is looking pretty intense up that way with snow accumulations up to 8inches. Winds will begin to slowly turn more west-northwesterly near the 290 trajectory putting most of western Pennsylvania in the line of fire for snow showers will a multi-band type setup heading into the Laurel Highlands. H850s will begin to fall to near –8C by mid morning Sunday with snow accumulations near 1inch across the Laurel Highland ridge tops. Flow continues to shift more westerly throughout the day with the most intense band definitely up towards Erie and Bradford. By late afternoon it appears Lake Huron-Lake Erie streamers may setup across the northern Mountains near Du Bois and Clearfield for some accumulations above 2inches. By Sunday evening flow turns due west near the 270 trajectory with 850s falling to near –9C across northern areas. Pretty decent moisture aloft with PWATs near .7inches along with some orographic lift will keep widespread snow shower activity over Pennsylvania during Sunday night with some flurries even making it east of the mountains. Late Sunday night lake effect machine shuts off for most part and lake effect band near Bradford moves north across the lake shore affecting the city of Erie with some moderate additional accumulations as flow turns 265 trajectory. Ahead of a slight ridging over the plains and next clipper with reinforcing cold shot will turn flow north-west north near 310 trajectory making more widespread snow shower activity over the state for Monday morning. H85s cool to near –10C during the day Monday with boundary layer temperatures below 0C. Clipper system will move over region with some widespread light accumulations. Winds will turn north shutting off lake effect machine for most part by Monday night, but clipper system will keep widespread snow shower activity over the state. It appears the GFS has the best hold on the lake effect outbreak, as NAM seems to CAP off environmental with some shear aloft keeping bands less organized. Simulated radars really seem to keep the band near Erie quite strong, and the greatest accumulations will occur there.
Snow Map from Saturday night through Monday late afternoon…
"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- 0.00inches
Monthly Total- Trace
Seasonal Total- Trace
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
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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