Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 9:02 PM GMT on November 19, 2008
"Afternoon Thoughts" (Updated 11/19)
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 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 11/19)
Ok this forecast discussion will be a bit different than usual because instead of posting a forecast scientific synopsis for Thursday through Saturday, I decided to keep this section just devoted to my forecast of the Alberta Clipper. The sections below will cover the rest of the weather conditions for the next three days.
A very dry atmosphere remains present with dewpoints very low and extremely low for November standards. A shortwave along with a rotating weak cold front will drop southeast from the Great Lakes and track just around the New York/Pennsylvania border bringing some light snows to the state. Some very impressive dendritic levels remain in place with some decent values of Omega. But with weakening isentropic lift and high pressure carving moisture out of the system located to the east, it will generally be a moisture starved system. But it does appear a decent light warm air advection snow will take place with what could be a pretty widespread 1inch of snow. On my snow map the region labled one to three inches will generally be on the lower end of the spectrum except for the west and northern mountains. With very cold temperatures aloft below -10C for H85s, and boundary layer temperatures into the mid 20s or lower, this could make for some decent snow ratios near 20:1 and this will help the fluffy snow across the northern border counties to maybe produce up to 4inches of snow on the northern sides of the west to east ridges with elevations above 2000ft. Some lake enhancement will also help those regions out with some more moisture. Generally QPF will be less than .15inches across the entire state with amounts lower to the south. Areas east of the mountains in the Lower Susquehanna Valley may see a coating to half inch of snow in some areas, but areas east of them will only see a few flurries. Best accumulations will be across Erie, Crawford-Warren, McKean, and Potter Counties. The best chance of seeing an inch of snow will be from the line Raystown Lake-Lewisburg-Mansfield and westward. But overall this should be a fairly widespread light snow event with generally a C-1inch in most locations adding to northern locale's snow packs. Clipper system will pull away completely moisture starved by mid morning Thursday. If anything with my clipper map, I probably went a bit to generous to southern areas, but I sort of have a feeling there will be a bit more moisture with the clipper than what some models show. I sort of like the GFS with this system.
Clipper Snow Map from Wednesday Night through Thursday morning...
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 11/19)
Thursday- Clipper system should be departing to the east of the region leaving behind a few snow showers particularily across the north country and flurries elsewhere. Additional accumulations will generally be less than one inch for most areas. Flow will begin to shift from the southwest to the northwest. Moisture will be picked up from the Great Lakes across western Pennsylvania in the form of more lake effect snow. Squalls will be particularily around the Laurel Highlands where favorable banding should bring at times 2inch per hour type snow rates particularily towards dusk. Highest accumulations will be around the higher elevations of southeastern Fayette County and southern Somerset County. But elsewhere accumulations could bring parts of western Pennsylvania a few inches of snow with some Huron-Erie streamers forming and heading towards Pittsburgh potentially around rush hour leaving some quick light accumulations. Winds will be gusty by late afternoon out of the northwest gusting to at times 30mph. Temperatures will be nearly 10degrees below normal with only eastern areas reaching the 40s while elsewhere across the state highs should be in the 30s. Acccumulations for lake effect will generally be the highest in the western slopes of the Laurel Highlands potentially upwards of 10inches of snow with most valley locations across western Pennsylvania near 2inches. Flow begins to become slightly more favorable for northwestern Pennsylvania to get in on the action later Thursday night with squalls forming across the Northern Mountains. Snow accumulations may approach 6inches in favorable snow belts. Lows statewide will be well below normal in the 20s.
Friday- Flow turns north-northwest keeping a widespread cyclonic flow over the state of Pennsylvania with cellular snow showers. Bands will begin to break up over the morning hours and turn into a widespread cellular nature. Most of the heavy snow accumulations will take place in the morning. Shortwave moves over region and enhances snow showers with the arctic front, even a bit of WINDEX showing up for the event. Snow showers will even make it east of the mountains potentially causing C-1inch even in some eastern locations. Some snow showers may reduce visibility to less than .25mile at times. Additional accumulations across western and northern Pennsylvania particularily the snow belts will result in 2-4inches of snow throughout the day. Highs will be well below normal by 10-15degrees with all locations having highs below 40degrees with some areas not getting out of the low 20s up near Bradford. By nightfall bands will begin to start breaking up with snow showers becoming more intermittent. Skies will slowly clear. With snow pack over many mountain areas, lows will drop to near record values across the north in the single digits with elsewhere lows generally in the teens with the southeast in the low 20s.
Saturday- The coldest day of the season will unfold on Saturday with temperatures aloft near -15C, anomalously cold for this time of year by several deviations. High pressure will remain in control with only a few snow showers across the snowbelts mainly in the morning. Additional snowfall will be around a dusting. Sunshine will prevail for most of the day and winds will generally not be as strong. Highs will be near 20degrees below normal and likely not hitting the freezing mark for a majority of the state, except the Philadelphia metro area. Highs may even stay just shy of 20degrees near Bradford with a nice snow pack reflecting the sunshine, but for most locales they will be in the upper 20s to low 30s. Nightfall will bring an extremely cold night. If winds can decouple along with clear skies, there could be some near record lows challenged with most locations below the 20degree mark. Stay warm that night.
"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 11/19)
A pretty significant outbreak of lake effect snow is headed our way once again. A clipper system will be departing during the morning of Thursday with some light synoptic snows over the region resulting in a few coatings to an inch or two. Winds will shift from the south-westsouth to the west-northwest with a 280 trajectory bringing impressive banding across the Laurel Highlands. Decent Omega and dendrite growth, along with ice crystal growth should result in some high DBZ bands. With Lake Erie water temperatures in the upper 40s and temperatures aloft below -10C in the 850 layer with 1000-500mb thickness levels near 520, some pretty unstable lake effect snow bands will be produced first across the Laurel Highlands with a nice upsloping flow. Orographic lift will aid highest elevations above 2500ft for nealy a foot of snow on the western facing slopes. Valley locations will see that total cut in half. Some high snow ratios are possible as shear values will be low leading to the development of some steady Huron-Erie streamers. Flow will begin to slowly shift near 300 trajectory by evening on Thursday with lake effect snow becoming more widespread over western and northern Pennsylvania with bands starting to develop in the northwest mountains. Snow accumulations be highest in parts of Crawford, Erie, and Warren Counties with some James Bay-Huron-Erie streamers. Once again snow rates may be high and with cold temperatures snow ratios will be near 15:1 for a pretty fluffy snow. By Thursday night flow will become more steady around 310 trajectory as arctic front approaches the region with weak shortwave. This shortwave will enhance snow shower activity, but with high inversion heights steady bands will begin to break up resulting in more cellular activity. Even some indices on the WINDEX index showing that there could be some heavy squalls including areas east of the mountains. Many areas may see coatings to an inch or two of snow in the heavier snow showers. All areas will likely see at least one snow shower. H85 temperatures continue to drop near -15C resulting in some pretty unstable air. Total snow accumulations for the entire outbreak will be nearly a foot in the northwest mountains and the Laurel Highlands with a widespread few inches of snow across western and northern areas. Elsewhere areas will see dustings to up to two inches of snow.
Additional Lake Effect Snow Map for Thursday Night through Saturday...
"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- 2-5.5inches
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- 24
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
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