Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 2:34 PM GMT on November 29, 2011
"Afternoon Thoughts" (Updated 11/29)
December is my favorite month of the year. Not only is it the start of the meteorological winter allowing my inner-weather nerdness to flourish, but it is also the beginning of the holiday shopping season. This beginning is certainly polarized as many people enjoy the season, while others cringe at the thought of the approaching stress. December is particularily a very busy and at times stressful month. Worries for holiday plans can cause family conflicts, financial worries, and a plethora of other problems. But the idea of the season shouldn't stem to a dislike. It is a season to enjoy the warmth inside one's home, and to celebrate surrounded by friends and family. It is the season where sparkling lights dot the dark horizon and soothing music echoes in our footstep. It should be a time for relaxation. But one look at the latest headlines the day after Black Friday shows it is anything but this soothing state. From shootings to pepper spray attacks, it is unfortunate to see this chaos for an xbox, etc. We all need to step back for a moment and reevaluate our priorities. Instead of trying to rush December, take a moment to enjoy the heightened spirit.
For now lets hope some wintry weather will come plunging across the east coast to enhance the spirit in the air.
Frusturation is beginning to grow for winter snow lovers as the pattern change continues to be delayed in the long range. The unfavorable Atlantic is continuing to allow the contiguous United States to be flowed with Pacific maritime air. The southeast ridge is also beginning to flex its muscle given a very typical moderate La Nina state. While it does appear December will not be anywhere close to those forecasts for bitter cold air and snow, the whole winter does not appear to be a lose. There are still signs winter will return with full avengeance. The pattern change date remains in question and continues to be pushed farther back. It is likely the winter will not round with averages with a sharply negative NAO like the previous few winters, but we are still in the general decadal negative NAO state. This winter will likely be a return to reality for most I-95 locations whom have been treated quite generously the past few winter seasons. I still believe snowfall will round the season with above normal totals for most locations, but the kickoff to this snowier regime may just be kicked back a tad.
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion"(Updated 11/29)
A cutoff low pressure aloft will continue to lift northeast across Ohio and the Great Lakes region while a strong cold front advances eastward. Increasing isentropic lift ahead of the front will allow for a large plume of stratiform rain to form in the very moist southerly flow. PWATs remain near +3SD allowing for periods of heavy rain. H85s will rise to near +10C ahead of the front for regions particularily near the coast allowing for well above normal temperatures; possibly into the lower 70s for the Delmarva and 60s elsewhere. QPF totals will generally range from 0.5-0.75in due to the quick movement of the band of rain. Colder air will wrap in behind the low pressure with H85s dropping below zero Tuesday night across Pennsylvania and western Maryland with surface temperatures falling below 50F. The rain will begin to taper off. The cold air may advance in quick enough for a few wet snowflakes across the mountains of northern Pennsylvania above 2000ft. No accumulation is expected through Wednesday night. The band of rain will lift through New England Tuesday night with similar QPF amounts. Temperatures will begin to fall behind the band across all locations as the front approaches.
A north-northwest flow will allow a few diurnal instability snow showers to occur late Wednesday, but high shear will limit an organized lake effect snow event. There is a slight potential for a few 1-3in amounts in isolated snow belt locations Wednesday night. Also behind the cutoff low, a moist northwest flow will allow for some upslope snow showers across western Pennsylvania and western Maryland. 1-4in of snow is possible from Garret County, MD up through the Laurel Highlands. A return to near normal temperatures is likely through Wednesday through Sunday with Saturday being the coldest day. High pressure will likely dominate the weather Thursday through Friday shutting off any lake effect snow activity. A weak shortwave will approach western New York Friday nght with light snow showers. The ECMWF prognostics are a bit more amplified showing the possibility for a coating to one inch of snow, but the GFS remains drier. In any case little to no accumulation is likely. Once again high pressure moves in towards the weekend.
Towards next week, a strong cold front will approach the region around Tuesday.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Lake Effect Snow Conditions" (Updated 11/29)
A strong cold front and associated cutoff low will continue to lift northeast across the Great Lakes. H85s will drop below 0C during the day Wednesday, but surface temperatures will generally remain above 36F. A north-northwest 310 degree flow will allow for a few instability snow showers off Lake Erie and Ontario for the Wednesday night into Thursday morning period, but unidirectional shear aloft will shred apart any organized streamer that tries to form. Lake effect activity will remain very disorganized. Temperature differentials will generally remain a marginal 8-10C limiting instability. Increasing upper level highs ahead of a high pressure will eliminate any activity by midday Thursday. A weak shortwave will approach the region towards late Friday night through Saturday, but QPF remains very light and generally less than .1in for all locations amounts limited to northern New England and western New York. Light snow showers are possible, but dry air should inhibit any snow accumulation. A 1032mb high pressure will move and center itself across central Pennsylvania with clear skies for the entire Northeast for the weekend. Little to no lake effect snow is expected over the next seven days.
"Current Great Lakes Water Temperatures"
(Courtesy of NOAA)
-Link to official river ice reports page from NWS... Link.
-Link to local ski resort snow conditions... Link.
"Current Northeast Snow Depth and Northeast Wind chills"
(Courtesy of Wunderground)
"Long Term Outlook" (Updated 11/29)
The global wavelength pattern has begun to shift slightly as a western ridge begins to flex itself allowing for a +PNA and -EPO. This will help to displace the Alaskan vortex slightly bringing a bit more cold air into the central and eastern United States. Current MJO forcing suggests entering waves 4-5 before beginning to wane through phases 6+. This will be a disaster for snowlovers as phases 4-5 are east coast ridging with phases 6+ favoring blocking and troughing. Given the raging +AO and +NAO, there has been little to no blocking across the northern Atlantic. Snow chances in a positive north atlantic oscillation state are reduced nearly by 50% or more especially for the Middle Atlantic. While not necessary to get a snowstorm in this region, it is very helpful. The southeast ridge will continue to be a noticeable presence during this two week period. While general wavelengths support a milder regime, several short and transient cold bursts are expected in the next two weeks. Any snow chances will be limited to the period around December 5-6 and/or December 12-14, but these chances remain very slim. Operational and ensemble models have hinted at these periods, but general support is very limited. Keep in mind the rare October snowstorm occured in a very unfavorable pattern period; all it takes is some luck in regards to timing with these short cold air masses. December 2011 could very well be similar to December 2006 in the snow and temperature department if we do not begin to see any MJO and blocking improvements. Approaching mid month, current ECMWF ensemble forecasts suggest a return to the dreaded +EPO with a mid month warm spell. The period 12/1 to 12/15 will end milder than normal for most locations, although not near as extreme as the late November period.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Anchorage, Alaska Tower Cam"
*Back due to popular demand!
"Monthly Temperature/Precipitation Outlook"(December)(Updated 11/29)
Many winter forecasts made back in the mid fall analyzed December as being the coldest month of the winter for much of the east coast. But now given the state of many global teleconnections, it appears December will continue the string of above normal temperature months. The month will open with a raging +AO nearly at 3SD and may be approaching a high in the first two week period. Corresponding with a +NAO, there will be little to no blocking associated over the Northern Atlantic. While the Atlantic remains dreadful, the Pacific is a tad more favorable early month with a return to a -EPO and +PNA favoring a west coast ridge. The MJO has been one of the driving factors in current wavelengths with phases 3-5 being traversed early in December. As the month progresses, there are signals the MJO heads back into unfavorable phases 2-4 and the EPO returns to a raging positive anomaly. This will allow for a mid month warm spell favoring the east coast and upper Great Plains. Around 12/20 or later, there are a few undefined signals indicating a sudden stratospheric warming event which may help to dislodge the positive NAO. Corresponding with a quieter sun towards the beginning of January, a return to slight blocking across the North Atlantic will be possible in this period.
Temperature- Temperatures will range well above normal on average for the month ranging from (+1.5F)-(+2.5)F for most climatological reporting stations. Temperatures will be seasonable to slightly above normal for the first week or two of December. While slight transient cold waves are possible, they will last only 1-3 days at most. By mid month a possible transition to a milder pattern is possible with well above normal temperatures. Approaching late in the month towards Christmas, there is a chance of a return to a colder regime as we get closer to January. This may allow for seasonalable to slightly below normal temperatures. There remains a great deal of cold air on our side of the pole through December, so whenever or if this pattern changes, there will certainly be quite an arctic blast.
Precipitation- A relatively active subtropical jet stream considering we are in a moderate La Nina regime will continue to allow for the development of storm systems across the southern states. Given the lack of blocking, many of these storms will cut to the west of the Northeast putting most locations in the warm sector. While there will be a few periods for colder air across the east coast, timing will need to be perfect to get a snowstorm. In general this pattern is terrible for Middle Atlantic to receive any snowfall. I do believe though there will be 1-2 synoptic events which may allow for near normal snowfall for many locations. If these do not occur, it will be a mild and snowless month. Given the lack of sustained cold air, even the lake effect machine will remain quiet for the most part. Precipitation in general will average near climatological norms.
"Temperature and Precipitation Outlooks from Climate Prediction Center for next 30 days"
(Courtesy of NOAA)
"Local Harrisburg Radar"
(Courtesy of WGAL)
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The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.