Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 8:23 PM GMT on November 29, 2010
"Afternoon Thoughts" (Updated 11/29)
Oh the sounds of the holidays. December is typically my favorite month of the year. Something about the holiday season is comforting to me. My family all live in a 20mi radius of me, so it is not like I do not get to see them often. Perhaps it is just the warmth of the decorations and cold air now outside. I love the thought of being trapped in a small mountain cabin with a large fireplace as a blizzard roars outside. But typically living here in the good ol' Middle Atlantic, it usually is a blinding rain as temperatures shoot up into the 50s while the Christmas lights short-circuit from the wet conditions. In any case, I am one who looks forward to this time of year. Perhaps this is because I am not the one spending nearly a thousand dollars on gifts, but oh well. Oh, and on December 9th I find out my decision for Cornell; that adds a bit of excitement to the thought of December, although it could be disappointment in the end run, lol. Most areas have now received at least their first trace of snow and some areas surprisingly their first accumulation on Thanksgiving. Middletown Airport measured .1in of snow on Thanksgiving. How they measured this beats me, as it was just rain and sleet here. The flurries followed on Saturday and were hardly anything noteworthy let alone measurable. The La Nina conditions are still in the moderate category in the equitorial Pacific despite a bit of brief warming from a weak westerly wind burst. But some recent upwelling has allowing SST anomalies to sink back to previous values. The north Atlantic continues to be a mess with unusual heights over northern Canada, Greenland, and Iceland. There is a very powerful and anomalous east based negative NAO, but yet really no 50/50 low. These strange teleconnections have been causing many problems on the long range GFS, GGEM, and ECMWF. This is the general theme of the weather for the upcoming week. Model prognostics should be taken with a grain of salt. Anyways hope everyone had a happy Thanksgiving and now lets take a look at several snow threats! By the way, my December foreacast will be coming out next week.
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion"(Pennsylvania, Maryland, Delaware)(Updated 11/29)
A strong cold front moving through the Midwest will continue to trek eastward gathering increasing moisture from the Gulf of Mexico. A strong southerly flow will allow a mid level cirrus deck to lower and thicken Monday night as PWATs increase to +4SD. The strong low level jet near 50knots will continue to increase as the pressure gradient tightens Monday night. The low pressure moving up threat Wisconsin will continue to deepen at nearly -1mb/hr lowering to 992mb. By Tuesday the trough will become negatively tilted with the jet streak situated over the Middle Atlantic. This will promote the threat of very heavy rainfall and high winds. H85s will rise to near +10C over southern Maryland as temperatures rise to near 10F above normal. Winds will increase at the surface under the jet streak. GFS BUFKIT data shows areas on the western facing ridges receiving gusts upwards of 55mph for the first half of Tuesday over western Pennsylvania and western Maryland. The rest of the region will be receiving gusts in excess of 30mph out of the southwest through Wednesday morning. It looks like the low pressure will redevelop along the jet streak in the northern Middle Atlantic as the primary low moves up into Canada. With Pennsylvania, Maryland, and Delaware being in the right front quadrant, there is the potential for a damaging wind band. There is little to no instability at the surface, but a bit of 100-200j/kg of elevated CAPE. In correlation with a 60knot low level jet, a few strong wind gusts may mix to the surface with an embedded frontal rain band. Current 4km HIRES NMM simulated radar indicates the highest potential for this embedded rain band to be across Maryland, Delaware, and extreme southeastern Pennsylvania early Wednesday morning before dawn. Copious amounts of moisture will drop a heavy rain over the entire region with QPF totals near 1-3in. At times the rain rate will be very high, but the fast movement of the stratiform rain shield should keep amounts below 4in. FFG is at or around 3in/12hr, so flash flooding is a possibility along smaller streams and creeks. I do not expect any main stem river flooding through the entire northern Middle Atlantic. Temperatures will also be interesting to follow during the period of unsettled weather on Tuesday and Wednesday. After lows in the 30s Monday night, the southerly flow and increasing clouds will shoot temperatures to near 50F on Tuesday and possibly near 60F for extreme southern Maryland. Temperatures will continue to rise slowly Tuesday night peaking early morning Wednesday. As the front passes through H85s will drop from near +10C to -2C. Surface temperatures will nose dive from the 50s to the 30s by Wednesday late afternoon. The cold air may catch up with some lighter precipitation along the front with rain changing to snow for areas west of Altoona-State College-Lock Haven and north of the Mason-Dixon line. Elevations above 2000ft in the Laurel Highlands and up across northcentral Pennsylvania may see a quick 1in of snow Wednesday midday. In general the frontal passage will push through eastern areas by mid afternoon Wednesday. Total QPF for most areas will be a heavy 1-3in. Southwest winds will be strongest over western Pennsylvania particularily along the ridgetops. But there will also be the threat of a low-topped convective band Tuesday night over Maryland, Delaware, and southern Pennsylvania capable of damaging winds. Widespread flooding is not likely due to the fast movement of the storm.
Colder and drier air will be ushered into the region by Wednesday night as the double barrel low pushes northeastward into the Canadian maritimes. The Northeast will then be under a cyclonic flow for the rest of the week. Some lake effect snow is possible, but generally the west-southwest flow aloft will keep the organized banding into New York State especially the southern Buffalo suburbs. See more below. Still orographic lift will aid in a general C-1in of snow for the Laurel Highlands through Thursday morning. High temperatures Thursday through Saturday will be around -5F below climatology for most locations under cyclonic flow. This means the typical strato-cumulus over the mountains with clearer skies in eastern areas courtesy of downsloping winds. The primary low from earlier in the week will become cutoff over Newfoundland towards late Friday and Saturday. This will add some moisture aloft and turn the flow a bit more northerly. Some lake effect snow moderate accumulations are possible Friday into Saturday over parts of Pennsylvania and western Maryland. This is supported by GFS QPF fields. Meanwhile a gathering shortwave over the Midwest will begin to plow eastward by Saturday afternoon. As for the shortwave, prognostics differ on amplication of this wave by Saturday night. See more below.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Lake Effect Snow Conditions" (Updated 11/29)
After a strong cold front passes through the entire Middle Atlantic, the region will be under the grip of a stark cyclonic flow. A double barrel low pressure will move northeast over the Canadian maritimes by Wednesday night and Thursday. H85s will fall to below -5C as far south as Washington DC. Initially on Thursday the flow will be around 260-270 degrees with relatively moist H7 levels. Omega values will be increasing with a bit of lake instability just 50mi east of the coast. This wind trajector will promote most of the lake effect snow bands to organize north of Pennsylvania very similar to this past week. I would suspect a relatively strong band of lake effect snow east of Lake Erie in New York State just north of Jamestown and inching north into the southern Buffalo suburbs. This plateau has a bit of a higher elevation than surrounding areas and may actually see a decent amount of snow Thursday through early Friday morning with accumulations up to 10in. Also another band is possible east of Lake Ontario and probably just north of Oswego. The band in southern New York State may clip parts of Erie, Crawford, and Warren counties in Pennsylvania with 1-4in of snow with perhaps higher amounts near the city of Erie. As a low pressure becomes cutoff over Newfoundland, the flow will turn more northwesterly with a trajectory near 300 degrees. This will promote more widespread lake effect snow across Pennsylvania and western Maryland for Friday and Saturday. Model QPF suggest a 0.3-0.4in for parts of the Laurel Highlands and northwestern Pennsylvania with total lake effect snow QPF from the band on Thursday near 0.7in for extreme northeastern parts of Erie and Crawford counties. Some lake effect snow flurries are possible into central Pennsylvania also Friday and Saturday with lighter orographic snows in through the Poconos with a general C-1in. Total snow accumulation on Friday and Saturday may be a general 2-5in for the Laurel Highlands and northwestern snow belts with 1-3in towards western Maryland. Temperatures will certainly be cold enough, but shearing winds aloft should prevent organized banding. Snow ratios will be around 12:1. An Alberta clipper will approach from the west towards Saturday afternoon. At least we can start building some snow pack over the higher elevation ski resorts of this soggy frontal passage this Wednesday. Interestingly enough, we still have yet to have a major lake effect snow outbreak and I doubt this one will be it.
"Current Great Lakes Water Temperatures"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 11/29)
As I am typing this, the hubub of activity is of course drawn to the December 6-7th and December 9th-10th time frames. Looking at specific model prognostics is purely pointless at this point. At first I will look at the setup. The east-based negative NAO will be continuing into the first December 6-7th period. But this blocking is a bit off-centered for our ideals and there is a lacking 50/50 low. The PNA will be neutral in this time frame coupled with a negative going to positive EPO. The cold air will definitely be available. We have a bowling ball shortwave dropping out of Canada and moving east (generally moisture starved through the Ohio Valley). Light snows (C-2in) will fall in its wake. A deep trough over the east coast may allow amplification of a redeveloping low off the Middle Atlantic coast. The trough is a bit broad for my liking, but none the less it has been steepening in recent model trends. A low pressure will develop off the coast and rapidly deepen; that I am pretty certain of. But the difficult part will be location, location, location. Climatology does not support a major snowstorm along the I-95 corridor with a high end moderate La Nina, but climatology can be broken considering the anomalous north Atlantic. The GGEM and ECMWF support a feasible solution with a low developing just southeast of the Delmarva off the coast throwing snow westward. The ECMWF probably overamplifies the low pressure retrograding it in New England for a major winter storm. But I am encouraged by trends of deeping the initial S/W and redeveloping in the northern stream. At this point, I think I am going to sound the potential for an accumulating light snow over Maryland and Delaware into southern Pennsylvania late this weekend. If this S/W trend continues to deepen, a more full fledge Miller B solution is quite possible. I feel that a more amplified scenario is more likely than a sheared out version like the GFS suggests. It is also likely this will trend a bit northward as climatology favors a stronger southeast ridge, unlike last winter. As for the 9-10th, at the time I will leave that for another day. But that period does offer potential for a winter storm too.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Anchorage, Alaska Tower Cam"
*Back due to popular demand!
"Monthly Temperature/Precipitation Outlook"(November)(Updated 10/23)
I think I am going to trend a bit on the mild side for the upcoming November despite interesting teleconnections. Mean 500mb guidance from the past week show a bit a southeast ridge beginning to flex its muscle into the southern Middle Atlantic. Latest 10/23/10 0utc GFS 10-14day 500mb mean actually supports this continuing in that range with a 588dm ridge over the southeast. Right now the polar vortex is just north of Alaska by about 200mi, which is good for now. But guidance suggests this may sink southward towards November. This tends to favor ridging over the east coast and troughing over the western United States up through Alaska and the Canadian Rockies. But current ensemble runs indicate a negative NAO to open up November. There will likely be an eastern cool pattern during the first week of November. The La Nina continues to show that it is already one of the strongest La Ninas on record. But it is encouraging to see little temperature drops in Nina 3.4 SSTs. For those looking for an early season snowstorm this year, a few encouraging signs can be found in the cryosphere. Levels are at around normal values, which are actually higher than the previous few years. Siberian snow cover has shown impressive gains in the last two weeks and has reached above normal levels. Also North America snow levels have increased in northern Canada and Alaska courtesy of the trough moving through and associated low presssure system. None the less, I believe typical La Nina conditions will dominate November's weather with a southeast ridge. But cooler weather may return towards the end of the month with perhaps the first inland snowfall in this time period around or just after Thanksgiving. We shall see how those wavelengths turn out. Precipitation chances are right around normal for all areas. The farther south one goes in the Middle Atlantic will dictate how anomalous the warmth is this month as weak troughing from the negative NAO may be enough to save some areas in Pennsylvania from the warmth.
"Temperature and Precipitation Outlooks from Climate Prediction Center for next 30 days"
(Courtesy of NOAA)
-Winter Outlook 2010-2011...Link.
"Here northeast of Harrisburg 2010-2011 winter statistics"
Current Snow Cover- 0in
Monthly Total (November)- Trace
Monthly Total (December)- Trace
Seasonal Total- Trace
Winter Weather Advisories- 0
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 0
Winter Storm Watches- 0
Lowest High Temperature- 35.8F
Lowest Low Temperature- 20.8F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
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