Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 7:17 PM GMT on November 30, 2009
"Afternoon Thoughts" (Updated 11/30)
All that can be said about this past November is it was hideous. One can argue repeatedly that climatology averages do not favor snow and how the troughs are usually to our west, but really looking at the month in general it was note the lack of snow that was so bothersome, it was the temperature. We had a beautiful storm track the second half of the month with several nor'easters, but we really did not blink an eye at each one as it was assumed to be rain. Overnight lows were the driving factor in the well above normal temperatures for the month as much of month faced extensive clouds and stratus especially over the eastern half of the state. Up until yesterday's low of 26.5F, I had not been below freezing since November 7th, which is ridiculous. Most Novembers even contain lows in the teens and usually most areas see at least flurries especially west of I-95. There was very little lake effect snow to be found courtesy of the Pacific air masses. It is amazing how our patterns switch from one extreme to the next especially after the bitter cold first 2/3rds of October to the very mild November. Monthly anomalies will be around (+3.5)-(+4.0) for most locations. If this pattern would have occurred in January, this would have been a disaster with rain storm nor'easters very similar to how the winter of 97-98 shaped up. That winter is remembered for being very mild courtesy of the strong El Nino on record. But the issue that winter was getting rid of the Pacific zonal flow as the subtropical jet allowed for many coastal storms and nor'easters, but temperatures generally supported rainfall. But this ENSO is very different from that winter, so I am not expecting anything similar. The likelihood of any winter month being like this past November is very slim. Now that tomorrow is December 1, it is the official start of the meteorological winter or should I say the start of headache seasons. There are many great memories of the last two winters here on the blog, but I can only imagine what would happen if we all actually saw a storm similar to PDII with snow measured in feet. Keep in mind El Nino winters hold some very big storms as we have already seen, so lookout by the time we get to February. My Christmas lights and tree are already up, so let’s get some snow to sparkle up the holiday mood. Have a wonderful day!!!
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion"(Pennsylvania, Maryland, Delaware)(Updated 11/30)
Monday night will feature a residual northwest flow as the cold front moves up the coast with a cyclonic flow in place. This will allow for H85s to drop below -5C with colder air flowing in at the surface under a breezy northwest surface wind gusting to around 30mph on the ridgetops overnight. This will allow for some lake effect snow especially for the northwest mountains under the 310degree flow becoming west-south west by Tuesday morning. MOS suggests lows below freezing for most areas west of I-95, but with some strato-cumulus in place and breezy winds I rose temperatures for lows by a few notches overnight for areas east of the Appalachians. Accumulations will be limited in the snow belts courtesy of the small dendritic growth heights and veering wind profiles shearing the tops of the streamers. Tuesday downsloping winds will allow for clearing skies east of the mountains with a few morning flurries and strato-cumulus over the Laurel Highlands and northwest mountains south through western Maryland. GFS and NAM 2m temperatures look a tad too cold for eastern areas where sunshine will prevail so highs will likely be around climatological normals. Clouds will begin to break up over the higher elevations by later in the afternoon with highs slightly below normal above 1800ft. High pressure moves over the region under a dry atmosphere to allow for a chilly night. But a weak southwest flow aloft will help to raise dewpoints slightly overnight. Still with clear skies and calm winds, radiational cooling should prevail with lows several degrees below normal generally below freezing for most areas and into the 20s for areas northwest of I-95. Cirrus begin to stream over the region towards Wednesday morning allowing lows to be reached around 2am and slightly rise towards dawn. A low pressure over Mississippi and Alabama will slowly gather strength near 1000mb as the anticyclonic flow over the Middle Atlantic pulls off into the Canadian Maritimes with rising H85s near +2C and 1000-500mb thicknesses rising to near 555dm. Low pressure begins to strengthen at -1mb/hr moving northeast up the Tennessee Valley allowing for strong southerly winds to cause very mild temperatures over the east coast for a time as H85s rise to near +10C, several deviations above normal. GFS 2m temperatures even indicate boundary layer temperatures in the lower to mid 60s with possible 70F readings over southern Maryland. The low pressure will go under rapid cyclogenesis as it moves northeast through western Pennsylvania. ECMWF seems to have a better hold on the strength of the surface low near 990mb, while GFS seems to overphase the low near 985mb near KJST. It appears the low will travel from KLBE to KDUJ to KSYR and continue to strengthen. Anomalous PWATs +2SD will accompany the low pressure on the east side with an easterly advection of moisture off the Atlantic also. Given warm front rises through eastern New England, it will allow for the dirty warm sector to be accompanied by elevated instability with MUCAPE values rising to near 50-100 j/kg especially over the Delmarva. A high shear atmosphere will occur with 850mb flight level winds rising to near 75knots as far north as KMDT. With a strong southeasterly flow, wave watch III model indicate waves heights rising to near 5-8ft with moderate to major beach erosion under the anomalous flow. Severe thunderstorms are a definite possibility for Delaware and southern Maryland with thunder potential as far north as I-80. GFS QPF indicates 1inch amounts generally over much of the northern Middle Atlantic with a bullseye over northern Delaware and southeastern Pennsylvania with 1.5inch amounts. But with river levels low and the quick movement of the front, flooding is not likely. Damaging winds are the primary threat with the front rain band behind the low and wind advisory type winds will continue to persist behind the low. The preliminary time frame of this amplified system is Wednesday afternoon through Thursday afternoon.
By Thursday H85 heights and temperatures will drop well below 0C to near -10C with a steep northwest flow under a tight pressure gradient allowing for strong winds with possible lake effect snow before veering winds allow for the winds to shift out of the west favoring New York State lake effect snow more than Pennsylvania and Maryland lake effect snow. Colder and falling boundary layer temperatures will prevail Thursday afternoon falling in most areas into the lower 40s. GFS indicates rapid temperature falls during the day from a high of 63 in KMDT to 43 by late afternoon/early evening. Orographic lift will aid in minor snow accumulations over the snow belts with around 1-4inches on average with the northwest mountains seeing a bit higher of totals into eastern Erie and Crawford Counties, and western Warren County. Friday looks very cold under a northwest flow regime with high temperatures 5F below normal generally in the 30s for most areas with low to mid 40s along I-95. Winds will shift for more northwest cutting off the lake effect snow machine in the northern Middle Atlantic. All eyes turn to the trough placement for possible prospects for the weekend. See long term section for more detail.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"7-Day Zonal Forecast Outlooks"(Pennsylvania, Maryland, and Delaware)(Updated 11/30)
Tuesday- Downsloping winds will allow for a typical December 1 day for locations east of the Appalachians with highs in the mid 40s to upper 40s across the metropolitan areas. Areas towards southern Maryland and Washington DC will see highs into the lower 50s with sunshine. Across the higher elevations a weak lake effect flow will persist allowing for diurnal strato-cumulus and a few snow showers. Highs in the upper 30s to low 40s are likely for elevations above 1800ft. Additional snow accumulation over the Laurel Highlands and northwest mountains of Pennsylvania will only be around C-0.5inch. By evening high pressure will allow for clearing skies across the northern Middle Atlantic with decoupling winds allowing for an ideal radiational cooling night despite dewpoints only in the upper 20s and low 30s. Clear skies overnight will prevail with a few cirrus especially over western Maryland and western Pennsylvania towards dawn. Lows will range from the mid 20s over northern Pennsylvania to low 30s over central Maryland and Delaware. Across southern Maryland and Washington DC along with southwestern Pennsylvania lows will be in the mid 30s.
Wednesday- Developing low pressure over the Tennessee Valley will allow for increasing clouds throughout the day over the Northern Middle Atlantic with water vapor imagery likely indicating streaming moisture up the coast in this time frame. Precipitation will begin to stream over the region starting in the southwest moving northeast with light rain likely reaching the Mason-Dixon Line by late afternoon. Rainfall across Maryland will only be a few hundredths to a tenth of an inch during the day. Highs will be in the 40s for most areas. By Wednesday night light to moderate rain will overspread over the region as a warm front lifts northward over the region allowing for a brutally warm night with rising temperatures into the upper 50s and 60s by 2am. Rain will begin to become more cellular and convective by daybreak on Thursday with heavier rainfall. Winds will also be on the increase out of the southeast. Rainfall totals over the region Wednesday night will likely be around .25inches or so.
Thursday- Elevated instability will allow for a slight severe weather threat during the first half of the day especially over the Delmarva where a damaging wind threat prevails under a high shear environment. Locally heavier rainfall totals are likely in this area. High temperatures will be reached during the morning hours for most areas before the cold front comes blasting through the region with rapidly falling temperatures into the 40s for most areas by afternoon from highs in the morning in the 60s to perhaps 70 over southern Maryland. Rainfall totals are likely near .5inches to perhaps 1inch for many areas depending on convection placement. Thursday night will feature temperatures falling into the 30s with lake effect snow beginning over the north and west with accumulations around 1-4inches in the typical snow belts. Winds will be very gusty overnight with advisory criteria winds over the valleys and gusts approach high wind warning criteria of 60mph+ over the higher elevations.
Friday- Towards Friday morning winds will begin to relax as the low pressure pulls off to the northeast. Lake effect snow showers will also weaken as the flow turns more westerly and the column begins to dry the 0-6km RH values. Highs Friday will be several degrees below normal with mostly cloudy skies over the northern Middle Atlantic with partly cloudy skies towards the coast under a typical northwest flow regime. Highs will range from the low 30s over the mountains to low to mid 40s near Washington DC and southern Maryland. Friday night will feature partly cloudy skies with flurries towards the snow belts with lows below freezing for most all locations.
"Current River Ice Reports and Ski Conditions" (Updated 11/30)
Lake effect snow is possible Monday night across the Laurel Highlands and northwestern mountains, which may help to build the snowpack for ski resorts for ski areas such as Four Seasons and Blue Knob. It finally appears snow-making opportunities will improve over the coming week after the passage of the anomalous low pressure Thursday. Accumulations Monday night will generally be 1-2inches for most areas favoring the typical snow belts and elevations above 2000ft. Ski resorts over the rest of the state including the Poconos will see a few flurries and just cold conditions. But towards Thursday a overphased low pressure moves through central Pennsylvania causing very heavy rain under +2D PWATs with strong southeast winds. This will cause very mild temperatures for a 12hr period, before heights come crashing down on the backside of the low pressure as more lake effect occurs Thursday night into Friday morning. Moisture and dynamics will be a bit more favorable in the 12hr period for lake effect than Monday night. 2-4in of lake effect snow is possible over the Laurels and Northwest with 1-2in towards Garret County, Maryland near the resort town of Deep Creek. Towards the latter half of Friday through the weekend the flow turns due west allowing for a general shut-down in lake effect streamers, but cold air and flurries will prevail. Snow-making looks ideal towards the weekend. Also there are a few signs that guidance wants to build moisture towards the Gulf of Mexico and send it up the coast in the December 5-8 time frame, so any snow would help area ski resorts. As for river and pond ice reports, they remain nil over the region with above normal temperatures. Water temperatures though remain cold with Lake Erie generally SSTs generally dropping through the mid to upper 40s. But towards the weekend shallow creek beds and ponds may begin to see some sheet ice form under anomalous cold weather. Still though for the next two to three weeks, ice will remain too thin to walk on for all areas. Ice fishing does not look favorable for the first half of this month as the pattern remains too transient and variable.
Blue Knob... Tubing Open.
Blue Mountain Ski Area... December 1
Camelback Ski Area... December 5
Ski Big Bear... December 12
Tanglwood Ski Area... December 18
Eagle Rock... December 19
Mystic Mountain... December 24
-Link to official reports page from NWS...Link.
-Link to local ski resort snow conditions...Link.
"Current Northeast Snow Depth and Northeast Wind chills"
(Courtesy of Wunderground)
"Lake Effect Snow Conditions" (Updated 11/30)
Several chances at lake effect snow will be possible during this upcoming work week as a series of frontal passages move through with colder air behind each front. The first lake effect event will be Monday evening and overnight as the cold front passes through allowing for slightly gusty northwest winds to prevail around 322degrees. Moisture aloft is plentiful with surface to 700mb aloft RH Values along with some Omega. Dendritic growth is weak as the airmass is not terribly cold and surface temperatures will remain marginal in the upper 20s and low 30s. H85s will be around -8C for northern Pennsylvania overnight. But veering winds will quickly shift winds to near 290 allowing for an unfavorable flow for lake effect snow in the northern Middle Atlantic. Still a few squalls may move through the Laurel Highlands south into Garret County, Maryland causing an inch of snow or so. Up through northwestern Pennsylvania several streamers may form allowing for 1-3inches with the higher snow totals towards the western Alleghany Plateau above 2000ft. By Tuesday morning winds will be out of the west-southwest ending the weak lake effect snow bands. Another lake effect snow event is possible towards this Friday after a strong inland low deepens over New England causing a tight pressure gradient and strong winds out of the northwest near 305degrees for the time being. H85s will drop at or below -10C along with plentiful moisture aloft courtesy of the conveyer of gulf moisture from the departing storm. Dendritic growth looks excellent, but the problem is it appears winds quickly shift to the west-southwest by Friday afternoon possible allowing for snow in Buffalo from lake effect, but that is not favorable for northern Middle Atlantic lake effect. Still the typical belts across the northwest especially in Warren and east Erie and Crawford County could pick up 2-4inches of lake effect snow. Also the Laurel Highlands towards Mt. Davis and Laurel Summit south to Deep Creek could see 1-3inches with higher amounts in the favorable western facing slopes courtesy of orographic lift. Ongoing flurries will persist through Saturday as a generally cold westerly flow remains dominate. Temperatures will range from 5-8F below normal, which should allow for the development of a snow pack over the higher elevations of Pennsylvania and Maryland. A few flurries are also possible downwind of the snowbelts towards the Poconos and Susquehanna Valley. It looks like finally a winter-like regime will occur over the northern Middle Atlantic especially over the higher elevations in the north and west. Also there is a slight possibility for a coastal storm towards the weekend, so if that does occur lake effect snow will resume after the low passage to the northeast.
"Current Lake Erie Wind Direction and Speed"
(Courtesy of NOAA)
"Current Lake Erie Water Temperature"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 11/30)
I am focusing on two tangents in the long term section; one being the winter storm threat in the December 5th-8th time frame and the second being the overall temperature pattern in the second week of December. Sullivanweather and I were mentioning through Wunderground mail, that we both see the December 5th and 8th as a possible threat for the first widespread synoptic snow over much of the Northeast. We have the large cold front on Thursday laying the foundation for H85s in the (-10s)C and a steepening trough with a strong jet streak with an active subtropical jet all leave the foundation for a coastal storm to form. Now we need to get the trough to turn negative tilted to allow for moisture from the Gulf of Mexico to climb the trough axis over the east coast. 11/30/09 12z GFS and Parallel 12z GFS both indicate a coastal storm on December 5. Now first glance look at the date, the legendary December 5 which produces snow it seems every year. I think 2002, 2003, 2005, 2007, 2008 all produced snow in Harrisburg, but do not hold me to those years for December 5 snow. Anyways it is difficult to get back to back storms as keep in mind the amplified low pressure on Thursday will move northeast through the center of the Northeast, but if this system would occur it would quickly be on the heels of this system. This is difficult to do, but I see how it can happen. 11/30/09 12z GGEM also shows a feature of interest in this time frame. If we get an impulse along the base of the 500mb jet and we get the trough a bit deeper and slower, then it is possible for a snowstorm. But this is all a hypothesis as there is a highly likelihood there will not even be a storm in this time frame, but there opportunity is there. The high likelihood is a storm moving offshore staying away from the coast. In any case stay tuned! As far as the pattern is concerned I am holding my ground for the pattern to be transient as far as cold shots. It appears there is some suggestions an Omega block forms over Alaska, which is not favorable for east coast snow and more favorable for Pacific Northwest storms. But it appears we may be able to get the block to shift east slightly and with the MJO entering phases 7/8, we may be able to keep weak troughing over the central and eastern United States. I will say it once and say it again, having weak troughing is more favorable for snow chances than a real amplified jet with arctic air. The pattern shaping up is similar to last December with chances of overrunning systems possible, but it appears with a west-based negative NAO forming later in the month, we may be able to see the storms run a bit farther south. The pattern holds opportunity and plenty of it despite a few inlands storms which will occur, but... I am not buying this extended arctic blast that people seem to be jumping on the bandwagon of. I am not sure why people are getting this idea with the upstream 500mb jet so unfavorable for deep troughing for an extensive period of time. Overall the second week of December looks to average slightly below normal temperature wise with above normal precipitation.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Anchorage, Alaska Tower Cam"
*Note I am only posting this towercam until snow starts falling over the northern Middle Atlantic, lol. For now we can all be jealous of the Alaskan snow.
"Monthly Outlook" (December)
November temperature forecast was a disaster. There were conflicting evidence for the temperature trend for November and I chose below normal to stay in line with the pattern of many below normal temperature months in a row, nearly 6 or 7. A generally zonal ridge under a Pacific jet occurred across the lower 48 during much of the month after a few below normal days in the beginning of the month across the Northeast. The MJO was the driving force behind the pattern along with the unfavorable Alaskan Vortex causing well below normal temperatures across Alaska. Alaskan vortices and Gulf of Alaskan Lows are the kiss of death for cold, but especially snow chances over the east coast. Also the Polar Vortex mentioned often in November was affecting the other side of the globe across Asia allowing for record snowfall cover in Siberia and record snows as far south as Beijing, China. Generally a large depreciative anomaly in snowfall occurred across the United States with major snowfall generally subject to mountainous areas. Temperatures were generally above normal for most areas across the northern portions of the United States. Closer to home in the Middle Atlantic anomalies for the month look to be near +3.5-4.0F for most areas, which is pretty impressive. As for precipitation, generally most areas received normal to below normal precipitation which actually went according to my forecast especially with my forecast of the storm track becoming more active towards the end of the month. And looking back through at our statistics most of the rain occurred toward the end of the month with nor'easters. The temperature forecast was a disaster though as my call for below normal temperatures was severely wrong for the reasons above. Anyways let’s leave on a positive note and look what is ahead for another difficult forecast, December... December forecast looks tricky and I am taking a slightly different route than many for my forecast. It appears the MJO forcing will weaken despite entering phases 6+7; this will have less of a driving force as it did in November. On the other side though phases 6/7/8 are very favorable towards east coast troughing. Anyways it also appears the Polar Vortex over the eastern hemisphere will retrograde west but over western Canada allowing for the Pacific jet to buckle perhaps leading to very cold weather over the Pacific Northwest into the Rockies for the first half of the month. Despite this Nina-like pattern, all hope is not lost as typically this would cause a strong southeast ridge to form. It appears the east-based negative NAO may become more favorable overtime turning more west-based, which would aid in a generally weak trough flow over much of the Midwest and east coast for the first half of the month. Also there are a few signs that the Omega block will slide east from Alaska to central Canada again favoring a weakening of a southeast ridge. And with the emission of several S/W out of the southwest, there is the possibility for the STJ to cause for some stormy times in the northern Middle Atlantic. A weak trough is better than a real amplified jet for snow chances. In any case I do not think this will be an overly snowy month as blocking will be limited to the north causing inland storms. But towards the second half of the month there are many more conflicting signals as ensembles point to a retrograding of the PV to a more favorable location over the Hudson Bay which would favor very cold air over the eastern United States, but some guidance suggests a breakdown in the negative EPO. I think I will take a middle ground with my transient pattern approach.
Temperature- I am forecasting near normal temperatures for December with general anomalies over the region around (-0.5)-(+0.5) with the colder anomalies across Pennsylvania as Maryland and Delaware may see a bit more impact from any southeast ridge that forms. It looks like the second week of the month will be pretty chilly along with the third week before the pattern begins to breakdown for a time being causing warmer temperatures before winter lashes in during the beginning of January. Overall December should have a bit of fun with storm chances and will not be a blowtorch as this past November.
Precipitation- Generally I expect above normal precipitation especially with a possible active storm track from the southwest along the peripheral of the base of the weak trough over the east coast. This favors overrunning precipitation events and possible east coast storms if the subtropical jet becomes active. This December could be very similar to last year's December with above normal precipitation and overrunning storms. As for snowfall I expect near normal snowfall, although I would not be surprised if some areas end up above normal especially over northwestern Pennsylvania. As for the first snow chance I like the December 5th-8th window for the first widespread snow. Just check out the parallel 11/30/09 12z GFS.
"Temperature and Precipitation Outlooks from Climate Prediction Center for next 30 days"
(Courtesy of NOAA)
-Winter Outlook 2009-2010...Link
"Here northeast of Harrisburg 2009-2010 winter statistics"
Current Snow Cover- 0inches
Monthly Total- 0inches
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- 41degrees
Lowest Low Temperature- 23.5degrees
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
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