Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 6:33 PM GMT on December 01, 2008
"Afternoon Thoughts" (Updated 12/01)
Welcome to the start of meteorological winter!!! While for many areas it seems like winter has been knocking at hour door for weeks, it is now the official start of the meteorological winter. All areas have seen a trace of snow across Pennsylvania so far and three quarters of the state has seen accumulating snow. Many areas in the snowbelts have seen record amounts of snowfall this season so far. Many ski resorts have opened up weeks earlier than normal. And for snow lovers we have what really could not be a better weather pattern for early season snows. We have plenty of cold air with a nearly stationary trough that has been over the east coast for several months now thanks to a relatively negative NAO through summer and then fall. I feel very confident on my winter outlook, which I issued back in the beginning of September over Labor Day Weekend. I then provided an update several weeks later on any changes. I was planning on issuing a third update for the start of the meteorological winter, but it just does not seem necessary. For links for my winter forecast see below towards the bottom of this blog entry. It is also hard to believe the holidays are just around the corner and that the start of the shopping spree has already begun. I hope everyone had a wonderful Thanksgiving. Only 25 more days to Christmas, lol. So I know people will be asking so are we going to have a white Christmas. While almost impossible to officially tell, it would appear odds are much higher for a white Christmas across the state as a whole than they have been in the last year. Back in 2002 was our last widespread white Christmas across the state with nearly a foot of snow in some areas including here in Harrisburg. That storm was part of the 2002-2003 winter, which would not stop. So lets take a quick trip on the memory lane train and take a look at some major winter storms that have impacted much of Pennsylvania. Recent memory suggests a snow drought and that global warming is taking all our snow. But is that really the case, in my opinion most likely not. I was looking back through some historical data for here in Harrisburg, and found that we go through periods of very snowy winters and dry winters have so 10 years. One of my favorite weather books in my weather library, “The Pennsylvania Weather Book,” by Ben Gelber takes a historical recap of all the major weather events in Pennsylvania’s storm history up through 2002. Looking back at historical data this was a very cold period in the early 20th century with the coldest winter on record for Harrisburg in 1904-1905 with an average temperature of 23.1degrees. Also in those winters in the early 20th century we had out coldest summer in 1903. Then jumping a few decades we came upon our warmest winter ever, which was in 1931-1932 with a toasty average temperature of 40.2degrees. Later in the 30s we had our least snowy season on record in 1937-1938 with only 8.8inches of snow. After the 30s we hit a several decade period of average winters until the 60s when the next trend of cold winters entered the picture with the snowiest winter on record in 1960-1961 with 81.3inches of snow at Middletown. Areas in the suburbs saw nearly 100inches of snow. The winters in the 60s were all relatively brutal. We then hit an unsnowy period in the 70s until 1978 when a severe snowstorm struck the east coast starting a new snow period into the 1980s with the heaviest snowstorm in a 24hour period hit Harrisburg in 1983 with 25inches also breaking other records such as 13inches of snow in a 6hour period in Harrisburg and 5inches of snow in one hour. Pretty impressive. The later 80s hit a quiet period in the snow and cold department before we got pounded in the winters of 92-93 and 95-96 with some major east coast snowstorm. The later in the 90s the strong El Nino made for a few very warm winters until 02-03 with nearly 65inches of snow in Harrisburg. After that winter well things in the snow department have been relatively quiet. So in Irving Berlin’s “I am dreaming of a white Christmas just like the ones I used to know,” that is not really the case. We have selective memories and for many of those born during the 60s they remember their childhood full of snow thanks to those snowy winters. All in all it appears we just go through trends and I do not see any information that would lead to me to think otherwise that our winters are becoming less snowy.
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion" (Updated 12/01)
A relatively unsettled, but yet quiet weather pattern is in store for this week as a series of troughs move through the Northeast. A deep trough moves into the region for Tuesday, but the coldest of the air stays to our west across the Midwest and Ohio Valley. H85s dip to near -7C across the state on Tuesday with surface temperatures several degrees below normal. The disturbance rotating along the trough will lift out to sea and a ridge builds in ending the lake effect snow, which should only deliver marginal snow amounts. 1000-500mb thicknesses rise above 540 across all of the state for Wednesday ahead of a very strong cold front along with an Alberta Clipper system. By Wednesday night the front will work across the region with a wind shift to the 300 trajectory and H85s near -15C across Pennsylvania for Friday. But for Thursday the front will bring a rain changing to snow scenario for western Pennsylvania and could deliver several inches of snowfall for areas even near Pittsburgh. For eastern Pennsylvania it will generally be rain. By Friday coldest air of the season hits with temperatures aloft several deviations below normal and the wind trajectory will shift to the 280degree delivering the northwest snow belts some decent accumulations. Saturday the trough remains parked over the region with 1000-500 critical thicknesses near 516. Lake effect snow will be ongoing across the state before another disturbance moves into the region for Saturday night into Sunday, which could deliver a widespread light accumulation across the entire state. Some models such as the GEFS and EURO want to develop a miller B coastal storm from the clipper, so that will be something to monitor in the coming week. Even colder air moves behind the clipper system with critical thickness near 504, which would deliver very cold temperatures. Overall the pattern is very favorable for clipper systems and cold fronts in the coming week.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 12/01)
Tuesday- Cloudy skies will persist across the state with a large stratocumulus deck across much of the state. The trough will be over the region with a disturbance enhancing lake effect snows for the western half of the state. Snow accumulations will generally be relatively light and a nuisance compared to what they have seen so far this season. Snow amounts in the western facing slopes in the Laurel Highlands will be near 1-3inches especially in parts of Cambria County. Snow amounts will be slightly higher in the northwest particularly in Erie with amounts in Crawford and Erie County near 3-5inches possibly up to 6inches along the higher hills of southeastern Erie County. Across central Pennsylvania and eastern Pennsylvania conditions will be cloudy with a few flurries at times. Temperatures will be near 5degrees below normal with highs near freezing across the west and highs in the low 40s across the east. Tuesday night will see partial clearing later in the evening with winds calming creating relatively decent radiational cooling conditions for lows in the upper teens across the north to mid 20s across the south.
Wednesday- Sunshine will prevail across much of the state as high pressure remains in control behind the departing trough. A few flurries cannot be ruled out in the morning across the northwest, but skies will be all sunshine statewide by afternoon. Winds will be out of the southwest up to 10mph ahead of the next system. Clouds will approach western Pennsylvania by afternoon ahead of next front. Highs will be a few degrees below normal across the north to seasonable temperatures across the south. Highs will be in the 40s statewide to maybe 50degrees in the metro areas of York, Lancaster, and Philadelphia. Overnight rain showers will approach western Pennsylvania with rainfall generally less than .1inch. Overnight precipitation will advance eastward into central Pennsylvania. Colder air will rush in backside of the frontal precipitation causing a rain changing to snow solution for western Pennsylvania. Snowfall amounts will generally be a coating to an inch or two. Lows will be relatively mild in comparison to what they have been with lows in the 30s statewide with a few mid 20s across the northeast mountains and Poconos.
Thursday- Scattered rain and snow showers will be across much of the state for the first half of Thursday as a cold front and clipper system moves through the state. Rainfall amounts will generally be less than a tenth of an inch and snowfall amounts will generally be an inch or less across western Pennsylvania. Temperatures will be several degrees below normal with highs falling from the low 40s into the low 30s by afternoon as arctic air approaches the region. Clouds will be widespread over the state. As the flow turns more northwesterly the lake effect machine will start up with orographic lift aiding in snow showers across the Laurel Highlands. Snow accumulations will generally be light and only a few inches. Thursday night the lake effect machine will really kick into gear with a northwest flow giving the western half of the state a favorable flow for widespread activity. Snow accumulations will be light to moderate with amounts in the snowbelts from 3-5inches. Lows Thursday night will be chilly and in the mid 20s for much of the state with some possible teens across the northern mountains near Wellsboro and Mansfield.
Friday- Snow showers will be widespread across western Pennsylvania for much of the day until late afternoon. Downsloping winds will bring brilliant sunshine to eastern Pennsylvania with a stratocumulus deck across western Pennsylvania. Additional snow accumulations will generally be light with amounts from 1-4inches of snowfall. Temperatures will be well below normal as the trough moves over the region with the coldest air of the season. Highs will be likely below freezing statewide even possibly into Philadelphia. Northwestern Pennsylvania near the Pennsylvania Icebox of Bradford may see highs in the upper teens thanks to a snow pack near a foot. Friday night will see very cold conditions as skies clear from east to west thanks to dwindling lake effect snows. Winds will also calm down from the northwest giving way to some radiational cooling for some of the coldest temperatures of the season. Dewpoints are progged to be in the single digits as far south as Harrisburg so temperatures will likely fall into the teens statewide with some single digits across the north. These lows are near 20degrees below normal.
"Current River Ice Reports and Ski Conditions" (Updated 12/01)
Well what a wonderful start to the ski season for much of the Northeast and especially some parts of the Pennsylvania snowbelts in the Laurel Highlands such as Shawnee Ski Area and Blue Knob. Snowfall has been very heavy over parts of the Laurel Highlands with parts of Somerset County, Erie County, Crawford County, and Warren County seeing nearly 40inches of snow already this winter. Other locations across the northeastern mountains have seen nearly one and a half feet of snow this season with some locations near two feet thanks to a few heavy early season snowstorms. Also with this very cold weather snow machines were able to make snow nearly every night throughout the end of November. Ski Rountop, which is just south of Harrisburg has opened the earliest it has in several or more years with even some fresh snow to boot along with the snow machines. Many other areas have had record early openers for the season. Parts of northern New England have had ski resorts operating since October thanks to the early season October 28 snowstorm. As for the ski resorts, most locations do not have all their runs open and snow tubing has yet to open for most locations. Looking at just the snowfall forecast for this week there are several opportunities for snow including lake effect in the beginning of the week, which should deliver some areas up to 3-5inches of snow in the northeast snow belts and near 1-2inches in the Laurel Highlands. A front passage on Thursday will also bring a C-2inches of snow for western Pennsylvania, and by the end of the week temperatures will be very cold and below normal by nearly 20degrees favoring some more lake effect in the snow belts. Towards the weekend a clipper system is progged to come down over the region with possibly a widespread light snow and looking ahead to next week the pattern is very stormy. Overall things could not look better for the ski season here in Pennsylvania. As for ice reports they still remain relatively slim, but many smaller farm ponds have started to ice up. Lake Erie water temperatures have also been rapidly declining, which should result in lake ice by mid December. Many of the other local streams have seen ice accretion too, making for a very early start. All of the ice statewide is not thick enough to walk on, so take precautions when around water surfaces this time of year.
-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 12/01)
A few periods of lake effect snows are possible this week. Starting Monday a deep trough will move into the region along with a shortwave rotating around the trough bringing and enhancing orographic and lake effect snows across western Pennsylvania. With snow ratios being relatively low near 10:1 and marginal boundary layer temperatures right around freezing, accumulations do not look to be too widespread more or less right around 1-4inches. Some more enhanced lake effect snow could occur in the northwest snow belts with 3-5inches possible near the Lake Shore near Erie. Overnight Monday night snow showers will become a little more widespread with a few snow showers making their way as far east as the central Ridge and Valley region. Ridge will build into the region by late Tuesday evening bringing an end to the snow showers across western Pennsylvania. It does not appear any organized banding will occur excluding the northwest snow belts near Erie. Later in the week a clipper system and nearly an arctic front moves through for Thursday with a rain changing to snow scenario. Flow turns northwesterly by late Thursday into Friday with some more organized lake effect snow banding into parts of the region. Snow accumulations will be moderate in the snow belts up to 6inches in some areas. But with high inversion and high shear values I do not expect a major lake effect snow outbreak by any means. Lake effect machine shuts off by Saturday as a ripple in the jet stream moves in with a clipper system then will enhance the flow back northwesterly bringing widespread lake effects to the western snow belts in the Laurel Highlands and northwest mountains. Heights drop to thicknesses near 525 and H85s near -15C bringing some very extreme instability to the region. Lake effect snow outbreak could be relatively significant, but that is still a long way out by nearly seven days. Overall appears that the lake effect machine will be pretty active throughout this coming week, but nothing should be overly significant and more advisory type amounts possibly up to 6inches in some locations.
"Current Lake Erie Wind Direction and Speed"
(Courtesy of NOAA)
"Current Lake Erie Water Temperature"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 12/01)
The upcoming pattern seems very volatile in terms of placement of the core of cold weather and tracks of major storms. One thing for sure though is there will be well below normal temperatures across parts of the CONUS and there will be a very active northern jet stream, which will favor big time storm development and even some decent warm air advection type snows. In the shorter term overall pattern it appears December clippers will be quite common. The difference in November clippers and December clippers is that December clippers tend to produce more widespread light snow accumulations thanks to the colder temperatures and higher snow ratios. GFS is very optimistic on a very cold pattern through the 10th of the month with temperatures aloft near -15C for most of the period and a very active clipper type pattern any of which could form a Norlun trough or a miller B type scenario and throw snow back over the east coast as it redevelops across the coast. 500mb pattern remains high amplified with quite a negative NAO, but the PNA is also headed negative from it’s current positive state. I would not be surprised if the GFS ensembles back off on the highly negative PNA in the coming days. After the 10th of the month both EURO ensembles/weeklies and GFS ensembles indicate the cold centered over the Great Lakes and Northeast. But the operational runs favor more of the core of cold air across the Midwest with a weak western Atlantic ridge keeping temperatures only slightly below normal over the east instead of well below normal. GFS though has been consistent with an arctic blast towards mid month with H85s as low as -30C across Minnesota on some of the runs. Some of the GFS runs even showed -20C 850s across the Northeast and through Pennsylvania. That would make for temperatures nearly 20-25degrees below normal. In any case those forecasts have been relatively inconsistent in terms of placement of the artic high. The overall pattern in my opinion though looks highly storm with cold blasts in between some slight warm ups. I do not see any extended period of warmth in the foreseeable future.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Monthly Outlook" (December)
So here it is the first month of the meteorological winter, and quite hard to believe at that. It feels like we were just watching severe thunderstorms role across the heartland and hurricanes roar across the Gulf of Mexico. But now it is our season for extreme weather; winter storms. Looking back at my November Outlook I called for normal to below normal temperatures with normal precipitation. That is very close to what actually happened and with the temperature department I nailed it spot on. Temperatures for the first half of the month were well above normal and by the second week temperatures plummeted to the coldest temperatures we had seen in November in quite a long time. Temperatures average below normal by a few degrees, but it could have been an even bigger anomaly if we had not seen that very warm outbreak in the beginning of the month. Snowfall I called for normal snowfall to above normal snowfall, and many areas across Pennsylvania are running 150% above normal in the snowfall department. The only area really lacking snowfall is in the Lehigh Valley where they have only seen a few coatings, even the Philadelphia snow season is starting off with a bang. Some areas in the snow belts near Erie have seen some of the snowiest weather in November in decades. Precipitation as a whole though was slightly below normal to normal in most areas. It seems we have been caught in a somewhat drier pattern lately in comparison to other years, still though we are far from a drought. So for December here is what I see…
Temperature- For quite a few months as far back as August, December was looking to be an extremely cold weather in comparison to normal. Now as we approach December, very little has changed in that regard. I am forecasting below normal temperatures across the entire state. Now the anomaly will not be extreme, but it will be enough for a couple of degrees below normal as a whole. I am expecting very cold weather for first week or two of December, before a more rollercoaster type pattern with cold followed by warmth. Then for the end of the month I think the coldest air moves over the Northeast with the coldest weather possibly of the whole winter. There are teleconnective signs of a decent negative NAO that would favor deep troughs over the east coast. But there are a few discrepancies with the models with some favoring a western Atlantic ridge and warm air up the east coast. But I still think the models think we are in a stronger La Nina pattern than we actually are. Just recently the climate CFS model which was forecasting a strong La Nina again, has now backed up to a weak La Nina which is more reasonable. I must also mention that now the CFS shows below normal temperatures across Pennsylvania for every meteorological winter month. All in all I think December will favor below normal temperatures with even some more favorable blocking scenarios towards mid to late month.
Precipitation- Lately we seem to have been in a drier spell, so I find it hard to forecast above normal precipitation. So my forecast calls for normal precipitation with above normal snowfall. Looking at all of the global models, the ECMWF, GGEM, and GFS they all forecast a much stormier weather pattern starting the second week in December and lasting for quite a while. The northern jet seems to become the focal point of all the weather with storms even coming into the northern US Pacific coast and traveling transient across the nation and out to sea in the Middle Atlantic. At times there may be phasing between the northern and southern jet, which could lead to some strong winter storms across the central and eastern US. I also believe the pattern favors many Alberta clippers in which some of them could even be Saskatchewan screamers. Lake effect machine may end towards later in the month as Lake Erie may freeze over this winter, especially with how the pattern is looking. Warm air advection snows are also possible.
"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- 0.75inches
Monthly Total- 0.75inches
Seasonal Total- 6.85inches
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- 28
Lowest Low Temperature- 14
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
Snow Map for December 6 - December 7....
*Note this snow map will be transferred to a new blog which will be coming sometime tomorrow.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.