Complex storm system before another cold air mass...
"Afternoon Thoughts" (Updated 12/11)
Excuse my absence this past week; it was quite a stressful week waiting for my decision in combination with our high school choir being chosen to sing for the Governor at the Harrisburg state capitol tree lighting. It is hard to believe my dreams of attending Cornell University are now a complete reality. While I found out online in a private Cornell account, my letter arrived in the mail today. I always prefer things in hard copy, so it was relieving to see the acceptance letter. While I feel accomplished and proud, I also feel lucky. There are thousands of applicants who also had just as high statistics (GPA/SAT/Class Rank) as me if not higher. Cornell was certainly a reach school for me, but I felt my unusual accomplishments in connection with my passion for meteorology set my application apart. I am a member of the Cornell college of Agriculture and Life Science class of 2015. Interestingly enough this class is also the sesquicentennial class (150 years). Anxiously I await the myriad of opportunities Cornell University will offer me. Initially I was expecting a rejection. For applying to an Ivy League school is more or less a lottery. Everyone applying is very capable and essentially on the same level with select few setting themselves apart. At 5pm eastern, early decision applicants were able to check their application decisions through a private account with a username and password. I was so nervous through much of Thursday, barely accomplishing a test and leaving yearbook afterschool a bit earlier than normal. A quick nap after school led to a few minutes before 5pm. As I reached for the mouse shaking to the point of not being able to click the button, relief came rushing in with a flood of unexplainable emotion. While I believe I would have been happy at any college I attended, this is a certain element of accomplishing my dream/reach school. My official major is Atmospheric Science. Thank you for all for support of my blog as I believe this certainly played a role in my application. Have a great day!
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion"(Pennsylvania, Maryland, Delaware)(Updated 12/11)
An upper level gathering strength over the Ohio Valley will continue to track northeast across western Pennsylvania up through western New York State. 850mb heights will rise well above 0C for the entire Pennsylvania, Maryland, and Delaware region. A dominate southeast flow off the Atlantic ocean will also promote boundary layer temperatures rising well above freezing for all locations with very little cold air damming courtesy of the lack of anticyclone to the north. But a bit of break in the cloud deck ahead of the precipitation will allow temperatures to drop to freezing or slightly below by late Saturday night, especially north of the Pennsylvania turnpike. As precipitation moves in from the western and south, a bit of freezing rain is possibly. Penndot road temperatures indicate most roads well below freezing, so travel may be tricky early Sunday morning before dawn across the I-80 corridor. But eventually temperatures will rise above freezing for all areas ending the threat. Highs on Sunday will be in the 40s for all areas and possibly near 50F across Delaware and southern Maryland. Less than a tenth of an inch of freezing rain is likely for all areas. The low pressure off the Virginia coast will not have too much of an effect on our precipitation, but some light spotty drizzle may move into southern Pennsylvania also Saturday night with a bit of freezing rain before the marine layer moves west with warming temperatures. As the double barrel low closes in on the area with an accompanied cold front, PWATs will rise to near +1SD with heavy rain overspreading the region. For most of Sunday the precipitation will be predominately rain with QPF totals near 1in or slightly less for much of the area. As the cold front moves west H85 thermals will drop to near 0C along a line moving west to east by Sunday evening. Temperatures will rapidly fall along and behind the front changing precipitation from rain to snow especially for western Maryland and western Pennsylvania. There will not be too much precipitation behind the initial front, but the primary upper level low will begin to intensify as it moves into northern New England. High resolution guidance suggests a weak deformation band as far south as Pennsylvania with some light 1-3in synoptic snow accumulations especially for western Pennsylvania, but also parts of central and northeastern Pennsylvania.
By early Monday morning drier air will flood the region with an area of subsidence. But quickly winds will increase out of the northwest cranking up the lake effect snow machine. Moderate to heavy snow bands will develop over the snow belts with heavy accumulations through Wednesday. See more details below. Highs will be well below normal under the typical northwest flow and generally below freezing for all areas and only in the upper teens for highs over elevations above 1500ft on Tuesday. Monday through Wednesday will be normal of that under a northwest flow with downsloping east of the mountains towards the I-95 corridor. Still a few flurries and snow showers may develop east of the mountains courtesy of favorable snow growth and elevated instability. By Wednesday weak upper level ridging will end the lake effect snow and allow for sunshine for many areas by afternoon. Towards Thursday and Friday high temperatures will modify, but still be below normal by about 5F for this time of year. A low will project out of the southern plains. At this point this system looks to be a general west to east moving system with snow north of the center of circulation. It remains under question of how far north the synoptic moisture will reach. Interestingly enough GFS ensembles are farther north than the operational model, which is usually a sign the operational GFS is too far south. The ECMWF is a bit weaker with the system shearing it out as it moves eastward. The GGEM and UKMET are stronger towards the GFS. At this point I think this has a pretty good potential of delivering an accumulating snow for parts of the Middle Atlantic. I am not sure how far north, but corresponding with a weak southeast ridge from the Nina, I would not be surprised to see a northern shift. At least this system will not be heading inland flooding everyone with warm air. Stay tuned. By the weekend behind the shortwave, the flow will turn west-northwesterly with a bit of lake effect snow. But accumulations will stay under 4in for the snow belts this time around. Temperatures will stay below normal.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Lake Effect Snow Conditions" (Updated 12/11)
Another very impressive lake effect snow outbreak will be occurring for the first half of this upcoming week. A double barrel low pressure system will track up through western New York State. This will flood much of the region with warmer air on Sunday as temperatures rise into the 40s. But a deep -2SD trough will quickly be sinking down through the Midwest with much colder air. The primary low pressure will situate itself just north of New Hampshire in Canada as it slowly becomes cutoff from the flow. By Monday, the entire Northeast will be entranced in a well-defined cyclonic flow. H85 thermals will drop to near (-15C)-(-17C) over the northern Middle Atlantic. The Great Lakes still have relatively warm sea surface temperatures. This air to water contrast will create a great amount of instability in the region in correspondence with a relatively moist northwest flow. As the low pressure pulls away, an area of dry air and subsidence will initially work into the region after the wrap-around snows by Monday morning. A tight pressure gradient between the primary low north of New England and the 1024mb high pressure sinking over the Midwest will create winds to gust 30-40mph over the entire northern Middle Atlantic with gusts reaching 45mph on the ridgetops. Increasing Omega and favorable dendritic growth layers will enhance sharp lake effect snow bands off of Lake Erie. The flow will initially favor a 300 degree trajectory. This will put the Laurel Highlands at a high risk of upsloping, orographically enhanced lake effect snow south through western Maryland. Snow ratios will be very impressive and nearly 30:1. Also has the northwest flow becomes dominate aloft and at the surface, the Huron-Erie streamer train will begin towards Monday night with heavy snows across the Laurel Highlands. By Tuesday a bit more northerly component begins with a 320 degree trajectory. This will bring lake effect snow bands off of Erie with a bit of Huron enhancement south into northwestern and northern Pennsylvania. Snow totals will quickly add up across the higher elevations of Erie, Crawford, Mercer, and Warren counties. 700mb RH values indicate a relatively moist flow considering the low 515dm 1000-500mb thicknesses. The extended northwest flow will bring lake effect snow showers southeast of the Alleghanies with an occasional streamer or two. Exact position remains uncertain but some areas could see a quick accumulation in the Tuesday time frame downwind of the Appalachians. In any case flurries will be common over all of Pennsylvania, Maryland, and Delaware for Monday through early Wednesday. Total snow accumulations will range from 6-14in across western Maryland up through the Laurel Highlands. Over northwestern Pennsylvania 12-24in is possible with snow totals in excess of 30in in isolated locations. Northeastern Pennsylvania over northern Susquehanna and Wayne counties will see 1-3in along with the Poconos in Carbon and Monroe counties. Across the northern mountains of Pennsylvania and central Alleghany plateau snow accumulations will be highly dependent on where streamers are setup with areal accumulations of 1-3in and isolated locations of 4-7in. Downwind of the mountains general T-2in accumulations are possible. Weak upper level ridging will cutoff the lake effect snow machine by Wednesday evening as a weak shortwave gathers energy in the southern Plains. I will likely be issuing a snow map in the coming days. Stay tuned!
*Note the higher snow totals will be favored to the higher elevations and typical snow belt locations. A few wrap-around snow showers and lake effect squalls may give areas downwind of the Appalachians a quick C-2in some areas.
"Current Great Lakes Water Temperatures"
(Courtesy of NOAA)
"Current River Ice Reports and Ski Conditions" (Updated 12/11)
This past week has greatly increased snow pack over the lake effect snow belts courtesy of a multi-day outbreak. Snow depths after some compacting were still near 40in in parts of northwestern Pennsylvania in Erie, Crawford, Mercer, and Warren Counties. Parts of the Laurel Highlands also saw nearly 1-2ft of snow. Elsewhere accumulations were spotty, but a weak warm front brought at least a heavy coating of snow to much of northern Maryland and most all of Pennsylvania. Several days of temperatures at or below freezing also allowed local ski resorts to begin making snow allowing for this weekend to be the opening date for many locations even south into Maryland. Parts of Garret and Alleghany counties in Maryland also received heavy lake effect snow accumulations with reports over two feet near Deep Creek, Maryland. Overnight temperatures have recently fallen well below normal courtesy of radiational cooling with even a low of -10 being reported in Potter County the other night in Pennsylvania. These cold temperatures have allowed for the buildup of ice on local waterways especially small lakes and ponds including small creeks. Even here in southcentral Pennsylvania, many farm ponds are frozen over. But even across the northern mountains of Pennsylvania and western Maryland, ice thicknesses remain less than the safe 4in, so it is advised to remain off. Unfortunately a low will track to the west of the northern Middle Atlantic for the beginning of this calendar week flooding the region with temperatures into the 40s accompanied by heavy rainfall. This will melt local waterway ice and snow across the lake effect snow belts. But cold air will come flooding into the region by Sunday evening turning remaining precipitation over to snow and possibly even creating flash freeze conditions by early Monday morning. The lake effect snow machine will begin in earnest for the beginning of the upcoming week with significant accumulations in the snow belts. See more information in the lake effect discussion. Also late week brings the chance for a synoptic snow, especially for southern areas. But some guidance suggests this will stay south into Maryland and Virginia. Generally well below normal temperatures and a few snow showers will allow all ski locations to open their slopes by the end of the week for the entire northern Middle Atlantic.
-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)
"Long Term Outlook" (Updated 12/11)
Below normal temperatures will continue into next weekend with the operational GFS indicating H85s around -8C for a majority of the week before Christmas, which would translate highs to be about 5F below normal. For the time being it does not appear any Arctic blasts are headed our way other than early this week. ECMWF ensembles support the anomalous negative AO, which will continue to strengthen the Atlantic blocking and increase height thermals over Greenland. The east-based negative NAO will also continue in the long range with a slightly negative to neutral PNA. This pattern will support troughing over the east coast in the extended range. A few wavelengths support a possible stormy pattern the week of Christmas also. Chances for a white Christmas are slightly higher than normal for the entire Northeast with a guaranteed white Christmas for all of the lake effect snow belts as cold air will secure the snow pack after several rounds of lake effect snow. Any warm up that shows on the models in the coming few days will likely be delayed courtesy of favorable cold wavelengths from Europe and Asia that will translate slowly eastward. Typically these troughing/upstream blocking scenarios always last longer than expected. Looking at possible storm dates, I really do not have any dates outlined out of interest. The extended ECMWF shows a few nor'easter threats towards the 240hr range, but nothing of any consistency. At this point as long as we have the colder temperatures, which are not too cold, then eventually most areas will see a snow threat.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Anchorage, Alaska Tower Cam"
*Back due to popular demand!
"Monthly Temperature/Precipitation Outlook"(December)(Updated 12/11)
After some procrastination, finally here is my December outlook. It is important to note we are in a high end moderate La Nina to strong La Nina. SSTs are well below -1C across the equatorial Pacific and have been cooling ever so slightly this last week courtesy of some upwelling. There are some predictions that the Nina will begin to rapidly end towards next month with some SST warming, but for now the short term is certainly favoring Nina climatology. But fortunately anomalous teleconnections will offer a unique pattern that has zero analogs. The Arctic Oscillation is progged to drop near the -4 or lower standard deviation. This will be likely the only time the AO has dropped that low under a strong Nina regime in December. Unfortunately this will make the monthly forecast very difficult; keep in mind last year's record breaking Arctic Oscillation. The unusual blocking upstream in the North Atlantic and Arctic the last two or three years is likely signaling the continuing theme of a negative decadal regime of the NAO. While there is not much support currently, I certainly believe the NAO is under the influence of decadal cycles similar to the PDO. With this very low NAO and especially AO, this certainly leads me to believe December will be a cold month with a greater chance of snow than typical strong La Nina December climatology. This actual is still in close correspondence with my winter outlook highlighting December as being colder than normal and snowier than normal. While many locations have yet to see accumulating snow, the last two or three weeks of December offer a very high probability of several chances at accumulating snows. Ensemble models indicate the PNA slowly rising to neutral and this may help allow the Pacific to cooperate and prevent storms from running inland. In fact with such anomalously high heights over Greenland, suppression may be a possibility in some instances. This is very anti-typical Nina for December, which typically supports a growing southeast ridge by late December. The Indian Ocean monsoonal patterns are showing signs of possibly allowing the MJO to pulse favorable for eastern snow chances. Guidance supports a stormy week or two before and after Christmas.
In any case I would expect December temperature anomalies to range from (-1.5F)-(-2.5)F for most climate reporting stations. This is a pretty significant cold forecast, but already many stations are at (-4F). That will be slightly modified overtime understandably so. As for precipitation, I expected above normal precipitation with above normal snowfall for all locations in the Northeast.
"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- 0.00in
Monthly Total (November)- Trace
Monthly Total (December)- 0.6in
Seasonal Total- 0.6in
Winter Weather Advisories- 0
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 0
Lowest High Temperature- 24.1F
Lowest Low Temperature- 12.8F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First accumulating snow - December 10 - 0.50in
"Local Harrisburg Radar"
(Courtesy of WGAL)