December 27-30 Clipper and Lake Effect Snow Potential...

Discussion...

Synoptic Snowfall:
This is likely going to be a quick and hard hitting 2-4 incher for a widespread area, blossoming into much heavier totals once into northern New England as the low strengthens. Once east of the apps, downsloping should make for little or no accumulations from both the clipper and lake effect, especially for the Susquehanna Valley of PA and points east and south. Meanwhile, while this system exits New England, the lake effect is going to kick up in earnest and add additional significant snows to the folks in the traditional favored areas. Once east of the apps, downsloping should make for little or no accumulations from both the clipper and lake effect, especially for the Susquehanna Valley of PA and points east and south.

..GLUNT.. 12/27/2009

Lake Effect Snow:
Off Lake Erie... snow bands should begin forming by Monday morning. Initially, flow will be more westerly which will produce moderate snows east of the lake into favored areas of Southern Erie, Wyoming, and northern Chautauqua and Cattaraugus counties. Total lake effect snowfall will likely range from 4-8” before winds begin shifting to the northwest and heaviest snows begin to setup from southern Chautauqua county NY to Ashtabula county OH by late Monday Night. Between then and Tuesday night, flow should remain fairly steady resulting in significant accumulations downwind, especially if any upstream connections become sustained for a long period of time. For this reason, we have also extended significant accumulations further inland to the highlands of interior western PA. By the time the snow winds down, total accumulations from Sunday Night thru Wednesday Morning will likely range from 12-24”where the most persistent bands develop.

Off Lake Ontario... snow bands should begin developing by Monday Evening. Initially the flow will be more westerly, resulting in moderate snows east of the lake over portions of Jefferson, Lewis, Herkimer, and Oneida counties. Total Lake Effect snowfall will likely range from 4-8” before winds begin shifting to the northwest and heaviest snows begin to setup over portions of Oswego, Oneida, Madison, Onondaga, Wayne, and Cayuga Counties by Tuesday Morning. Between then and Wednesday Afternoon, flow will remain fairly steady resulting in significant accumulations downwind. At the same time, multi-bands off Cayuga and Seneca Lakes should be impacting a large portion of South Central NY and far Northeastern Pennsylvania. By time the snow tapers off Wednesday Afternoon, Total accumulations of 6-10”are likely across portions of Tompkins, Tioga, and Broome Counties in areas where the most persistent bands occur. Further north, greatest amounts should be focused over portions of Madison, Onondaga, Oswego, Oneida, Wayne, and Cayuga Counties, where localized total accumulations will likely range from 12-24” in areas where the most persistent bands occur, with lesser amounts of 6-12”likely across portions of Chenango, Cortland, and Seneca counties.

It should also be noted that considerable blowing and drifting of the snow is likely, especially Tuesday into Wednesday.

..EGAN.. 12/27/2009

December 25-27, 2009 Ice Event...

Discussion...
Here is our updated ice map for this storm. We decided to downgrade our 0.25-0.50 zone from our forecast from last night to a dashed zone for the possibility of having a few reports of Ice Accretion exceeding 0.25", but we are not expecting widespread amounts exceeding .25” at this time.

The other area of growing concern is across the North Country region of Upstate New York, specifically the Saint Lawrence River Valley and northern Adirondacks. The GFS is advertising an abundance of QPF in this corridor, which if right, could mean widespread significant icing of >.25”, however we suspect the GFS is a tad overdone in bringing this much QPF to the area, and we therefore are accepting a more NAM-like QPF field here. If by chance the GFS is correct, we think some of the QPF would likely be spent on a snow/sleet mixture to start as well as occasionally mix in, thereby reducing the icing potential. Having said this, we have highlighted this region for the possibility of localized areas receiving upwards of .25” of ice, although we are not anticipating widespread amounts exceeding .25” at this time.

Another area to keep an eye on is the Catskills region of Central New York, where HPC has actually pegged a 40% probability for 0.25” or greater. The amount of QPF is a question mark for this area however, so we decided to leave them out of a localized 0.25-0.5” zone.

All in all, confidence remains fairly high that many folks across the interior Northeast will experience an advisory-level event (.10-.25”Ice Accretion) with regard to icing.

Switching gears to the snow/sleet accumulation potential, the 2 most favorable areas to experience any kind of accumulation will be across the Adirondack region of Upstate New York as well as across Upstate Maine. In both these areas, a snow/sleet mixture is likely to start off, and could accumulate up to 1-3” before event transitions to more of an Ice threat with sleet and freezing rain becoming the dominant precipitation types, and eventually plain rain showers in most areas.

..GLUNT/EGAN.. 12/25/09

Lake Effect Snow Event for Upstate NY (12-15-09)

Discussion...
Most areas should only see Advisory-level amounts, with a few localized amounts exceeding 7" by the time everything winds down on Thursday. Best chance of this is likely to be in the vicinity of I-90 in North Central NY in and around the Syracuse Metro. Lesser amounts of 3-4" could be realized in the Finger Lakes region between now and Wednesday Morning when the flow is more straight out the Northwest before activity lifts to the north and east for much of the day on Wednesday. There should be some enhancement off the Finger Lakes overnight Tonight, which could bring accumulating snow to parts of the Northern Tier of PA in Bradford/Susquehanna Counties, but generally no more than a localized inch or two, and mainly in northern towns.

Elsewhere, just a general 1-3" across much of Western NY into Northwestern PA with the passage of the current front as well as from snow squalls/showers traversing thru off Lake Erie. Best area for accumulating snow off Lake Erie should be over the ridge from interior Erie County PA thru Chautauqua/Erie Counties in Western NY, where localized amounts up to 7" or so could fall by Thursday Morning.

..EGAN.. 12/15/09

December 8-9 Winter Storm...

Discussion...
Basically expecting Advisory level snow amounts over most of Upstate NY into interior New England. Going with 6-12 amounts in the favored upslope regions and higher terrain of interior Northern New England. The other area of concern is over the Adirondacks of Northern New York State where amounts in excess of 6" may also be quite common. We decided to hold off on a full-blown area of 6-12 up there on the hunch that they we do expect there to be mixing towards the latter stages of the event, and also that QPf amounts may be a tad overdone up there, especially on the GFS. This is something that NWS Burlington mentioned earlier, and we are going to take them up on that.

So, what we ended up doing was keeping overall amounts in the 3-6" Range with the idea that 5-6" amounts should be common, but we also highlighted the Dacks with a empty 6-12" zone meaning we expect there to be isolated amounts exceeding 6", but not widespread enough for a full-blown 6-12" zone.

Here is my educated guess at a more pinpoint accumulation for 10 selected sites on our map...

KBUF- 2"
KUNV- 3"
KAVP- 3"
KSYR- 4"
KBGM- 4"
KALB- 4"
KBDL- 4"
KBTV- 5"
KSLK- 6"
KCAR- 10"

..EGAN.. 12/8/09

December 5-6, 2009 Winter Storm Outlook...

Discussion...
Basically from 3 days ago, I said I agreed with HPC's D3 4"+ Outlook, which was centered over the Appalachian Ridges of Western VA and adjacent Eastern WV. That idea has stuck, and this is reflected in our accumulation outlook for this storm by a 3-6" region over this area.

Because of factors like the forward speed of the storm, Liquid:Snow ratios likely being <10:1 in most areas, and rather warm ground temperatures, we are taking the conservative route with a general 1-3" snowfall, with the possibility of a few localized areas picking up slightly more, perhaps 4 or 5". The region with the best chance of this happening is the area which we have highlighted by the hollow (as opposed to filled) 3-6" range, which extends from South Central PA to interior Eastern New England.

Previous Discussion from Mike...
Ultimately, the heaviest snow that will fall from this system is going to be in the mountains of the VA/WV border up into the NOVA (northern VA) region, where a general 3-6 inches will fall. This region has been the area showing the best probabilities on the SREFs from Ewall of having 4+ inches of snow. Further north, we have continued the zone as our trademark dashed area. Generally, outside of the solid 3-6 zone, we expect a widespread 1-3 inch snowfall. The dashed area indicates where some more widespread 2-4 amounts may occur with the possibility of an isolated higher amount here and there. You'll notice this is backed pretty far from the big cities, where I think there may be some precip issues at the onset and accumulation issues when its snowing due to temps. Back in the dashed zone, there will be better conditions for some higher ratio snows coupled with half decent precip. But generally for all of the megalopolis, a 1-3 inch snowfall is our call.

Things to watch:
-The western edge of the 1-3 may end up not being far enough west, especially closer to the Mason-Dixon and points south.

-New England snow totals may be a bit conservative and may end up warranting the solid 3-6 area.

..EGAN.. 12/5/2009