Area Forecast Discussion
Issued by NWS Binghamton, NY

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000 FXUS61 KBGM 201137 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 637 AM EST Mon Nov 20 2017 .SYNOPSIS... Accumulating lake effect snow will continue in North Central New York this morning, shifting mainly north of the New York Thruway by mid morning. However, at least scattered snow showers and flurries can be expected across the rest of Central New York today and even Northeast Pennsylvania this morning. Milder temperatures and dry weather are expected into Tuesday. && .NEAR TERM /THROUGH TONIGHT/... 315 AM Update... Evolution and eventual end of ongoing lake effect snow will be the main forecast issue in the near term. Lake Huron to Lake Ontario connection became established over the last several hours, which on radar has stretched a 20-35 dBZ band of snow across Onondaga and Madison Counties, reaching in pieces to the Cooperstown area. Under the heaviest part of the band, 1 to 2 inch-per-hour snowfall rates are likely occurring. Visibility has been about a half mile at times at Syracuse and Rome overnight. As the lake-to-lake connection band became dominant, the earlier one in Oneida County dissipated. However, upstream the boundary layer flow is already beginning to back westerly as evidenced by the shifting band in western Lake Ontario. As flow continues to back across our region, there will be a lifting of the primary lake band northward along and then north of the NY Thruway this morning, which will get Oneida County back into the snow. All told, an additional 2 to 5 inches of snow is expected from 4 AM through early afternoon in the Lake Effect Snow Warning area, with locally higher amounts in far northern Onondaga-Madison Counties. The Warning goes through 1 PM, but Onondaga-Madison- Southern Oneida counties will probably be able to be dropped well ahead of that time as the band lifts. Lake Ontario has not produced the only action, however. Lake Erie has also caused band extensions to reach into the Twin Tiers and even the greater Wilkes-Barre/Scranton metro and the Poconos at times. The resulting dusting of snow, and temperatures falling below freezing causing ice within previously wet roadways, will mean slick spots still possible on untreated roads. Scattered snow showers and flurries will still occur at times this morning for Northeast PA-Southern Tier NY, and into the afternoon for the rest of Central NY. This will be courtesy of Lake Erie moisture as flow continues to back westerly to west-southwest with time. That being said, warm air advection aloft will cause compression of the cloud layer to significantly limit snowfall rates. Temperatures today will quietly sneak up in the mid 30s-near 40 for highs, which along with dry air and west winds gusting 15-25 mph, as well as ground temperatures still well above freezing; will tend to melt or sublimate the fluffy lake snow. Higher terrain of Central NY however will struggle to get above the lower 30s. Southwest to south flow, and warm air advection aloft, will lead to a clearing sky into tonight. Temperatures will settle into the upper 20s-lower 30s this evening, then hold fairly steady overnight. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Mild SW flow continues Tuesday as a low pressure system and associated upper level trough move across northern Ontario. Expect plenty of sunshine with highs mainly in the low 50s to even some mid 50s across the warmer spots such as the Wyoming Valley and western southern tier into the Lake Plain. The cold front associated with this low will move across the area after midnight Tuesday night bringing with it a swath of rain showers which will change over to snow showers in the cooler air behind the front. Not expecting this will amount to much accumulation....at most a coating to half inch, if that by Wednesday morning with any accumulation being mainly limited to higher terrain areas of central NY. The other complicating factor with this part of the forecast will be that some of the models (GEM and ECMWF) hook this front up with some moisture coming up from the south which could enhance precip a bit over eastern zones through the Catskills. This will have to be monitored for future updates. Lows by Wednesday morning will be generally in the low to mid 30s. For Wednesday, some lingering precip will continue to be possible into the morning with otherwise a mainly dry and cooler day behind the front. The one exception will be across northern counties where some weak lake effect snow will be possible around the I-90 corridor in the cold NW flow off the lakes however this doesn`t look to amount to much. Highs will generally range from the mid 30s to low 40s, mildest over NE PA and Sullivan County. High pressure builds in for Wednesday night setting the stage for a cold night under mainly clear to partly cloudy skies with light winds. Lows will be mainly in the low to mid 20s with some teens possible across the colder spots in Steuben County as well as the Catskills. The ridge of high pressure moves off to the S/E Thanksgiving Day but conditions stay mainly dry with sunshine giving way to some increasing late day clouds ahead of the next front approaching from the north. A developing W/SW flow could spark a few lake effect flurries late day north of I-90 but this should not be of any consequence. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... 320 pm update... Upper low moves from the Hudson Bay into Quebec Thursday night into Friday, bringing a cold front into the Upstate. We may see a little bit of light snow over (mainly) the northern tier of counties Friday in association with the front. By Friday evening, though, the boundary layer flow is expected to become southwesterly and set up a low-level warm advection pattern over the region as the front moves back north as a warm front. Forecast confidence wanes from there. Plenty of discrepancies are evident with regard to timing, evolution, and impacts from the next system. In general, expect precipitation probabilities to increase heading into next weekend as the upper-level storm system pushes a surface low from Ontario into Quebec. Depending on the upper trough`s amplitude, this could push the associated cold fronts through the region sometime between Saturday night and Sunday night. I`ve stayed fairly close to the model blend during this period given evolutionary uncertainty. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Lake effect snow will be winding down today, but the main Lake Ontario snowband will still impact KSYR and KRME through 14Z and 17Z respectively with below alternate minimum visibility at times. Scattered flurries will be found elsewhere, courtesy of Lake Erie moisture drifting by the area, but with few if any associated restrictions. VFR will become predominant across the region, with 4-6 kft agl ceilings lifting and scattering out with time. WNW winds of 9-12 knots, with gusts of 16-20 knots, will slacken while backing southwest late afternoon through evening. Though the sky will clear out into tonight, there will also be an increasing southwesterly low level jet of 35-40 knots which will cause development of low level wind shear for at least the NY terminals; it will be borderline for KAVP. Outlook... Tuesday...VFR. Tuesday night through Wednesday...Restrictions possible in scattered rain/snow showers. Wednesday night through Friday...Mainly VFR.
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&& .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...Lake Effect Snow Warning until 1 PM EST this afternoon for NYZ009-018-036-037. && $$ SYNOPSIS...MDP NEAR TERM...MDP SHORT TERM...PCF LONG TERM...DAB AVIATION...MDP

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