725 FXUS61 KBGM 171729 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 1229 PM EST Tue Dec 17 2019 .SYNOPSIS... A low pressure system will bring snow and a wintry mix to the area today as it slides through the Mid-Atlantic region. It will turn much colder with numerous snow showers and possible snow squalls on Wednesday as an arctic cold front moves through. Below zero wind chills expected Wednesday night into Thursday. && .NEAR TERM /THROUGH WEDNESDAY/... 1025 AM UPDATE... Radar composite shows more cellular precipitation over the southern 3/4 of the forecast area with patch coverage. CAMs show this trend continuing through the morning and into the afternoon with still some patches of heavier precip. Thermal profile gradient has stabilized and I do not expect any further northward push of the milder air, and in fact it should start to retreat to the south and east later in the day as the low passes off to the east. While the heavier precip has passed, will continue with the Advisories where they sit as patch freezing rain and snow will continue and roads will likely remain slippery, especially considering that temperatures are well below freezing over most of the area. 640 AM Update... Snow and mix line continues to hug the Route 17 corridor, but is very gradually continuing to nudge north. NE PA now has a mixture light freezing rain, freezing drizzle and sleet pellets. North of the NY southern tier, the rest of CNY will continue to see periods of light to moderate snow through the day. There will be a tight snowfall gradient along the Route 17 corridor, with totals of just 1-3" along the immediate NY/PA border region...then higher amounts of 3-6 inches across the rest of CNY. NE PA will not see much if any additional snow accumulations, with just coatings to additional sleet. The main impact here will be from continued periods of freezing rain and icing; with up to two- tenths of an inch of ice expected. The freezing rain will likely transition to plain rain in the Wyoming Valley, south of Scranton by late morning or midday. The rest of the near term forecast remains on track. 400 AM Update...Current observations and KBGM CC radar data shows mixing (sleet and freezing rain) marching north; now along and south of the route 17 corridor. North of here, into the central NY light to moderate snow was falling. Considering the latest observations and trends in the latest guidance...lowered snow amounts further across NE PA, where there will be more ice and sleet. Ice accumulations between 0.10 and 0.25 inches are now expected across the Poconos, southern Wayne county, Pike county and into Sullivan county NY. Still expecting a stripe of higher snow amounts just north of where the longer duration mixing takes place...current best projections put this band of 4-7" snow totals just north of I-86/Rte 17, up the I-88 corridor then bounded to the north by US-20. North of US-20, this storm will be all snow, and with higher snow to liquid ratios, still looking for totals of 3-6 inches by this evening. Current winter weather advisories look good and are well on track. Snowfall totals will be lower than initial projections across much of NE PA and Sullivan county NY...but the ice and sleet here could sill impact travel. Surface temperatures are expected to hover in the mid 20s to lower 30s all day....except they could break the freezing mark, rising into the mid-30s in the Susquehanna, Lackawanna and Wyoming Valleys of NE PA. There is still a low chance that a narrow stripe of locally higher snow amounts develops across central NY, which could push warning criteria (6-8") but at this time feel this potential is too low, and would be very localized. The snow and mixed precipitation tapers off from SW to NE this afternoon or early evening. Much colder air aloft and eventually at the surface begins to filter into the area on a NW flow this evening. 850mb temperatures fall to around -10C by 10 PM. Surface convergence develops, which should aid in the development of an organized, NW to SE oriented, lake effect snow band off of Lake Ontario by late evening. This snow band will likely impact Onondaga, northern Madison and Oneida counties for a period of time. It looks to be rather transient, lifting off to the north during the overnight as winds back more westerly. This should limit accumulations, but could still see a quick 1-3 inches locally. The rest of the forecast area will be mainly dry tonight, with perhaps just a few flurries around. Breezy northwest winds 8-15 mph turn west, the eventually southwest toward daybreak. Wednesday: Surface low pressure system (a clipper) passes by to our north across Ontario Canada in the morning. Out ahead of the arctic cold front winds turn southwesterly for a time...but the cold air aloft will still be in place, so expect a spray of lake effect snow showers off of Lake Erie to move into our western zones early to mid-morning. Then, the strong arctic cold front marches across the area late morning to early afternoon. There is good model agreement that parameters will be very favorable for convective type snow showers and squalls as the front passes through. Latest guidance is showing steep low level lapse rates in the boundary layer (up to 10k ft agl), between 50-120 J/kg of most unstable CAPE, strong pressure rises and low level winds up to 30 kts. Do not think there will be enough instability in a deep enough layer for any thunder, so removed from the forecast for now. These will bring the potential for brief heavy snow, significantly reduced visibility, and blowing snow. Snow amounts will not be particularly heavy, only up to 2 inches or so through the day...but travel could certainly be impacted from the low visibility and roads quickly becoming snow or ice covered. Surface temperatures briefly rise into the mid-20s to lower 30s out ahead of the front...but then quickly fall through the 20s and into the teens by late afternoon. Northwest winds 15-25 mph with gusts up to 35 mph will create areas of blowing/drifting snow by late afternoon and evening, along with wind chills around 0 to 10 above by sunset. 850mb temperatures fall to near -20C by evening. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... An Arctic front will pass east of the region Wednesday night. West-northwest winds will continue to pull lake effect snow showers across Upstate NY, but accumulations should remain on the light side due to strong low level shear and falling dew points. Temperatures will fall into the single digits in the Twin Tiers. Wind chill values of -5 to -10 are forecast across the region. The subsidence inversion will fall by Thursday as high pressure slides across the region. Light snow showers will persist as temperatures reach the 20s. High pressure will yield clear weather Thursday night. Temperatures will fall into the single digits. && .LONG TERM /FRIDAY THROUGH MONDAY/... High pressure will remain in control of our weather on Friday and Saturday. Quiet weather is expected as temperatures rise into the 20s on Friday and to near 30 on Saturday. A weak wave could bring a stray snow shower to Northern NY on Sunday. Otherwise, fair weather will continue. Temperatures will slowly rise through the period, reaching the upper 30s on Monday afternoon. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Messy weather bringing IFR and LIFR conditions to the TAF sites. Low level clouds and moisture associated with the low moving up the coast will keep the low conditions in the area this afternoon, with snow at times and freezing rain at BGM and AVP. Drier air begins to filter in tonight as the low exits so conditions begin to rise and many locations reach VFR levels overnight. Strong arctic front sweeps through on Wednesday bringing snow squalls and briefly lower conditions near the end of the TAF period. Outlook... Wednesday night...MVFR/IFR restrictions with snow showers and squalls in CNY. MVFR AVP. Thursday...VFR. Possible restrictions in CNY due to lingering lake effect snow showers. Thursday night through Sunday...VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 4 PM EST this afternoon for PAZ038>040-043-044-047-048-072. NY...Winter Weather Advisory until 4 PM EST this afternoon for NYZ022-024-055>057-062. Winter Weather Advisory until 6 PM EST this evening for NYZ015>018-023-025-036-037-044>046. && $$ SYNOPSIS...DGM/MJM NEAR TERM...DGM/MJM SHORT TERM...DJP LONG TERM...DJP AVIATION...DGM/MJM