Area Forecast Discussion
Issued by NWS Binghamton, NY

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815 FXUS61 KBGM 280547 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 1247 AM EST Tue Feb 28 2017 .SYNOPSIS... Coastal high pressure will keep temperatures mild into the middle of this week. A strong storm system moving out of the central United States will drag showers and thunderstorms across New York and Pennsylvania on Wednesday. Colder air will follow for the end of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... National radar mosaic shows patchy light echoes heading toward northeast PA and central NY. This very light precipitation and/or virga was associated with a shot of warm air advection. Since moisture was lacking we don`t expect much from this first batch. Water vapor imagery shows an upper level wave moving rapidly into the Ohio Valley and Lower Great Lakes. This feature will enhance warm air advection/isentropic lift into the overnight hours as it moves through and increase chances for sprinkles/flurries or even light rain/snow showers. We don`t see any snow accumulations as precipitation will be light and boundary layer temperatures marginal. Made just a few minor changes to the previous forecast. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/... A trough over the central U.S. will strengthen on Tuesday, and another disturbance will shoot out of the upper level flow and move across our region. A very warm air mass will push into NY/PA (+8C 925 mb), and breaks of sunshine are forecast for Tuesday afternoon once the warm front passes. Highs will reach well into the 50s for most areas in southerly flow with some areas potentially even reaching the lower 60s depending on how much sun occurs. The warmest areas will be the lake plain and the valleys of NE PA. Pattern becomes increasingly stormy heading into Tuesday night and Wednesday. The next wave will bring increasing clouds with chances of showers returning by late Tuesday into Tuesday night with another wave likely bringing more showers later at night toward 12z Wednesday. Forecast models indicate elevated instability creeping in overnight with theta-e ridge and very strong LLJ at 850 mb near 50 knots so we have added the slight chance of thunder beginning overnight Wednesday continues to look interesting as far as possible severe weather potential but there is still a lot of uncertainty in the forecast due to the early AM clouds and showers which may limit destabilization. In terms of details, slowly amplifying trough moving ewd across the central US early Wednesday morning will combine with ridging aloft and strong WAA across the mid- Atlantic region and become the focus of convective showers and storms over NY and PA Wed midday into the afternoon and evening. Much of ne PA and central NY will be situated within the warm sector of a low passing through Ontario with temperatures reaching into the 60s...possibly to near 70 again in some spots. NAM indicates ML CAPE values topping out around a few hundred J/kg to possibly as high as around 1000 j/kg over NE PA with the GFS showing lower values. Again tricky forecast as AM wave will bring showers and possible storms with the better chance of stronger storms occurring in the afternoon as a more organized pre-frontal area of showers and thunderstorms may develop. Both low level and deep layer shear values will be very impressive with models showing 0-1/0-3/0-6 km values of 35/45/70 knots. Also, 0-1 km helicity values will likely be near 300 m2/s2. The question will be instability...if enough is realized the potential would be there for a scenario similar to what happened Saturday but this is far from certain. The potential hazards are damaging winds, hail and maybe a tornado or two not out of the question. May also see the potential for additional flash flooding as PWATs hover around 1 inch, and the threat for quick heavy downpours develops in the convection. Flash flood guidance is still very low for portions of s-central NY and ne PA due to the recent snow melt and also the 1- 1.5 inches of rain this area received on Saturday. So, with saturated soils any additional heavy rainfall will not be able to infiltrate the ground and become runoff. This all said, will continue to highlight hazards in the HWO and also note that SPC maintains area in a marginal risk for severe weather Wednesday. Should forecast confidence increase in severe weather, this could be upgraded. After the front moves through Wednesday night, temperatures will drop sharply with showers/storms possibly ending as snow showers. There will also be strong, gusty winds behind the front on the synoptic scale due to strong pressure gradient on the backside of departing low. Temperatures bottom out in the 20s to low 30s Wednesday night and won`t rise much Thursday with some lingering snow showers. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Period begins with the NE US in a deep trough and a cold NW flow of air. Lake effect snow showers will continue into Friday morning just to be followed by a shortwave clipper system dropping through the Great Lakes. This will re-energize the lake effect with 850mb temps still around -20C. Wave exits early Saturday allowing high pressure to build into the area. This should a mostly sunny day as ridging builds aloft ahead of system deepening over the northern plains. Warm front pushes late Saturday and early Sunday developing some weak isentropic lift. Best support for precipitation will remain north and west of the area but some light snow is certainly possible overnight. Still enough cold air to allow frozen precipitation. Later Sunday, warm air advection going again in full force with strong ridging aloft and weak surface high pressure.This should allow for a mainly dry day for the end of the weekend. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Mainly VFR/unrestricted conditions are again foreseen through the valid TAF period. By later Tuesday evening (02-03z Wednesday onward), an area of showers and lower ceilings could begin to impact KAVP, KELM, and KBGM. MVFR-fuel alternate restrictions were introduced at this point. E-SE surface winds around 5 kt overnight and early Tuesday, will turn S-SE at 8-10 kt for most of Tuesday, before becoming gusty at a couple of sites Tuesday evening (20-25 kt gusts, namely KITH and KSYR). LLWS could become a concern later Tuesday night, but likely not until after 06z Wednesday. OUTLOOK... Wednesday...Occasional restrictions likely in rain showers and thunderstorms. Thursday/Friday...Possible restrictions in snow showers. Saturday...VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...PCF NEAR TERM...DJN/PCF SHORT TERM...PCF LONG TERM...DGM AVIATION...DGM/MLJ

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