621 FXUS61 KBGM 110000 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 700 PM EST Sun Dec 10 2017 .SYNOPSIS... Scattered snow showers tonight, mainly in central NY, with a period of locally heavy snow in northern Oneida county. Quiet on Monday before a clipper system brings potentially significant accumulating snow Monday night through Tuesday. There will also be a period OF lake effect snow Tuesday night through Wednesday night that could bring additional significant accumulations to Central NY. && .NEAR TERM /THROUGH MONDAY/... 645 pm update Adjusted the forecast based on the latest radar/hi-res model trends for the lake effect snow tonight. Tried to tighten the PoP gradient, indicating the highest chances for snow across northern Onondaga and Oneida counties for the first half of tonight. Then, late tonight or early Monday morning a subtle, low level arctic frontal boundary will cross Lake Ontario and move into the northern portion of our CWA. It is likely this feature will pick up the ongoing LES band over Lake Ontario and push it inland (south), toward Syracuse/Rome...at least briefly early Monday morning. Winds will shift to the northwest behind this front over the northern third of the forecast area...the front will wash out and dissipate before reaching the NY/PA border. The snow shower activity could briefly make it south to around Penn Yan, Ithaca and Cortland before tapering to flurries mid-morning Monday. Further south, it should remain dry but mostly cloudy through the near term period. Snow accumulations tonight into Monday morning will range from 2-4 inches in far northern Oneida County (where the winter weather advy for lake effect snow continues)...to 1-2 inches for Syracuse and Rome and less than 1 inch elsewhere. Overnight lows dip into the lower to mid-20s areawide. Highs on Monday will be in the mid to upper 20s north...with lower to mid-30s across our PA zones. 245 pm update... Main forecast concerns in the near term remain focused on the scattered snow showers across central NY and ne PA this afternoon and evening, and the return of a lake effect snow band off Lake Ontario into the Thruway in central NY tonight...tapering off Monday morning. A Winter Weather Advisory for Lake Effect Snow remains in effect for northern Oneida county...through 7 am Monday morning. Conditions continue to be favorable for snow showers this afternoon as strong cyclonic flow in a very cold air mass persists. Intense LES bands downwind of Erie and Ontario continue as of 3 pm this afternoon...and large scale, scattered snow showers linger over a good portion of central NY and far ne PA. Boundary layer has become deep enough to entrain some dry air aloft...which is acting to mix some of the cloud cover out. As this occurs though, the BL is able to heat up and slowly becomes more unstable which produces more clouds and snow showers as a result. The flow is expected to back to the sw this evening and as that occurs, the LE bands will shift further to the north. The diurnal heating will weaken this evening as well with the loss of sun, and allow the scattered snow showers to taper off. So...most of the late evening and early overnight hours may be quiet and cool with temperatures tonight falling into the low to mid 20s. Later tonight and Monday morning the flow will veer back to the w/nw and shift the Lake Ontario band back into central NY. As this occurs though the inversion heights will fall below the DGZ...which will act to diminish the snow production significantly. The LES band will likely become diffuse and weak Monday morning before falling apart altogether. However, there will likely be a period tonight across portions of Oneida county where the snowfall rates ramp up for a brief period of time and drop an additional 1 to 3 inches on top of the 1 to 3 they already received earlier today. Other areas to the south will likely see an inch or less. The rest of Monday looks quiet and on the cool side with highs only into the upper 20s across the north, and the lower to mid 30s in ne PA. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/... 330 PM Update Model guidance is showing increasing confidence in a low pressure system moving across NY Monday night into the day on Tuesday. The latest guidance tracks the center of the surface low over Lake Erie, then to a position near Rochester by Tuesday morning. Ample warm air advection precipitation(snow) is forecast to develop out ahead of this low pressure system, beginning late Monday evening for much of our forecast area. With the track of the low to our north, this will keep surface winds out of the south-southeast and breezy at times (10-20 mph). This type of flow will keep some areas downwind of the higher Catskills and especially Poconos shadowed from the higher precip/snow rates. By midday Tuesday the surface low begins to jump, and reform along the New England coast. This could allow for some enhanced wrap around snowfall to impact the far eastern portion of our CWA during this time...but the snow will really pick up just off to our east...over far eastern NY and New England. Right now, storm total snowfall from this first system is forecast to range from about 1-3 inches for our NE PA zones...with 2-4 inches for our NY zones...except 4-8 inches in Oneida County where the southerly flow upslopes in the Southern Tug Hill plateau. Will hold off on any winter headlines at this time, and let the evening/overnight shift take another look at the latest model guidance trends. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... 330 PM Update...Closed mid/upper low moves overhead Tuesday night into Wednesday as strong cold air advection continues. This will bring lake effect/enhanced snows across much of the area with a northwest flow and deep moisture. Best chance for potentially significant accumulations will be over over the higher ground of central NY, particularly the Finger Lakes but expect measurable snow down into NEPA as well. It is likely that headlines will eventually be needed for parts of the area for this event. Preliminary forecasts point to the potential for 3-6 inches of snow across most of our NY zones...with locally higher amounts were the lake bands set up. Amounts during this time will be lighter in NE PA, and could range from 1 to 3 inches, mainly in the higher terrain. Little change through Wednesday as 850 mb temps bottom out near -18C over the area and the NW flow lake snows continues. Flow becomes more westerly and relaxes on Thursday so snow showers will taper off. However, unsettled weather will continue through Friday with trofiness aloft, a clipper moving into the Great Lakes, and systems running up the coast to our east. Confidence in forecast is low to moderate until Friday when global models diverge quite a bit on positioning and timing of disturbances diving around the base of the trof and interacting with the front along the coastal plain. Chance PoPs during this time and some moderation of temperatures with flatter flow and slight warm advection. Temperatures look to potentially warm above freezing into the mid-30s to lower 40s by next Sunday, as a storm system passes by well to our north. This system will bring chances for rain and snow showers, and perhaps some mixed precipitation. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Expect mainly VFR or MVFR conditions to persist through the overnight hours with just a few flurries around. The exception to this will be at KSYR and KRME, where periods of snow showers will continue until Monday morning and will create MVFR to occasional IFR CIGS/VIS. Snow will taper off between 13-16Z Monday morning at KRME and KSYR, with conditions returning to VFR here after that time. Winds will veer to the nw later tonight as a frontal boundary drops down from the north. This wind shift will mainly be felt at KSYR, KRME and KITH...but could also briefly make it south to KBGM and KELM. Wind speeds will mainly be from 7 to 15 kts tonight into Monday morning. Monday afternoon winds become light and variable, before shifting to the south-southeast Monday evening and increasing. Outlook... Monday afternoon...Generally VFR. Monday night through Tuesday...A period of snow likely with restrictions as a clipper system moves through the region. Tuesday night through Friday...Snow showers and associated restrictions, mainly NY terminals due to lake effect. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...Winter Weather Advisory until 7 AM EST Monday for NYZ009. && $$ SYNOPSIS...BJT/MJM NEAR TERM...BJT/MJM SHORT TERM...MJM LONG TERM...MJM AVIATION...BJT/MJM