Area Forecast Discussion
Issued by NWS Binghamton, NY

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000 FXUS61 KBGM 121449 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 949 AM EST Thu Dec 12 2019 .SYNOPSIS... Lake effect snow showers north of the New York Thruway will gradually taper off through mid morning. Otherwise, high pressure will provide a period of dry weather for the region through at least Friday morning. Low pressure is expected to organize as it tracks up the eastern seaboard and bring rain to the area Friday night and Saturday. Rain may briefly end as snow late Saturday as the storm systems pulls away from the area. Another round of lake-effect snow showers is likely for the second half of the weekend. && .NEAR TERM /THROUGH TONIGHT/... Only minor adjustments to the forecast with the mid-morning update. Forecast discussion below on track. 4 AM Update... Overnight surface analysis shows a 1039 mb surface high centered to our south across NE MD-SE PA. Westerly flow around the high will subside this morning as the ridge axis that extends northward moves into the area. Latest GOES-16 satellite imagery shows a lake-effect cloud band extended eastward from Lake Ontario into our far northern zones of C NY (north of the NY Thruway). Despite poor radar coverage with KTYX radar down and other nearby radars overshooting the low-topped convection embedded within the LES band, New York State Mesonet (NYSM) webcams show light snow continuing to fall overnight across western and northern Oneida Co. (likely extending a bit southward into far northern Onondaga and Madison Counties. Snow depth readings at these same NYSM sites in far N/W Oneida Co. estimate 2-3" of snowfall since yesterday afternoon. An additional 1" or so is possible early this morning before the LES activity dissipate by late morning. Outside of the narrow lake-effect cloud band, subsidence under the high will allow for a sunny start to the day for most locations. Mid and high clouds will overspread the area from the west later this morning and afternoon as mid-level WAA and upper-jet dynamics arrive ahead of a weak disturbance. Forecast highs ranging from the upper 20s across the higher elevations of CNY to mid 30s in the Wyoming Valley are 4-8 degrees below normal. The center of the surface high shifts off the New England coast tonight although models do show the ridge axis noses southwestward along the eastern seaboard (indicative of cold-air damming along eastern side of the Appalachians). Southerly return flow aloft around the offshore ridge will continue to advect warmer air northward up the eastern CONUS. There are indications that a marine stratus deck develops along the Mid-Atlantic coast and expands northeastward into NE PA and the W Catskills by early morning. The southerly winds should keep the boundary layer decently mixed and prevent temperatures from bottoming out. Nonetheless, it will still be a seasonably cold night with lows in the lower to mid 20s (pockets of teens in the western Catskills and southern Tug Hill Plateau). && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... 645 AM Update... Quick update to account for the gradual northward retreat and overall weakening of the lake-effect snow band east of Lake Ontario. Additional snowfall amounts this morning in N/W portions of Oneida Co. should be under a half inch. Also updated the temperatures with a few sites in the Finger Lakes region (including ITH and NO3) dropping into the single digits. 4 AM Update... A complex storm system will initially be comprised of an area of low pressure over the Central Plains and another low centered along the northern Gulf-of-Mexico coast on Friday. A secondary low is expected to develop along a warm front/coastal front boundary along the Southeast Coast Friday night. Models still show this secondary coastal low deepening rather quickly as it lifts northward up the Mid-Atlantic coast early Saturday and through the upstate NY late Saturday. The track of the low still looks to be far enough inland to yield a mainly rain event for our forecast area. However, the leading edge of precipitation could potentially produce isolated pockets of freezing mainly across the higher elevations of the Poconos and western Catskills. This icing potential would be very brief (though models tend to erode the shallow cold wedge near the surface too fast in cold-air damming setups) and contingent on the precip arriving early enough in the day (late morning, early afternoon at the latest) for the residual cold air to still be in place. The steadiest rain looks to overspread the area late Saturday night and continue into Sunday morning. Based on the current QPF ranging between 0.75" and 1.25", not expecting much in the way of flooding issues with this event aside from localized poor drainage issues. Depending on the exact track of the low and how quickly wrap around precip shuts off, rain may end as snow once the colder air moves in on the backside of the system. There is uncertainty with the timing of a changeover but it could conceivably occur as early as Saturday afternoon across our far western zones. Models generally agree that the low will rapidly deepen while it passes by the area and moves roughly down the Saint Lawrence Seaway Saturday night into Sunday. The broad cyclonic wind field around it will thus enhance, which along with the steep boundary layer lapse rates of wrap-around cold air advection, will result in a brisk day Sunday. Westerly winds appear likely to gust frequently in the 25-35 mph range, with isolated 40 mph gusts not totally out of the question especially for the northern zones. After lows of around 30 to mid 30s Saturday night, temperatures move little Sunday under continued gusty cold air advection, resulting in highs of lower 30s-near 40. Steadier precipitation will diminish to scattered showers as Sunday carries on, before ending as the moisture lifts south to north. Type will be heavily reliant on elevation - mainly snow showers in high terrain and mainly rain showers in the valleys. Total snow Saturday night through Sunday will be pretty nominal for most locations, though northern Oneida County could end up with a few to several inches. Additional snow, of the lake effect variety, could occur north of the New York Thruway Sunday night as 850mb temperatures briefly dip into low to mid teens Celsius below zero in west or west-northwest flow. Lows Sunday night will be mainly 20s, except for mid teens in northern Oneida County. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... 4 AM Update... With our active pattern continuing unabated, a brief break much of Monday, is likely to give away to another system moving southwest to northeast through the general area late Monday into Tuesday. All models have the system yet differ in whether tracking the primary low just south of the area as per the ECMWF, or further northwest like the GFS-Canadian models. However, even the relatively cooler ECMWF manages to get above freezing at 850mb for a sizable chunk of the area. A snow to wintry mix scenario is anticipated for Monday night into Tuesday. There could be some snow and/or ice accumulations with this, but things could easily change considering it is quite a ways out; we will better figure out the details in coming days. It could quickly transition to rain with a northwest track, or remain mostly snow-freezing rain mix with southeastern one. However it works out, a piece of Arctic air is projected to dip behind the system into our area as we head into Midweek. As usual, this scenario could produce lake effect snow. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Lake-effect snow showers have finally pushed north of RME. However, forecast soundings show MVFR CIGs lingering at RME through the late morning. Elsewhere, VFR is expected today with mid- and high-level clouds streaming into the area. Winds vary between NW and SW early this morning but speeds continue to decrease (generally under 7 kt) as the pressure gradient relaxes. Winds back more out of the S this afternoon with speeds below 10 kt. Mainly VFR tonight with a strengthening southerly return flow. Winds at the surface look to increase to 8-13 kt this evening with occasional gusts near 20 kt favored at our NY terminals. Forecast soundings show a strengthening SW low-level jet to near 50 kt at 2 kft AGL for our western-most terminals (SYR, ITH, and ELM). LLWS was added with the 12Z TAFs for these western terminals. Outlook... Friday...Low clouds with CIGs borderline IFR-MVFR criteria may try to sneak into our S/E terminals (AVP-BGM-ELM) just before sunrise Friday morning. These low clouds may expand farther N/W throughout the day with rain moving in late. Friday night and Saturday...Flight restrictions expected in periods of rain. Saturday evening through Sunday...Continued flight restrictions into Saturday night. Rain may changeover to snow from W-E before it ends Saturday night. Gradual improvement in CIGs expected on Sunday as the steady snow ends. However, lake-effect snow showers will result in more localized restrictions, especially for NY terminals. NW winds will be breezy. Monday...VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...JRK NEAR TERM...JRK/MWG SHORT TERM...JRK/MDP LONG TERM...BJG/MDP AVIATION...JRK

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