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Area Forecast Discussion
Issued by NWS Binghamton, NY
Issued by NWS Binghamton, NY
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --978 FXUS61 KBGM 201804 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 204 PM EDT Tue Aug 20 2024 .SYNOPSIS... Cool and breezy conditions are expected this afternoon into Wednesday with scattered lake effect rain showers this afternoon and isolated thunderstorms Wednesday afternoon. Quieter and warmer conditions are expected for the second half of the week. && .NEAR TERM /THROUGH WEDNESDAY/... 1230 pm Update... Radars show scattered showers forming downwind of Lake Ontario mainly around Onondaga County to the highlands northeast of BGM. Around this area, there were more isolated showers or sprinkles with little if anything in northeast PA. The low-level flow was northwesterly around 320 to 330 degrees and with Lake Ontario surface water temperatures around 22C we are seeing lake effect/enhanced rain showers develop with the days heating. There was an upper level low over southwest Quebec with some synoptic moisture wrappring around it as well into central NY. Unseasonable low 850 mb temperatures were advecting southeast across NY and PA with 850 mb temperatures down to +4C this afternoon leading to an 18C differential with the Lake Ontario temperatures. So we have scattered lake effect rain showers mainly in central NY downwind of Lake Ontario with sprinkles elsewhere. Made some adjustments to previous forecasts mainly for POPs based on current radar data. 915 AM Update... For this update, tweaked POPs for lake enhanced rain showers based on current radar trends. Only minor changes needed. Upper Level low was dropping southward from southern Quebec and will combine with low-level northwest flow across Lake Ontario to produce scattered rain showers and sprinkles downwind into central NY and northeast PA. 603 AM update... Still seeing some very light echoes dropping north to south from either Lake Ontario or the Finger Lakes or both in the form of very light rain or drizzle. No significant changes made to the forecast at this time. 333 AM update... Main concerns in the near term are centered around the lake effect clouds and light rain showers on and off today, followed by additional chances for lake effect showers tonight and through the day Wednesday, along with afternoon weak thunderstorms with potentially some graupel or small hail. Cold core upper level low currently situated over southern Quebec this morning with a steady flow of cool Canadian air advecting south on the back side of the low over southern Ontario and and eastern Great Lakes. This air mass dropping in from the north has a relatively deep layer of dry air aloft, but has been able to tap into the warm waters of Lake Ontario to generate low level lake effect clouds south of the lake. 850mb temperatures around +2 to +3 deg C, combined with lake sfc temps around 21 deg C will continue to be sufficient for inland lake effect moisture in the form of clouds and light rain showers today into tomorrow. It will definitely feel more like fall today with highs in the 60s, plenty of strato-cumulus clouds, and brisk N/NW winds gusting to 20 mph. Some breaks in the clouds this afternoon should induce only a weak amount of low level instability...enough to regenerate the low clouds and keep the light rain showers going. Model soundings are hinting at a mid level capping inversion that, if simulated correctly, will keep a decent lid on any widespread precipitation, at least today. The chances for rain increase tonight as the upper low over southern Quebec drops S into northern NY. The favorable position of this upper level feature, combined with a compression of the boundary layer and most of the moisture in the low levels being concentrated in the lowest 10kft will allow the chances for rain showers to increase (up to 40-60 pct chance) late tonight and early Wed morning...mainly over the Finger Lakes and adjacent areas of the southern tier of NY. The potential for scattered showers in addition to weak thunderstorms continues through the day Wednesday as the upper low tracks east into VT/NH. A deeper and more moist air mass will be entrained into the system by Wed afternoon , and when combined with the large scale forcing and the cold temperatures aloft/steep lapse rates, the threat for thunderstorms increases. The storms should be relatively low- topped...up to 20kft or so, but given the wet-bulb zero height around 6000 ft, it should not take much to generate small graupel or hail and subsequently a few lightning strikes. The most favorable time for TS will be in the afternoon when the boundary layer will be the most unstable. Sfc based CAPE values 100-300 J/kg are possible. The convection is expected to subside around or just after sunset. Daytime high temperatures on Wed should be only into the lower to mid 60s once again, with breezy NW winds 10 to 20 mph. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/... A broad upper level low will continue to slowly move northeast across New England Wednesday night and Thursday. However, west to northwest flow will continue to bring in some clouds and sprinkles or light showers to portions of central New York. Coverage decreases with the low now departing. As is typically the case, the NBM is likely way to fast with clearing on Thursday. A very chilly airmass should continue to be present under the upper level low with morning temperatures near 50 and highs struggling to 70 for most of the area. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... High pressure then builds into the area Thursday night. With clear skies, light winds and residual moisture fog could develop and become widespread toward sunrise Friday. Temperatures start a warming trend going from near 50 well into the 70`s. Our region then ends up on the front end of an omega block late this week into early next week. A few ensemble members try to sneak a disturbance from the north into the region at some point early next week. However, the majority of members are dry at this point each day. An overall warming trend should continue with humidity starting to edge upward as the airmass moving in is more seasonable. Still highs in the low to mid 80`s with lows around 60. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...-- Changed Discussion --Conditions were mainly VFR across all terminal sites with mainly BKN celluar cumulus and a few rain showers. There is a chance that at KSYR, KITH and BGM that a shower could drop ceilings to MVFR this afternoon. Then into this evening, conditions should remain VFR for the most part with MVFR ceilings coming in later tonight as an upper level low drops southward. Winds will be northwest around 8 to 13 knots gusting between 15 and 20 knots through the day this afternoon...before subsiding below 5 kt after 00Z this evening. .Outlook... Wednesday night...Mainly VFR with intermittent MVFR cigs. Afternoon showers and isolated weak thunderstorms are possible with small hail or graupel not out of the question. Thursday through Sunday...Mainly VFR with high pressure over the region.-- End Changed Discussion --&& .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...BJT/DJN NEAR TERM...BJT/DJN SHORT TERM...MWG LONG TERM...MWG AVIATION...DJN