Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 191950 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 350 PM EDT Sat May 19 2018 .SYNOPSIS... A warm front will bring widespread rain showers to the North Country mainly this afternoon. Scattered showers and a slight chance of thunder are expected tonight as temperatures warm overnight. Sunday morning a frontal system will pass through the region with showers ending and some clearing behind it for Sunday afternoon with temperatures in the 60s to around 70. High pressure quickly builds back in to start the work week with above normal temperatures and dry weather. && .NEAR TERM /THROUGH SUNDAY/... As of 123 PM EDT Saturday...No changes were needed with this update. Rain is spreading across the region at this hour, though it may take a bit for the leading edge to reach the ground. Temperatures are currently in the upper 50s to mid 60s and should warm another few degrees this afternoon. The forecast has this covered, so have just made some slight adjustments to temps to match the latest observations. Previous discussion...Clouds starting to increase this morning ahead of a warm front. Expecting breezy south winds associated with developing low level jet of 20 to 30 knots at 1000 feet. This jet will help to increase moisture with clouds lowering and thickening during the late morning. Mainly light rain showers should arrive between 10-noon south and noon- 2pm central and 2-4pm near the international border. Some downslope shadowing is possible in the Champlain valley with developing 850mb southwest jet of 40 to 50 knots off the Adirondacks. Temps warm into the 50s south to mid 60s north through midday, but cool back into the lower to mid 50s this afternoon after the rain arrives and wet bulb cooling takes place. Rain will become more showery in nature Saturday night as the best warm advection and overrunning lifts northeast of the area by the evening hours. Some of the area, especially in northern NY may get into the warm sector while east of the Greens its less likely. South to southwest winds pick up in the Champlain Valley westward with a low level jet aloft with gusts of 20-30 mph. Shower chances become less early tonight as the warm sector aloft and dry slot moves in tonight there could be a period during the night without much going on before a cold front approaches the St. Lawrence Valley by early Sunday with an increase in precip probabilities. Models continue showing some CAPE to around 250 J/kg, mainly elevated, while the GFS is less. The Showalter index is slightly negative and Ks in the 30s, so a rumble of thunder is not out of the question and have slight chance in the forecast but coverage is low. Simulated satellite from the BTV WRF continues to show some embedded convective cells in the warm sector on the edge of the warm front aloft and the cold front closer to the St Lawrence Valley. The cold front on our doorstep by 12z Sun with showers ahead and along the front but clearing behind. The front will move steadily southeast Sunday with a decreasing probability of precipitation from northwest to southeast but should clear most of our area by early afternoon. Timing will play a role in the instability ahead of the front and indications are that some weak instability will develop mainly southeast VT (near VSF) and points south. Again MUCAPE only near 250 J/kg so not including thunder for Sunday morning. Looking like about a half inch of rain is expected with locally 0.75 in any heavier showers or embedded thunderstorms. Temperatures Saturday night will be steady or rising ranging from early evening lows the upper 40s east of the Greens to mid to upper 50s in the St. Lawrence valley rising through the 50s to around 60 by Sunday morning. Gradual clearing is expected on Sunday afternoon behind the front with NW winds of 10 to 20 kts and high temperatures close to normal with readings in the mid 60s mountains to lower 70s in the lower Champlain and CT valleys. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
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As of 350 PM EDT Saturday...A quiet start the work week is expected for Monday as surface high pressure builds into the region along with abundant sunshine. Aloft we remain in west/northwest flow with a departing upper trough to the northeast so winds will be brisk in the 10-15 mph range, but with steep low level lapse rates and 925mb temps in the mid teens above zero celsius, it`ll feel pretty good out there with surface temps warming into the 70s area-wide. Monday night begins clear with winds dropping off supporting excellent radiational cooling, but after midnight high clouds will be on the increase making the min temp forecast tricky. Trended towards colder guidance thinking high clouds will only slightly temper cooling, with lows generally ranging from the mid 40s to low 50s. On Tuesday, the main idea is that a weak shortwave trough will traverse the region during the afternoon and evening hours, but confidence is low on precip potential due to difference in guidance on the northern extent of deeper moisture. Think there will likely be some isolated showers around but will offer chance pops for now based on uncertainty. Highs will generally be in the 70s again, with milder overnight lows in the upper 40s to mid 50s.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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As of 350 PM EDT Saturday...Overall, next week looks rather dry as behind the aforementioned shortwave trough passage, high pressure builds in for the remainder of the week through Friday. We potentially get a glancing blow of cooler air from an upper trough passing northeast of the region Wednesday, but highs will still be in the upper 60s to low 70s, which is right about normal for this time of year. Slightly warmer temperatures are expected for Thursday and Friday, before our next chance for precipitation comes Friday night into Saturday. Increasing southwesterly flow between Bermuda high pressure and a cold front pushing into the upper Mid-West will potentially tap into rich Gulf moisture Saturday afternoon, with the wildcard being the juxtaposition of a potential tropical system as depicted in the 12Z GFS. Time will tell on how this all plays out.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/... Through 18Z SUNDAY...VFR conditions will give way to MVFR ceilings as light rain associated with an approaching warm front spreads into the region this afternoon. Ceilings will drop to 1500-2500 ft over the next couple of hours, then remain so through a good part of tonight into Sunday morning, though there will be a break in the rain for a bit on either side of midnight. Local IFR will be possible late tonight, particularly at KSLK. Conditions will improve from west to east late Sunday morning as precipitation ends behind a cold frontal passage. Winds will increase from the S this afternoon around 10-15 kt with gusts up to 20 kt or so. Gusts should be limited after 18z during the rain, however the exception may be RUT with may maintain gusty SSE winds through 00z. Areas of LLWS and turbulence area expected after 03z around 2000 ft but lowering to 1000 ft with the warm front aloft with a strong 35-50 kt SW jet just above the surface. Outlook... Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Slight chance SHRA. Tuesday Night: Mainly VFR, with areas IFR possible. Chance SHRA. Wednesday: Mainly VFR, with areas MVFR possible. Chance SHRA. Wednesday Night: VFR. Slight chance SHRA. Thursday: VFR. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Hastings/Sisson SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Hastings/Sisson

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