Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 271748 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 148 PM EDT Sat May 27 2017 .SYNOPSIS... Memorial Day Weekend looks to start out great with dry weather and fair conditions expected for today and Sunday along with a warming trend. The back end of the weekend will see showers returning to the area late Sunday night into Memorial Day. A pattern change will see slightly cooler temperatures and a chance for showers almost each day next week. && .NEAR TERM /THROUGH SUNDAY/... As of 148 PM EDT Saturday...Shallow cumulus forming over the mountains this afternoon as steep low level lapse rates have developed. Vertical depth of moisture is limited...so feel convective potential is limited as well. Thus have removed the slight chance of showers wording from the forecast for Essex county New York. Otherwise...going forecast in good shape and no other changes needed. Previous discussion... High pressure builds into the region for most of the Memorial Day weekend. This will lead to a warming and drying trend for today into Sunday. Lingering clouds will remain around through mid-afternoon today before more discernible clearing happens overnight into Sunday morning. The dry and warmer weather continues on Sunday as the high pressure ridge crests over the area bringing another day of fair conditions. High temperatures for Saturday will be in the upper 60s to low 70s while overnight lows will be in the mid 40s to low 50s. With Sunday`s decreased cloud cover and weak southerly flow, high temperatures mid to upper 70s with some valley locations possibly touching 80. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/... As of 328 PM EDT Friday...Will see another pattern change beginning Sunday night as 700mb shortwave ridge translates ewd into the Gulf of Maine and broad/closed mid-tropospheric low shifts slowly ewd across the Great Lakes region and Ontario. Onset of mid-level height falls and developing cyclonic flow aloft occurs during Sunday night, though the 00Z ECMWF is about 6 hrs slower than 00z GFS with arrival of shortwave trough/vorticity max embedded in swly flow moving into the North Country. Have gone with more consistent GFS timing for now, which means likely PoPs (70%) for showers into nrn NY during the pre-dawn hrs Monday, with chance PoPs (30-50%) across VT. It appears that best synoptic/QG forcing will occur during Monday morning, with widespread shower activity associated with strongest 850mb WAA. Overall QPF generally 0.25" - 0.50". Should see partial clearing occurring later in the day Monday as 850mb warm front shifts north and east of the region. Can`t rule out a few additional late day showers with weak surface based instability possible. Have included slight chance of thunderstorms late in the afternoon for the St. Lawrence Valley area and s-central VT. 00Z GFS SBCAPE values reach 600 J/kg at KMSS at 21Z/Mon. In terms of temperatures, the increasing clouds will keep overnight lows mild Sunday night, generally in the low-mid 50s (except upper 50s in the St. Lawrence Valley). There is an increase in S-SW gradient flow, reaching 10-20 mph after midnight in the Champlain and St. Lawrence Valleys. This will also help with low-level mixing, keeping temperatures from dropping significantly. A lake wind advisory may ultimately be needed for Lake Champlain later Sunday night into Monday morning associated with this increase in southerly gradient winds. With only partial clearing expected later Monday, high temperatures will range from the low-mid 60s across central/ern VT, the upr 60s in the Champlain Valley, and mid 60s (Adirondacks) to lower 70s (St. Lawrence Valley) across northern NY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 328 PM EDT Friday...Large mid-upper level low pressure system will be our controlling weather feature through much of the long-term period. This vertically stacked system will drift slowly ewd from the nrn Great Lakes/Ontario Monday night, ewd into wrn Quebec by Thursday. Northern NY and New England will be embedded in associated cyclonic flow, with several shortwave troughs crossing the region from WSW-ENE Tuesday through Friday. It appears the best chance for shower activity will generally be during afternoon periods, with combination of relatively steep mid-level lapse rates and surface heating resulting in shallow instability and shower development. Have indicated likely PoPs Tuesday afternoon, followed by 30-50% chances for Wed/Thu/Fri afternoon. Temperatures will generally reach the low-mid 70s on Tuesday, followed by upr 60s to lower 70s Wednesday, and mid-upr 60s on Thursday as thermal trough aloft gradually shifts ewd into our region. Min temperatures will range from the upr 40s to mid 50s...close to seasonal averages for late May. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Through 18Z Sunday....Overall looking at VFR conditions through much of the period. The exception to this will be at KSLK and KMPV where clear skies and light winds later tonight will allow for the development of fog and low clouds in the IFR to VLIFR categories. This should take place between 06z and 14z. Winds will generally be under 10 knots through the period. Outlook... Sunday Night: VFR. Chance SHRA. Memorial Day: MVFR. Breezy. Likely SHRA...Slight Chance TSRA. Monday Night: VFR. Chance SHRA. Tuesday: VFR. Breezy. Chance SHRA. Tuesday Night: VFR. Chance SHRA. Wednesday: VFR. Chance SHRA. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...MV NEAR TERM...Evenson/MV SHORT TERM...Banacos LONG TERM...Banacos AVIATION...Evenson

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