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Area Forecast Discussion
Issued by NWS Burlington, VT
Issued by NWS Burlington, VT
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187 FXUS61 KBTV 121038 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 638 AM EDT Mon Aug 12 2024 .SYNOPSIS... Scattered showers will develop today, but overall rainfall will be relatively light and most of the time it will be dry. A couple thunderstorms are possible in the afternoon. Temperatures will be below average, but there will be a drying trend toward mid-week and temperatures will rise to around seasonable levels. && .NEAR TERM /THROUGH TUESDAY/... As of 633 AM EDT Monday...An area of lake-effect rain showers has moved into far southern St. lawrence County. They should move out within the next hour or two before more widespread showers develop this afternoon. Clouds are prevalent over northern areas but southern areas are mostly in the clear. However, clouds will develop there this morning as well. Overall, the forecast is in good shape so few changes were made. Previous Discussion...There are only a few lingering showers left at this point, and mostly dry conditions will prevail for the rest of the night. Fog has begun to develop in parts of eastern Vermont and it should spread to many of the favored valleys. Boundary layer winds and some cloud cover should limit much fog from forming elsewhere. This morning, southwest flow will develop and bring some Lake Ontario moisture into North Country. The region is currently under the influence of an upper-level low centered to the north over Quebec. A shortwave will pivot around the low this afternoon and move through the region. Combined with diurnal heating and decreasing temperatures aloft, scattered to numerous showers will develop, particularly over northern areas. There will be a couple embedded thunderstorms, and with just enough instability, a few of these could contain small hail. Overall, the instability should be a bit less than yesterday but the air aloft will be colder. Temperatures will also be cooler than the past few days, with highs only reaching the mid 60s to mid 70s. The upper level low remains in place for tonight into Tuesday, but the coldest air aloft passes to the east. Combined with a lack of impactful shortwaves pivoting around it, Tuesday should be mostly dry. There could be an isolated shower across the higher terrain but dry air at the mid-levels will try to inhibit anything from forming and try to keep any rain from reaching the ground. With more sunshine and a lack of showers, temperatures will rise to the 70s and low 80s. The humidity will remain low with dew points in the 50s to around 60 for most areas. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 345 AM EDT Monday...Synoptic scale pattern shows mid/upper lvl trof acrs the NE CONUS with building sfc high pres from the central Great Lakes. The combination of northwest flow aloft and a weak embedded 700-500mb s/w wl interact with limited moisture and instability to produce a 15 to 30% probability of showers/storms on Weds aftn. Greatest potential for measurable precip looks to be acrs the eastern Dacks into parts of the central/northern Green mtns of VT. Overall impacts and coverage wl be minimal given the weak forcing and available moisture. As sfc high pres builds into our cwa, expect areas of patchy fog both Tues night and Weds night, especially given recent rainfall and saturated ground conditions. The areal coverage wl depend upon clearing and bl winds, but climo favored look most likely at this time. Lows range from the upper 40s to upper 50s both Tues/Wed nights with highs mid 70s to lower 80s on Weds aftn with comfortable humidity values. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 345 AM EDT Monday...Mid/upper lvl trof prevails on Thurs into Friday and may actually retrograde back to the west on Thurs, before weak sfc ridge builds for Friday into early Saturday. Guidance has come into better agreement for additional showers with embedded storms on Thurs aftn, with greatest potential acrs northern VT, including the NEK. Have continued with pops in the 30 to 50% range for now, but given trends a bump toward likely maybe needed over the NEK on Thurs aftn, given latest moisture/instability progs. GFS/ECMWF both show a pocket of sfc based CAPE values in the 800-1200 J/kg with increasing forcing associated with 5h vort dropping south in the northerly flow aloft. Have west to east pop gradient, as best forcing/moisture is located over central/eastern VT, with less favorable parameters over northern NY, which is closer to building ridge. Temps look near normal on Thurs/Friday supported by progged 925mb temps of 18-20C. Next weekend is looking unsettled as next large scale synoptic mid/upper lvl trof and associated series of boundaries approach the NE CONUS. Guidance is still offering some differences in the timing and magnitude of system, but general idea of unsettled wx looks likely, especially late Sat into Sunday. Dynamics look potent associated with abnormally strong cyclonic circulation and if enough instability can develop, the potential for a few stronger storms wl need to be watched. Plenty of time to access the shear/instability parameters this week, but something to monitor as we head toward next weekend. As southerly flow develops thru a deep layer by next weekend, expect increasing humidity values, especially by Sunday, which wl result in muggy overnight lows. Have highs generally in the mid 70s to mid 80s with lows upper 50s to mid/upper 60s by next weekend. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Through 06Z Tuesday... Most terminals are currently VFR and they should remain that way for the rest of the night. The exception is SLK and ceilings there should lower from MVFR to IFR later in the night. Fog development is unlikely at any of the terminals tonight. Ceilings will rise during the day today and everywhere should reach VFR. Scattered showers and a couple thunderstorms will pass through the region this afternoon and into the evening. They could briefly lower visibilities to MVFR or even IFR at any of the terminals. These showers will slowly dissipate this evening. Winds will generally be southwesterly tonight and into the morning, before turning northwesterly in the afternoon after a cold front comes through. LLWS is not a concern. Outlook... Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Patchy BR. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. Chance SHRA, Slight chance TSRA. Thursday Night: VFR. NO SIG WX. Friday: VFR. Slight chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Myskowski NEAR TERM...Myskowski SHORT TERM...Taber LONG TERM...Taber AVIATION...Myskowski