Area Forecast Discussion
Issued by NWS Burlington, VT

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181 FXUS61 KBTV 262302 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 702 PM EDT Wed Apr 26 2017 .SYNOPSIS... A building ridge of high pressure will result in much above normal temperatures on Thursday with mostly sunny skies...except some lingering clouds across central and eastern Vermont. Temperatures will warm into the 70s with some lower 80s likely in the warmer valleys. A weak front will produce scattered showers on Thursday night into Friday with rainfall generally under a quarter of an inch. Mild on Saturday with a chance of showers and cooler and drier on Sunday. && .NEAR TERM /THROUGH THURSDAY/...
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As of 702 PM EDT Wednesday...Going forecast in good shape with just a few tweaks to temperatures and dew points to match current conditions. Otherwise quiet night with no more rain... some lingering clouds...and plenty of low level moisture around to have some fog develop later tonight. Previous Discussion... Water vapor continues to show our cwa between building heights and dry air to the west and cyclonic circulation and deeper moisture to our east. As mid/upper level ridge continues to develop overnight across our western/central cwa...expecting some clearing skies...which combined with light winds and plenty of low level moisture will aid in the development of fog. Best opportunity for fog will be slv and deeper/protected valleys of the dacks. Meanwhile...south to southeast low level flow continues across central/eastern vt...with additional low level moisture advecting from south to north across this region. Expecting low clouds with areas of br to redevelop across our eastern mtns tonight. Temps with some clearing earlier western sections and high sfc dwpts in the 50s will be challenging...but mainly 40s dacks to l/m 50s. On Thursday...forecast focus will be low clouds especially eastern/central sections associated with southeast 925mb to 850mb flow of 15 to 25 knots. Soundings at mpv show some breaks developing after 17z Thursday...with 2m temps only in the mid 60s. Meanwhile...downslope drying off the greens with progged 925mb temps between 17c and 19c support highs well into the upper 70s to lower 80s eastern cpv. Lake breeze will keep near Lake Champlain and western cpv...much cooler with highs mainly in the mid 60s to lower 70s depending upon location away from the lake. Warmest readings on Thursday will be across the dacks with lower 80s likely from Edwards/Fine to Potsdam to Malone...with slightly cooler immediate slv.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 310 PM EDT Wednesday...Models have come much more into agreement with timing of a cold front Thursday night. Have used a blend of hi-res models for better defining the hourly progression of the front and associated precipitation. Models do have a minimal amount of instability ahead of the front, however dynamics are in short supply and with the overnight timing, we don`t have daytime heating. Thus expect a broken line of showers to trek eastward fairly quickly. Thinking late evening in the St Lawrence Valley to about daybreak in the Champlain Valley then by mid-morning exiting Vermont. Coverage and intensity of precipitation will be diminishing as the front moves east, so overall QPF will be less than 1/4". Given the instability signals, can`t rule out a rumble of thunder, so have maintained "slight chance" levels of thunder. All the clouds will keep it very mild. Lots of 50s overnight, perhaps staying above 60F in the Champlain Valley. Friday isn`t looking all that bad. Westerly flow develops, with drier air moving in. 925mb temperatures are still relatively mild, ranging from about 18C far west to 23C or so far southeast. This will support above normal highs from the mid/upper 60s west to upper 70s across the lower CT River Valley in southeast Vermont. Friday night, pretty quiet, though clouds will start increasing ahead of the next cold front, though lows will still be a good 10F degrees above normal. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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As of 310 PM EDT Wednesday...Fairly changeable weather through the period, however the longer term models are in pretty darn good agreement. That raises the overall confidence of what is expected. Taking it day by day... Saturday: Cold front will be moving across the region during the day. Not a lot of moisture or instability or dynamics with it, but enough for a few spotty rain showers. We should still see above normal temperatures despite the clouds and showers. Looks like warmest temperatures will be south and east. Clears out for Saturday night as a weak ridge of high pressure tries to build in as the front stalls just to our south. Lows will be near normal, and probably patchy frost around given clear skies and relatively light winds. Sunday: Seasonable temperatures, and dry for at least the first part of the day. Clouds will increase during the afternoon with initial push of warm air advection aloft associated with a pretty big low well to the west. Can`t rule out a few spotty light showers across western sections of northern NY during the afternoon. Monday/Tuesday: Looks like southerly flow will strengthen and push a warm front through and north of the region Monday, putting us into a mild warm sector. It`s possible we`ll get into a solid dry slot for Monday afternoon, and if that happens we could have enough sun to push temperatures well into the 70s. Not confident enough about that right now, so stuck to model blend for highs (still mid-upper 60s). Decent southerly jet with 40-45kt at 850mb that develops. Should be breezy in the Champlain Valley at least. Tried to increase wind gusts a little from raw model output (which tends to way underestimate wind gusts). Perhaps 25-35mph gusts. A front comes through Monday night into early Tuesday. Models indicate some weak instability, so went ahead and tossed in mention of slight chance of thunderstorms. Should be a widespread rain event, perhaps 1/2" to 1" of rain, which should not cause any significant hydro problems on rivers. Residual clouds/showers around on Tuesday in a breezy westerly flow, though not terribly cold as this storm system originated in the southern Plains and isn`t really tapping into any very cold air. Wednesday: Still weak troughiness around along with plenty of low level moisture, so chance level PoPs and at least partly cloudy skies look good. Flow aloft turns more northwest and does start to bring in cooler temperatures from Canada, so at this point it looks like highs will be a few degrees below normal and primarily in the 50s.
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&& .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... Through 18Z Thursday...Very challenging aviation forecast with low confidence in overall flight categories and potential impacts on TAFS overnight. Current obs show a wide range of conditions from ifr at mpv in low clouds to vfr at btv/pbg/slk. Thinking mainly mvfr/vfr this afternoon with another hour or two of ifr at mpv. Winds generally light and variable...except northeast at mss btwn 5 and 10 knots. Tonight...lots of low level moisture is lingering with surface dwpts in the low to mid 50s...57 currently at slk...thinking with some clearing over the SLV/northern NY areas...temps will drop below cross over values with areas of fog/br possible after 04z. Have mention ifr prevailing with lifr tempo btwn 07-11z at mss/slk. Meanwhile...thinking southeast flow of low level moisture will help advect ifr cigs back into MPV by midnight or so. Rest of taf sites will remain between vfr/mvfr overnight. Winds shift to the south/southeast on Friday with mvfr trending to vfr at all sites by 15z. Outlook... Thursday Night: VFR. Chance SHRA. Friday: VFR. Chance SHRA. Friday Night: VFR. Slight Chance SHRA. Saturday: VFR. Chance SHRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight Chance SHRA. Sunday Night: VFR. Chance SHRA. Monday: VFR. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Evenson/Taber SHORT TERM...Nash LONG TERM...Nash AVIATION...Taber

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