Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 231127 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 727 AM EDT Sun Jul 23 2017 .SYNOPSIS... A dry and seasonably cool day is expected across the North Country today to end the weekend. Chances for precipitation increase tonight though as an upper level trough will bring widespread rain to the region late tonight through Tuesday along with much cooler temperatures. High pressure and warmer temperatures return for Wednesday, with showers and thunderstorms returning on Thursday along a passing cold front. && .NEAR TERM /THROUGH MONDAY/... As of 724 AM EDT Sunday...Surface high pressure over the region this morning will largely remain in control providing dry conditions to end the weekend, but a fast northwesterly flow aloft will have clouds increasing through the day helping to limit high temps to the mid/upper 70s. Active weather returns tonight though, mainly after midnight, as a well advertised upper level low currently tracking into the western Great Lakes slowly shifts east to the St. Lawrence Valley and northern New York by the end of Monday. Increasing southwesterly flow aloft will usher in some modest PWATs, climbing to near 1.5" across northern New York and 1.25" eastward with precipitation becoming widespread through Monday as surface low pressure takes shape over the eastern Great Lakes. It will be a damp and raw day with temps only topping out in the 60s. Instability is rather meager at the surface which will limit thunderstorm potential, but steeper mid-level lapse rates of +6-7C/km support the idea some embedded thunder so have kept in a slight chance of that. Otherwise, the main threat during the period will be the potential for bouts of heavy rain, mainly across northern New York where rain/storms look to pivot during Monday morning as the mid/upper level circulation slows/stalls across the St. Lawrence Valley. Rainfall here through Monday will look to be in excess of 1 inch and potentially close to 2", but the good news is that 3-6 hour flash flood guidance is in the 2-3" range, so while area rivers will see modest rises, no flooding is expected. Eastward, QPF will be in the 0.50-0.75" range. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/... As of 400 AM EDT Sunday...Widespread showers then continue Monday night before tapering off through the daylight hours on Tuesday as shortwave energy and accompanying longwave trough pivot through the area. Good upper dynamical support warrants pops on the higher end (60-90%) Monday night when best coverage will occur. Patchy fog also a good bet, especially in favored locales though I really can`t rule it out anywhere. The thunder threat will remain rather minimal, mainly confined to our southwestern-most counties in the evening hours where some weak mid-level instability will linger. Additional rainfall totals generally in the 0.25 to 0.50 inch range through this period. Temperatures hold seasonably cool with lows in the 50s and corresponding highs on Tuesday in the 60s to locally near 70 in the SLV where some partial late day sun will be possible. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 400 AM EDT Sunday...Pretty much a persistence forecast will be offered for the middle to later portions of the work week with this morning`s global output maintaining good consensus by and large. A general drying trend will occur by Tuesday night into Wednesday as expansive surface high pressure builds east from the Great Lakes and Ohio Valley as 500mb heights slowly build. With a return of partial to full sunshine, temperatures respond in kind by returning to near late July seasonal norms with highs in the 70s to around 80 and overnight lows in the 50s to lower 60s. Patchy fog a good bet once again Wednesday night with partially clear skies and moist ground from early week rainfall. By Thursday into Thursday evening data continues to support a weak cold front sweeping through the area with scattered to numerous showers and thunderstorms. While a widespread severe weather threat appears rather minimal at this point, a favorable afternoon frontal passage combined with modest boundary layer instability and shear would seem to promote at least a few stronger cells. Time will tell. Behind this feature the picture becomes a little unclear as we progress toward next weekend. This morning`s ECMWF has abandoned the wild, deep closed low scenario offered by its 07/22 12Z run showing a somewhat more progressive flow across the northeastern quarter of the nation. The GFS shows a somewhat murkier solution showing the frontal system becoming bogged down to our immediate south, eventually becoming entangled with several weak coastal waves and keeping a modest shower threat across the eastern and southern portions of the forecast area. At this point will maintain a blended solution showing at least a lingering threat of showers in these areas into Saturday, though admittedly this is a low confidence forecast at this point. Temperatures hold near seasonal norms with highs in the 70s to near 80 and lows in the 55 to 65 range. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Through 06Z Monday...Overall VFR conditions are expected through the next 24 hours with SCT-BKN mid clouds currently over the region increasing to BKN-OVC through the day. Rain encroaches from the SSW late, after 08Z with ceilings lowering, but remaining largely VFR through the end of the period. Exception will be KSLK where ceilings will trend to MVFR around daybreak Monday. Winds will be light north/northeast less than 10 knots through the period, except locally southeast at KRUT during the overnight hours. Outlook... Monday: VFR/MVFR. Breezy. Likely RA...Slight Chance TSRA. Monday Night: MVFR. Likely SHRA...Patchy FG. Tuesday: VFR/MVFR. Chance SHRA. Tuesday Night: VFR/MVFR. Patchy FG. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR. Likely SHRA...Likely TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...JMG LONG TERM...JMG AVIATION...Lahiff

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