Area Forecast Discussion
Issued by NWS Burlington, VT

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456 FXUS61 KBTV 231856 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 256 PM EDT Sun Jul 23 2017 .SYNOPSIS... 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. The showers will be heavy at times over northern New York. High pressure and warmer temperatures should return by Wednesday however a frontal system will bring showers and thunderstorms on Thursday. && .NEAR TERM /THROUGH MONDAY NIGHT/... As of 219 PM EDT Sunday...Our brief reprieve of calm weather ends this evening as an upper level low over the Great Lakes will bring showers back to the North Country to start the work week. As the upper level low tracks towards the Saint Lawrence valley a series of low pressure systems will bring widespread rainfall to the region. The first of those lows will move into northern New York which happens this evening ushers in thicker cloud cover and enhanced PWAT. Consensus of the guidance brings the PWATs to 1.5-1.6 across the Saint Lawrence valley with 1.2-1.4 across Vermont which is slightly above normal based on the ALY sounding climatology. As the showers increase through the Monday it should be pretty much a washout across the North Country. Temps will be seasonable cold as we`ll be 15 degrees below normal. Concerning the showers, with the above normal PWATs and persistent rainfall, I did keep with the previous forecaster`s idea that the rainfall will be heavy at times. As the first surface low tracks up the Saint Lawrence it should bring a burst of moderate rainfall overnight and then as the upper level low tracks closer the parent low will pivot and begin to dive southeast. This should mean that northern New York receives the most significant rainfall as the energy from the systems will be focused on that area for the longest period of time whereas eastern Vermont will see slightly less total rainfall. Between 1-2 inches will fall over northern New York with between 0.5-1 inch of rain should fall over Vermont. Flooding isn`t currently a concern because RFC flash flood guidance is nearly 2 inches in the 1 hour and between 2-3 in the 3 hour range. There should be enough instability and cold air aloft to support some embedded thunder with the showers mainly over northern New York. && .SHORT TERM /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 /18Z SUNDAY THROUGH FRIDAY/... Through 18Z Monday...Overall VFR conditions are expected to deteriorate as a low pressure system will bring showers to the North Country between 8-10z Monday. Ceilings should be mostly VFR until late in the period when MVFR ceilings will be possible most likely at SLK/MPV. OVC 2500-3000 feet ceilings should move into the region between 13-15z tomorrow expect for PBG where downsloping should keep ceilings as VFR. Winds will be light north/northeast less than 10 knots shifting to southeast during the overnight hours tonight. Outlook... Monday Night: MVFR. Likely SHRA. 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. Thursday Night: VFR. Chance SHRA...Slight Chance TSRA. Friday: VFR. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Deal NEAR TERM...Deal SHORT TERM...JMG LONG TERM...JMG AVIATION...Deal

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