Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 310159 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 959 PM EDT Sat Jul 30 2016 .SYNOPSIS... A slow moving upper level disturbance and associated rich moisture moving out of the Ohio Valley will bring periods of rain showers Sunday into Monday, possible lingering into early Tuesday. High temperatures will reach the low 80s today, but then generally in the low to mid 70s for the Sunday through Tuesday time frame with abundant cloudiness. High pressure returns Wednesday through Friday with warmer and more humid conditions. && .NEAR TERM /UNTIL 11 AM SUNDAY MORNING/...
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As of 959 PM EDT Saturday...Temperatures running a few degrees colder in spots, mainly across the north, and so with this update I`ve made some slight adjustments to temps to get those more in line. Northern extent of shield of rain across southern New England, Hudson Valley area ahead of a warm front continues to make very slow northward inroads. Current radar trends depict showers in southern parts of Bennington and Windham counties to our south. Recent HRRR and RAP output suggest a continued slow northward advance in rain showers is expected and have left PoPs alone for now as they seem to reflect these ideas pretty well. Skies will remain clear across areas to the north where the coldest lows - in the mid 50s - will be found. Comparatively warmer lows in the upper 50s to lower 60s across southern VT. Previous near-term discussion from this afternoon follows... Looks fairly quiet tonight, though will see some lowering and thickening clouds especially in the south as a slow moving 500mb trough moves slowly east. The 500mb ridge axis is over the area right about 12z Sunday and should hold off precip for most areas until the but looks like a rising chance in south central VT by daybreak Sunday. Models vary on timing of precip northward on Sunday but general consensus is that it basically takes much of the day for the rain to move north reaching the international border by late afternoon/eve. It looks like most of the rain will be light stratiform variety but some moderate rainfall will be embedded with relatively weak qg forcing from 850mb warm advection. Looks like any instability will be off to our south and west for the bulk of the day so little chance of any thunder through the day. Temperatures a bit tricky with less clouds north vs south so lows tonight generally cooler north in the lower 50s in the NEK to the lower 60s south and west where its cloudy. Highs on Sunday will be warmest north in mid to upper 70s while in the south it may not reach 70 depending upon the time the rain arrives.
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&& .SHORT TERM /11 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... As of 325 PM EDT Saturday...Rain shield will continue to slowly advance northward Sunday night and into Monday, offering a wet close to the weekend. Both global and mesoscale model QPF output continues to suffer from model- generated convective bullseyes in their respective QPF fields in various different locations. While PWAT values are seasonably high around 1.5 to 1.7", there really isn`t much in the way of instability to speak of given the time of day, overcast skies and poor low and mid-level lapse rates. Because we aren`t likely to see much in the way of thunder to enhance rainfall rates, think higher QPF as seen in some guidance and WPC seems a bit overdone. Generally stuck close to 15z SREF/12z GFS/12z NAM blend for PoPs/QPF/Wx. A steady light to moderate rainfall seems the more likely outcome with the heaviest precip falling Sunday night into early Monday. It appears the steadiest precip generally comes in two waves - one is the south- to-north moving axis associated with the warm front, and another later in the day Monday from the upper trough axis. While rainfall should provide beneficial given the dryness, there may be areas of localized ponding in poor drainage areas. Factoring in rainfall for Sunday, forecast amounts are between 0.75" to 1.25". Should greater instability be realized that currently indicated, these values may be locally higher. Temperatures Sunday night stand to be pretty mild and more humid. With anticipated cloud cover and at least a light south wind, expect temperatures to fall very slowly to lows in low to mid 60s, a few degrees warmer than recent MAV/MET MOS output. On the flip side, high temperatures Monday were undercut a couple degrees compared to MOS given the extensive cloud cover. Values are in the low 70s, only a few degrees higher than lows the evening before. Lows Monday night in the upper 50s to lower 60s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 325 PM EDT Saturday...After a wet Monday, global models then point to mid-level height rises associated with ridging aloft Tuesday through Thursday. GFS and ECMWF want to show isolated showers or thunderstorms but this seems overdone and have kept the forecast dry. 850 mb temperatures warm each day and are up in the +13 to +15C range supporting another period of above-normal temperatures in the low to mid 80s. Thursday will continue the trend of above-normal temperatures, but we will start to see more of a southwesterly breeze and also an increase in humidity levels. Still dry but warm and humid with highs into the upper 80s (maybe spot 90) with lows Thursday night in the upper 60s. It appears Friday potentially may have a window for active weather as mid-level flow tightens across the Great Lakes and wind fields strengthen, as a cold front moves into a warm and humid antecedent air mass. There`s some difference between the GFS and ECMWF when the front crosses through our area Friday, which has implications on available instability, with the GFS suggesting an afternoon frontal passage. It`s very early but on the synoptic scale, there appears to be potential for stronger thunderstorms Friday. Definitely is something that should be monitored in subsequent model runs. && .AVIATION /02Z Sunday THROUGH Thursday/... Through 00Z Monday...VFR conditions will persist through tonight, then deteriorate to mvfr vis in rain from mid morning onward. High level cirrus spreading into the region from the south at early evening associated with initial batch of rain moving across southern NY. This will give BTV`s TAF sites only VFR ceilings overnight, with no precip. Given the cloud cover followed previous shifts thinking of no fog forecast for KSLK/KMP, with clouds keeping radiational cooling from happening. Next low that will be the rainmaker starting sunday moving into the Ohio valley. Increasing moisture and lift with this system will slowly lower ceilings but remain at VFR levels. Rain to move in from the south, 14-18Z in the south and after 18z in the north. Began with VCSH until chances increase well into likely category, then went with prevailing mvfr vis in rain. Light winds but generally a southeast component. Outlook 18z Sunday through Wednesday... 00z Monday-00z Tuesday: Intervals of MVFR in shower activity Sunday afternoon through Monday with slow moving upper trough. 00Z Tuesday through Wednesday: Upper trough brings lingering showers Monday night into early Tuesday with periods of MVFR and brief IFR possible. Then clearing with VFR conditions as high pressure returns Tuesday afternoon through Wednesday. May see areas of nocturnal fog 06-12Z Wednesday SLK/MPV with localized LIFR conditions. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Loconto/Sisson SHORT TERM...Loconto LONG TERM...Loconto AVIATION...Hanson

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