Area Forecast Discussion
Issued by NWS Burlington, VT

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852 FXUS61 KBTV 181810 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 210 PM EDT Fri Aug 18 2017 .SYNOPSIS...
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This afternoon, we`ll have areas of sunshine, however the increasingly humid airmass will result in a few showers or thunderstorms late in the day and into the evening. Some storms could produce heavy downpours. Any showers and storms come to an end later tonight. On Saturday expect a chance for showers in the afternoon...but the areal coverage will be scattered in nature. Highs on Saturday will be in the mid 70s to lower 80s. Drier air will begin to move into the region on Sunday with highs once again in the mid 70s to lower 80s.
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&& .NEAR TERM /THROUGH SATURDAY/... As of 1005 AM EDT Friday...late morning refresh is primarily to sync the forecast up with the latest radar/satellite/surface observation trends. The bulk of the widespread steady showers are mostly east of the region at this time. Mid-level water vapor from GOES-16 shows quite a bit of dry air across the St Lawrence Valley (although low level moisture remains, thus still a deck of lower clouds out there), with deeper moisture east half of the forecast area. The previous forecaster`s concept of a lull for mid-day with a just a few showers/t-storms developing later this afternoon still looks good. The latest runs of the HRRR, and the 06z BTV 4km WRF show this scenario. Have folded their outputs into the PoP forecasts to show the mid-day lull and late afternoon slight uptick in shower coverage. Given precipitable water values this afternoon and evening will still be 1.5" or so, especially eastern sections, any t-storm we do see will have a decent downpour with it. Otherwise, ingredients for stronger/organized t-storms don`t look all that great at this point. Bottom line -- much of the rest of the day won`t be too bad. The sun will eventually break out for most of the area, and showers/t-storms will only be scattered about. Previous Discussion... Low level warm air advection is enhancing showers across northern New York this morning and Showalter Index values are slightly negative for indications of elevated instability. We have seen some lightning with this activity and given the continued existence of elevated instability through about 800 am this morning...will continue to mention isolated thunderstorms over northern New York. The showers will move across Vermont this morning with noticeable clearing/drying moving into northern New York during the morning hours. There will likely be a lull in precipitation around midday with dry weather expected through about 500 pm before instability develops from the Champlain Valley westward in advance of an approaching cold front. Deep layer shear will also be increasing over the Saint Lawrence Valley but at the same time dry air aloft will move into that area. So feel that area remains dry late in the day...but from the northern Adirondacks into the Champlain Valley can see scattered showers and isolated thunderstorms developing. Not the most favorable instability and shear in this area...but enough for the convective threat. Dew points will be well into the 60s at that point and can see heavy downpours with any of the convection. At this time will not put in any enhanced wording...but will need to keep an eye on the wind gust potential. Feel best threat for strong to severe storms will remain south of our area...from the Albany area down into eastern Pennsylvania/northern New Jersey where deep layer shear and instability are aligned with each other and are sufficiently strong. High temperatures today will be interesting with readings in the upper 60s to lower 70s in the east to the lower 80s in the west. For tonight scattered showers and isolated thunderstorms should end by midnight as cold front moves east of the region. Lows will be in the upper 50s to upper 60s and would not be shocked to see fog develop with higher dew points and additional low level moisture from Friday`s precipitation. On Saturday main upper trough is still to the west of our area and will be approaching by late in the day. Can see the chance for some afternoon showers as this feature approaches and enhances dynamic support over the region. West to southwest flow aloft will allow for slightly above normal temperatures with highs in mid 70s to lower 80s. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 454 AM EDT Friday...Chance for showers Saturday night as upper level trough and short wave energy passes overhead. Dry weather returns for Sunday with surface high pressure ridge building into the north country. Temperatures Saturday night will be slightly warmer than normal with clouds and chance for precipitation, then back to near normal values on Sunday with dry and seasonable weather expected. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 454 AM EDT Friday...Our weather will be dry from Sunday night through early Tuesday with surface high pressure remaining the main synoptic feature. On Tuesday a weak low will pass north of our area and we will have a chance for some showers from Tuesday afternoon through early Wednesday. Upper level trough will linger a bit behind this system, and bring a chance for showers through the end of the period. Monday and Tuesday will be the warmest of the week ahead of approaching cold front, max temps reach the mid to upper 80s. Temperatures will be a bit cooler than normal towards the end of the week with upper level trough bringing clouds and precipitation to our area. Highest pops will be Tuesday night and early Wednesday with the actual frontal passage. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Through 18Z Saturday...a mix of conditions across the region, with VFR across most of northern NY, and MVFR across eastern/southern Vermont. A few showers are also near RUT as I type. Trends should be toward VFR, except eastern Vermont where MVFR ceilings will likely hang on. During the evening we expect scattered showers to redevelop and move across the region. However the confidence in exact timing and location are such that "VCSH" is the best that can be placed into the TAFs right now. Expect MVFR ceilings to also redevelop across much of the area, along with at least a "light" (4-6sm) fog. Guidance suggests that IFR due to visibilities of 1-2sm and ceilings under 1000ft will develop in locations east of the Green Mountains (eg: MPV), with some as well across the `Dacks. Conditions will start to improve after 13z Saturday. Outlook... Saturday Night: VFR. Chance SHRA. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Chance SHRA...Slight Chance TSRA. Tuesday Night: VFR. Chance SHRA...Slight Chance TSRA. Wednesday: VFR/MVFR. Likely SHRA.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson/Nash SHORT TERM...Neiles LONG TERM...Neiles AVIATION...Nash

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