Area Forecast Discussion
Issued by NWS Burlington, VT

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043 FXUS61 KBTV 291935 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 335 PM EDT Wed Mar 29 2017 .SYNOPSIS... Deep low pressure over central Quebec will continue to provide abundant cloud cover to the North Country today, along with areas of fog and drizzle this morning, and some scattered rain and snow showers across north-central Vermont this afternoon. A brief period of sunnier and drier conditions is expected on Thursday as a ridge of high pressure builds over the region, but unsettled weather returns for the end of the week and into the weekend, as another storm system will bring valley rain and mountain snow Friday into Saturday. && .NEAR TERM /THROUGH THURSDAY/... As of 718 AM EDT Wednesday...Deep low pressure over central Quebec this morning continues to provide abundant low level moisture to the North Country in the form of areas of cold drizzle and fog with current temps ranging through the 30s. Cold air advection continues through the day on northerly flow, and while precipitation chances generally wane across the majority of the region, additional shortwave energy rounding the base of the upper trough will skim along the international border maintaining the threat for scattered valley rain and mountain showers across central and northern portions of Vermont through the afternoon. Abundant cloud cover will persist through the day as well, keeping temps in the mid 30s to low 40s in the valleys while the higher summits gradually fall through the 20s. For tonight, the upper trough finally begins to swing east of the area with surface high pressure and and upper ridging over the Great Lakes and Ohio Valley edging ever so slowly eastward towards the region. Low levels finally begin to dry out with subsidence aloft winning out, so a gradually clearing of skies is expected though mainly after midnight with valley locales clearing the most, mountain areas less so. Lows will range mainly in the 20s with some teens in the Adirondacks. Thursday will be the best day of the week as the aforementioned high centers over the Northeast with skies continuing to clear through the day. Unfortunately temps won`t really change to much as weak cold air advection will continue on light northerly flow, but we should realize widespread highs in the low/mid 40s. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 341 AM EDT Wednesday...Most active period of weather then affects the region by late Thursday night and especially Friday into Friday night as upper closed energy tracks east from the Ohio Valley into the Mid Atlantic region. The forecast remains quite complex in regard to precipitation timing, amounts and type with lower boundary layer thermal profiles playing a critical role through the period. This is not uncommon with early spring systems with subtle changes of 1 to 2 degrees either way potentially leading to large differences in sensible weather. For now will maintain our prior idea of snows arriving into our southwestern counties later Thursday night into mid morning on Friday before a transition to all rain in lower elevations, or rain/snow mix from 1000-2500 feet on Friday as precipitation shield advances into the remainder of the forecast area. At higher elevations above 2500 feet p-type may remain as all snow. Negligible amounts of sleet or freezing rain is expected. Lows Thursday night mainly in the 20s with afternoon highs on Friday from 35 to 40 below 1500 feet and 30 to 35 above that level. Bulk of precipitation then affects the area Friday night as warm thermal advection aloft will be peaking and as thermal profiles cool slightly a transition to all snow is expected after midnight. Amounts may be a bit tricky as flow trends southeasterly and some slight shadowing effects may occur. Time will tell. I was also cautious in leaning too high on our QPF given known model high bias during warm thermal advective events. Nonetheless the potential will exist for a light to moderate wet snow accumulation in many areas with higher amounts possible in elevated southern terrain. Did lean on the milder side of guidance given clouds and lack of appreciable low level advection - mainly lower to mid 30s (upper 20s at elevation). Please see our winter weather page at www.weather.gov/btv/winter for specific accumulation forecasts and probabilities. By Saturday widespread light snows taper to scattered rain/snow shower activity as system exits the Mid Atlantic coast and gradually loses influence. Any additional snow accumulations will be minor as late day temperatures top out in the upper 30s to lower 40s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 335 PM EDT Wednesday...A low pressure area will off the southern New england coast early Saturday. Expecting steady precipitation Saturday morning to taper off by Saturday afternoon, as the low pressure area slides east out to sea toward Georges Bank by early Saturday evening. Will have slight chance pops for some snow showers Saturday night into Sunday. A ridge of high pressure will build into the region Sunday night and Monday, with fair and dry weather expected. Models showing some significant differences late Monday night and Tuesday through Wednesday. GFS brings in a chance of rain or snow on Tuesday and Wednesday, while The ECMWF model has precipitation further south and mainly south of New England for Tuesday and Wednesday. Thus, forecaster confidence is low for the Tuesday and Wednesday forecast, given the model differences. Thus, have stuck with superblend pops for Tuesday and Wednesday, and will have a chance of rain and snow in the forecast at this time. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... Through 18Z Thursday...Mainly VFR conditions expected through the period as a ridge of high pressure builds slowly southeast from Canada through the period. Expecting some areas of flurries or light snow showers, with some areas of MVFR ceilings, mainly between 18Z Wednesday through 04Z Thursday. Most of the flurries or light snow showers will be confined to the Adirondacks and the Green Mountains. Outlook 18Z Thursday through Monday... 18Z Thursday through 12Z Friday...VFR under high pressure. 12Z Friday through 00Z Sunday...MVFR/IFR in periods of rain and snow. 00Z Sunday through 00Z Monday...Areas of MVFR in scattered light snow showers. 00Z Monday through 00Z Tuesday...Mainly VFR conditions expected as a ridge of high pressure builds into the region. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...JMG LONG TERM...WGH AVIATION...WGH

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