Area Forecast Discussion
Issued by NWS Burlington, VT

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658 FXUS61 KBTV 182352 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 652 PM EST Sat Feb 18 2017 .SYNOPSIS... A ridge of high pressure will slide east of New England tonight, with a weak mid level trough passing to our north across Quebec Sunday into Sunday night. This system will bring the possibility of light rain or snow showers, primarily later Sunday into Sunday night, with the best prospect for light precipitation in the form of snow showers across the Northern Green Mountains and northern Adirondacks. We`ll see increased clouds for Sunday, but temperatures will remain in the upper 30s to lower 40s for valley highs. Dry and seasonably mild weather is expected Monday and Tuesday with high pressure in place. The next weak mid- level disturbance approaching from the west will bring chances for light mixed wintry precipitation Tuesday evening through Tuesday night. A more significant precipitation system is possible Friday into Saturday. At this time, it appears the system at the end of the week will bring windy, mild, and rainy conditions. Temperatures are generally expected to be above average this week. && .NEAR TERM /THROUGH SUNDAY NIGHT/... As of 652 PM EST Saturday...Little overall change to the previous forecast for this evenings update, but did opt to reduce sky cover and chances for precip through the first half of the night based on current satellite trends. Some minor tweaks to hourly temperatures as well as many location are still hovering in the 40s with southerly winds gusting in the 10-20kt range. As winds taper off some temps should fall more later through the night. Previous Discussion...Seeing some melting snow across the region this afternoon under nearly full sunshine and with 2-m temperatures reaching the mid-upr 40s, and locally into the lower 50s across the St. Lawrence Valley of NY. Readings at 20Z include 48F at BTV, 50F at SLK, and 53F at MSS. NWP thermal profiles have generally been too moist/stable at low-levels with current warm advection regime over the existing snowpack. As such, it appears low-level moisture and cloudiness is overdone in most of the models for tonight, and winds are too light. Seeing gusts 25-30kts at times in the Champlain and St. Lawrence Valleys, and that should continue until around sunset. Moderate p-gradient remains in place tonight as well, so anticipate continued mixing overnight with winds 5-10kts and veering into the SW and eventually into the west for Sunday morning. The 850mb thermal ridge (+8C per RAP analysis at 17Z over Lake Ontario) will also crest over the North Country tonight...so will see temperatures much more mild than last night. Generally looking at lows in the upr 20s to lower 30s, warmest around Lake Champlain and in the St. Lawrence Valley. A few deeper valleys should decouple east of the Green Mtns, and may see some localized readings in the low-mid 20s in those locations. For Sunday, will see mid-level height falls along the intl border associated with shortwave trough moving across srn Quebec. This nrn stream wave is associated with limited moisture, but continued veering of the low-level wind profile will set up a favorable NW upslope flow regime, especially Sunday aftn into the first half of Sunday night. Thus, looking for increasing cloudiness areawide Sunday, with occasional light snow showers developing across the higher terrain, and occasional flurries/sprinkles across the nrn valleys. At the surface, it does appear that a weak cold front will push swd into the region late Sunday aftn into Sunday evening, with better chances for snow showers briefly Sunday evening thru about 06Z Monday. Daytime highs Sunday generally expected in the upr 30s to lower 40s, and then falling back into the mid 20s with nw winds and stronger CAA regime Sunday night. May see a few slick/icy spots across higher elevation roads/passes, but overall snow accumulations later Sunday/Sunday night only expected to be a coating to 2"...highest from Mt. Mansfield to Jay Peak. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 340 PM EST Saturday...Northerly, mainly cool and dry, flow from eastern Canada will be the story Monday. There will probably be some flurries or light snow showers Monday morning in the northern mountains as with the exiting upper level trof. Otherwise a progressive high amplitude ridge at 500 mh and high pressure at the surface stretching from Hudson`s Bay south to Florida will move over eastern CONUS and Canada through Tuesday morning. Temperatures will be pretty close to average with highs in the mid 20s to lower 30s on Monday and lows 5 to 15 degrees by Tuesday morning. On Tuesday, high pressure moves east and a warm front will bring increasing clouds from west to east through the day. NY will be cloudy with rain showers or mixed precipitation developing during the afternoon reaching BTV by evening and then into eastern VT. It looks to be fairly fast moving and the NAM/ECMWF solutions are a few hours behind the GFS. QPF is fairly light as result on the order of 0.10 to as much as 0.20". With temperature profiles right around freezing and wet-bulbing down around dark, just about any kind of precip could fall. Best chance of mixed precip will be in the Adirondacks, KMSS area, and Green mountains east where surface temps will be slightly below freezing. High temps mainly in the 30s Tue and 25 to 35 Tue night. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 340 PM EST Saturday...The long term features mainly above normal temperatures which seems like a good bet. However, lots of spread in the models/ensembles with regard to speed and amplitude of features mid to late week, but come into slightly better agreement that ridging develops in the east Friday in advance of another more significant trof and storm system by next weekend. Wed and Thu look like only a slight chance of a rain or snow shower as a weak quasi stationary frontal system is in the area. Increasing chances of showers by later Friday into Saturday with rain showers changing to snow showers as low pressure and its associated frontal system approaches the region. The model consensus at this point is for a primary low to pass north and west of region. GFS ensemble mean similar but show more of a double barrel low pressure with a secondary low along the coast. It`s still a long way out with lots of possibilities. Temperatures look to be mainly in the 40s for highs and lows in the lower 30s. It is interesting that the ensemble MOS means are running cooler than the operational models. In fact, by Sat there are 10-20 degree spreads in both ECMWF and GFS ensemble high and low temps probably related to the timing and location of the storm system. Stay tuned. && .AVIATION /00Z Sunday THROUGH Thursday/... Through 00Z Sunday...VFR through the forecast period. SKC to trend BKN/OVC in the 035-060 AGL range in the 06-12Z time frame except for KRUT which should remain generally SKC. These cigs should then persist through the end of the forecast cycle with some periodic very light shsn or flurries potentially affecting higher terrain. Winds generally south/southwesterly 6 to 12 knots and occasionally gusty at favored terminals overnight, veering to west/northwesterly after 18Z Sunday with passage of weak cold front. Outlook 00Z Sunday through Thursday...Will see periods of HIR TRRN OBSCD through 12Z Monday with mtn snow showers expected across the Adirondacks and nrn Greens. Any precipitation will be light. In terms of the TAF locations, any light pcpn most likely to affect MPV/SLK. Another shortwave trough approaching from the west will bring a period of light rain/snow Tuesday night with brief intervals of MVFR conditions possible. Significant precipitation is currently not expected during the outlook period. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/Lahiff SHORT TERM...Sisson LONG TERM...Sisson AVIATION...Banacos/JMG

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