Area Forecast Discussion
Issued by NWS Burlington, VT

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752 FXUS61 KBTV 101446 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 946 AM EST Mon Dec 10 2018 .SYNOPSIS... Mainly dry today with high pressure building across the region. A couple of weak upper disturbances will bring colder than normal temperatures and chances for light snow through mid week. A gradual warming trend is expected towards the end of the week, but the possibility of significant precipitation is looking less likely for next weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 945 AM EST Monday...Overall, no major changes to the forecast. Adjusted sky cover to account for good amount of clearing across the area as surface high pressure continues to build in. Just some pesky low level clouds trapped beneath the inversion, especially along the northern Champlain valley/International Border and mountain areas. Anticipate this to gradually clear throughout the morning with many locations seeing sunshine this afternoon. Only other thing of note is there are still some very scattered light snow shower activity in the vicinity of the Montpelier airport, however it looks very localized as area webcams are showing clear skies and no precipitation. Previous Discussion... Noted increasing reflectivity returns showing up on radar over portions of the northwestern Champlain Valley, with light snow being reported at KPBG and showing up on some webcams. This is likely due to some light northeast upslope flow, as evidenced by automated sites across the area. Also a bit of snow still being picked up in a couple of Northeast Kingdom observations. Have added some flurries into the forecast for the next few hours in these locations, but don`t anticipate to last long or amount to much as drier air will continue to move south out of Canada. Low clouds have been persistent this morning as well as moisture lingers under the subsidence inversion. Have increased cloud cover through the morning hours accordingly, but still anticipate some breaks later this afternoon. Otherwise the forecast remains in good shape and no other changes were needed this morning. Previous discussion...A cold front will finish crossing the region early this morning, bringing a reinforcing shot of cold air. Any lingering snow showers or flurries will quickly come to an end as this colder and drier airmass spreads southward. Anticipate clouds to break up a bit as we head toward the afternoon; however, mountain areas may stay a bit cloudier owing to cold air advection and the possibility of moisture becoming trapped under the subsidence inversion. Tonight will remain dry under increasing clouds. Below normal temperatures prevail today and tonight; daytime highs will be in the upper teens to mid 20s while overnight lows will range from around 0 to around 10 above. Some spots may be colder depending on how much clearing is able to occur tonight. For Tuesday...yet another weak shortwave will slide southeast from the northern Great Lakes/southern Ontario. As has been the trend over the past several days, moisture with this system will be relatively meager. However, some lake enhancement will be possible through the day Tuesday as the flow turns more to the southwest. Hence expect some snow showers to develop downstream of Lake Ontario during the day, with the favored locations in northern NY getting an inch or so of snow accumulation during the day. Areas along and east of the Champlain Valley will remain dry, with just increasing clouds. The southwest flow will bring warmer, though still below normal, temperatures on Tuesday as well; highs will be in the mid 20s to around 30. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... As of 259 AM EST Monday...A shortwave trough embedded in northwesterly mid-level flow will traverse nrn NY and VT during Tuesday night. Given limited moisture availability with this system (precipitable water values only 0.2- 0.25 per 00Z GFS), best chances for periods of light snow will be across St. Lawrence and Franklin Counties, where WSW low-level flow from Lake Ontario will result in some low-level moisture advection and orographic ascent into the Adirondacks. Highest PoPs (50-60%) are focused across St. Lawrence county and the nrn Adirondacks, with generally 20-50% PoPs further east. Could see a coating to 1" of snowfall across nrn NY with this system, but with high snow-to- liquid ratios 18:1 to 22:1 should see limited impact for travel. As the system and weak sfc reflection pass to the east toward 12Z Wednesday, light northerly flow will allow shallow layer of colder air to filter southward into our region from Ontario and srn Quebec. Thus, should see lows mainly in the teens for Tuesday night. Continued light north winds expected at 5-10 mph on Wednesday, and potential for trapped stratus layer, will keep temperatures below normal for mid- December during the day Wednesday. High temperatures mainly in the upper teens to lower 20s for Wed aftn. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 259 AM EST Monday...If clearing of low clouds can take place, radiational cooling should be ideal for Wednesday night as sfc 1032mb anticyclone crests over VT with light wind conditions. At this point, anticipate mostly clear skies yielding widespread low temperatures in the single digits, and should see a few below zero readings across the nrn Adirondacks and across Vermont`s Northeast Kingdom. As the sfc anticyclone drifts east of New England on Thursday, should see a developing southerly return flow across the region along with moderating temperatures. Highs Thursday should reach the mid-upr 20s, followed by highs 35-40F for Friday and into the low to mid 40s potentially for Saturday. Synoptic evolution continues to be complex with variability in the 00Z NWP modeling suite. Strong southern stream wave is expected across the srn Plains into the sern states Thu/Fri, but models are trending away from a phasing of this system with the northern stream jet, thus decreasing the chances for significant precipitation across the North Country Friday and Saturday. This is especially true of the 00Z ECMWF soln, which keeps any significant precipitation well south of the area. A weaker northern stream trough would bring a chance of rain/snow showers Friday night into Saturday per the 00Z ECMWF. The 00Z GFS operational run brings a leading northern shortwave trough across NY and New England during Friday into Friday night, but again, bulk of better forcing and moisture remains south of the North Country. The 00Z FV3 remains with the best chance of precipitation for the North Country, with 980mb low over central NY at 18Z Saturday and potential for moderate to heavy rainfall and possible windy conditions along the western slopes of the Green Mtns. At this point, forecast mainly reflects a blend of the GFS and ECMWF, with potential for light rain/snow mainly Friday night into early Saturday, and then trending drier for later in the weekend. Have lowered PoPs accordingly, mainly 50-60% for Friday night, and decreasing to 40-50% during the day Saturday. Given the wide range of solns, will need to continue to monitor trends for Friday and the weekend. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... Through 06Z Tuesday...Primarily VFR conditions through the next 24 hours, with local MVFR at some sites. Stratus remains blanketed over much of the region, with ceilings generally AOA 3500 ft. However, sites such as KSLK and KPBG are reporting 1 1500-2500 ft deck, along with reduced visibility in light snow. This may continue through 15z or so, but overall trends will be for ceilings to lift and all sites to be VFR by late this afternoon. Some clearing possible this evening, but clouds will once again thicken and lower later tonight as low pressure approaches from the northwest. North to northwest winds 5 to 10 kt will continue through the period. Outlook... Tuesday: Mainly VFR, with local MVFR possible. Chance SHSN. Tuesday Night: Mainly VFR, with areas MVFR possible. Slight chance SHSN. Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. Slight chance SHSN. Thursday Night: Mainly MVFR, with areas VFR possible. Slight chance SHSN. Friday: VFR. Chance SHRA, Slight chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Hastings NEAR TERM...Hastings/LaRocca SHORT TERM...Banacos LONG TERM...Banacos AVIATION...Hastings

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