Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 171936 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 336 PM EDT Sat Mar 17 2018 .SYNOPSIS... High pressure is in store this weekend, but seasonally cold weather and gusty winds will continue, especially on Saturday. Some scattered snow showers will be possible Saturday morning, mainly in the northern mountains which would be the only precipitation on an otherwise dry weekend. The jury is still out on a potential low pressure system that may have the makings of the fourth nor`easter that New England has seen in the last few weeks with current trends keeping the system largely south of the area for now. && .NEAR TERM /THROUGH SUNDAY NIGHT/... As of 1053 AM EDT Saturday...Tweaked temperatures a bit to better reflect the upstream cold air moving in behind a cold front. The upstream air mass is cold enough to offset morning solar heating and allow temperatures to remain constant or drop a few degrees this morning before raising a few degrees this afternoon during peak heating. Have also blended some HiRes winds in to the near term forecast to better capture the timing/strength of the increased winds and gusts along and behind the frontal passage. Overall, still on track for a blustery cold day more reminiscent of January or February than late March. In addition, increasing instability with the cold push is allowing for some isolated quick hitting snow showers over the northern Adirondacks. Have also updated PoP grids to include these showers, using hires models to capture their evolution as the triggering upper wave pushes south and east through the early afternoon. Previous discussion...While a most of the weekend will be dominated by high pressure, Saturday morning starts with strong upper shortwave trough that digs into the region at daybreak and moves quickly south of the CWA by mid afternoon. With this a very cold airmass for this time of year moves in with temperatures 10 to 15 degrees below normal. Along with this colder air a chance for snow showers to Saturday morning. While across the northern half of the CWA, SBCAPE of 100-150 J/kg look possible as indicated by 00z NAM-12km and model soundings suggest convective depths extending up close to 700mb with trough passage, QPF looks to be less than 0.15" and will limit widespread snow squall activity. Though some flurries or a quick snow shower is possible during the morning hours Saturday, especially across northern VT. A possible snow squall isn`t completely ruled out and will continued to monitored with any potential increased moisture coming out of Canada this morning. A strong jet will accompany the shortwave as well, and with decent mixing expect gusty winds will continue much the day Saturday. Drier air works in Saturday afternoon, bringing the shower potential to an end and even allowing for some much missed sunshine by late in the day. However, with gusty winds and temperatures only in the teens and 20s, it will definitely be a cold day more reminiscent of January in spite of any sunshine. Skies will clear and winds lessen overnight Saturday night as high pressure builds across the region, and this combined with nice fresh snowpack will make for a very cold night indeed. Lows drop down into the single digits areawide, with negative numbers likely in the Northeast Kingdom and Adirondacks. Even with the winds decreasing, look for higher elevations to see wind chills in the negative teens. Cold temperatures and northerly flow and dry conditions will continue on Sunday with less cloud cover than Saturday. Look for high temperatures to be not much better than Saturday with the valleys only reaching the low 20s and other locations in the teens. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
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As of 335 PM EDT Saturday...This period will feature much below temperatures and dry conditions as cold northwest flow prevails with sfc high pres anchored just south of Hudson Bay. The forecast challenge for Monday into Monday Night will be temperatures as position of sfc high may keep atmosphere just mixed enough to prevent temps from completely bottoming out. Progged 850mb temps modify slightly by 18z Monday with values btwn -13c and -16c, which with good mixing and sun should result in high temps mid teens mountains to mid 20s valleys with a few upper 20s possible. Still 10 to 15 degrees below normal for mid/late March, normal high at BTV is near 40f by early next week. Still some gradient with position of sfc high pres to our northwest on Monday Night...but with clear skies thinking winds will decouple in protected valleys with lows -5F NEK/SLK to lower teens CPV/SLV and lower CT River Valley. However, would not be surprised with a few readings between -10f and -15f by early Tuesday Morning if high clouds can stay to our south.
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As of 335 PM EDT Saturday...Long term will continue to support mean mid/upper level trof across the eastern conus with undefined split flow between northern and southern streams. Latest guidance shows northern stream jet with northwest flow aloft prevails across the northern Great Lakes into the NE CONUS with no interaction with southern stream...which should keep the storm track to our south this upcoming week. This pattern supports much below normal temps and limited chances for precip...and is very similar to our pattern in early January, except now we are in mid/late March and temps will be warmer. Interesting GFS bukfit for BTV shows only 0.01 qpf through 12z Thursday...indicating how dry the northwest flow will be. Still have to watch southern stream energy ejecting toward the mid atlantic states and associated sfc low pres...but all guidance shows this system staying to our south attm...with no real northern stream interaction. The upper level pattern and associated pieces of short wave energy becomes very complex and messy toward mid week, which results in plenty of uncertainty. The combination of departing low pres southeast of the BM and high pres anchored over Hudson Bay will help to provide region with a modifying arctic air thru late week. ECMWF and GEM are much more aggressive with deepening trof and associated low level caa for next weekend with another shot of reinforcing cold air possible...which seems reasonable given upper level pattern. Progged 850mb temps warm between -8c and -10c by midweek supporting highs back into the mid 20s to mid/upper 30s. Little change anticipated in 925mb to 850mb thermal profiles through most of the week and into early next weekend. Temps will slowly modify toward normal levels by Friday...before additional cooling arrives next weekend or early the following week.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/... Through 18Z Sunday...Primarily VFR conditions will persist through the TAF period with the main aviation concern being gusty northwesterly winds this afternoon. Expect winds to decrease to the 10-20 knot range around 22Z, and then slacken to under 10 knots overnight as high pressure builds in. A few isolated snow showers are occurring amid the unstable atmosphere this afternoon, but these will weaken by evening as the atmosphere stabilizes. Any areas that do see a snow shower could see conditions temporarily drop to MVFR/IFR, but the deterioration of flight conditions would be short lived due to the isolated nature of the showers. After 00Z, expect dry weather and VFR conditions through the remainder of the TAF period. Outlook... Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: Mainly VFR, with areas MVFR possible. NO SIG WX. Wednesday: Mainly MVFR, with local IFR possible. Slight chance SHSN. Wednesday Night: Mainly VFR, with local MVFR possible. Slight chance SHSN. Thursday: Mainly MVFR, with local IFR possible. Slight chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Verasamy NEAR TERM...RSD/Verasamy SHORT TERM...Taber LONG TERM...Taber AVIATION...RSD is the U.S. government's official web portal to all federal, state and local government web resources and services.