Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 172004 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 404 PM EDT Sat Mar 17 2018 .SYNOPSIS... High pressure will deliver a fairly quiet, albeit cold, start to the week. Still watching a coastal low that will develop midweek, however current indications are that this low will remain well to our south and be a non-factor for us in the North Country. Temperatures will be around 10 to 20 degrees F below normal, with the cold temperatures lasting through the week as we remain under predominantly northwesterly flow. && .NEAR TERM /THROUGH SUNDAY NIGHT/... As of 355 PM EDT Saturday...A look at regional observations this afternoon paints the picture, showing a distinct cold front working its way south over southern Vermont and the North Country of New York. Along and behind the front, temperatures have dropped or remained fairly steady through the morning and gusty northwesterly winds peaked this afternoon. Once the sun sets this evening, the deeply mixed boundary layer will decouple, allowing a surface inversion to develop. This will result in rapidly decreasing winds this evening along with plummeting temperatures tonight. Persistent northwesterly flow will continue to tap into a continental polar airmass over Quebec, pulling unseasonably cold air southeastward into New England. 925 mb temps overhead will fall to between -16 and -19 C. Surface winds will taper off as ridging builds, however the center of the high pressure will remain well to our northwest over Central Canada, so not expecting calm winds. Somewhere in the 5-10 knots range would make sense, which would limit the degree of radiational cooling that can be achieved overnight. Also working against maximum radiational cooling will be some lingering low level moisture that hiRes models are indicating may remain trapped below the inversion overnight. All these factors taken into account, it`s still going to be a cold night. Have knocked down forecast temperatures to below guidance as models rarely capture the degree of cooling in setups like this. However, the forecast hinges on how much moisture remains trapped in the surface layer; if we`re able to dry out completely, forecast won`t be cold enough. Current thinking is that we`ll see temperatures drop into the lower single digits below zero in the northern Adirondacks and the Northeast Kingdom, while the rest of Vermont and the Saint Lawrence Valley will bottom out in the single digits above zero. Will be monitoring cloud cover through the night and adjust forecast as needed. By Sunday morning, a weak surface low will enter the forecast picture. This low and its associated clouds are currently visible on satellite imagery over central Ontario. Overnight, expect the weak system to continue on its southeastward track and move into western New York by Sunday morning. The better impacts of this low will remain to the southwest of our forecast area, however we can expect some increasing clouds during the day over northern New York and then into southern Vermont and maybe an isolated snow shower or two as the system passes by to our south and west. After this feature clears the forecast area, we should be drier as ridging once again builds from central Canada. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... 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. && .LONG TERM /TUESDAY THROUGH SATURDAY/... 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. && .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...RSD NEAR TERM...RSD 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.