Area Forecast Discussion
Issued by NWS Burlington, VT

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794 FXUS61 KBTV 210902 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 402 AM EST Tue Feb 21 2017 .SYNOPSIS... A weak disturbance and associated ribbon of mid level moisture will produce scattered rain showers late this afternoon across northern New York. This threat of showers will spread into Vermont overnight...with a few pockets of light freezing rain possible in the deeper valleys. Very minimal ice accumulation if any is anticipated...with temperatures in the upper 30s to mid 40s today. A big warming trend is expected for most of the week with more showers anticipated on Thursday Night into the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 401 AM EST Tuesday...1031mb high pres centered over eastern VT this morning will shift east...while decaying short wave energy and associated ribbon of 850 to 500mb moisture approaches our western cwa by 00z Weds. Latest trends have been for this moisture to weaken as it encounter mid/upper level ridge across the ne CONUS and limit the overall qpf output over our forecast area. GFS/NAM and local WRF show up to 0.10 for mountain zones...with a trace to 0.05 most other locations. Developing 850mb southwest winds of 20 to 25 knots will produce modest low level warm air advection today with 925mb temps ranging from near 0c NEK to +6c western dacks/ anticipating a large spread in highs today. Also...playing a factor will be amount of sunshine and how quickly clouds spread from west to east across our cwa...but thinking highs range from the mid/upper 30s NEK to mid/upper 40s SLV/Western Dacks with maybe a few lower 50s near Potsdam/Edwards. Tonight...soundings show deep dry layer between 925mb and 700mb becoming saturated as moisture advection occurs on south to southwest winds. Thinking temps fall early as some evaporational cooling occurs...but with clouds and developing southerly flow of 10 to 20 knots...especially cpv/slv temps hold mainly in the mid/upper 30s to near 40f most of the night. East of the greens still looking at some pockets of <0C temps in the protected valley with the potential for some spotty freezing rain. Given the marginal temps and scattered precip/very light qpf...not anticipating widespread coverage of freeze rain and very minor ice accumulation. If needed will handle with a sps. Wednesday...low to mid level warm air advection continues with progged 925mb to 850mb temps climbing between 2c and 4c. However...soundings especially the nam shows plenty of low level moisture trapped below thermal inversion between surface and 850mb. Is this overdone again or do we see lots of low clouds and limited sun on Weds...keeping our temps on the cooler side of guidance with some areas of light precip. Soundings show this moisture mixing out...especially during the afternoon hours as top of the mixed layer winds increase between 15 and 20 knots and drier air aloft is advected toward the surface. Will trend toward the warmer side of guidance and keep forecast mainly dry at this time...with highs mainly lower 40s northeast kingdom to near 50f cpv/slv and western dacks. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 358 AM EST Tuesday...Thursday will see another low pressure system from the Great Lakes region pass to the north of the CWA. Light showers, mainly in the northern half of the forecast area, are expected with the system passes north of the border and into northern Maine. QPF is minimal with this system with the Adirondacks seeing a couple tenths of an inch, the Northern Vermont counties seeing around a tenth and the rest of the state seeing only a few hundreths of an inch. Southerly flow will continue to boost temps well above seasonal norms for Thursday with highs in the 50`s for the majority of the area and overnight lows in the mid to upper 30`s. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 358 AM EST Tuesday...Friday sees low pressure tracking north and west of our region from the Great Lakes Friday through early Sunday morning. Models are in general agreement of a warm front lifting through the region Friday afternoon/evening with precipitation ramping up through the day Saturday with the peak Saturday afternoon/evening just ahead of the passage of a cold front. Winds out ahead of the front could lead to gusty conditions and potential advisory level winds especially across the Champlain Valley as the 00Z GFS indicates 850mb winds to reach 65 knots Saturday afternoon. After frontal passage, rain will switch over to snow showers Saturday night with the strong cold air advection. Very warm temperatures are expected Saturday ahead of the cold frontal passage. Temperatures overall look to be in the 50s with the Champlain Valley pushing a record breaking 60. A sharp cold front will drop temps quickly back into the 20s Saturday night. Possible flash freeze issues are possible with temperatures dropping so sharply after a moderate rainfall. Moving into next week, more seasonable weather will return for Sunday through Tuesday. && .AVIATION /09Z Tuesday THROUGH Saturday/... Through 06z Wednesday...High pressure across area bringing mostly clear skies and VFR conditions to the region through overnight period. Will see increasing clouds above 15kft after 12Z Tuesday as high clouds advance from W-E ahead of the next trough across the Great Lakes. Precipitation arrives in St. Lawrence Valley near 00z Wed and eventually sweeps east. Activity is light with showery rain or freezing rain in eastern VT with MVFR cigs due to pcpn. Light and variable winds overnight but as high pressure system shifts to the east, will see winds developing from the south toward daybreak Tuesday, increasing to 10-12kts with gusts to 20kts at BTV by 18z Tuesday. Outlook 06z Wednesday through Saturday... A weak trough will bring periods of light rain, with pockets of freezing rain east of the Green Mtns during Tuesday night. Brief MVFR conditions are possible with this system, mainly during the pre-dawn hours Wednesday. Generally returning VFR with high pressure Wednesday afternoon through Friday morning. Warm front approaches from the southwest Friday afternoon with increasing chances for rain and periods of MVFR/IFR conditions. Will also see possible sfc wind gusts locally in excess of 25kts with low-level turbulence and wind shear late Friday through Saturday as deep low pressure passes to our west across the Great Lakes and Ontario. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...MV LONG TERM...MV AVIATION...Banacos/SLW is the U.S. government's official web portal to all federal, state and local government web resources and services.