Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 181953 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 253 PM EST Wed Jan 18 2017 .SYNOPSIS... Plenty of clouds will persist over the area tonight through Friday. Some light precipitation is also possible tonight into the first part of Thursday, mainly some light rain or light snow...but there may also be some light freezing drizzle across part of northern New York and northern Vermont. The clouds will also keep above normal temperatures over the region through Friday as well. && .NEAR TERM /THROUGH THURSDAY/... As of 157 PM EST Wednesday...Plenty of fine details for the tonight through Thursday time period. For tonight...plenty of low level moisture will exist over the region along with areas of fog as satellite imagery shows plenty of clouds upstream headed our way. The warmer temperatures over the fresh snowpack should also enhance the potential for some fog and have included for the entire area. Weak shortwave trough moves across eastern Canada tonight and could see some light snow over the area later tonight...mainly over the northern and central sections of Vermont. Any accumulations would be less than an inch. Of note however is the loss of ice in the clouds...especially over northern New York tonight. This would set the stage for some light freezing drizzle and have included in the forecast. On Thursday...looking at plenty of cloud cover all day and with upper ridge building in...low level inversion strengthens to keep clouds and some fog in over the area. As will be the case tonight...warmer air over fresh snowpack will also help enhance the potential for low clouds and fog over the area. Will keep the idea of areas of fog going for Thursday with highs in the 30s to around 40. In addition...areas over northern Vermont may have a little light snow early...but ice goes away in the clouds and some light freezing drizzle may occur in this area as well. Drier air finally moves in during the afternoon hours on Thursday. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
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As of 255 PM EST Wednesday...Large scale synoptic pattern shows mid/upper level ridge directly overhead with building 1020mb surface high pres. This results in a steepening subsidence inversion with very light winds through the vertical profile and plenty of low level moisture trapped below thermal inversion. Forecast challenge will be determining if depth of moisture is enough to produce areas of patchy drizzle/freezing drizzle...especially Thursday Night...followed by any potential clearing on Friday Afternoon. Based on sounding profiles and available moisture thinking any drizzle/freezing drizzle would occur above 1500 feet mainly Thursday Night and again on Friday Night. Overall areal coverage will be limited along with impacts...as temperatures will be holding in the upper 20s to mid 30s for lows during this time period. Daytime temperatures on Friday will be tricky with sharp inversion...supporting higher temps in the mid/upper slopes and cooler values in the deeper valleys like the CT River Valley...Champlain and Saint Lawrence Valleys. Highs mainly in the mid 30s deeper valleys to lower 40s, very difficult to place this detail into the grids. Based on moisture depth of 2000 to 3000 feet...would not be surprised if summits breakout on Friday Afternoon. Have continued with previous forecasters idea of trying to show summits in the clear on Friday Afternoon.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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As of 255 PM EST Wednesday...Pattern becomes more active by early next week with large scale system expected to impact our forecast area. Still plenty of uncertainty on impacts...timing...and thermal profiles. On Saturday...weak 5h vort and thin ribbon of dissipating mid/upper level moisture tries to break down mid/upper level ridge across the NE CONUS. Expecting very little fan fair associated with this energy/moisture...as ridge holds in place. Increasing moisture profiles may produce some very light rain or snow on Saturday with temps mainly in the mid 30s to lower 40s. Potent energy moving into CA on Fri/Sat will quickly eject into the southern Plains by Sunday with a developing and closing off deep full latitude trof taking shape across the eastern CONUS. This system will have plenty of moisture from the pacific sub-tropical jet and moisture advection from the Gulf of Mexico as pws climb between 0.75 and 1.50 inches. A deep south flow aloft and strong 925mb to 850mb flow from the southeast will help to advect this moisture into our region on Monday into Tuesday as surface low pres is located over the mid Atlantic States. Have noted the nose of a 50 to 60 knot southeast 850mb jet angling into our region...resulting in lots of downslope shadowing in the precip fields across the western slopes/northeast Kingdom associated with this system. The potential for gusty southeast downslope winds will need to be watched...along with how much warm air can be advected into our region. Given placement of 1030mb high pres over eastern Canada...some low level cold air will linger to support a snow/sleet/freezing rain threat initially...but this area of high pres is not very cold...so threat is minimal at this time. Next threat with warmer temps and rain...will be to watch area waterway for potential rises and ice jams...all elements to monitor as we move closer to this system. My initial thoughts are lots of items to watch...with some potential impacts...stay tuned. Thermal profiles continue to support much above normal temps through the period...especially overnight lows. Over the weekend progged 925mb to 850mb thermal profiles hover around 0c...with limited mixing supporting highs mainly in the mid 30s to l/m 40s. Lows with clouds will hold mainly in the upper 20s to mid 30s...but if more clearing develops than anticipated much cooler values can be expected...especially in snow pack mountain valleys on Sunday Night. early next week...highs continue to be in the 30s to near 40f with lows mainly in the mid 30s.
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&& .AVIATION /20Z Wednesday THROUGH Monday/... Through 18Z Thursday...A wide range of conditions exists across the area this afternoon with MVFR to LIFR ceilings and IFR to VFR visibilities. Unfortunately these conditions will continue to be rather variable through about 00z and then there will be an overall trend toward lower ceilings and visibilities during the overnight and morning hours on Thursday. During this time period were should see fairly widespread IFR and LIFR ceilings and IFR to MVFR visibilities. Other than some brief snow showers there may be some light freezing drizzle tonight...especially at KMSS and KSLK. Winds will trend toward light and variable at all locations through 00z and remain there for the remainder of the period. 18z Thursday - 18z Friday - dry weather is expected but the potential for low clouds and fog creating MVFR and IFR conditions will exist during this period. 18z Friday through Monday - VFR conditions are expected through the period. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson SHORT TERM...Taber LONG TERM...Taber AVIATION...Evenson

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