Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 181435 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 935 AM EST Mon Nov 18 2019 .SYNOPSIS... Freezing rain will move into southern and eastern Vermont this afternoon with a mix of freezing rain and sleet moving into western Vermont and northern New York during the evening and overnight hours. This mix of precipitation will change over to snow prior to sunrise on Tuesday and will gradually taper off during the afternoon hours on Tuesday. Quieter weather is expected on Wednesday and Thursday but another storm system will move into the region on Friday. This system will likely bring a mix of rain and snow to the North Country. && .NEAR TERM /THROUGH TUESDAY/... As of 927 AM EST Monday...Overall forecast remains on track this morning. Cloud cover is creeping across the whole region and over the Adirondacks now. Warm air advecting over the cold air near the surface will keep conditions cloudy with periods of drizzle/freezing drizzle possible late morning/early afternoon. Otherwise, mainly minor tweaks to the previous forecast based on the discussion below. Previous Discussion...Temperatures overnight have been 10 to 15 degrees warmer than yesterday morning as warm air advection coupled with increasing cloud cover stifling our cooling. Clouds cover will continue to work into the region this morning but weak and blocked flow has kept the clouds on the windward (southern and western) slopes of the Adirondack and Green Mountains. The coastal low developing well off the coast of North Carolina and Virgina has tracked further east than the guidance showed this time yesterday. The observed pressure falls from the few buoys and coastal sites show the low will likely continue to track to the northeast through the remaining morning hours which should take this low well east of the benchmark. This will likely yield very little precip working into the North Country through the morning and afternoon hours as the main moisture axis will be shunted eastward. Some wrap- around precipitation will be possible across eastern Vermont during the mid to late afternoon hours which looks like it should fall as freezing rain. The big question across southern and eastern Vermont this afternoon will be the degree of heating at the surface. Any fluctuations a degree or two warmer than the current forecast would likely yield a transition from freezing rain to just a cold rain but the northerly flow developing this morning should help replenish the cold air and negate the latent heat release from the falling freezing rain. Heading into the evening and overnight hours, things begin to get even more interesting. A negatively tilted 850-500 mb trough will move across the North Country with strong synoptic forcing and upper level diffluence. The combination of these features will allow precipitation to overspread the North Country between 8 and 11 PM. Much of this precipitation will start off as freezing rain with warmer air overrunning a below freezing surface. The thermal profiles remain the most challenging aspect of the forecast as the placement and timing of the upper level trough will impact the degree of cold air advection and the ultimate transition from freezing rain to an hour or two of sleet and eventually over to snow. Freezing rain amounts are slightly less for the Champlain Valley given the latest data with less than a tenth of an inch expected but up to two tenths of an inch is still possible for southern and eastern Vermont. It should be noted that the 06Z NAM has come into very good agreement with the 00Z GFS and 00Z ECMWF in regards to the precipitation tonight which begins to increase our confidence in a mixed precipitation event happening through the overnight hours. It looks like most places will transition to snow before the morning commute on Tuesday but the possibility of an icy layer on the roadways with falling wet (8:1 to 10:1 ratio) snow will create some very slick surfaces. Snowfall will taper off from southwest to northeast throughout the day on Tuesday before ending in northeastern Vermont by late afternoon. Overall snowfall accumulations look to range from 1-3 inches with some local amounts near 4 inches across the northern Green Mountains. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... As of 410 AM EST Monday...Tuesday night and Wednesday will be relatively quiet in relation to the near term. A negatively tilted upper level trough will pass to our South during these 2 periods. Will be tough to rule out some light snow showers with the upper trough and associated vorticity advection nearby. Temperatures will warm a bit, but still remain below seasonal normals. Mainly cloudy conditions are anticipated. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 410 AM EST Monday...Wednesday night and Thursday will trend drier with surface and upper level ridging building over the north country. Headed into Thursday night, a low pressure system will lift northeastward from the Great Lakes into Quebec. Will have chance for rain showers with this feature on Friday, though nothing very significant with best forcing remaining closer to parent low well to our North. Better chance for precipitation in our area will come on Friday night as surface cold front crosses the area and we`ll have better forcing with the surface feature. At this time looks like precipitation would start out as rain and then change to snow or snow showers with cold air advection behind the surface front. Pretty decent upper level trough and shortwave energy also passing through on Friday night. Showers will end during Saturday morning. The rest of Saturday heading into Saturday night would mainly be dry with some weak surface ridging. Headed into Sunday a weak clipper type low crossing the North Country will bring another chance for light snow showers. Surface and upper level ridging will return once again for Monday and Tuesday. Very changeable patterns in the extended portion of the forecast will keep the weather active. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... Through 00Z Tuesday...An MVFR stratus deck continues to creep across southern Vermont and portions of northern New York this morning. Weak and blocked flow has kept the stratus from advancing across KSLK and KMSS. Light southeasterly winds should continue this morning with the surface winds shifting to the north/northwest by this afternoon. The onset of precipitation is not expected to start until after 00Z. Have included mention of -FZRA and -PL at all TAF sites except KMSS. It definitely looks like the onset of precipitation will be some form of mixed freezing rain and sleet that will likely transition to snow after 06Z. Outlook... Tuesday: MVFR/IFR conditions possible. Chance SN, Chance RA. Tuesday Night: Mainly MVFR, with areas VFR possible. NO SIG WX. Wednesday: Mainly MVFR, with local IFR possible. Slight chance SHSN. Wednesday Night: Mainly VFR, with local IFR possible. Slight chance SHSN. Thursday: Mainly VFR, with local IFR possible. Slight chance SHRA. Thursday Night: Mainly VFR, with areas MVFR possible. Likely SHRA, Chance SHSN. Friday: Mainly MVFR, with areas IFR possible. Likely SHRA, Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Weather Advisory from 6 PM this evening to 1 PM EST Tuesday for VTZ001>009-016>018. Winter Weather Advisory until 1 PM EST Tuesday for VTZ010>012- 019. NY...Winter Weather Advisory from 6 PM this evening to 1 PM EST Tuesday for NYZ027-028-030-031-034-035. && $$ SYNOPSIS...Clay NEAR TERM...Clay/Haynes SHORT TERM...Neiles LONG TERM...Neiles AVIATION...Clay

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