Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 232354 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 654 PM EST Tue Jan 23 2018 .SYNOPSIS... Rainfall will continue through the early evening hours before becoming more focused on the higher terrain. As colder air moves in this evening expect a transition back to snow with 1 to 2 inches possible in the higher terrain. We`ll see another chance for rainfall and another warm up heading into the weekend as a system will bring rain and snow to the region. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... As of 444 PM EST Tuesday...Latest web cams across through North Country and reports are coming in with localized patchy dense fog across the region. So we`ve updated the forecast to include mention of patch dense fog. Main concerns are that with the evening commute and rapidly deteriorating visibilities travel conditions could become hazardous quickly. Previous discussion...Light rain continues across the North Country with temperatures warming into the mid 40s across northern New York while only warming into the upper 30s east of the Greens. Latest MRMS/URMA rainfall estimates show between 0.2-0.5 inches of rain has fallen across northern New York and between 0.5-1.0 inches fell. We are only just starting to see an response on the rivers levels now and so we`ll continue to monitor the rivers as we anticipate modest rises on many Vermont locations. The rain comes to an end this evening as cold air pushes in behind a cold front overnight. Rain will transition to snow around 7-9 pm and become concentrated over the higher terrain and the light snow will slowly taper off by mid morning. Temps through the overnight will slowly fall into the the low 20s and even teens across northern New York. With cold air advection pushing into the North Country I don`t anticipate temps warming much if at all during the day Wednesday. Highs will be in the upper teens to low 20s with the warmest temps near Lake Champlain. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... As of 336 PM EST Tuesday...Thursday/Thursday night will be the coldest period of the week as flow turns increasingly northwesterly behind the departing early/mid week system. This will usher in a colder air mass from central Canada featuring 850 mb temperatures nearing -20C. At the surface, high pressure will build in from the west, resulting in a cold but mainly sunny day Thursday with rapid overnight cooling Thursday night. Look for daytime highs in the teens Thursday dipping down to near zero Thursday night, with readings below zero expected in the northern Adirondacks in NY and east of the Green Mountains in VT. Winds will be lighter Thursday than Wednesday, however even the 5-10 mph winds forecasted will make for cold wind chills Thursday morning through Thursday evening. While the building high pressure will create a subsidence inversion between 800 and 900 mb, the surface boundary layer will continue to be fairly well mixed. Some gusts of 15 to 20 mph, particularly Thursday afternoon, can`t be ruled out. The winds will subside by Thursday evening, further supporting the rapid radiational heat loss overnight. Starting Friday morning, the center of the surface high will shift further east and offshore, allowing for widespread southerly return flow over the eastern US. This will set off a warming trend throughout the day Friday that will allow daytime high temperatures to top out in the 20s throughout northern NY and VT. Friday will feature a few more clouds than Thursday, however will still be dry and overall a good day to get some fresh air and sunshine before the next system steals our remaining sun over the weekend. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 500 PM EST Tuesday...An increasingly amplified upper-level pattern will develop towards the end of the week featuring a building subtropical ridge off the east coast and a digging trough upstream over the central US. Between these two features, deep southwesterly flow will direct warm, moist maritime tropical air from the Gulf Coast towards the northeastern US. Models continue to have difficulty coming to a consensus with the handling of the overall evolution of the longwave pattern, with the deterministic GFS holding strong with remarkable run- to-run consistency as the main outlier. Previous runs of the ECMWF/CMC have favored a higher amplitude trough digging over the central US. This higher amplification solution (ECMWF/CMC) results in a slower progression of the trough, allowing for increased moisture transport and warm air advection into our area than the more progressive GFS solution. With fairly high spread between the individual GFS ensemble members and the latest 23.12Z ECMWF trending towards the lesser amplified GFS, thinking it`s still to early to completely rule out any solution. However, continued to trend the extended forecast towards the ECMWF/CMC higher amplified solution, with higher temperatures and categorical PoPs Sunday. Much uncertainty exists however in the amount of warming (affecting precipitation type forecast), timing, and QPF associated with the system. With the heavier use of the ECMWF/CMC, the long term forecast features building cloud cover and warmer temperatures Saturday, followed by a cold front passage Sunday. The passage of the cold front will bring quite a bit of rain Sunday that will transition to snow Sunday night as temperatures drop. Overall, it wouldn`t be out of the question to get close to an inch of QPF out of this system Sunday through Monday, renewing hydro concerns once again. Behind the front, temperatures will begin another downward trend for the early to mid part of the next work week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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Through 00Z Thursday...Challenging 6 hour aviation forecast with rapidly changing conditions expected as surface cold front is moving across the cpv now. This front will be accompanied by a brief 10 to 20 minute heavy rain shower along with a wind shift to the west. Winds will become gusty at times up to 30 knots which will help to quickly break up the fog at mpv. Meanwhile...expect lingering rain/snow showers to redevelop over northern ny/slv with periods of mvfr cigs/vis. Have placed a tempo from 03-06z of 2sm vis with -sn and mvfr cigs at slk. Breezy winds will prevail across all taf sites from the west/northwest at 15 to 25 knots into Weds with mvfr cigs becoming vfr by 16z Weds. Winds will decease to under 10 knots by sunset on Weds. Outlook... Wednesday Night: VFR. NO SIG WX. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: Mainly VFR, with areas MVFR possible. Slight chance SHRA, Slight chance FZRA, Slight chance SN. Saturday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance SHSN. Sunday: Mainly MVFR, with areas VFR possible. Likely RA.
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&& .HYDROLOGY... As of 353 PM EST Tuesday...Widespread rainfall will continue through the evening however the bulk of the rainfall has already fallen. Current data suggests that between 0.25-0.75 inches of rain fell over Northern New York with between 0.50 to 1.00 inch falling over Vermont. Given the substantial loss of snowpack across lower elevations during last week`s storm, and the fact that the warm- up will be of lesser magnitude we are not expecting significant ice movement or and only modest water rises on area rivers at this time. This is in close agreement with NERFC guidance and our latest river forecasts. Nevertheless conditions will continue to be monitored closely over the next 36 hours. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Deal NEAR TERM...Deal SHORT TERM...RSD LONG TERM...RSD AVIATION...Taber HYDROLOGY...WFO BTV is the U.S. government's official web portal to all federal, state and local government web resources and services.