Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 210825 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 425 AM EDT Fri Oct 21 2016 .SYNOPSIS... Rain event persists over the North Country as a mid-level longwave trough continues to dig south and east from Canada. This trough will become negatively tilted late Friday into early Saturday, keeping frontal boundary, associated surface low pressure system and rain over the region through Saturday night/early Sunday. Colder air will filter in behind this system along with northwest flow producing upslope rain and snow showers Sunday through Tuesday. Another surface low pressure system looks to affect the Northeast Thursday. && .NEAR TERM /THROUGH SATURDAY/... As of 425 AM EDT Friday...No big changes. Bulk of precip over Nrn NY and NW VT this morning. With mid-level trough expected to become negatively tilted this afternoon, precip shield looks to pivot NW providing break in rain to VT and portions of Champlain Valley late morning to early afternoon. At the same time, NAM and GFS indicate strong low level deformation producing moderate to heavy rain at times over Nrn NY, before weakening as we head into the evening hours. For this afternoon, the most uncertainty lies with exact positioning of surface low pressure and, therefore, wind direction as there will be a markedly sharp wind shift over the region. Models continue to indicate moisture from coastal system will feed into the NE low pressure system latter half of today into tonight. This combined with diffluent mid-level flow will result in possible periods of moderate rain over VT, especially during the overnight. Saturday morning, models find more consensus on surface low positioning along the southern New England coast, traversing northward during the day. This means deep NW flow over the North Country will bring in colder air and terrain enhanced rain showers. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 400 AM EDT Friday...Rain will gradually change to snow over the higher elevations of the Adirondacks and Green Mountains Saturday night as a closed upper low moves over the region which will provide dynamical cooling aloft with a change to snow over the higher elevations. Have leaned toward the warmer GFS MOS guidance for min temperatures Saturday night, as the NAM MOS guidance looks too cold. Also, combination of cloud cover and gusty west winds will help to keep air well mixed and will help to keep temperatures up. Thus, have lowered snowfall amounts a bit from the previous forecast given a slower changeover to snow in the higher elevations. Models showing precipitation winding down across the region Sunday morning, with most of the activity done by midday on Sunday. Models show the region will still be under cyclonic flow Sunday night from the departing surface low pressure area over Quebec Sunday night. Have kept in some slight chance pops for rain or snow showers Sunday night. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 400 AM EDT Friday...The north country remains under cyclonic flow from the departing surface low pressure area over eastern Quebec Monday and Tuesday. Thus, have kept in slight or low chance pops for rain or snow showers for Monday and Tuesday. High pressure will build slowly east from the Great Lakes Tuesday night, with mainly fair and dry weather from Tuesday night through early Thursday. On Thursday, a warm front will approach the region from the Great lakes and the Ohio valley. Have put in a chance of rain showers into the forecast for mainly Thursday afternoon. && .AVIATION /09Z Friday THROUGH Tuesday/... Through 06z Saturday...MVFR/IFR conditions persist throughout this long duration event, coming to an end Sunday night. Rain more persistent over Nrn NY this morning through early afternoon. Then increased moisture from subtropical system feeds into the NE low affecting our area Friday afternoon. This will allow resurgence in moisture and rain to spread east as the NE low swings from PA to the srn New England coast Friday night. Winds gusty where it isn`t raining and LLWS possible over SLK this morning. Low level jet weakens and exits east early Friday. Outlook 06z Saturday through Tuesday... 06z Saturday through 00z Monday: A prolonged period of unsettled conditions is expected with widespread MVFR/IFR in periods of rain. 00z Monday through 00z Wednesday: A mix of VFR/MVFR with upslope showers in NW flow. && .HYDROLOGY... As of 425 AM EDT Friday...Rainfall amounts ranging from 1-1.5 inches have already fallen across the St Lawrence Valley, northeastward across the northern Champlain Valley this morning. Rain will continue today through Sunday, being most persistent over the St Lawrence Valley and Adirondacks. An additional 1 to 3 inches is expected. Given most of the region is in moderate to severe drought...we are not anticipating any widespread hydro issues. However...some minor urban and street flooding is possible associated with the heavier rainfall rates on Friday with leaves clogging storm drains. Otherwise...some modest rises in local rivers and streams are likely this weekend...but no widespread flooding is anticipated. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...KGM NEAR TERM...KGM SHORT TERM...WGH LONG TERM...WGH AVIATION...KGM HYDROLOGY...KGM is the U.S. government's official web portal to all federal, state and local government web resources and services.