Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 191144 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 744 AM EDT Wed Apr 19 2017 .SYNOPSIS... A series of low pressure systems will move from west to east across northern New England today through Friday. Expect showers to increase over the area this afternoon and tonight before ending early Thursday morning. Drier weather briefly returns Thursday afternoon but a second low pressure system moves in Thursday night and Friday morning for widespread rainfall across the region. Drier weather returns once again for Friday afternoon through the first part of the weekend. && .NEAR TERM /THROUGH THURSDAY/...
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As of 744 AM EDT Wednesday...Going forecast in good shape with no real changes needed at this time as clouds will continue to increase this morning as well as the winds. Best precipitation chances come this afternoon and tonight. Flood warning issued earlier for Lake Champlain continues as the lake just went above flood stage at Rouses Point. Previous Discussion... Updating the forecast discussion to indicate a flood warning was issued for Lake Champlain versus the initial thinking that only a special weather statement would be needed. Already seeing a northward push of water toward the Canadian border early this morning and we have not even developed the strongest south winds yet. Speeds will increase into the 25 to 35 knot range and push even more water northward plus develop 3 to 6 foot waves. The lake level is already high and with these expected conditions...flooding is likely to occur from the Burlington area northward. Already seeing the lake level near 100 feet at the Rouses Point gage so it should not take much to go just above that and enhance the potential for flooding. The flooding threat will exist today into tonight and start to diminish as winds taper off later tonight. Otherwise...water vapor imagery shows shortwave trough moving across the area early this morning and this feature is helping to moisten up the atmosphere...but not enough to produce any precipitation. It will be the second shortwave trough...currently over the Upper Midwest that should help moisten the atmosphere sufficiently to produce precipitation. Expecting rain showers to start moving into northern New York this afternoon and across Vermont during the late afternoon and evening hours. Looking at a general tenth to a third of an inch of rain with the second shortwave...highest amounts over northern New York and the northern half of Vermont and lesser amounts over central and southern Vermont. Highs today will generally be in the 50s with 40s in the mountains. The showers will come to an end after midnight as the shortwave trough moves east of the region. It now looks like a good part of the day on Thursday will be dry before another shortwave trough approaches the region Thursday night. We should be able to see some sunshine Thursday with highs in the 50s and some lower 60s down across south central Vermont.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 333 AM EDT Wednesday...Really not a whole lot of change from the previous forecast thinking, or my own from yesterday with the main changes being to slow precip arrival Thursday night just a tad, and lower storm total QPF values slightly. Vertically stacked low pressure entering into the western Great Lakes Thursday night will track east/northeast over the Ontario/Quebec border by Friday morning, and further northeast into central/southern Quebec Friday night. A deep moisture feed on southwesterly flow between the low and high pressure anchored off the Southeast coast will spread steady rainfall across the North Country from west to east late Thursday evening through Friday morning with PWATS 2-3 standard deviations above normal producing 36 hour rainfall totals by Friday evening averaging around 0.75" with some isolated amounts up to and inch possible. Overall not looking for any widespread hydro issues with area waterways running high, but a few concerns remain. See hydro section below for the details. Relatively progressive nature of the system has the bulk of precipitation exiting to our east Friday afternoon as a mid-level dry slot builds in and the trailing surface cold front approaches. As the front swings through the region Friday night we could see a resurgence of precipitation across portions of central/northern Vermont as the flow turns west/northwest and is marginally blocked. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 333 AM EDT Wednesday...Overall trend for the long term period will be towards quieter weather once we get through Saturday morning where the aforementioned surface low continues to exit east off the Maine coast Friday night, and the parent upper trough swing through. A few isolated to scattered showers will be around early Saturday morning, but by the afternoon surface high pressure begins to build southeastward from southern Ontario/Quebec and will dominate the North Country`s weather through Saturday night with dry conditions expected. For the Sunday/Monday timeframe overall we continue to highlight mainly dry conditions but the forecast area will be in a squeeze play between a northern stream trough and southern stream energy pulling through the central/south East Coast. The latest CMC and ECMWF support the northern stream system dominating and remaining unphased with only a thin ribbon of enhanced moisture swinging through the region Sunday night into Monday morning, while the GFS is slightly stronger with the southern stream. With either solution, we`ll offer low chance for showers across our southern zones during this period, but could see PoPs increasing with time is trends change. High pressure does look to return for Monday/Tuesday. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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Through 12Z Thursday...VFR conditions are expected through at least 18z with only mid and high level clouds moving into the region. Eventually showers and lower clouds will move in between 18z and 06z with MVFR/VFR ceilings and visibilities expected. Gusty south to southwest winds will also develop after 14z with gusts in the 20 to 30 knot range through 00z before tapering off. Showers will also taper off after 06z. Outlook... Thursday: VFR. NO SIG WX. Thursday Night: VFR/MVFR. Breezy. Definite SHRA. Friday: VFR/MVFR. Breezy. Chance SHRA. Friday Night: VFR. Chance SHRA. Saturday: VFR/MVFR. Chance SHRA. Saturday Night: VFR. Slight Chance SHRA. Sunday: VFR. Slight Chance SHRA.
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&& .HYDROLOGY... With two systems bringing rainfall to the North Country this week there are a few concerns on area rivers/streams/lakes which continue to run high with continued higher elevation snowmelt, albeit a bit slower lately due to seasonal temperature. Basin average QPF through Friday from the 2 storms will be in the 0.75-1.25" range across the region with latest ensemble and local model forecasts showing the potential for a few northern gages to reach action and minor flood stage by Friday afternoon. Lake Champlain continues to creep ever so slowly closer to flood stage (100 feet) every day, and expect minor flooding to occur by this weekend, while rivers of greatest concern to reach minor flood stage are the Ausable, Barton, Winooski, Mad, and Missisquoi at this time. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Evenson HYDROLOGY...Lahiff

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