Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 212333
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
733 PM EDT Tue Aug 21 2018

.SYNOPSIS...
Conditions will begin to deteriorate tonight as an upper level
trough of low pressure displaces high pressure and brings the return
of rainfall to the region. Rain will continue through Wednesday
afternoon before exiting to the east. Skies will clear heading into
Thursday and will continue to remain mostly clear through the first
half of the weekend. Temperatures will remain near normal with
temperatures a degree or two with each passing day.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 726 PM EDT Tuesday...Appears best large-scale forcing and
timing of bulk of shower activity will be a bit slower than
previous forecast. Monitoring trends at 2315Z, 1003mb sfc low is
located west of KBUF with broken line of convective storms
extending from wrn Lake Ontario swd across swrn NY into wrn PA.
Leading band of showers have also developed across ern Lake
Ontario swd into s-central NY. Thus, appears we`ll see some
scattered -SHRA beginning around 02Z for St. Lawrence County,
but best axis of moderate showers will generally occur after
midnight, and during the pre-dawn hours across VT. Instability
gradually wanes to the east of ongoing activity (and with onset
of diurnal cooling cycle). Thus, anticipate thunderstorm threat
will be isold, and kept just a slight chance across Franklin NY
and St. Lawrence Counties thru midnight. Prevailing southerly
gradient flow and widespread mid-level clouds will keep
temperatures from falling very quickly overnight. Temperatures
should hold in the lower 70s overnight at BTV, and generally in
the mid-upr 60s elsewhere.

Previous Discussion...Low pressure currently spinning just
north of Lake Erie will continue to slide off to the northeast
overnight, dragging its attendant cold front in its wake.
Showers associated with a shortwave ahead of the upper trough
are moving into the St Lawrence Valley at this hour, and this
activity will gradually spread northward through the evening
hours. The best dynamics will remain to our north, but can`t
rule out a stray rumble of thunder or two. Otherwise, mainly
scattered to numerous showers expected tonight, first in
northern New York, and likely not reaching eastern Vermont until
midnight or later as the pre- frontal trough moves eastward.
PWATS will again approach 2 inches as moisture streams northward
ahead of the front, so some briefly heavy rain will be possible
as well. This influx of moisture will also keep temperatures up
in the 60s to around 70 tonight. The cold front will push
eastward across the region Wednesday morning into early
afternoon, and this may again serve as the focus for a few
thunderstorms. Drier air will spill into the region behind the
front, bringing showers to an end from west to east during the
late afternoon/early evening hours. Rainfall totals will be a
quarter to a half inch. Tomorrow`s highs will be cooler than
today owing to more cloud cover and the aforementioned frontal
passage, mainly in the lower to mid 70s, with some spots in the
higher elevations staying in the 60s. The other concern for
tonight and Wednesday will be gusty winds, first south to
southwest ahead of the front, then turning to the west and
northwest post-front tomorrow afternoon. Gusts up to 25 mph will
be possible. For Wednesday night...clearing skies and
continuing northwest flow will allow for a refreshing night in
the mid 40s to mid 50s.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 345 PM EDT Tuesday...Thursday and Thursday night will
feature dry weather with seasonable temperatures. High pressure
will shift eastward into our area bringing a cooler and drier
air mass with it, providing the North Country with a very
pleasant day. Thursday night will see the high pressure ridge
build and crest overhead, so we`ll have an ideal radiational
cooling night.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 345 PM EDT Tuesday...Ridge of surface high pressure will
remain over the region through Friday night with fair weather
continuing through this time frame. High pressure slides East
and off the coast Saturday, and a weak upper level trough will
approach from our west. As the center of the surface high shifts
to the Mid-Atlantic, mid to upper-level flow will becoming
increasingly westerly and tap into warmer air from the central
US. This will allow for surface temperatures to warm back up to
the upper 70s/low 80s range. To our west a closed upper level
low over the Northern Plains will become an open wave and lift
north of our region. Still a lot of uncertainty but we may end
up seeing some showers from this Saturday night, but very weak
forcing. Heading into next week, we may see a large scale
pattern change with the northern tier of the country seeing a
more westerly and progressive weather pattern.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...VFR conditions will continue for the
next several hours before beginning to trend downward during the
overnight hours. Based on upstream observations, MVFR ceilings
are expected over northern New York around 03Z to 04Z while
Vermont sites will likely take until 08Z to trend downward.
Current thinking is that precipitation will come through rather
piecemeal which will make it a little difficult time time
visibility reductions from rainfall. However, it looks like the
convective nature of the rainfall will dwindle prior to hitting
the North Country and we will be left with the remnants of prior
convection. This should lead to mostly VFR visibilities through
the period although KMPV could see some reduction down to 3
miles around sunrise. A wind shift from the south to northwest
is expected on Wednesday generally beginning around 14Z to 15Z
with winds in the 12 to 18 kt range.

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: VFR. NO SIG WX.
Saturday Night: VFR. Slight chance SHRA.
Sunday: Mainly VFR, with areas MVFR possible. Slight chance SHRA,
Slight chance TSRA.

&&

.MARINE...
A lake wind advisory is in effect for tonight through Wednesday
as south winds increase into the 15 to 25 knot range tonight, then
shift to the west Wednesday afternoon. Winds of this magnitude
will create waves of 3 to 5 feet and rather choppy
conditions, especially over the northern half of Lake Champlain
tonight and then the east side of the lake on Wednesday once
the winds shift to the west.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Hastings
NEAR TERM...Banacos/Hastings
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Clay
MARINE...Evenson



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