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Office: BTV

FXUS61 KBTV 211932

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

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.


As of 331 PM EDT Tuesday...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.


As of 431 AM EDT Tuesday...As the cold front departs to our
east, a deep, drying northwesterly flow will become established
over the forecast area. Accordingly, showers will taper off
through the overnight hours. Clearing through the night may
result in the development of some patchy fog in some
climatologically favored locations, however northwesterly winds
just off the surface will work against widespread development.
Still, any sheltered areas that are able to decouple overnight
could see some mist/fog. The North Country will see a shot of
relatively cold air Wednesday night behind the departing system;
lows will generally be in the 40s to mid 50s.

Still on track for a very pleasant Thursday as high pressure
over the Central US shifts to the Mid-Atlantic. 925 mb temperatures
15-17C support highs generally in the mid to upper 70s. Mixing
of the boundary layer will transport drier air aloft down to the
surface, so expect a refreshing afternoon as dewpoints drop to
the 40s and a light northerly/northwesterly breeze is established.


As of 431 AM EDT Tuesday...Ridging builds in Thursday night and
remains in control through Friday night...keeping fair weather
in place to end out the work week. 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. The ridge will shift
offshore over the weekend, while further upstream a closed low
from the northern Plains will become an open wave and lift
northeastward over eastern Canada/northeastern US. There remains
some uncertainty in the strength of the ridge and whether or
not the ridge will essentially deflect the wave's energy to our
north or not. Thinking the ridge will keep us dry Saturday, but
models are starting to indicate the ridge may break down enough
to open the door to energy from the aforementioned shortwave
Sunday...resulting in the potential for some rain showers/weak
thunderstorms. Still much uncertainty in how this will play out.
Overall the general setup is not impressive; dynamics are weak,
moisture is increasing but nothing atypical for August values,
amount of instability able to be realized over the forecast area
is questionable... Have introduced some PoPs in the 20% to 35%
range Sunday, but will be able to better hone the forecast with

Looking towards the next week, seeing signs of a large-scale
pattern change from the western US ridge/eastern US trough setup
that has dominated the latter half of our summer thus far.
Broad ridging looks to encompass the southern half of the United
States by Monday, allowing the general weather pattern to
become increasingly progressive over the northern tier of the
country. Thus, have kept precipitation chances in the 15% to 40%
range for Monday and Tuesday.


Through 18z Wednesday...Mainly VFR conditions are expected
through 00z or so with just mid and high clouds spreading over
the region. Lower ceilings will move in from west to east this
evening and overnight along with rain showers. Visibility and
ceilings will only lower to MVFR overnight, with the exception
being KMPV and KSLK which will see ceilings below 1000 ft late
tonight into early Wednesday. Showers will begin to end from
west to east after 12z Wednesday and ceilings will rise late in
the forecast period. Winds will mainly be south to southwest
through the period with gusts in the 10 to 20 knot range.


Wednesday: Mainly VFR, with local IFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday Night: VFR. Slight chance SHRA.
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.


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.




NEAR TERM...Hastings