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000
FXUS61 KBTV 190245
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1045 PM EDT Tue Sep 18 2018

.SYNOPSIS...
A few showers are possible this evening as a strong cold front
pushes south through the area. Behind this front, variable
clouds and cooler, more seasonable weather is expected tonight
into Thursday. The next chance of showers comes Thursday evening
ahead of a warm front which will pass through the region by
Friday morning. It will be windy and warm Friday before another
strong cold front brings another chance of showers or a
thunderstorm by Friday night. A much cooler Canadian airmass and
its associated high pressure moves in for Saturday.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 1043 PM EDT Tuesday...Late evening update included adding
patchy fog across s-central VT, promoted by the shower activity
occurring mainly 23-01Z. May see the fog become more intermittent
as cold front settles southward into Rutland/Windsor counties
next 1-2 hrs, with developing northerly wind shift and increased
mixing potential.

Previous Discussion...We did it again. Another 80 degree day at
BTV which puts us at 82 for the year and second place all time
behind 86 back in 2016. In fact, we`ve hit 86 at BTV and close
to our record high of 87 set last year.

Shallow cold front continues to progress swd across the forecast
area this evening, draped across the Northern Adirondacks into
the southern Champlain Valley and newd across central/nern VT.
Much of the low-level cold advection appears to be originating
from the Gulf of St. Lawrence and St. Lawrence Valley, with
strong nely flow noted across srn Quebec. In fact, temperatures
are only in the mid 40s in the Quebec City area and nwrn ME...so
definitely a marked air mass change overnight. Winds shift to
northerly and increase to 10 to 20 mph locally a bit stronger
indicated around lake Champlain with good mixing as cooler air
moves over the unseasonably warm lake waters in the lower 70s.
Temps will fall back through the 70s to around 60 by sunset in
the the far northern higher terrain.

A few lingering showers across southern Rutland county will
depart to the south late this evening. Based on satellite trends
to the north, will see an increase in low cloudiness overnight
as frontal inversion sharpens. May even see some patchy drizzle
across far n-central into nern VT late given maritime origin of
the air mass. Some patchy drizzle may also be possible in the
higher terrain. Overnight lows tonight should range from the
upper 40s to mid 50s north and mid to upper 50s south.

Morning stratus in most areas early Wednesday will slowly lift
and break up by afternoon as mixing processes deepen and the
aforementioned inversion weakens as high pressure moves eastward
across southern Quebec and heights rise aloft. With 925 temps
ranging from 10 to 14C looking for highs in the mid 60s to lower
70s.

High pressure ridging down into the area from Canada and the upper
level shortwave ridge crests of the region Wednesday night it should
be mainly clear and cool leading to dense valley fog in the usual
places but it could be more widespread. Expect lows in the upper 40s
to low 50s in Vermont, and upper 30s to upper 40s in northern New
York.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 304 PM EDT Tuesday...500 mb heights will be increasing throughout
the day on Thursday as a result of a a deepening upper level
trough over the upper Midwest. This should help to make Thursday
a bit warmer than previous days with high temperatures
increasing into the mid 60s to lower 70s (which is a few degrees
above climatological normal). The aforementioned upper level
trough will continue to deepen throughout the day and as a
result, a surface low pressure system will quickly develop over
the Great Lakes region on Thursday. A warm front associated with
this low will skirt the North Country late Thursday afternoon
and through the overnight period into Friday. Isentropic lift
ahead of the warm front should help bring some light rain to
northern New York and the northern half of Vermont. One thing to
keep an eye on will be an increasing southwesterly low level
jet Thursday night. This could easily create some upslope and
downslope precipitation patterns with westerly facing slopes see
higher rainfall amounts while the Champlain Valley could see
little rainfall.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 304 PM EDT Tuesday...Following the warm front that works through
the region Thursday night, Friday looks to be a bit warmer with
high temperatures in the upper 60s to around 80 degrees with
the warmest temperatures being in the Champlain and St Lawrence
Valleys. The temperature forecast is subject to change as the
forecast is very dependent on the timing of a cold front that is
expected to move through the region Friday night. The surface
low associated with this system will track well north of the
North Country, which is typically not favorable for widespread
rainfall or strong thunderstorms. In addition, there will be the
passage of a pre-frontal trough out ahead of the cold front
which piecemeal upper level support even further. However, given
that there is around a 50-60 kt 850 mb jet, there will be
strong shear present. The amount of instability is yet to be
determined but is worth monitoring since this front looks to be
a pretty strong one.

This cold front will bring quite the pattern change to the region
with a strong Canadian high pressure system lingering behind the
front. Initially, a strong burst of southerly winds is expected
Friday afternoon out ahead of the front as the pressure gradient
tightens with high pressure to our south and a deepening low
pressure system to our north. Widespread winds in the 10 to 20 mph
range with gusts upwards to 40 mph in some locations will be
possible. The strongest winds look to occur over Lake Champlain
where sustained winds of 20 to 30 mph with gusts to 40 mph look
likely at this moment.

Following the cold front on Saturday, both high and low temperatures
are expected to be below climatological normals. High on Saturday
through Monday will generally be in the upper 50s to mid 60s with
lows around 40 to the lower 50s. Saturday night looks to be the
coldest night as Canadian high pressure will linger overhead with
clear skies prevailing due to lack of moisture and increased
subsidence. It looks quite likely that parts of the Northeast
Kingdom and northern Adirondacks will see a good frost or possibly
even a freeze Saturday night while other locations linger in the
upper 30s to upper 40s.

Any chances of rainfall after Friday look pretty slim as high
pressure continues to reign supreme through the beginning of next
week. There will be another deepening trough over the western half
of the U.S. during the beginning of next week which will bear
watching as it will be the next big system to impact us sometime
during the middle of next week.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...Mainly VFR conditions early this evening,
but as sfc cold front progresses southward, anticipate an
increase in post-frontal cloudiness overnight. Most TAF sites
will see a trend toward BKN-OVC015-030 with HIR TRRN OBSCD after
04Z or so. Winds have shifted N-NW at all TAF locations, and
will continue N-NW 8-12kts thru the overnight hrs as colder air
mass filters into the region. Vsby generally unrestricted, but
could see some patchy drizzle/6SM BR late (08-12Z).

Currently thinking stratus layer will gradually break and lift
15-18Z with light northerly winds for the daylight hours on
Wednesday. Thus, should see a gradual trend back to VFR
conditions by late morning or the early afternoon hours on
Wednesday.

Outlook...

Wednesday Night: VFR. Patchy BR.
Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA, Patchy BR.
Thursday Night: Mainly VFR, with areas MVFR possible. Likely
SHRA.
Friday: Mainly MVFR, with local IFR possible. Likely SHRA.
Friday Night: Mainly MVFR, with areas VFR possible. Likely SHRA.
Saturday: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Sisson
NEAR TERM...Banacos/Sisson
SHORT TERM...Clay
LONG TERM...Clay
AVIATION...Banacos/Sisson