Current conditions from King Hill
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  Thursday September 20, 2018


NWS Area Forecast Discussion

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FXUS61 KBTV 181905

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

A few showers are possible this afternoon and early 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.


As of 215 PM EDT Tuesday...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.

MLCAPE of 250-500 J/kg right ahead of the front will still keep a
slight chance of showers going through sunset but looks like enough
of a mid-level cap to keep most of the convection in check. Wouldn`t
be surprised if there were a lightning strike or two somewhere this
afternoon if the cap can be broken.

Speaking of the front, temperatures are in the mid to upper 40s just
north of it in northern ME and Quebec city and as mentioned earlier
there are really parts to the cold front. First the front coming
southeast from near MSS at this hour and part two coming southward
from the Quebec. Hi-res models in agreement that it`s the air to the
north that will surge southward, especially in the Champlain Valley
by this evening. 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.

Any lingering showers dissipate this evening as colder air
filters south/southwest into the area and variable clouds
prevail under a fairly sharp frontal inversion. Some patchy
drizzle may be possible in the higher terrain as low level
moisture will be abundant in blocked upslope flow. Right now
held off on fog due to cold advection and low level
clouds/stratus but if it clears, could be some that develops.
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

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


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.


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.


Mainly VFR trending MVFR tonight as two separate cold fronts drop
south into the area late this afternoon/evening with a chance of
light showers. Scattered nature of activity warrants only VCSH in
the forecast at this point. Light winds shift to northerly around 6
to 12 knots with locally gusts to 20 knots possible especially at

The forecast problem tonight is cigs and vsby. Currently thinking it
will be more of a stratus vs fog situation under cold advection so
have left fog out of the TAFs but there is still some chance of IFR
cigs/vsby if the fog develops tomorrow morning if enough clearing
takes place and winds become light. For now have developing cigs
lower to MVFR stratus at northern terminals behind the front. Kept
cigs going most of the night lowering further around sunrise Wed
before lifting and breaking up 15-18Z with light northerly winds.


Wednesday Night: VFR. NO SIG WX.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.
Thursday Night: MVFR/IFR conditions possible. Likely SHRA.
Friday: Mainly MVFR, with local IFR possible. Likely SHRA, Slight
chance TSRA.
Friday Night: Mainly MVFR, with local VFR possible. Chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Slight chance
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. Slight chance SHRA.




NEAR TERM...Sisson

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