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  Thursday September 20, 2018

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 181817
AFDBTV

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
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 disssipate 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 earlly 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/...
As of 324 AM EDT Tuesday...Low-level flow Thursday will become
increasingly southerly as a warm front advances northeastward
towards the forecast area. High clouds will spread in from the
west, thickening and lowering throughout the day. At this point,
it looks like precipitation associated with the warm front will
hold off until Thursday evening, so have kept PoPs below 30%
most of the day. Rain showers should start Thursday evening in
northern New York, while Vermont will stay dry until Thursday
night. Highs Thursday will be in the mid 60s to low 70s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 324 AM EDT Tuesday...A low pressure system tracking
northeastward from the Great Lakes Region through central Quebec
will control our weather Thursday night through the first part
of the weekend. The system`s warm front will spread some rain
through the forecast area Thursday night. Best upper-forcing at
this point will remain well to our north, but a large area of
synoptic-scale ascent over the northeastern US within the warm
air advection regime should allow most areas to see some
measurable precipitation.

By Friday morning, the forecast area will be solidly within the
warm sector of the cyclone, and a fairly warm, but windy, day
can be expected. 925 mb temperatures will shoot up to 20C.
Should see pretty good cloud cover through the day which will
limit solar heating, but the warm nature of the air mass will
support surface temperatures in the upper 70s. A 50+ kt
southwesterly low-level jet will be present within the warm
sector of the cyclone. As the boundary layer becomes
increasingly well mixed through the day, many areas will see
gusts in excess of 25 mph. Strongest winds will be in the Saint
Lawrence Valley and over higher elevations of the northern
Adirondacks/Green Mountains.

A cold front will sweep through Friday night/Saturday morning,
triggering some additional showers and an abrupt transition to
cooler, fall-like weather. High temperatures over the weekend
will only top out in the low to mid 60s. Nights will be cool and
crisp, with lows in the upper 30s to upper 40s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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
BTV.

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.

Outlook...

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
SHRA.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. Slight chance SHRA.

&&

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

&&

$$
SYNOPSIS...Sisson
NEAR TERM...Sisson
SHORT TERM...RSD
LONG TERM...RSD
AVIATION...Sisson



 
 
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