816 
FXUS61 KBTV 141929
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
329 PM EDT Wed Oct 14 2020

.SYNOPSIS...
A ridge of high pressure over the North Country will drift
eastward late tonight into Thursday. Meanwhile, a slow moving 
front will approach from the eastern Great Lakes. An increasing 
southerly flow will bring windy and warm conditions to the 
region on Thursday, with valley highs in the low to mid 70s. The
frontal zone will bring periods of rain showers to the region 
Thursday night. A frontal wave will bring additional rain and
possible mountain snow Friday night into Saturday. The heaviest
precipitation amounts are expected across central and eastern
Vermont, where rainfall totals may exceed one inch. 

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 255 PM EDT Wednesday...Pleasant afternoon ongoing with
shortwave ridging building ewd from the ern Great Lakes.
Temperatures are near climo norms for mid-October with valley 
readings in the low-mid 60s and scattered fair weather cumulus
clouds from the Adirondacks eastward. 

We'll see surface ridge crest over the North Country between
00-03Z. As it shifts rapidly ewd, will see southerly winds 
begin to increase overnight, and more sharply toward daybreak on
Thursday. NWP guidance continues to show 50-60kt 850mb jet 
moving into northern NY in advance of frontal system moving into
sern Michigan and sern Ontario toward 12Z Thursday. Consistent 
with previous forecast, appears highest wind gusts will occur 
09-15Z Thursday across the northern slopes of the Adirondacks, 
where localized gusts to 50 mph are possible, ewd to the 
Champlain Islands/Grand Isle County. Later in the day, may see 
more swly channeled flow into the St. Lawrence Valley, with 
gusts 35-45 mph locally there into the afternoon hours. Have 
maintained the Wind Advisory for much of northern NY into Grand 
Isle VT from 05AM to 08PM Thursday, through highest wind threat 
will be during the morning into the early afternoon hours. 

In terms of temperatures, may see a few lows overnight in the 
upper 30s across far nern VT, but generally looking for lows in 
the 40s elsewhere with PBL mixing mitigating radiative cooling. 
Temperatures will fall rather quickly after sunset, but then 
should level off after midnight. 

On Thursday, the 925mb temperatures surge on the southerly flow
to 14-16C, and should support highs in the low-mid 70s most 
locations on Thursday afternoon. Some high clouds will provide 
filtered sunshine at times, but provided clouds remain thin, a 
few upper 70s are possible as well. Front is expected to have 
anafrontal structure, and as boundary progresses ewd, will see 
increasing clouds and increasing chances for showers across the 
St. Lawrence Valley and Adirondacks late in the afternoon toward
the evening hours within the frontal zone. Rainfall amts up to 
a tenth of an inch are possible, especially across southern St. 
Lawrence County. 

Frontal zone will shift slowly ewd across nrn NY into Vermont
during Thursday night. Will see increasing chances for rain
areawide with overnight conditions and diminishing wind speeds.
Additional rainfall amounts between 0.1-0.2" expected. Lows
Thursday night generally expected in the 45-50F range. 

&&

.SHORT TERM /FRIDAY/...
As of 346 AM EDT Wednesday...A cold front will enter the St. Lawrence
Valley Thursday night and will bring some rain showers to northern
New York during the overnight hours. The low pressure system this
front is attached to will be tracking across northern Quebec and
will be weakening as it continues to shift to the north and east.
This should really limit the dynamics across the region and is
expected to limit rainfall initially as all guidance shows the front
stalling and shearing apart. Friday for the most part is expected to
be dry as the lack of any appreciable forcing should only support
some scattered shower activity. By late Friday afternoon, steady
rain is expected to move into southern Vermont and begin to spread
north as a decent rain event begins to unfold.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 346 AM EDT Wednesday...The upper level trough across the Ohio
River Valley Friday night and as it does so, it'll take on a
negative tilt. The once washed up cold front will begin to slide
eastward with all guidance showing strong frontogenetic forcing
along the leading edge of the front. This area of surface
convergence has shifted eastward compared to models 24 hours ago
which is do to a developing surface low off the New England
coastline overnight Friday. This small feature will have a big
impact on our rainfall totals across the region as it'll
significantly impact the moisture advection across the northeastern
US. Ultimately, this will lead to a tight gradient in rainfall
amounts with the highest amounts occurring across eastern Vermont and
the lowest amounts across the St. Lawrence Valley. We are still
looking at very favorable jet dynamics, moisture convergence and
surface convergence which is expected to bring a period of moderate
to heavy rainfall between 8 PM Friday night through 11 AM Saturday.
During this time, rainfall amounts between a half of an inch across
the St. Lawrence County to nearly an inch and a half of rain across
western Vermont is expected. Eastern Vermont will likely be the
winner of the rainfall lottery thanks to the forecasted track of the
surface low and could see 2-2.5 inches of rain. Looking at some of
the Meteorological Model Ensemble River Forecasts (MMEFS) run by the
Northeast River Forecast Center, we will likely see some decent
rises on Vermont rivers given the rainfall. In addition, there is a
small chance (less than 20%) at this time that a few rivers may rise
above minor flood stage. This is something we will continue to keep
an eye on in coming days but widespread flooding is not anticipated
at this time.

It's still looking like we could see snow on the back end of the
system at higher elevations. The NAM, GFS, ECMWF, CMC and UKMET all
show a stripe of snow across the northern Adirondacks and the Green
Mountains with a snow level somewhere between 3500 and 4000 ft. We
ran some preliminary grids and it looks like the northern
Adirondacks could see 2-5 inches at the higher peaks with 1-2 inches
across the higher peaks of the Green Mountains. Given the ground
temperature is well above freezing as we've seen only a handful of
freezes this fall, accumulating snowfall is not expected near sea-
level although some rain/snow mix may fall as low as 2500 ft.

Given the progressive nature of the upper level low, rainfall will
come to a quick end Saturday afternoon and will be replace by a 1030
mb high pressure Saturday night. After a dry day on Sunday, we will
return to a wet and unsettled period of weather through the first
half of next week. Another frontal system looks poised to enter the
region during the first half of next week but there are huge
discrepancies across the global guidance as the flow remains quite
amplified.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Through 18Z Thursday...Main issue during the TAF period will be
the development of gusty S-SW surface winds and LLWS toward 
daybreak Thursday. A strong low-level jet (50-60kt at 2-3kft 
AGL) will create areas of turbulence and wind shear between 
09-17Z Thursday. Have included LLWS for all TAF locations. It is
expected that channeled flow in the Champlain and St. Lawrence 
Valleys will yield sfc wind gusts in excess of 25kts at 
BTV/PBG/MSS at times late Thursday morning into the afternoon 
hours. Other than the wind concerns, conditions are expected to 
remain VFR through the period. The developing winds overnight 
are expected to limit fog/br potential. 

Outlook...

Thursday Night: VFR. Chance SHRA.
Friday: Mainly VFR, with areas MVFR possible. Likely SHRA.
Friday Night: Mainly MVFR, with areas VFR possible. Definite RA,
Likely SHRA.
Saturday: Mainly VFR, with local IFR possible. Likely SHRA.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Monday: Mainly VFR, with areas MVFR possible. Slight chance SHRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Wind Advisory from 5 AM to 8 PM EDT Thursday for VTZ001.
NY...Wind Advisory from 5 AM to 8 PM EDT Thursday for NYZ026>028-
     030-031-087.

&&

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