Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Burlington Vermont
643 PM EST Thu Nov 21 2019
changeable weather is expected over the next two day
across the north country. An upper level trough of low pressure and
its associated cold front will bring some rain and snow showers to
the region tonight along with the potential for some very light
freezing rain east of the Green Mountains. As the cold front moves
across the area on Friday expect gusty winds southwest to west
winds. In addition...rain showers will be changing over to snow
showers late in the day Friday before coming to an end Friday
evening. High pressure builds in for late Friday night and Saturday
bringing drier weather to the area along with slightly below normal
temperatures.Pitation to the region on Sunday, in the form of
rain and wet snow.
Near term /through Friday night/...
as of 327 PM EST Thursday...expect quite a few changes with the
weather over the next 36 hours. Increasing clouds tonight and
warm air advection will limit the amount of cooling over the
area tonight...with lows likely being in the evening hours and
then slowly rising overnight. This should help to limit the
freezing rain potential as low level temperatures to support
freezing rain will only exist for a very short time east of the
Green Mountains in Vermont. Plus the amount of precipitation
expected overnight where the thermal profile supports freezing
rain will be limited. As a result...can see a trace to maybe
0.01 inches over parts of north central and northeast Vermont.
Meanwhile the remainder of the area would experience rain or
snow showers with any snow accumulations less than an inch.
A cold front will be moving across northern New York during the late
morning hours and across Vermont in the afternoon. Mixing will take
place with this front and wind gusts in the 25 to 35 mph range can
be expected with temperatures gradually falling behind the front.
Temperatures will be warm enough for precipitation to mainly be
in the form of rain showers...but change to snow showers later
in the day. Snow squall parameter suggests there could be a
convective element to the showers Friday afternoon...but
temperatures should be warm enough for precipitation to be more
rain showers than snow showers. Nevertheless...best chance for
these convective showers will be from the Champlain Valley
eastward Friday afternoon.
Precipitation quickly comes to an end Friday night as the cold front
moves east of the region and high pressure builds in. Lows Friday
night will be in the mid teens to mid 20s with winds gradually
tapering off and clouds slowly decreasing in areal coverage.Ield
gusty surface winds of 25-35 mph during Friday afternoon.
Short term /Saturday through Saturday night/...
as of 248 PM EST Thursday...Saturday will be dry over the area as
large-scale ridging builds in. Post-frontal clearing will allow
for partly to mostly sunny skies during the daytime hours. 850
mb temps will start off cold behind the front Saturday morning
(generally -6 to -7 deg c), but warm air advection will develop
during the day. By Saturday night, 850 temps will have risen to
near 0 deg c. In terms of sensible weather, this means a chilly
morning with improvement throughout the day as temps top out in
the mid to upper 30s. Clouds will begin to increase Saturday
evening through Saturday night as a coastal low pressure system
rides up the mid Atlantic coast. Overnight lows will be occur
early for most of the area, with near constant or slightly
rising temperatures forecast through the night. Lows will be in
the mid to upper 20s. The exception will be the Northeast
Kingdom of Vermont, where clouds will be later to arrive and
potential for radiational cooling is the greatest. This area
will reach lows in the upper teens to low 20s.
Long term /Sunday through Thursday/...
as of 248 PM EST Thursday...most challenging part of the long term
forecast continues to be a low pressure system that will track
from the mid-Atlantic coast to off the New England coast Sunday.
Still a variety of solutions among the models as to the exact
track of the low, which makes for a difficult precipitation
forecast given that we'll be on the northwestern periphery of
the system. The trend in the 12z deterministic model suite for
both the NAM and the European model (ecmwf) has been to track the system further
south and east, while the CMC and the GFS are holding onto a
more coastal track that would result in more precipitation for
our area. Given the wide range of solutions on the track, it's
difficult to go into specifics at this point on the storm. In
terms of impacts, driest solution (nam) would keep any
precipitation associated with the system out of our forecast
area, while the most bullish, furthest west solutions (cmc and
gfs) would bring just a few inches of wrap-around snow to our
area. Given the fast-moving nature of the system (open wave
aloft), not concerned at this point for anything more than a few
inches of snow or rain/snow mix in Vermont/northern NY, but
will adjust forecast if anything changes. Best chances for
accumulations will be in southern Vermont and along western
slopes of The Greens. Can't rule out some mixed precipitation
with the event either, but too early to have a handle of thermal
profiles with the uncertain track.
The system will exit the area Sunday night, followed by a dry start
to the work week with high pressure building in. The next chance
for widespread precipitation will be Wednesday as the next low
pressure system tracks through the area.
Aviation /00z Friday through Tuesday/...
through 00z Saturday...a mix of mainly VFR/MVFR over the next 24
hours as low pressure and associated cold front cross the
region. Scattered shower activity associated with this feature
generally expected in the 00-18z time frame, though uncertainty
in overall coverage warrants mainly vcsh in terminal forecasts
at this point. Main concern overnight through mid-morning Friday
will be southwesterly low level wind shear in the 35-50 kt range
at all terminals. During this period expect moderate to
occasionally robust mechanical turbulence on departures and
approaches. Surface winds mainly light southerly through 06z,
increasing into the 10-18 kt range and trending gusty
to 25 kts thereafter, backing to west/northwesterly in the
18-00z time frame behind frontal passage.
Friday night: VFR. No sig weather.
Saturday: VFR. No sig weather.
Saturday night: VFR. Slight chance snow.
Sunday: MVFR/IFR conditions possible. Chance shsn, chance rain showers.
Sunday night: mainly IFR, with areas MVFR possible. Chance shsn.
Monday: mainly MVFR, with local VFR possible. No sig weather.
Monday night: VFR. No sig weather.
Tuesday: VFR. No sig weather.
south winds will be increasing this evening across Lake
Champlain with south winds of 15 to 25 knots expected along with
gusts to 30 knots at times. These conditions will continue
through midday on Friday...then a cold front moves through and
shifts winds to the west. Speeds will remain in the 15 to 25
knot range before slowly tapering off Friday night. Waves will
build to 3 to 5 feet causing rather choppy conditions...especially
over the northern portion of the lake later tonight through
Friday morning...then across the eastern part of the lake when
the winds shift to the west.