Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 181855

Area Forecast Discussion
National Weather Service Burlington VT
155 PM EST Sat Nov 18 2017

Strong low pressure will pass through the region tonight into
Sunday with widespread rainfall and milder temperatures. Rain
will taper to snow showers on Sunday afternoon as much colder
air surges back into the area along with gusty winds. The
general weather pattern quiets down from Monday onward into much
of next week with mainly dry and seasonably cold weather
expected for the Thanksgiving holiday.


As of 949 AM EST Saturday...For the late morning refresh, made
some slight modifications to the hourly PoP and weather fields
through early afternoon based on radar trends. There is a narrow
band of light precipitation that is moving toward the St
Lawrence Valley. This is associated with some warm air advection
aloft. Based on upstream obs, some light precipitation is
making it to the ground. The 13z HRRR seemed to capture this
feature the best, and I like it`s evolution. Basically this
precipitation will progress northeast but dissipate as it does
given the dry low level airmass that is in place. Still may see
a few sprinkles of rain. Given the dry airmass, can`t rule out a
few ice pellets or a snowflake mixing in as the light
precipitation causes evaporational cooling.

Prior discussion...
Quite the variety of weather is expected over the next 36 hours
as deepening low pressure tracks from the Ohio Valley into the
St. Lawrence Valley by Sunday morning. From a broad perspective
the overall theme of the forecast remains the same with
thickening clouds expected today before widespread precipitation
arrives by early evening into the overnight hours.
Strengthening southerly flow and warm thermal advective
processes will push boundary layer temperatures above freezing
in most locales by mid to late afternoon such that mainly a
steady light rain is expected. The only exception would be a
brief period of mixed precipitation at onset at mountain summit
level and possibly across portions of far northeastern VT. Given
the strength of the synoptic background southerly flow have
generally downplayed this threat however. Highs today to top out
in the upper 30s to mid 40s for most spots with readings
holding steady in VT overnight, and falling through the 30s
toward morning across northern NY as cold front sweeps through.

By Sunday the cold front surges quickly across the remainder of the
forecast area, clearing well east by afternoon as the ~980 mb
surface low races northeast toward the Gulf of St. Lawrence by early
evening. Robust 3-hourly pressure rises behind the frontal boundary
should ensure a windy afternoon as steadier rains transition to snow
showers and flow trends northwesterly. Accumulations should be
minor, though amounts from a dusting to 2 inches will be possible
across the St. Lawrence Valley and higher terrain of the
Adirondacks/Greens by early evening. Using an upward adjustment
factor from 160-190 percent yields gusts into the 30 to 45 mph range
with highest gusts in favored westerly downslope areas of the
eastern Adirondacks and eastern Greens/CT River Valley. Temperatures
will take on a typical cool-season non-diurnal trend as highs from
the upper 30s to mid 40s will be reached in the morning before
values slowly fall into the upper 20s to mid 30s by late


As of 154 PM EST Saturday...Deep cold trof rotating out of area
during this period with building heights and zonal flow and
surface ridging while the main surface high is located along the
mid-Atlantic coast.

Primarily dry and unseasonably cool with gusty NW winds of Sun-Sun
ngt gradually diminishing and shifting W-WSW. Highs 25-33. Return
flow Monday night means not as cold as Sun ngt-Mon morning with the
exception of eastern VT and lows in the 20s with teens in NE VT and
deep Adrndks Vlys.


As of 154 PM EST Saturday...Primarily a very broad cyclonic
flow pattern for the period with very minor disturbances and
slight roller coaster of temperatures but largely below normal.
There is an outside threat of a coastal storm Wed-Wed ngt but
most current indications are keeping this a mid-atlantic and
then out to sea storm with no impacts for our area but still
worth monitoring for the next few days.

Tuesday: High pressure sliding offshore for a return flow ahead of
northern stream shortwave for moderating temperatures in the 40s.
Northern shortwave and cold front move across area Tue ngt and
largely exit by Wednesday. This will bring rain to mixed rain/snow
showers and colder air once again.

Wednesday: Cold front exiting region, although we still must look to
our south and model trends about possible coastal. Currently,
exiting drier conditions with some mountain snow showers possible
with temperatures in the 30s/40.

Thanksgiving: Quiet with surface high in control but the eventual
approach of another northern stream shortwave by Thursday night.
Currently dry with temperatures in the 30s.

Thursday Night/Friday: Much of the energy with northern stream
shortwave is in Canada but can`t rule out some isold/sct snow
showers, especially in the mountains. Lows in the 20s and Highs in
the 30s, a tad milder than Turkey day.

Friday night/Saturday: We return to a more zonal flow with another
minor shortwave and surface reflection moving along the Great Lakes
and international border withsome decent warm-air advection ahead of
it for light snow/snow showers Friday night and scattered rain/snow
showers on Saturday with temperatures in the mid-upper 30s.


Through 12Z Sunday...Mainly VFR through 00Z Sunday with
thickening mid/high cloud cover as light winds trend
south/southeasterly at 5 to 10 kts (northeasterly at KMSS).
After 00Z Sunday widespread rain affects all terminals with
ceilings lowering to MVFR in the 015-025 AGL range in general.
Some occasional VFR may continue at KBTV/KPBG/KRUT. Winds
continue south to southeasterly from 5 to 10 kts (northeasterly
at KMSS) and will trend modestly gusty into the 13 to 18 kt
range at KRUT/KBTV/KPBG/KSLK terminals late.


Sunday: Mainly MVFR, with local IFR possible. Windy with gusts to
35 kt. Definite RA, Chance SHRA, Chance SHSN.
Sunday Night: VFR. Chance SHSN.
Monday: Mainly VFR, with local MVFR possible. Slight chance SHSN.
Monday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance SHSN.
Wednesday: Mainly VFR, with local MVFR possible. Slight chance
SHRA, Slight chance SHSN.


As of 337 AM EST Saturday...A Lake Wind Advisory is in effect
for today as southerly winds increase into the 15 to 25 knot
range by this afternoon and significant wave heights build into
the 2 to 4 foot range with a moderate chop. These conditions may
prove hazardous to those operating small craft, especially on
the broad lake and in bays/inlets with southerly exposures.
Gusty south winds will gradually abate tonight, though increase
sharply from the northwest by Sunday as a strong cold front
sweeps across the area.




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