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Office: BTV

FXUS61 KBTV 210305
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1005 PM EST Tue Nov 20 2018

.SYNOPSIS...
Light snows will taper off this evening with additional minor
accumulations possible. A strong arctic cold front will sweep
across the area on Wednesday with falling temperatures and
periods of snow showers and heavier snow squalls. Very cold and
blustery weather is expected for the Thanksgiving Holiday,
though temperatures moderate considerably by this coming weekend
into early next week with renewed chances for light rains and
snows.

&&

.NEAR TERM /UNTIL 11 AM WEDNESDAY MORNING/...
As of 947 PM EST Tuesday...Snow showers have come to an end for
the most part over the forecast area as shortwave ridging builds
in. Made minor tweaks to the forecast to account for
temperatures trends, but overall forecast is in good shape going
forward.

Previous Discussion...The forecast remains largely on
track for tonight as an approaching polar longwave trough
interacts with low pressure departing through the Gulf of Maine
into the Canadian Maritimes. Models have remained quite
consistent showing light northwesterly flow interacting with
moisture and diffluence from the upper trough to produce
lingering light snows and/or snow showers across the area
through early evening before activity wanes/ends overnight.
Additional minor accumulations of a dusting to perhaps 2 inches
will be possible through this time frame with the greatest
coverage occurring in east central and northeastern VT. By later
tonight a brief window of quiet weather is expected as weak
subsidence in lower levels bridges across the area. During this
period variable cloud cover will persist, though will have a
tendency to scatter out somewhat in the broader valleys. Low
temperatures to bottom out generally in the 15 to 25 degree
range by sunrise as winds trend light south to southwesterly
around 5 mph.

Active weather then returns during the daylight hours on Wednesday
as we continue to monitor a strong early season arctic front surging
southeastward from central/southern ON/QC. Based off model-
blended timing progs, the front should clear through northern NY
by late morning to around noon, and through VT by early to mid
afternoon. More importantly, models remain on track showing a
compact, though robust shortwave trough and vorticity maximum
riding along the international border as the front passes.
Strong front-end PVA, moisture convergence, low level
frontogenesis and lower-end boundary layer instability should
accompany this feature. Additionally, an impressive surface
pressure rise/fall couplet remains evident in this morning's
model output, and with such strong isallobaric forcing a 2-4
hour window of higher PoPs for snow showers and heavier snow
squalls will be maintained with this package. Accumulations
should remain on the sigher side given the quick moving nature
of the front (dusting to 2 inches), though brief whiteout
conditions and gusty winds to 40 mph will be possible with
heavier activity as it passes which has the potential to create
brief, though locally hazardous travel conditions.

&&

.SHORT TERM /11 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 319 PM EST Tuesday...By Wednesday night flow trends gusty
northwesterly behind the front as temperatures fall sharply,
bottoming out in the +/- single digits and wind chills ranging
from 0 to 10 below in the valleys, and from 5 to 15 below in the
mountains. Northwesterly flow interacting with residual low
level moisture from the Great Lakes and Lake Champlain should be
enough to keep scattered to occasionally numerous light snow
showers going across elevated terrain at least through Thursday
morning with additional light accumulations possible. Winds
remain gusty into the 20 to 30 mph range through mid afternoon
on Thursday before slowly abating by evening as arctic high
pressure nudges closer. High temperatures to only top out from
10 to 18 above. Summit weather will be considerably worse during
this time frame with stronger winds and lower wind chills so
plan accordingly if venturing to the slopes on Thanksgiving Day.

Quiet/cold conditions then continue for Thursday night, though with
with the surface high bridging overhead winds will trend light and
lower wind chills shouldn't be as problematic. Low temperatures by
Friday morning to generally range from 5 above to 10 below, though
locally a bit milder near Lake Champlain.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 329 PM EST Tuesday...The long term features a transition period
of short term ridging and reprieve from the anomalous cold over the
weekend followed by a gradual redevelopment of a deep trof over the
eastern US next week. As the trof develops several short waves
will move through our region bringing more inclement weather
with a mix of precipitation.

It will continue unseasonably cold Friday with a large Canadian high
pressure system over the northeast and a ridge aloft moving in.
Should be some sunshine mixed with a few clouds and highs in the
teens and lower 20s.

The ridge aloft crests over the region by Saturday morning but a
return S-SW flow begins from west to east along with some high
clouds so expecting early lows from the single digits northeast
to the teens in the Champlain and St. Lawrence valleys.

Saturday with the surface high off the coast bringing a southerly
flow with increasing Atlantic warmth and moisture. Looking like
balmy high temps in the 30s for the most part. The approaching upper
level short wave trof will bring an increase in chances of rain or
snow by Sat evening into Sunday morning. All indications are
pointing to a warming thermal profile above 0C up through 850mb and
surface temperatures mainly in the 30s Sat night. Could be some
light freezing rain in spots like eastern VT/NEK where surface temps
may hover near freezing but for now keeping it simple rain or snow
until details become clearer.

It looks like a break in the action Sunday into Sunday night as
another short wave ridge moves through. Little change in temps with
readings still in the 30s to near 40. The real deepening of the
upper level trof takes place Monday into Tuesday with low pressure
moving from the midwest into the northeast. Details at this point
have yet to be ironed out with the track of the low, where and if it
redevelops, however, most likely scenario given the arrival of
warmer air will be a mix of rain and snow. Again little change in
temps this whole time with lows either side of freezing and highs in
the 30s to near 40.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...Snow showers will continue to linger from
KSLK eastward over the next several hours before tapering off
from west to east. By 04Z, it looks like all snow showers will
exit the forecast area with most places improving to VFR
conditions. Any areas that see snow showers over the next few
hours will see visibilities drop to 1 to 3 SM but ceilings will
continue to rise. KSLK will likely remain MVFR through the
overnight hours with upslope flow keeping them lower than the
other terminals. A band of heavy snow showers is expected to
develop over northern New York around 12Z on Wednesday and move
into the Champlain Valley around 15Z/16Z and eastern Vermont
around 18Z. Periods of visibilities dropping below 1 mile
appears quite likely although confidence on timing will be
fine-tuned in the upcoming forecasts. Gusty winds will accompany
these showers, with the strongest winds expected in the
Champlain Valley as winds gusts up to 25 kts from the west/southwest.


Outlook...

Wednesday Night: VFR. Chance SHSN.
Thanksgiving Day: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. Slight chance RA, Slight chance SN.
Saturday Night: Mainly VFR, with areas MVFR and IFR possible.
Likely RA, Likely SN.
Sunday: Mainly VFR, with local IFR possible. Chance SHRA, Chance
SHSN.

&&

.CLIMATE...
The record low max temperature for Burlington for Thanksgiving Day
is 19 degrees, set on Thanksgiving Day (November 24th) 1938.

Below are some daily climate records for November 22nd and
23rd.

November 22nd:

        Record Low Daily Max  /  Record Low Daily Min

Burlington:     22 (2008)     /     3 (1969)
Plattsburgh:    24 (2008)     /     6 (1972)
Montpelier:     18 (2008)     /     2 (1964)
St. Johnsbury:  22 (2008)     /    12 (2014)
Saranac Lake:   10 (1987)     /    -2 (2000)
Massena:        22 (1989)     /     0 (1972)


November 23rd:

        Record Low Daily Max  /  Record Low Daily Min

Burlington:     20 (1914)     /     2 (1972)
Plattsburgh:    23 (1989)     /     6 (2000)
Montpelier:     21 (2000)     /    -1 (1972)
St. Johnsbury:  22 (2000)     /     7 (2000)
Saranac Lake:   18 (2000)     /   -11 (1932)
Massena:        18 (2008) /         0 (2000)

&&

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

&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG/RSD
SHORT TERM...JMG
LONG TERM...Sisson
AVIATION...Clay
CLIMATE...RSD