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  Monday March 18, 2024

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 190207
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1007 PM EDT Mon Mar 18 2024

.SYNOPSIS...
Periods of snow showers, mixed with rain in the valleys are
expected through mid week. Best chance of over 4 inches
accumulation will be over 1000 feet elevation as well as
topographically favored upslope locations of the Green Mountains
and the Adirondacks. Only minor accumulations are expected in
the Champlain and Saint Lawrence valleys. A strong cold front
overnight Wednesday will lead to below normal temperatures on
Thursday and Friday. Unsettled weather may return for the
weekend, but forecast confidence is very low at this time.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 1004 PM EDT Monday...Minor changes needed with late
evening update, but overall fcst remains in good shape. Radar
shows intervals of upslope snow showers continuing acrs northern
Dacks into parts of the central/northern Greens. Based on
upstream radar and water vapor trends, feel areal coverage of
precip wl decrease aft 06z as weak ridging develops. The pop/qpf
and snowfall have this covered well. Temps are a bit tricky this
evening with northern NY running a few degrees cooler, while VT
is a few degrees warmer as winds have been slow to shift to the
west/northwest, especially central/southern CPV. Did make some
minor tweaks to hrly temps, but overall fcst remains in good
shape.

Previous discussion below:
The one word to describe the weather through Tuesday night is
unsettled. Current mesoanalysis shows up to 200 J/kg of CAPE
which doesn`t sound like a lot but it`s enough to help support
snow showers across the region. The cause for this instability
is a pocket of cold air aloft that continues to get colder as
cold air advects southward. This should drive a period of snow
showers into this evening and overnight period. With prevailing
west to northwest winds, which could be gusty up to 30 mph at
times, good upslope flow is expected on the windward side of the
Adirondack and especially the western slopes of the Green
Mountains. Snow is going to be very elevationally dependent
meaning those in low elevations will likely see little to no
snow through Tuesday while locations above 1000, 2000, and 3000
ft could see more and more snow the further up you go. For
example, we currently have an inch or less in the forecast for
much of the Champlain and St. Lawrence Valleys but have 8-12
inches in the forecast for Jay Peak and Mount Mansfield. This
will be great for those who enjoy spring skiing and a nice bonus
for an overall lackluster winter for much of the North Country.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of Monday 3 PM EDT...A potent piece of northern stream
shortwave energy will trigger another round of convective snow
showers and even a few embedded snow squalls. Snowfall
accumulations look to be topographically driven and elevation
dependent. Strong cold air advection will result in lapse rates
of over 8.5C/km up to 800mb as well as 50-100 J/kg of surface
based CAPE. Indeed, the SLU snow squall parameter is non-zero,
with somewhat higher amounts across the Adirondacks and
Northeast Kingdom. In addition, it would also be a breezy to
even blustery day on Wednesday, with west winds gusting over
25-30 mph at times. During the day on Wednesday, most of the
accumulations should be confined to the terrain mainly above
1000 ft elevation as 925mb temperatures remain in the 0 to -2C
range. So expect minimal accumulation, with the best chance for
a quick coating of roadways during a heavier snow shower or
embedded squall in the valley locales. It would be a different
story, however, across the typically favored upslope areas of
the Adirondacks and spine of the Greens, where upwards of 4
inches could accumulate. High temperatures top out in the low to
mid 40s across the valleys and mid to upper 30s across the
higher terrain.

It does get more interesting overnight Wednesday as cold air
advection continues. 925mb temperatures fall sharply into the -7 to -
10C range, allowing it cold enough for snow to accumulate even down
to the valley. However, the jet dynamics remain northern stream
dominated, with minimal southern stream connection. The result is
continued bouts of convective snow showers overnight Wednesday. A
feature that bears watching is the 700mb low potentially closing
off, which would lead to more impressive widespread snowfall amounts
of over 4 inches rather than being orographically driven. However,
the current suite of global deterministic guidance shows the low
closing to our east, which would favor the best snow across Maine.
And if we were to examine ensemble guidance, there remains little to
no indication that the upper low will actually close off, so the
most likely solution remains a terrain dependent snowfall event,
with minor accumulations across the valleys. If the upper low does
close off as some deterministic guidance are suggesting, then
Northeast Kingdom could see higher amounts. But until more evidence
presents itself, that is a low probability outcome.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of Monday 3 PM EDT...Upslope snow showers taper off during
the day on Thursday. It will be an unseasonably cold day on
Thursday. With 925mb temperatures -9 to -12C, highs might
struggle to approach the freezing mark with the exception of the
Champlain Valley and southern VT. Thursday night would be a
cold one with lows in the single digits to low teens, except mid
to upper teens in the Champlain Valley. Friday looks to be
another day of below normal temperatures in the upper 20s to mid
30s. For reference, typical highs are in the mid 30s to low
40s. Heading into the weekend, we warm to near seasonable
temperatures. There is potential for some form of unsettled
weather due to the development of a coastal storm. However,
there remains too much uncertainty in the storm track and
consensus among model guidance to articulate any potential storm
impacts at this time. Stay tuned.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Although most terminals are currently
VFR, variable flight categories will be possible this evening as
snow showers persist across the region making for bouncy flight
categories. The best potential for IFR conditions will be at
KEFK and KSLK due to more confidence in snow showers, although
given the variability TEMPO groups were utilized. Outside of
snow showers, a mix of VFR and MVFR ceilings will persist until
around 12Z when most terminals should trend towards VFR. Winds
overnight will generally be less than 10 knots and
westerly, become gusty after 15Z.

Outlook...

Tuesday Night: Mainly VFR, with areas MVFR possible. Chance SHSN.
Wednesday: Mainly VFR, with local MVFR and IFR possible. Likely
SHRA, Likely SHSN.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHSN.
Thursday: VFR. Chance SHSN.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: Mainly VFR, with local MVFR possible. Chance SHSN.
Saturday: Mainly MVFR, with local VFR possible. Chance SHSN,
Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Chai
NEAR TERM...Clay/Taber
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Kremer


 
 
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