Area Forecast Discussion Issued by NWS Burlington, VT
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000
FXUS61 KBTV 182253
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
653 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/...
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As of 643 PM EDT Monday...The locals like to call this pattern
bread n butter, where conditions are favorable for upslope
accumulating snow showers every 6 to 12 hours, and produce free
refills daily. Crnt radar is showing the areal coverage of mtn
snow showers and mix rain/snow in the valleys increasing this
evening associated with a sfc cold frnt and weak embedded s/w.
As flow continues to shift back to the west/northwest in the
925mb to 850mb layer, expect upslope snow showers to prevail
most of the night acrs the northern Dacks and central/northern
Greens. A sharp and highly elevational snowfall gradient is
anticipated from a dusting to an inch possible valleys to 2 to 6
inches mtns by morning. Temps have cooled quicker than expected
acrs the SLV this evening, so have made the hrly temp
adjustment and added more snow than rain. Otherwise, precip type
should be mostly snow at all levels by 02z this evening, which
is covered in fcst. No additional changes made attm.
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.-- End Changed Discussion --
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.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 /00Z TUESDAY THROUGH SATURDAY/...
Through 18Z Tuesday...Outside of a burst of snow this morning,
snowfall has generally been light throughout the day. Most
locations seeing snow are reporting 3-4 SM vsby with ceilings
in the 1500 to 2500 ft range with VFR conditions outside of snow
showers. This trend is expected to continue into the evening
hours before ceilings drop below 3000 ft at most terminals. Snow
showers this evening could pick up in intensity and produce
brief IFR vsby at KEFK, KSLK and KBTV but these should be
directly tied to snow showers with quick improvement after they
pass. Winds will remain gusty from the west/northwest at 15 to
25 knots through 23Z with winds weakening to less than 10 knots
overnight. Winds will again become gusty after 15Z Tuesday.
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. Slight chance SHSN.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. Slight chance SHSN.
Saturday: Mainly MVFR, with local VFR possible. Slight chance
SHRA, Slight chance SHSN.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Chai
NEAR TERM...Clay/Taber
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Clay