FXUS61 KBTV 210513
Area Forecast Discussion
National Weather Service Burlington VT
113 AM EDT Tue Mar 21 2023
Brisk south to southwest winds will relax tonight leading to
seasonably chilly conditions. Chances for snow showers will increase
by morning over northwestern portions of northern New York,
then more valley rain and mountain snow showers will develop
during the day. These showers gradually will progress southward
associated with a weak cold frontal passage. Thereafter, milder
weather and a wet period is expected Wednesday night through
Thursday, followed by a more potent storm that may impact the
region over the weekend.
.NEAR TERM /THROUGH WEDNESDAY/...
As of 107 AM EDT Tuesday...Have updated to decrease pops acrs
the SLV/Western Dacks as radar is showing some light returns,
but given dry llvls no obs/web cams are showing any precip
reaching the ground. Have continued to mention chc/low likely
pops for some very light mostly snow showers thru early this
morning, with minimal accumulation expected. Temps hold mainly
in the upper 20s to lower/mid 30s.
Previous Discussion: As the spring Equinox arrives this
evening and sun sets on the day, the mainly fair weather cumulus
present towards the International Border will give way to clear
skies. That region will join the rest of our Vermont and New
York, while breezes relax as a nocturnal inversion develops.
However, with a modestly strong low level jet focused on the
southern half of the region and at least 15 knots of westerly
flow at 925 millibars areawide tonight, don`t expect total
decoupling to support tanking temperatures despite clear skies.
Where a snow cover is most fresh and winds subside temperatures
should cool most effectively tonight, but generally have lows in
the 22 to 32 range, mildest in the wide valleys of the
Champlain and St. Lawrence.
While no significant impacts are expected, do expect to see
quite a bit of elevation-dependent snow shower activity across
most of our region tomorrow associated with a weak cold front.
Precipitation amounts, mainly a trace to 0.1" but locally up to
0.2" in the higher terrain, will be limited by both moisture and
lift. However, there will be enough instability and forcing for
ascent to see showers, with briefly heavier elements, blossom
during the day. The more organized snow showers will be in the
early morning hours closer to the better moisture source (Lake
Ontario). Over time, transport of low level west- southwesterly
flow generally will pool moisture along the front farther east,
especially the northern half of Vermont. As the air mass aloft
will be sufficiently cold, it will be a boundary layer question
for precipitation type at the surface.
With springtime mixing depths, even with snow cover lower
elevation sites will have too deep of a warm layer to see snow
and surface temperatures rise into the 37 to 42 range, or even
milder in our southern valleys. Snow levels generally look to
have a north to south gradient and be roughly 1000-1500 feet
when greatest chances of precipitation occurs, thereafter
falling from north to south as colder air aloft slides southward
along with the cold front. Behind the front, lighter snow
showers will likely continue in the favored upslope locations as
moisture depth decreases but blocked northwest flow helps
squeeze out some precipitation. By late evening, little or no
precipitation should be remaining in our area and precipitation
chance drop to nil by daybreak Wednesday. Another surge of low
level wind and potential lingering cloud cover leads to forecast
temperatures tomorrow night being a bit milder than normal in
northern New York/south central Vermont, but closer to normal in
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 307 PM EDT Monday...The pattern becomes active again for the
middle of the week, but not until Wednesday night where before that,
surface high pressure and a weak upper ridge will support dry
conditions for Wednesday with highs ranging from the upper 30s along
the international border to around 50 in the lower Connecticut River
Valley. Thereafter, a surface frontal boundary will lift northward
through the region Wednesday night with perhaps some scattered
valley rain and mountain snow showers, but better forcing won`t
arrive until Thursday where shortwave energy ejecting from a
decaying upper trough over the northern plains will ride eastward
along a fast westerly flow aloft and bring numerous rain showers to
the region as the aforementioned warm front sags back south as a
cold front. Right now medium range guidance isn`t in great agreement
with how much QPF we`ll see, but a general tenth to quarter inch
seems reasonable. Showers taper off Thursday night as the front
moves south of the forecast area. Highs Thursday will range through
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 307 PM EDT Monday...Heading into the end of the work week and
weekend the focus shifts toward the potential for an strong low
pressure system to impact the region over the weekend. Strong
surface high pressure centered over Quebec will bring a partly sunny
and dry day for Friday with highs back to seasonal normals in the
upper 30s to low 40s. But by Friday night, low pressure looks to
develop over the lower Mississippi River Valley and track into the
Ohio Valley by Saturday morning. Thereafter, there is a general
consensus in the long range guidance that this primary low will
continue northward through the Great Lakes Saturday/Saturday night,
while secondary cyclogenesis occurs along the mid-Atlantic coast. As
is to be expected this far out, just how deep this secondary low can
develop and it`s track is highly uncertain, and will play a large
role in the ptype forecast heading into Saturday night and Sunday.
Given it`ll be late March with an increasingly higher sun angle,
surface temperatures will be marginally warm above freezing, but
colder air may persist mid-slope to the summits allowing for a
wintry mix or all snow. At this point, we continue to increase PoPs
as it`s almost a certainty it will precipitate, but we`ll offer up
valley rain and mountain snow for the ptype for starters, but
certainly can`t rule out anything at this time.
.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
Through 06z Wednesday...Mainly VFR conditions expected the next
12 to 24 hours with brief periods of MVFR and low prob chance of
localized IFR at MSS/SLK. Crnt radar shows light precip acrs the
SLV, but sfc obs/web cams indicate no precip is actually
reaching the ground attm. Have utilized tempo for MVFR VIS/CIGS
with light snow mainly acrs our northern taf sites of MSS/SLK
and EFK with just vcsh elsewhere. Any lingering precip should
shift east of taf sites by early aftn, with expected winds shift
to the northwest btwn 5 to 10 knots btwn 17z-20z today. This
developing upslope flow may result in some mvfr cigs at SLK/EFK
and MPV thru the early evening hours, before improving
conditions to VFR is likely.
Wednesday: VFR. NO SIG WX.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
Thursday: Mainly MVFR, with local IFR possible. Definite SHRA.
Thursday Night: MVFR/IFR conditions possible. Chance SHRA.
Friday: Mainly VFR, with local MVFR possible. NO SIG WX.
Friday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday: VFR. Likely SHRA, Chance SHSN.