St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

019
FXUS61 KBTV 152259
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
659 PM EDT Thu May 15 2025

.SYNOPSIS...
Daytime showers and thunderstorms will gradually increase in
extent each day as a series of troughs swing through while we
remain warmer and more humid than normal. The greatest potential
for precipitation will be late Friday and again on Saturday
afternoon, with cooler conditions arriving on Sunday that will
linger into the first half of next week.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 656 PM EDT Thursday...No big changes for the first
evening update. Updated forecast to reflect current radar
trends. Some scattered showers with embedded thunder continue,
but have started to become a bit more progressive than earlier
this afternoon when the basically stayed in one place over
Rutland county. Showers should die down after sunset with loss
of daytime heating and little bit of instability that was able
to develop. Minimum temperatures overnight will range from the
lower 50s to lower 60s. Previous discussion follows.

Mainly pinprick showers have developed along lines of HREF
guidance. A larger cluster has formed over Rutland County and
has anchored to terrain with limited motion. About 2/3rds of an
inch have fallen over various sites around the storms, but where
there has likely been the most over Clark and Bird Mountains
where radar is estimating 1.25" has fallen, there are no sites
to provide ground truth, unfortunately. With shear only around
10, no synoptic forcing, and poor lapse rates, any storms will
remain garden variety with erratic motions that could result in
additional precipitation bulls-eyes. Activity will diminish
slowly tonight. There`s still some elevated instability
lingering. However, there`s no mid- level warm advection or
increasing southerly flow. Convective activity could
sporadically increase at times overnight, but the trend will be
decreasing coverage. Unfortunately, another humid night in the
mid 50s to mid 60s is expected.

Friday continues to appear more active with better convective
parameters across the board with upper 70s to lower 80s and 60s
dewpoints. Another trough will provide marginal synoptic
forcing. Forecast skew-Ts still suggest tall, skinny CAPE
profiles with low shear across the region. It will take until
mid-afternoon for the region to destabilize. So the best chances
for showers and storms will be in our climatological 1-10 PM
window. Slow moving thunderstorms with heavy rainfall will be
the main concern for Friday. The trough will depart after
midnight, but increasing warm advection behind it and present of
a nocturnal LLJ may allow for a few pinprick showers or storms
to linger overnight. Little change to warmth and humidity will
keep overnight lows in the mid 50s to mid 60s another night.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
As of 303 PM EDT Thursday...An upper level low slowly makes its
way into the region over the weekend, pushing through a few
fronts/troughs on Saturday. There look to be broken rounds of
showers and thunderstorms associated with these features, with
some gaps in between. The first round should move into northern
New York in the early morning and Vermont in the late morning.
It does not look like a significant amount of instability will
develop before this round comes through, so any storms should be
under severe levels. There looks to be at least a partial gap
in the afternoon before another broken line comes through later
in the day. Adequate shear should be in place, but it will be
relatively weakly forced and there are questions on how much
instability will develop. If adequate clearing can occur between
the lines, there is a low severe chance for the second line,
and the SPC has therefore placed the region in the Marginal
risk. East of the Greens, southeast flow will keep a cooler
marine modified airmass in place and may prevent any
thunderstorms from forming at all. There will be favorable
conditions for heavy rain with any storms that develop, though
there looks to be decent storm motion so any consistently
training looks unlikely. However, the threat of flash flooding
cannot be completely ruled out. As the low passes overhead and
to the east, moist northwest flow develops on the backside for
Sunday. There will be upslope showers throughout much of the
day. Temperatures will also be much cooler, with highs in the
50s and low 60s for most places. The low looks to slow down once
it moves off the coast so these showers may continue into
Monday, especially across eastern areas. Conditions will still
be too warm for snow at any of the high peaks.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 303 PM EDT Thursday...A much cooler pattern will continue
for next week as northerly cyclonic flow looks to dominate. A
few showers are possible on Tuesday and Wednesday as a couple
weak shortwaves look to pivot around the upper low to the east,
but it should remain mostly dry. A slow moving nor`easter will
make a run at the region for mid and late week, and while its
exact track and speed are still uncertain, there is again the
potential for an extended period of steady rain. Temperatures
may be cold enough during it that the highest peaks see a little
bit of snow. If the wetter solutions verify, highs may be in
the 50s for most areas. Even if this surface low misses to the
east, there will be a cold upper level low on the western side
so there will likely be some afternoon showers regardless. The
cooler and unsettled weather looks to continue into the weekend,
though it will likely not be a consistent steady rain.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Through 18Z FRIDAY...Conditions are mainly VFR, but 1500-3000
ft agl ceilings, mainly over eastern Vermont, are present.
Showers are popping up now, but the extent is not going to be
great this afternoon. The primary focus will be near KRUT, but
the probability is also relatively higher (30%) over KMSS and
KPBG. If any cell directly impacts a terminal, a very brief drop
to 2 SM will be possible, but showers will be small and short-
lived. So primarily indicated 4-6SM. Beyond 00z, winds will
become light and variable. Some patchy fog is possible,
especially over any terminal where precipitation occurs.
However, we are not in our climatological fog season, and noted
BCFG for now to re- evaluate later. At least 1500-3000 ft agl
ceilings will return over KSLK, KRUT, KEFK, and KMPV, but may be
possible at any terminal. Southwest winds pick up beyond 14z at
5 to 10 knots.

Outlook...

Friday Night: VFR. Chance SHRA, Slight chance TSRA.
Saturday: Mainly VFR, with local MVFR possible. Definite SHRA,
Slight chance TSRA.
Saturday Night: Mainly VFR, with areas MVFR possible. Chance
SHRA.
Sunday: Mainly MVFR, with local IFR possible. Likely SHRA.
Sunday Night: Mainly MVFR, with local IFR possible. Chance SHRA.
Monday: Mainly VFR, with local MVFR possible. Chance SHRA.
Monday Night: VFR. Slight chance SHRA.
Tuesday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Neiles
SHORT TERM...Myskowski
LONG TERM...Myskowski
AVIATION...Haynes