St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

714
FXUS61 KBTV 151750
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
150 PM EDT Fri May 15 2026

.WHAT HAS CHANGED...
As of 233 PM EDT Thursday...

The timing of a trough on Saturday evening is somewhat earlier
with this latest update.

&&

.KEY MESSAGES...
As of 221 AM EDT Friday...

1. The upper low responsible for rainy weather will pull away
later today with rain chances decreasing after tonight.

2. Building heat is anticipated through early next week.

3. Above normal temperatures are expected for the start of next
week.

&&

.DISCUSSION...
As of 221 AM EDT Friday...

KEY MESSAGE 1: The center of a strong upper low is skirting the
Pennsylvania-New York border on its way eastwards. Some dry air has
wrapped into it this evening, present much of Vermont now. Wrap
around activity now mostly resides over northern New York a few
showers in Vermont. As the upper low starts making eastward
progress, wrap around will arc southeastwards with a gradual
decay as it becomes increasingly disconnected from the Atlantic
moisture source. By late morning and early afternoon rain will
exit east.

Steady clearing is expected on the western edge of the upper low.
Temperatures will climb into the 60s to near 70 as we finally get
some sunshine. Cool temperatures aloft and lingering moisture will
result in marginal surface instability, up to 250 J/kg. So isolated
to scattered showers will develop during the afternoon and evening
hours. Loss of daytime heating and some incoming mid-level dry air
will put a stop to shower activity tonight. A ridge will begin to
nose in, and this will add some light, but steady winds. These winds
will be lighter across Vermont, and so some level of decoupling is
possible. Guidance is mixed on the potential, but given 1-2" of
recent rain, it probably won`t take much to fog across Vermont.

KEY MESSAGE 2: A narrow upper ridge will crest Saturday with
southwesterly flow bringing widespread 70s to the area. Modestly
compacted pressure gradients will result in breezy flow, with winds
10-15 mph developing later Saturday morning, and with gusts of 20-30
mph. After having slowed the timing of the trough on Saturday,
today`s guidance has decided to reverse course. Assessing the model
soundings, low-level conditions will be quite dry (min RH around 30-
40%). Most precipitation will likely evaporate and not truly
measure, but did raise PoPs with human factors in mind for all the
weekend activities. Any rain that falls may also trigger some gusts
to mix from aloft due to the evaporative cooling. Fortunately, the
bulk of the stronger flow aloft arrives after this mid-level
moisture tracks east, but highly localized stronger gusts cannot be
discounted.

Saturday night into Sunday, the trough will shift southeast, but not
cleanly make it out before the heat of the day. So areas along the
international border will be closer to 70 while southern Vermont
should see a few readings in the lower 80s. A spot shower will be
possible in the Northeast Kingdom on Sunday, but much of the region
will be largely dry.

A more substantial upper ridge will build on Monday. A strong warm
front will pass northeast Monday morning. Without a pocket of
increased vorticity and meager moisture, this front will likely
slide through without triggering rain. Although it may not take much
to spark a shower if anything is running around "upstairs", as there
is some mid-level instability, and so I won`t say that it`s
impossible. The increase of south to southwest winds will
announce the arrival of the front and associated warmth.
Temperatures will ascend into the 80s outside the Northeast
Kingdom on Monday.

KEY MESSAGE 3: A warming trend will continue into the first half of
next week as ridging builds into the region. Tuesday looks to be the
warmest day, with high temperatures climbing into the 80s for most
locations, with 925mb temperatures around 22C to 25C. These
temperatures will be the warmest of the year so far, so it is
important to remember to stay safe in warmer temperatures by staying
hydrated and take frequent breaks if working outside. Overnight lows
look to be above normal as well, generally in the upper 40s and 50s,
warming to almost 60 for Tuesday night. A few chances for
precipitation may be possible early next week as a shortwave moves
through the region, which could have an impact on how high
temperatures climb on Tuesday. A more robust frontal boundary look
to move through the region for mid-week, bring increased chances of
showers and thunderstorms, with more seasonable conditions expected
later in the week behind the front.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Through 18Z Saturday...We started off the morning with highly
variable ceilings across the forecast area. These ceilings have
lifted to VFR levels at all TAF sites except KMSS and KRUT as of
18Z. Still observing some scattered clouds around the 1500-3000
ft level, so have included some tempo groups for the first few
hours of the TAF for brief periods of MVFR ceilings. However,
expect improving trend to continue, with all TAF sites forecast
to lift to and remain VFR from 21Z onward.

The fog forecast tonight is a little tricky with mixed
signals... increased moisture from recent rainfall but still
some winds just off the surface that will keep most areas
somewhat mixed. Thinking the 5-15 knot flow just off the surface
will limit fog development to just the sheltered valleys of
eastern Vermont. Have kept mention of fog out of all the TAFs at
this moment, but there remains a small chance of some fog
overnight tonight at KMPV, most likely between 09Z and 11Z.

Outlook...

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

&&

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

&&

$$

WHAT HAS CHANGED...Haynes
DISCUSSION...Haynes/Kremer
AVIATION...Duell