St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

344
FXUS61 KBTV 040708
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
308 AM EDT Mon May 4 2026

.WHAT HAS CHANGED...
As of 308 AM EDT Monday...

Increased winds across the St Lawrence Valley on Tuesday and tweaked
arrival timing of showers and embedded thunderstorms on Tuesday
afternoon/evening.

&&

.KEY MESSAGES...
As of 308 AM EDT Monday...

1. Periods of breezy southwest winds expected at times today
through Tuesday, along with temperatures climbing into the 70s by
Tuesday.

2. Occasional showers with embedded thunderstorms are expected
on Tuesday afternoon and evening, with additional showers
anticipated into Weds. Storm total rainfall amounts of 0.50 to 1.50
inches possible, but threat for flooding is low.

3. No major impacts or significant weather expected late week
into the weekend, as the pattern continues to support unsettled
conditions with below normal temperatures.

&&

.DISCUSSION...
As of 308 AM EDT Monday...

KEY MESSAGE 1: Upper air analysis and latest GOES-19 mid level water
vapor imagery shows weak embedded s/w with pocket of mid lvl
moisture associated with waa lifting acrs northern NY this morning.
This energy and dynamics wl continue to produce a few scattered
showers this morning, mostly near the International Border.
Developing southwest flow at all levels of the atmosphere wl occur
with moderately strong llvl waa. Progged 925mb temps climb btwn 9-
11C by 21z this aftn, with some partly sunny skies should support
highs well into the 60s most locations. Tonight 925mb to 850mb jet
of 35 to 50 knots strengthens acrs our cwa ahead of approaching
mid/upper lvl trof and associated cold frnt. This increasing pres
gradient should result in a very mild night, especially wider
valleys, where winds wl stay mixed and limit temps from falling.
Have trended toward the 75th NBM for lows, which supports values in
the mid 40s east of the Greens to mid/upper 50s SLV and CPV.
Localized areas near PBG could decouple and drop into the upper 40s.
Expect light winds in the deeper/protected valleys of
central/eastern VT, while exposed summits and wider valleys see
localized gusts 25 to 35 knots tonight.

Gusty south/southwest winds are expected on Tuesday, especially
northern NY, including the SLV where progged 850mb jet of 55 to 60
knots is anticipated. NAM12KM and NAM3KM soundings show favorable
mixing under warming bl temps on Tues, with top of the mixed layer
winds of 45 to 55 knots, while bottom values are in the 35 to 40
knot range, supporting localized gusts up to 45 mph possible. NAM
solutions seem to be the most aggressive with channeled southwest
flow and favorable mixing profiles, while GFS and HRRR are slightly
weaker. If trends continue a low end wind advisory could be needed
for the SLV and portions of the northern Dacks on Tues for localized
gusts 45 to 50 mph. Also, the timing of clouds/precip is important
toward the amount of llvl instability/mixing, as earlier arrival
limits sfc heating and depth of mixing and would support lighter
winds per GFS solution. Elsewhere, winds 10 to 20 mph with gusts 20
to 35 mph is expected over the CPV and parts of central/eastern VT.
Given llvl wind profiles our first Lake Wind Advisory of the season
is likely late tonight into Tues. Still have to watch how the cooler
lake water can stabilize bl and limit mixing.

KEY MESSAGE 2: SPC has upgraded the Day 2 outlook to place a marginal
(1 out of 5) risk of severe storms acrs our cwa for Tues. From my
perspective the potential for strong to severe storms is not ideal,
given bl dwpts only in the upper 40s to lower 50s, limited or
delayed height falls associated with approaching mid/upper lvl trof
and weak convergence with pre-frontal trof/differential heating
boundary. Crnt thinking some modest instability develops btwn 15z-
18z Tues with ML CAPE values in the 500-1000 J/kg range, while low
to mid lvl wind fields strengthens, increasing favorable deep layer
shear in the 35 to 50 knot range. As showers with embedded rumbles
of thunder develop by 18z, expanding cloud canopy under less than
ideal southwest flow wl help to stabilize environmental conditions.
This combined with strengthen wind fields wl shear off vertical
development of convection and could limit strong/severe potential.
Given pre-storm thermo-dynamics and vertical wind profiles, feel
probability of any severe development is <5% attm. Localized
hodographs in the CPV are impressive, showing large cyclonic
curvature, supporting potential supercells, but instability
parameters are marginal. Temps under southwest waa should warm well
into the 70s before the rain arrives.

Showers with embedded rumbles of thunder on Tues evolves into a
widespread cold stratiform rainfall on Tues night into Weds, as weak
sfc low pres develops along a slow moving boundary. MBE vector
analysis shows progressive individual elements moving southwest to
northeast, but eastward progression of line is very slow at 4 to 8
knots, given deep unidirectional flow paralleling boundary. This wl
result in slow moving rain elements on Tues night into Weds, with
the potential of 1 to 2 inches of rainfall from the eastern Dacks
into most of VT. The probability of flooding is low, given recent
dry weather and modest rainfall rates. Lows wl drop back into the
40s on Tues night and only warm into the 50s on Weds. A cold, raw
and wet Weds is anticipated.

KEY MESSAGE 3: Aside from Friday night when consensus is strong on dry
weather, some chances for showers will persist through the weekend
with another longwave trough parked over the area. These showers
should tend to be scattered rather than widespread, and mostly
diurnally-driven as steep low level lapse rates lead to shallow
instability. Note that while the large scale pattern is similar to
what we saw this past weekend, the airmass doesn`t look quite as
chilly. A low level southwesterly wind is indicated among all model
clusters through most of the weekend across the region. In relation,
AI-GEFS 850 millibar anomalies bottom out near the 25th percentile
Friday evening with gradual improvement after that point, reaching
near normal on Sunday. These low level temperatures support highs
that are currently forecast in the low to mid 60s in the lowest
elevations, and mid to upper 50s elsewhere, during the weekend.
Relatively light winds aloft and breaks in cloudiness, dependent on
timing of shortwave troughs passing through, could support frost and
freeze conditions each weekend morning.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Through 06Z Tuesday...Across a relatively compact area showers are
pushing eastward across the airspace this morning. They should
mainly affect northern terminals between about 08Z and 14Z.
Brief MVFR visibilities and/or ceilings during these showers are
possible, but used mainly PROB30 groups given scattered nature
of the showers, particularly at Vermont sites.

Otherwise, ceilings should be generally 3 to 7 thousand feet
agl, except at SLK where upslope flow and advection of moist air
has led to ceilings at 900 feet as of 0530Z. Think this could
persist before showers arrive, with some slight improvement to
MVFR conditions favored thereafter. Clouds are expected to
become broken and trend scattered after showers pass this
afternoon.

Mixing of southwesterly boundary layer winds will result in
some low level turbulence during the afternoon. The low level
jet will strengthen after 00Z leading to resumption of LLWS late
in the period. Flight conditions will remain VFR.

Outlook...

Tuesday: VFR. Windy with gusts to 30 kt. Chance SHRA, Slight
chance TSRA.
Tuesday Night: Mainly VFR, with local MVFR possible. Definite
SHRA.
Wednesday: Mainly MVFR, with local IFR possible. Definite SHRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Thursday: VFR. Slight chance SHRA.
Thursday Night: VFR. Chance SHRA.
Friday: Mainly VFR, with local MVFR possible. Chance SHRA.

&&

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

&&

$$

WHAT HAS CHANGED...Taber
DISCUSSION...Taber/Kutikoff
AVIATION...Kutikoff