St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

064
FXUS61 KBTV 172321
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
721 PM EDT Thu Apr 17 2025

.SYNOPSIS...
Dry and breezy conditions will continue this afternoon before
temperatures fall quickly overnight. Similar conditions to today
will continue for Friday before a frontal system and scattered
precipitation chances arrive Friday night into Saturday. Brief
drying and above average temperatures are expected Sunday
before more unsettled weather arrives to start next week.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 718 PM EDT Thursday...No significant changes were needed
with this update. Clear skies dominate the region this evening,
with just a few wispy cirrus clouds overhead. Temperatures have
started to cool as expected, given the dry airmass; lows tonight
will be in the 20s to around 30F, coldest in the Adirondacks and
Northeast Kingdom. Winds will abate overnight as well. The
forecast has this covered, so just made a few tweaks to sky
cover and temperatures to match the latest conditions.

Previous discussion...Abundant sunshine and breezy northwest
flow resulted in decent warming and dry conditions areawide
today. Wind gusts up to 25 mph are expected to continue,
especially in valley locations through this afternoon, before
calming overnight. Dry conditions have dropped relative
humidities into the 20-30% range, which can lead to isolated
fire weather concerns, however, these conditions will quickly
wane by sunset. Temperatures will quickly fall after sunset
tonight as strong radiational cooling, under clear skies, drop
into the low 20s across the Adirondacks, and mid to upper 20s in
the valleys. Models have been higher on dew points throughout
the day as compared to observations, which would indicate an
underestimating of lows tonight, and thus blended in some 10th
percentile temperature guidance for tonight, especially in the
Adirondacks.

Mountain clouds and high clouds will move in near sunrise ahead
of a frontal system tracking out of the Great Lakes. A quasi-
stationary boundary will become draped across lower Ontario
Friday with a warm front extending from Lake Ontario through the
lower Adirondacks. Southerly warm air advection will help to
bring temperatures above average Friday with values near 60 for
all locations. Ahead of the front dry air will remain
entrenched with relative humidities in the 25-40% range with
wind gusts up to 30 mph. The warm front will slide north across
the region with scattered precipitation chances beginning Friday
afternoon. Dry air will inhibit most rain chances in Vermont
through Friday evening. Across the St. Lawrence Valley, a
pronounced elevated mixed layer accompanying the warm front will
lead to enough instability for a few scattered thunderstorms to
form, particularly along the international border. Some of these
thunderstorms could produce lightning, and locally moderate
rainfall at times. No heavy rain or hazardous wind or hail is
expected from these storms. Scattered showers will continue
across the area from west to east Friday night into Saturday,
still mainly confined to the northern regions of New York and
Vermont. QPF amounts have still shown a lessening trend over
several of the CAM runs.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 318 PM EDT Thursday...We will be firmly positioned in the warm
sector of a deepening sub 1000mb surface low. Lack of greenery,
increasingly dry mid-level air, and 925hPa temperatures of around 15
C suggest we can easily make a run for the mid to upper 70s.
However, scattered showers may still take place within deep
southwesterly flow. This will also produce gusty conditions. How
that impacts whether mixing keeps temperatures down or promotes some
adiabatic warming, we`ll see.

Precipitation will be in the process of exiting east Saturday
morning with the surface low. The attendant cold front will wash out
as it approaches the region while 500hPa upper high at 590 dam will
nudge northeast concurrent with a sharp upper trough across the
Great Lakes. Accelerating flow channeled between these features will
temporarily disrupt our moisture connection from the Gulf.
Additionally, rising heights and an increasing inversion should
result in general clearing throughout the day. Warm advection, a
prefrontal trough, and some diurnal destabilization may try to
produce scattered showers, but the combined forcing does not appear
sufficient to break the capping inversion, and any afternoon
activity should be pretty sparse. If there is thunder, the
international border will have the best chances due to proximity to
the surface low.

One feature we will be monitoring Saturday afternoon is the fast mid-
level flow and how efficiently it can mix to the ground. There are
some hints of compression with the capping inversion sinking to
summit level while 850mb flow will be 45 to 55 knots. There seems to
be some differences with how sharp the inversion layer will be with
higher resolution models suggesting a stronger warm nose. We`ve got
one more cycle before Saturday afternoon in the range of HREF
guidance. EC EPS guidance does signal a 60-90 percent chance of
downslope winds exceeding 34 knots. NBM mean gusts are generally in
the 30 to 35 knots range, and the 90th percentile gusts do hint a
reasonable worst case exceeding 40 knots. So it`ll be something to
keep an eye on. At present the forecast depicts near 30 knots gusts
Saturday afternoon, with gusts to 35 along the northern slopes of
the Adirondacks.

Moisture fluxes briefly return Saturday night ahead of the cold
front that will sweep southeast. This will produce additional
scattered showers. If enough hangs around approaching Sunday, there
could even be a handful of mountain snow reports as temperatures
return into the mid 30s to mid 40s at lower elevations and below
freezing at summit level.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 318 PM EDT Thursday...A secondary frontal boundary will pass
south Sunday morning alongside a fairly strong vort max. However, by
this point, there should be too little moisture to produce much,
except perhaps at summit level. Beneath the upper low and under
breezy northwest flow, Sunday will be colder with a 20+ temperature
swing compared to Saturday. Our progressive cycle will continue. A
pleasant Monday will unfold beneath deep layer ridging, and then
rain and perhaps some thunder arrives for Tuesday, then followed by
relatively dry conditions Wednesday, and then more showery weather
along a front that appears could stall in the vicinity.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday...Clouds have all but dissipated and moved
out leaving clear skies at all terminals. This trend will
continue through the TAF period. This clearing has led to breezy
northwest winds between 10-15 knots with gusts up to 25 knots
across the area, especially in valley terminals. Winds aloft are
causing light to moderate turbulence, especially at mountain top
elevations. Terrain confined winds are expected after 23Z with
surface winds becoming variable and calm through the remainder
of the TAF period.

Outlook...

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

&&

.CLIMATE...
Several sites have a chance to tie their record High Minimum
temperature this Saturday.

Record High Minimum Temperatures:

April 19:
KBTV: 56/1914
KPBG: 55/1976
KSLK: 50/1976

&&

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

&&

$$
SYNOPSIS...Danzig
NEAR TERM...Danzig/Hastings
SHORT TERM...Haynes
LONG TERM...Haynes
AVIATION...Danzig
CLIMATE...BTV Team