Brattleboro, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

166
FXUS61 KALY 040556
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
1256 AM EST Wed Dec 4 2024

.SYNOPSIS...
A clipper system will bring widespread snowfall beginning this
afternoon and continuing into Thursday with locally moderate to
heavy accumulations across the Mohawk Valley, southern
Adirondacks and southern Greens. Cold and windy conditions
develop behind an arctic cold front Thursday afternoon into
Friday along with lake effect and upslope snow showers. Friday
will feature the coldest temperatures of the season thus far.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
An upper level trough axis has departed the region to the east
as weak upper level ridging builds in overnight. Most of the
snow shower and flurry activity has ended except for a few
locations across southern Vermont and these will continue to
diminish overnight. As flow turns southwesterly, snow showers
from a lingering lake effect band off Ontario may clip far
northwestern portions of Herkimer County with a light dusting of
accumulation. Otherwise, a dry and cold night is expected with
lows mainly falling into the teens to low 20s except for some
single digits, especially across the Adirondacks.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/...
Key Messages:

- A clipper system will bring widespread snowfall later Wednesday
into Thursday with windy conditions and lake effect and upslope snow
showers developing behind the passage of an arctic cold front.

- A Winter Storm Watch remains in effect for portions of the
Adirondacks, western Mohawk Valley and southern Vermont from
Wednesday afternoon/evening into Thursday night.

- Winter Weather Advisories are in effect for portions of the
eastern Catskills, southern Adirondacks, Lake George/Saratoga
Region, Berkshires and southeast Vermont Wednesday afternoon/evening
into Thursday night.

Discussion:

An upper-level trough/clipper will approach the area late Wednesday,
which will lead to another widespread snow for portions of the area.
It will be a dry day to start, with clouds increasing and thickening
from west to east by late morning with increasing moisture aloft.
Warm air advection/isentropic lift will result in snow beginning to
overspread the area Wednesday afternoon, with snow initially favored
over the foothills of the southern ADKs (central Herkimer,
southern Hamilton and northern Fulton counties) thanks to
orographic enhancement. Wet bulb processes will eventually allow
snow to begin to fall elsewhere, though this may be delayed as
fcst soundings show a layer of low-level dry air to overcome
mainly in the valleys. Downsloping effects will be possible
within portions of the Capital District due to the southwesterly
flow aloft from the Catskills reducing amounts there. Marginal
temperatures should limit snow accumulations across the mid-
Hudson Valley. Across southern Vermont, the Froude number less
than one will favor blocked flow and snow favoring the upwind
side of the southern Green mountains (i.e. Bennington County),
where the highest amounts are anticipated.

Snow will continue Wednesday night into Thursday morning before
transitioning to lake effect and upslope snow showers with an arctic
cold front. Localized snow squalls are also possible with steep low
and mid-level lapse rates aloft favored Thursday morning into the
early afternoon. Additional light to moderate snowfall accumulations
are expected Thursday into Thursday night before the trough begins
to depart and high pressure noses in from the west, especially in
higher elevations of the western Greens.

The highest snowfall totals (combining the synoptic and lake-
effect/upslope snow) remain favored across portions of the ADKs,
western Mohawk Valley (especially north of the Thruway) and in
Bennington County, VT where 6 to 12 inches of snow is possible, with
locally higher amounts possible in higher elevations of the ADKS and
Greens. Following coordination with surrounding offices, a Winter
Storm Watch remains in effect for these areas. Winter Weather
Advisories have been issued for for portions of the eastern
Catskills, southern ADKs, Lake George/Saratoga Region,
Berkshires and southeast Vermont where snowfall totals around
2-6 inches are favored (higher amounts possible in Windham
County in southeast Vermont near the Greens).

Behind the arctic front on Thursday, windy conditions are expected
with gusts around 30-40 MPH, with the higher end favored mainly
across the Mohawk Valley and eastern Catskills. This could lead to
areas of blowing and drifting snow.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Key Messages:

- Confidence remains high for below normal temps Fri through the
weekend.  Wind Chills or feel like temps will be in slightly below
zero to single digits range Fri - Fri night with blustery winds.

- Low to moderate confidence a frontal boundary and low pressure
system brings slightly milder temps and rain to most of the region
Mon night through Tue.

An upper level trough will continue to be across southeast Canada,
the Great Lakes Region and Northeast Friday into the weekend. Strong
cold advection continues in the wake of the arctic cold front across
the forecast area. H850 temps will be -1 to -2 STDEVs below normal
based on the latest NAEFS.  Max temps will be 10 to 15 degrees below
normal with highs in the 20s to lower 30s with some teens over the
higher terrain. Deeper mixing and a sfc strong pressure gradient
over the region will promote blustery northwesterly wind gusts 20 to
35 mph.  Apparent temps/wind chills will be mainly in the single
digits to lower teens, but some below zero readings are possible
over the higher terrain. Some lake effect snow showers will persist
across the western Dacks and Mohawk Valley Fri with light accums.
The winds gradually diminish Fri night but weak impulses in the
northwest flow will allow isolated to scattered snow and flurries to
persist from the northern Catskills, Capital District and northern
Berkshires northward.  Lows will be mainly in the teens to lower
20s.

The weekend features a slight modification of temps by Sunday, as
the low and mid level flow becomes flatter. High pressure builds in
from the Southeast/Lower Mid Atlantic States.  A weak warm front
moves through by Sunday.  Some persistent lake effect/upslope snow
showers and flurries continue on Saturday.  Some of the medium range
guidance show some weak warm advection Sat-Sat night.  Chances of
pcpn are in the 20-40% range from the I-90 corridor north for light
snow accums.  Highs will mainly be in the 20s to lower 30s Saturday
and slightly uptick into upper 30s to lower 40s in the valleys and
upper 20s to mid 30s over the higher terrain on Sunday. Another
chilly night is expected Sat night with lows in the teens with
variable clouds.

Early next week a pattern shift is evident in the ensembles and
medium range guidance, as the mid and upper level trough weakens
over the Northeast with ridging building in off the East Coast.  A
storm system organizes over the Lower MS Valley extending into the
Great Lakes Region. Low to mid level warm advection increases ahead
of cold front that drops south but then lifts north as a warm front
late Monday into Tuesday.  Some rain may mix with snow over the
higher terrain but valleys may hold as rain.  Overall, precipitation
chances increase into the likely range (55-74% range) Mon night into
Tue based on the NBM, but the specific timing of the widespread pcpn
event varies Mon-Tue. Unsettled weather early next week with temps
trending closer to normal for early December.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will prevail at all terminals through 19 UTC as
clear skies fade behind increasing high clouds in response to
upper level ridging exiting to our east and moisture increasing
aloft. Clouds will lower through the afternoon becoming MVFR by
21 - 00 UTC at GFL, PSF and even ALB for a period as an area of
snow showers pushes through. Included a TEMPO group for light
snow and MVFR cigs/vis during this window. Then, steadier snow
overspreads the terminals by 01 - 04 UTC resulting in MVFR
vis/cigs that last through the end of the TAF period. Given
higher confidence for IFR cigs at PSF, included lower ceilings
in its TAF. IFR cigs possible at GFL and ALB but not enough
confidence to include in this update.

Otherwise, light and variable winds through sunrise before south
to southeasterly winds become sustained 7-12kts with gusts up
to 15- 20kts by 15 - 17 UTC. Breezy winds continue through the
afternoon and increase further by 20 - 23 UTC and last through
the end of the TAF period with southerly winds becoming
sustained 10 to 15kts and gusts up to 20-25kts.

Outlook...

Wednesday Night: High Operational Impact. Breezy. Definite SN.
Thursday: High Operational Impact. Windy With Gusts To 32 kts. Definite SHSN...SN.
Thursday Night: Moderate Operational Impact. Windy With Gusts To 31 kts. Chance of SHSN.
Friday: Low Operational Impact. Breezy. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Low Operational Impact. Slight Chance of SHSN.
Saturday Night: Low Operational Impact. Slight Chance of SHSN.
Sunday: No Operational Impact. NO SIG WX.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Storm Watch from this afternoon through late Thursday
     night for NYZ032-033-038-082.
     Winter Weather Advisory from 1 PM this afternoon to 1 AM EST
     Friday for NYZ039>042-047-050-054-083-084.
MA...Winter Weather Advisory from 8 PM this evening to 10 AM EST
     Thursday for MAZ001-025.
VT...Winter Storm Watch from this evening through late Thursday
     night for VTZ013.
     Winter Weather Advisory from 7 PM this evening to 1 AM EST
     Friday for VTZ014-015.

&&

$$

SYNOPSIS...Rathbun/Speck
NEAR TERM...Rathbun
SHORT TERM...Rathbun/Speck
LONG TERM...Wasula
AVIATION...Speciale