FXUS61 KBTV 231127
Area Forecast Discussion
National Weather Service Burlington VT
727 AM EDT Thu Mar 23 2023
Widespread light to moderate rain will push across the region
today in advance of a cold front. This front will bring cool
and dry weather for Friday with some sunshine returning. Then as
a stronger low pressure system passes to our northwest, an
elevationally dependent mixed precipitation and snowfall will
unfold over the region Saturday into Saturday night.
.NEAR TERM /THROUGH FRIDAY/...
As of 720 AM EDT Thursday...No big changes for the 730 AM
update today, rain is spreading into our region from the west as
expected and pretty much on time. Rain will continue to spread
across our forecast area today, then exit to the east after 00z.
Previous discussion follows.
Rain will spread from west to east into our region today as a
low pressure system lifts well to our north. Southerly flow will
be in place ahead of the cold front which crosses the region
this afternoon. Widespread light to moderate rain is
anticipated, with around two tenths of an inch to a half an inch
of rainfall expected. Briefly heavier showers are possible with
any elevated instability favored in our southern areas. Maximum
temperatures today will range through the 40s with some lower
50s in southern Vermont. Combination of rainfall and warm
temperatures will lead to snowmelt across the region.
Precipitation will become more terrain enhanced towards the
afternoon hours and first part of the overnight before coming to
an end. Rain showers should come to an end before colder air
moves into the region. Minimum temperatures tonight will range
from the mid 20s to lower 30s, this will slow down the snowmelt
drastically. A much quieter day is expected for Friday with
brief surface and upper level ridging building into our area.
Temperatures will be cooler than the past several days, peaking
in the mid 30s to lower 40s, some mid 40s in southern Vermont.
With drier air moving into the region, should see some sunshine
by Friday afternoon.
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 356 AM EDT Thursday...Little change noted from recent
guidance package with just minor tweaks needed to previous fcst
ideas. The progged synoptic scale pattern remains unchanged with
potent 5h energy and associated sub 990mb low pres lifting from
the MS River Valley into the central Great Lakes by 00z Sun,
while weak secondary low develops over SNE. Strong 925mb to
850mb waa on gusty progged 850mb jet of 50 to 60 knots wl create
a challenging thermal profile and associated ptype issues. Area
soundings continue to show a deep dry layer btwn sfc and 500mb
as precip approaches associated with ribbon of very strong 850
to 700mb fgen forcing on Saturday. This should lead to
evaporational cooling to support a burst of mostly wet snow as
best dynamics lift from southwest to northeast acrs our cwa btwn
16z-22z Saturday. Given bl temps hovering around 32F or even
higher in valleys, the accumulation efficiency wl be limited and
confined to mainly grassy and snow pack surfaces. However,
given embedded heavier precip rates associated with robust waa
lift/moisture, expected a few hours of accumulating snowfall
with a quick 0.5 to 3.0 possible. Given thermal profiles a
strong elevation dependent gradient from valleys to summits wl
be anticipated for leading burst of waa precip.
Meanwhile, as warmer air aloft races from southwest to
northeast associated with strong southwest llvl jet, thermal
profiles support a mix of wintry precip and mainly rain in the
valleys Sat night. Still have noted a cold layer btwn sfc and
900mb of temps btwn 0C and -5C, while near 850mb temps warm to
+5C, supporting a messy mixture of sleet/snow and pockets of
freezing rain, especially midslopes on east side of the Greens
and midslopes of the eastern Dacks. Placing this detail in the
grids is nearly impossible, given complex thermal profiles, but
main impact wl be to ski conditions and lift operations at local
resorts, along the Green Mtn Spine. Any additional snow/sleet
accumulations overnight on Saturday wl be confined to the
eastern Dacks and mainly east side of the Green Mtns, with an
additional 1 to 2 inches possible on Sat Night. For event total
snowfall is mainly a dusting to 1 inch valleys to 2 to 5 inches
mtns with highest totals eastern Dacks and favorable southeast
upslope areas of the central/southern Greens.
Given the southeast 925mb flow and southwest 850mb flow,
expecting event total qpf to be highly trrn driven for this
event. Have bumped winds up along the northern dacks along the
Route 11 corridor with gusts 35 to 45 mph possible and acrs
portions of the Western Slopes on Sat evening. Eventually a cold
rain develops acrs the SLV/CPV and downslope areas of the
northern Dacks and Western Slopes on Sat Night, with some
potential fog/br in the deeper/protected valleys. Temps remain
steady in the upper 20s to mid 30s, with some warmer into the
lower 40s possible due to downslope winds.
The next order of business is potential for a few embedded
rumbles of thunder btwn 04z-08z Sunday associated with potent 5h
s/w energy and ribbon of enhanced 700 to 500mb lapse rates >7.0
C/km and axis of elevated instability of 300 to 500 J/kg. For
now wl just mention in afd as a heads up potential, but if
instability trends continue the addition of thunder maybe
needed. Event total qpf wl range from 0.25 to 0.75 with
localized higher amounts possible in heavier convective elements
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 356 AM EDT Thursday...Mid/upper lvl circulation quickly
races toward eastern Canada while double barrel/elongated sfc
low structure is located from south of Hudson Bay toward the
central Maine Coast. This lack of strong caa, best deep layer
moisture near the International Border and west to southwest
925mb to 850mb flow wl limit backside upslope precip for this
system. Have continued chc/low likely for the morning hours, but
taper off to schc/chc by evening. A more typical atmosphere is
progged to develop with cooling aloft associated with upper lvl
trof builds acrs our cwa on Sunday, so have mention of rain/snow
based on freezing levels. Temps range from the upper 20s/lower
30s to mid 40s warmer valleys. Monday is quiet as weak ridging
aloft and at the sfc builds into our cwa. For midweek still
plenty of inconsistency amongst our guidance with regards to
another potential system. For now, have continued with previous
fcster idea of low chc pops for Tues/Weds time frame. GFS/CMC
show mostly a suppressed system this run, while ECMWF has
stronger system with greater qpf further north. Still plenty of
time to fine tune details over this upcoming weekend and into
early next week. Temps look to remain near seasonable levels in
the mid 30s to mid 40s and lows mainly in the 20s.
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Through 12z Friday...All terminals are currently VFR, except for
MPV which is already IFR. Rain will become widespread this
morning, with MVFR conditions becoming widespread with some
localized IFR possible. Later in the afternoon rain will come
to an end though lower ceilings may linger for awhile. Winds
will be out of the south this morning, then veer to northwest
overnight behind the frontal passage.
Friday: Mainly VFR, with local MVFR possible. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: Mainly VFR, with local MVFR and IFR possible. Definite
RA, Definite SN.
Saturday Night: Mainly MVFR, with areas VFR possible. Definite
RA, Likely SHRA.
Sunday: Mainly MVFR, with areas VFR possible. Chance SHRA, Chance
Sunday Night: Slight chance SHSN.
Monday: NO SIG WX.
As of 425 AM EDT Thursday...A low chance of river flooding will
be monitored for the late Thursday into Friday morning period
in response to light to moderate rainfall with basin averages of
0.2" to 0.5" and snow melt up to 1". As dew points rise through
the 30s today, snow will ripen with continued melting at lower
elevations. Therefore, modest to sharp river rises may occur by
late Thursday into Friday in the watersheds with runoff
primarily due to snow melt.