-5.0F
Current conditions from King Hill
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  Monday January 21, 2019

 

NWS Area Forecast Discussion


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FXUS61 KBTV 211538
AFDBTV

AREA FORECAST DISCUSSION
National Weather Service Burlington VT
1038 AM EST Mon Jan 21 2019

.SYNOPSIS...
As strong low pressure exits northeast of the region this morning,
lingering light snow is expected to continue across northern
portions of the North Country through much of today, with additional
light accumulations expected. In addition, arctic air filtering into
the region ahead of approaching high pressure will provide
dangerously cold wind chills of 20 to 35 below through the day as
well. Fair and dry conditions are expected on Tuesday, with highs in
the teens and lighter winds, before developing southerly winds ahead
of an approaching upper level disturbance from the Great Lakes
brings our next chance for precipitation on Wednesday.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 1035 AM EST Monday...Arctic conditions continue today and
tonight with areas of very light snow and dangerously low wind
chills. Currently -3F at BTV (1530Z) with wind chills 20 to 30
below in the Champlain Valley. Only minor adjustments with the
morning update...

Previous Discussion...Surface low pressure which brought a
major winter storm to the region yesterday continues to track
northeast into the Canadian Maritimes this morning but the
parent upper level circulations are still moving through the
region producing very light snow across northern portions of the
forecast area. 700mb low to our east this morning continues to
provide wrap-around moisture to the low levels and combined with
the 500mb trough passage this afternoon will continue to
provide light snow through much of the day until drier air works
in this afternoon and evening as surface high pressure begins
to build in from the west. Arctic airmass associated with this
high is already building in at the low levels with surface temps
across the region already in the single digits to teens below
zero combining with moderate northwesterly winds to cause wind
chills in the 20-35 below range. Surface temps don`t warm too
much today under strong cold air advection with highs struggling
to hit zero. Winds will only get stronger as the day wears on
as the pressure gradient between the departing low and
approaching high tightens, so wind chill headlines continue into
this afternoon and will likely need to be extended into
tonight.

For tonight into Tuesday fair conditions are expected as the
aforementioned surface high and upper level ridge crest over the
region. The combination of fresh snowpack and clear skies will be
favorable for excellent radiational cooling with likely the coldest
night of the winter for most locations. Winds gradually slacken as
the high builds in, but expect enough wind to persist to support
wind chills in the 15-25 below range to continue headlines. Lows
will be widespread int the single digits to teens below zero with 20-
30 below likely across the Adirondacks. Light southerly return flow
develops Tuesday as the high shifts over the eastern seaboard
allowing temps to rebound into the single digits and teens above
zero in the afternoon.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 305 AM EST Monday...The short term starts out quiet on
Tues Night with warming temps overnight and developing southerly
winds. Developing 925mb jet of 35 to 45 knots with aligned
channeling up the slv/cpv will create areas of blowing snow
overnight into Weds. Have placed localized gusts up to 25 to 35
knots, with highest values over near Lake Champlain. Otherwise,
temps continue to warm thru the teens and into the 20s to near
freezing overnight. Coldest values east of the Greens. On Weds
expect a period of snow showers to lift from southwest to
northeast across our cwa. A general dusting to 3 inches
anticipated with highest amounts in the dacks and
northern/central Green mtns. Strong 925mb to 850mb southwest jet
of 45 to 55 knots by 18z Weds will result in some downslope
shadowing in the cpv. Progged 925mb to 850mb temps approach 0c
by 00z Thurs, supporting mainly 30s, but some cooler values in
the upper 20s likely east of the Greens.

By Weds night into Thurs morning still a large degree of
uncertainty on potential development of wave along boundary and
potential for additional precip. In addition, low level thermal
gradient tighten from west to east, making precip type
challenging. The CMC/ECMWF show most of our cwa well established
in the warm sector with 850mb temps btwn 2-4c with brisk
southwest flow paralleling approaching front. This would support
additional qpf in the 0.25 to 0.50 range with highest values in
our central/eastern cwa. Given very cold sfc temps, would expect
areas of freezing rain, especially east of the Greens.
Meanwhile, gfs shows a much more progress system with developing
westerly flow quickly sweeping boundary east, with limited
lingering moisture Weds night into Thurs. This would also
support developing low level caa quickly and a change back to
mostly snow. Given uncertainty continue to mention high chc to
likely pops overnight with temps holding mainly in the 30s,
except upper 20s east of the Greens. Will continue to mention
rain/snow based on sfc temps, but some wintry mix is likely
needed in the upcoming days.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 305 AM EST Monday...The aforementioned boundary is
eventually moving thru our cwa by 00z Friday and precip will end
with a brief period of light accumulating snowfall. Given the
uncertainty on timing of boundary and sfc development have kept
temps mainly in the 30s on Thurs with mention of rain/snow based
on sfc temps. Have noted ecebtv is showing high of 44f, while
mexbtv is 38f, highlighting the uncertainty. Drier and cooler
air returns on modest low level caa Thurs night with some
lingering upslope snow showers. Temps drop back into the teens
and 20s with brisk west/northwest winds.

More uncertainty develops with secondary surge of potential
arctic air on Saturday, with latest 00z GFS much more aggressive
with low level caa. For example gfs shows 925mb temps near -32c
by 12z Sat, while ecmwf is -20c over northern NY. In addition,
gfs shows potent 5h energy with sharp sfc convergence and ribbon
of deeper moisture moving across our cwa Fri Night/Sat, with
the potential for embedded snow squalls, while ecmwf is much
less amplified. Have continue to mention high chc pops for now
with a blend for temps, which supports mostly below normal
values for the upcoming weekend.

Overall pattern does become more interesting again late Sunday
into early the following week, as large scale trof with
numerous embedded pieces of energy deepens over the
central/eastern Conus. Meanwhile, as trof amplification occurs
developing mid/upper level ridge builds over the western Conus
and with another ridge over the northern Atlantic. Timing of
individual s/w`s in highly amplified patterns is difficult but
model consensus shows southern stream energy enhancing sfc low
pres over the se conus around hour 160. The uncertainty develops
does the low pres make the turn and come up the coast for
potential impact on our cwa, or slide out to sea. I did notice
almost half the gfs ensemble members show a significant system
with impacts across our cwa, while the 00z ecmwf ensemble mean
has center of low pres very close to Cape Cod. In addition, this
idea is supported by the 00z operational runs of the CMC and
ECMWF. Still many days away and plenty of time to watch
mid/upper lvl trof evolution and associated sfc low pres track,
for potential impacts.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
Through 12Z Tuesday...Very light snow will remain persistent at
northern terminals through mid-day with mainly MVFR ceilings
and visibility before snow rapidly decreases in coverage after
18Z and skies scatter to FEW-SCT VFR by 00Z. Winds will remain
brisk out of the north/northwest increasing to 12-15kts after
13-14Z with gusts 20-25 kts through midnight before abating.

Outlook...

Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. Windy with gusts to 30 kt. Chance SHSN.
Wednesday: Mainly VFR, with areas MVFR and IFR possible. Windy
with gusts to 35 kt. Likely SHSN.
Wednesday Night: MVFR/IFR conditions possible. Likely SHSN,
Chance SHRA.
Thursday: Mainly MVFR, with areas IFR possible. Likely SHSN,
Definite SHRA.
Thursday Night: Mainly MVFR, with areas VFR possible. Chance
SHSN.
Friday: Mainly VFR, with local MVFR possible. Chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Wind Chill Warning until 1 PM EST this afternoon for
     VTZ001>012-016>019.
NY...Wind Chill Warning until 1 PM EST this afternoon for
     NYZ026>031-034-035-087.

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Banacos/Lahiff
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...Lahiff


 
 
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