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  Wednesday December 13, 2017

 

NWS Area Forecast Discussion


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FXUS61 KBTV 090817
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
317 AM EST Sat Dec 9 2017

.SYNOPSIS...
Variably cloudy skies will persist across the North Country
tonight, between an area of low pressure across the central
Great Lakes and a developing low off the coast of the Carolinas.
Conditions will generally be dry tonight and Saturday morning,
with just a few mountain or lake effect flurries possible,
mainly across northern New York. The coastal low will track
southeast of New England late Saturday into Saturday night,
bringing light snow to central and eastern Vermont, especially
during the first half of Saturday night. Light accumulations of
one to three inches are possible across eastern portions of
Vermont. Thereafter, an Alberta clipper will bring additional
chances for light to moderate snowfall late Monday night into
Tuesday. Temperatures will generally trend colder next week,
especially in the wake of the clipper system during the mid to
later portion of the work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1258 AM EST Saturday...Overall forecast in good shape
with just some minor tweaks to match current conditions. Any
chance for precipitation will be out in the Saint Lawrence
Valley where some lake effect clouds/snow persist.

Previous Discussion:
Narrow ridge of high pressure in place over PA/NY will bring
relatively quiet weather conditions tonight into Saturday
morning. The 700mb shortwave trough in the central Great Lakes
has backed the low-level flow enough that lake effect snow has
largely dissipated off Lake Ontario. Will still be dealing with
lake effect clouds advecting across our region, especially into
the Adirondacks and St. Lawrence Valley, with just a few upslope
flurries possible in the nrn mtns. With the variably cloudy
conditions expected, decided to go a few degrees above the MOS
consensus tonight, with limited radiational cooling. Overnight
lows generally expected in the low-mid 20s, except some upper
teens east of the Green Mtns and in the Adirondacks if
sufficient breaks can develop later tonight. P-gradient weakens
during the overnight. The prevailing S-SW winds 5-10 mph this
afternoon will generally become light and variable after sunset.

On Saturday, wave low off the North Carolina coast will track
northeastward to near/just SE of the 40N 70W benchmark at 00Z
Sunday, and toward southern Nova Scotia by 06-09Z Sunday. Will
see an increase in mid-upr level clouds thru the day Saturday,
with high temperatures in the low-mid 30s. Based on 12z NWP
guidance suite, it continues to appear that central/Eastern VT
will get into the wrn fringe of the precipitation shield
associated with synoptic forcing late Saturday afternoon into
Saturday night. Highest PoPs generally 00-06Z Sunday, ranging
from 70% in the CT River Valley, down to 40% or so in the
Champlain Valley. Looking for a light snow accumulation of
1-3"...with around 1" for MPV and generally 2-3" in the CT River
Valley. Not anticipating any major travel issues, but some
slowdowns due to snow covered roads can be expected Saturday
evening/night east of the Green Mtns, including along I-89/I-91.

Mid-level trough shifting ewd from NY/PA may bring a few
additional snow showers to the region later Saturday night, and
have indicated a more widespread 20-30 PoP across the region
during the pre-dawn hrs Sunday. Again, prevailing overcast
should preclude much radiative cooling with lows mostly in the
low-mid 20s for Sunday morning.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
As of 315 AM EST Saturday...By Sunday night, the base of the
mean 500 mb trough axis swings through the Northeast pushing an
accompanying weak surface trough southward into our area. Modest
surface convergence should allow a period of scattered
flurries/snow showers to affect mainly central and northern
counties through the overnight hours as winds trend light
northwesterly over time. Minor accumulations of a dusting to 2
inches will be possible and is in agreement with this morning`s
deterministic output, though it will be on the fluffy side with
snow ratios generally ranging in the 18-23:1 range. Low
temperatures to range mainly through the teens to locally around
20 near Lake Champlain.

Quiet weather is then expected for Monday as surface high pressure
quickly skirts across the area with light winds and partly sunny
skies. Model-averaged 925 mb temperatures at 18Z range from -6C to
-13C south to north. Using a climo-adjustment of adding +7C to
 these values for the December/January period yields highs in
 the upper teens/lower 20s north and in the 23 to 28 range
 across central/southern counties.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 315 AM EST Saturday...Thereafter, the overall synoptic-
scale picture from a CONUS perspective remains largely unchanged
throughout much of next week as a seasonably deep longwave
upper trough remains in place from the Central Plains eastward.
This will keep temperatures on the chilly side with daily highs
mainly in the teens and 20s and overnight lows in the single
digits to teens. Individual bundles of energy moving through the
mean cyclonic flow aloft will create near daily chances of
light snow/snow showers across the area, especially in the
northern mountains. The strongest of these features still
appears on track to affect the area Monday night into early
Wednesday as northern stream clipper-type energy takes a
favorable track atop the region. Widespread, accumulating light
to modest snowfall is expected during this 36-hour period during
which several inches may fall. Being of continental origin the
system will have only modest moisture to work with (PWATS around
0.25 inches) so not looking at anything exceptionally heavy.
That said, snow ratios are somewhat above average so a first
guess would suggest a possible advisory-level event for
portions of the area with the northern mountains having the most
favorable chances. Time will tell.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
Through 06Z Sunday...Overall looking at VFR conditions through
much of the period. Area will be in between systems with an
upper level trough remaining to our west and deeper moisture
off the Eastern Seaboard. However...the moisture to our east
will work its way westward this afternoon and tonight and light
snow should work into eastern Vermont and KMPV will have the
potential to experience MVFR ceilings/visibilities with all
other aviation sites remaining in the VFR category.

Outlook...

Sunday: Mainly VFR, with local MVFR possible. Chance SHSN.
Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHSN.
Monday: Mainly VFR, with areas MVFR possible. Slight chance SHSN.
Monday Night: Mainly MVFR, with areas of IFR possible. Chance SN.
Tuesday: Mainly MVFR, with areas of IFR possible. SN likely.
Tuesday Night: Mainly MVFR, with areas of IFR possible. Chance SN.
Wednesday: VFR/MVFR. Chance SHSN.

&&

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

&&

$$
SYNOPSIS...Banacos
NEAR TERM...Banacos/Evenson
SHORT TERM...JMG
LONG TERM...JMG
AVIATION...Evenson



 
 
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