Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
303 am EST Wednesday Dec 11 2013
snow showers and perhaps a heavier snow squall are expected
Wednesday ahead of a strong Arctic cold front. Highs on Thursday
will only be in the teens area wide and not much warmer Friday.
Perhaps a few snow showers each day. A storm system will probably
affect the region late Saturday into Sunday, bringing the
possibility of a widespread snow.
Near term /until 6 am this morning/...
as of 1216 am EST Wednesday...only minor adjustments to cloud
cover with latest update. Currently less clouds than advertised in
some areas...but they are expected to fill in once again towards
morning. No other changes at this time.
forecast remains on track as we head into the late evening and
overnight hours. Did opt to trend min temperatures up by 1-3 degrees
based off latest lamp guidance and owing to the fact that we'll
likely maintain at least some light to modest winds/mixing in the
planetary boundary layer overnight. Areal coverage of flurries/shsn remains unchanged
with spotty coverage across the higher terrain of central/eastern
Vermont...and slightly better coverage across the western/southwestern
dacks in closer proximity to intensifying Lake Ontario snow band.
Accumulations fairly negligible in Vermont...though perhaps an inch or
two possible in the dacks from Minerva/olmsteadville to Newcomb at
the eastern terminus of the snow band. Have a great night.
Short term /6 am this morning through Friday/...
as of 350 PM EST Tuesday...as we start Wednesday, we should
continue to see the lake effect band shift a bit more, spreading
some snow showers into southeast St Lawrence County and southern
Franklin County in northern New York. Could be a few inches of
accumulations in isolated spots. Later shifts will need to check
out the need for any lake effect snow advisories.
Otherwise the main weather maker will be an approaching cold front
that is associated with the upper trough. Elements still look to
be in place for a 6 hour window where that front could generate
localized snow squalls. Have a little bit of instability and with
the southwest winds ahead of the front, that will provide both
some frontal convergence and be able to tap moisture from the Lake
Ontario snow band. Main period is about 20z when the front and it's
associated snow showers and squalls will be up along the New York/Canada
border to about 03z when it reaches a line from northeast Vermont to
the southern Champlain Valley.
The snow squalls could dump 1/2" or so in less than 30 minutes,
and lead to some slick Road conditions. A brisk southwest wind,
gusting 25 to 30 miles per hour will also blow that snow around, causing even
more reduced visibilities.
That front will also usher in some cold air. 850mb temperatures
ahead of the front will be around -18c (already chilly to begin
with) and fall to -20 to -24c after. How cold it gets Wednesday
night will depend on whether we clear out. Still maintain some
cloudiness, but still cold enough to go sub-zero in the colder
areas and just single digits in the "warmer" valleys.
Thursday will be cold. Teens will be it for the highs. Decent
amount of low level moisture around, so don't be surprised for a
Long term /Friday night through Tuesday/...
as of 301 am EST Wednesday...little overall change from previous
forecast thinking for this version of the extended forecast from
Friday night Onward with increasing confidence that we'll see
some snowfall this weekend.
Fairly benign weather starts the period for Friday night and
Saturday with surface high pressure in place but a fast westerly
flow aloft. The result will be generally cloudy skies and a few
flurries or light snow showers possible along with continued below
normal temperatures with lows in the single digits and highs in the
Weather becomes more active going into Saturday night and Sunday as
we continue to monitor the possibility of a coastal storm bringing
accumulating snowfall to the north country. There remains decent
consistency between the European model (ecmwf) and GFS in regards to the overall
synoptic features and storm track...but some differences in the
finer details such as quantitative precipitation forecast. The main idea is that low pressure
develops over the Delaware-Maryland-Virginia peninsula Saturday night and travels
northeast right over or just inside the benchmark Sunday morning.
While this is usually a favorable storm track for significant snow
across portions of the btv County Warning Area...the upper flow is problematic as
the 500mb and 700mb lows are off to our west/northwest with a
broad middle/upper level flow out of the southwest. Not exactly the
ideal setup if you want big snow...and feel the model forecast quantitative precipitation forecast
may actually be a little overdone over our area. Nevertheless...we
will get some snow...though looking more like an advisory level
event at this time.
After this system exits the region Sunday night...it's replaced by high
pressure both at the surface and aloft. Strong cold air advection
under clearing skies and light winds will lead to a chilly Monday
night where temperatures area-wide could be in the single digits above and
below zero. Very little quantitative precipitation forecast will be seen for the remainder of the
forecast period though Tuesday night with the high overhead...and
temperatures will remain below normal.
Aviation /08z Wednesday through Sunday/...
through 06z Thursday...generally VFR conditions are expected
through the period though chances for MVFR/IFR snow squalls exist
this afternoon as an Arctic boundary sags southward through the
area. Too early to time such a mesoscale feature hitting a terminal
so will just include some vcsh for now... winds
overnight turn southwesterly after 12z...then back to west/northwest
behind the boundary and could be gusty at times.
Outlook 06z Thursday through Sunday...
06z Thursday through 12z Thursday...lingering MVFR to IFR snow
showers possible...though conditions improving to VFR.
12z Thursday through 00z Sunday...generally VFR with isolated/scattered
snow showers possible...especially at kslk.
00z Sunday through 00z Monday...MVFR/IFR snow likely.