Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
357 PM EDT sun Mar 9 2014
despite mostly sunny skies this afternoon...the weather pattern
turns more active with two clipper systems producing modest snow
accumulations tonight and again on Monday night. A brief break is
anticipated early Tuesday ahead of a potential storm bringing wet
and heavy snow to the north country around midweek.
Near term /until 6 am Monday morning/...
as of 343 PM EDT Sunday...though skies are mostly sunny this
afternoon...changeable weather expected for this evening as a middle-
level shortwave trough and associated surface low will be moving
southeastward from the Great Lakes region. Visible satellite
imagery already beginning to show middle- to high- level clouds
entering into eastern Ontario associated with this feature. Expect
clouds to begin to increase tonight as combination of increasing
low- level warm air advection and modest qg forcing overspreads
northern New York and Vermont. A northwest- southeast oriented warm
front/baroclinic zone should help to focus a primary area of
steady light snow from the Adirondacks into the western half of
Vermont. The bulk of the snow looks to fall between 03-11z with
probability of precipitation ranging from high chance across eastern Vermont to
categorical across northern New York and the Adirondacks. The
progressive nature of the system and the lack of both deep
moisture and stronger Omega for optimal dendrite growth will limit
quantitative precipitation forecast/snow accumulations to a dusting to 2" for the lower elevations
with up to 3" across the higher terrain of the Adirondacks and the
western greens. Will mention in severe weather potential statement.
Non-diurnal temperature trend expected this evening as expected
cloudiness...increasing southwest winds and aforementioned warm
advection takes place overnight. 850 mb temperatures to range from near -8c
in the Saint Lawrence valley to -12c in northeast Vermont. Lows in
are likely to occur early in the evening in northern New York and
the Saint Lawrence valley...with eastern Vermont likely to be where
the coldest lows are to be found. Expecting lows in the teens in
eastern Vermont to the lower 20s in the Champlain and Saint Lawrence
Short term /6 am Monday morning through Tuesday night/...
as of 343 PM EST Sunday...lingering light snow showers are
expected to open the first part of the day Monday but do expect an
overall decreasing trend in probability of precipitation. The active pattern continues
however as a second clipper system embedded in fast northwest flow
aloft then sets its sights on the north country later Monday and
especially Monday night. This one however is a little bit stronger
and is also projected to take a more northerly track. Best
synoptic forcing moves across the north country late Monday into
Monday night with probability of precipitation increasing to likely for the northern half
of the County Warning Area with chance/high chance for southern Vermont. West-
southwest low- level trajectories suggest potential downsloping
will help keep associated quantitative precipitation forecast/snow amounts at a minimum in the
Champlain Valley. Highest quantitative precipitation forecast amounts are to the north (between
15-.2") where snow amounts of 1-3" are expected...highest across
the higher terrain of northern Vermont. Snow amounts do taper to
d-1" for the Champlain Valley and southern Vermont.
Middle-level flow then turns more zonal for Tuesday with lingering snow
showers across the Northeast Kingdom ending Tuesday morning.
Conditions do begin to trend dry during the afternoon as a weak surface
high develops. It's really more of a relative area of high pressure
between the departing second clipper and a developing storm system
in the Ohio Valley area. Both GFS...sref mean...and European model (ecmwf) solutions
show a low-level baroclinic zone from the developing Ohio Valley
system extending into central New England after midnight with axis
of higher relative humidity overriding this boundary. Therefore...i've opted to
trend probability of precipitation upward through 12z Wednesday.
Temperatures during the period mostly above normal with daytime
highs in the 30s to near 40 and lows in the upper teens to the
Long term /Wednesday through Sunday/...
as of 351 PM EDT Sunday...confidence increasing that significant
coastal system will impact the north country Wednesday into
Thursday...as models now in fairly good agreement.
Both GFS and European model (ecmwf) show upper trough digging southeast across the
central Great Lakes Wednesday into Wednesday night...with southern
stream shortwave moving out of the Central Plains into the Tennessee
Valley Wednesday and to the middle Atlantic coast Wednesday night.
All 12z model solutions indicate phasing of these streams. This
allows for development of deep but fairly progressive trough to
move across the northeast Wednesday night into Thursday. Surface
low prognosticated to be in lower Ohio Valley Wednesday morning...after
which time it will deepen in response to injection of upper
energy...making its way to position along Jersey coast Wednesday
evening...over Cape Cod midnight Wednesday night and near Nova
Scotia Thursday morning. Favorable track of surface and 850 mb low.
This combined with influx of moisture into system along with good
upper level support and frontogenetic forcing support the generous
quantitative precipitation forecast amounts indicated on latest model runs. Using a blend of the 12z
guidance...we are now looking at precipitation amounts ranging from
around 0.25 inches Saint Lawrence to as much as 1.25 inches
central/southern Vermont. Looking at a snow event...although it will
be marginal for snow/rain mix over the valleys of southern Vermont
Wednesday afternoon. If current trends continue...winter storm
watches will eventually be needed for most of the area for a
heavy wet snow Wednesday into Thursday morning. Enough confidence
to increase probability of precipitation to categorical for much of the area.
Snow showers will linger across the mountains of northern Vermont
Thursday. Otherwise...drier conditions return to the north country
Thursday afternoon/night as system departs to the east and weak
ridging develops. Temperatures fall back to below normal with lows Thursday
night ranging mostly from 5 above to 5 below zero...with brisk
northwest winds subsiding after midnight.
A clipper system will race eastward across central Ontario into
Quebec Friday into Friday night...bringing a chance of snow
showers. Still chance few snow showers Saturday as cold front
associated with this system moves across the area. Upper trough
over the region Sunday...so a few mountain snow showers still
possible. Maximum temperatures Friday will be in the upper 20s and lower
30s...warming to the upper 30s and lower 40s Saturday...and
cooling a few degrees on Sunday.
Aviation /20z Sunday through Friday/...
through 18z Monday...VFR conditions this afternoon with mainly clear
skies as ridge of high pressure moves across the region. Conditions
deteriorate rapidly this evening as high moves east and warm front
approaches. Expect increasing clouds with lowering ceilings as
snow develops from west to east across the area between 01z and
05z Monday with a period of IFR visibilities and mainly MVFR ceilings.
Conditions improve between 10z and 15z Monday as snow ends and
conditions become mostly VFR.
Outlook 18z Monday through Friday...
18z Monday through 00z Wednesday...occasional MVFR with possible IFR in snow
00z Wednesday through 12z Wednesday...mainly VFR.
12z Wednesday through 12z Thursday...IFR in snow in NE coastal storm.
12z Thursday through 00z Friday...improving to VFR.
00z Friday through 00z Saturday...mainly VFR.