Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
954 PM EST Sat Mar 8 2014
a surface cold front will continue to move away from our region
tonight...while surface high pressure builds into the north country.
This will provide our region with clearing skies and cool
temperatures tonight into Sunday. A few flurries will be possible in
the mountains...but no snow accumulation is expected. Next weak
system arrives with more clouds and snow shower activity on Sunday
night into Monday...along with near normal temperatures.
Near term /until 6 am Sunday morning/...
as of 954 PM EST Saturday...the warmest spots this evening are in
southern Vermont as skies remain broken to overcast there...but
elsewhere skies are mostly clear for much of the north country
with temperatures generally in the upper teens to the 20s. Dry air
continues to filter in from ridge of Canadian high pressure to the
northwest. Current forecast still is in good shape...though
temperatures and dewpoints look to be a bit on the low side
especially overnight. Still enough northerly mixing helping keep
temperatures from falling too much despite the mostly clear skies.
GFS lamp guidance has also been trending upward with both
temperatures and dewpoints this evening. So I did increase hourly
temperatures/dewpoints and lows slightly upward. The changes bring lows
ranging from near or slightly below zero in the Adirondacks to the
middle/upper teens in southern Vermont where clouds and winds will
take longer to let up.
Short term /6 am Sunday morning through Monday night/...
as of 330 PM EST Saturday...an active northern stream jet with limited
available moisture will result in several light snow events with
temperatures slowly warming to near normal values by Monday. Surface high
pressure overhead on Sunday will produce mainly clear skies with cool
temperatures associated with northerly winds. Temperatures on Sunday will be 10 to
15 degrees blw normal with highs mainly in the teens to middle 20s.
Prognosticated 850 mb temperatures between -14c and -16c...with sun and some mixing
may result in a few readings in the upper 20s across the warmer
valleys/uhi areas. 1000 to 500mb relative humidity quickly spreads from west to
east across our County Warning Area after 18z Sunday ahead of our next weak clipper
system. This moisture combined with increased lift from middle level
warm air advection and some q-vector convergence from several embedded 500 mb vorts
will produce a light accumulating snowfall. Soundings show favorable
relative humidity profiles through the snow growth region and some weak upward vertical velocities between
875mb and 700mb...resulting in good flake size and 25 to 1 or so
snow ratios. Will mention likely/Cat probability of precipitation with a dusting to 2 inches
valleys and 2 to 4 inches in the mountains by middle morning on Monday.
First system quickly shift east of our County Warning Area by 15z Monday...as next
warm air advection lift and weak surface low pressure arrives by 00z Tuesday. This will
produce another round of light accumulating snowfall on Monday
night into Tuesday. Stronger south to southwest between surface and 850mb
at 30 to 40 knots will result in some shadowing across the cpv and
temperatures warming overnight. The slightly warmer thermal profiles will
result in lower snow ratios around 15 to 1...but given slightly
better relative humidity profiles and lift...another dusting to 1 inches is
likely valleys to 1 to 4 inches in the mountains snowfall/quantitative precipitation forecast will be
fine tuned as events get closer and we can use hi resolution
models to better resolve terrain impacts. Temperatures will continue to be blw
normal for Sunday night into Monday...with lows in the teens/20s
overnight and highs in the 20s to middle 30s on Monday. Temperatures are
expected to warm overnight on Monday night...associated with
southerly winds and developing precipitation. Expecting lows to range
from the l20s nek/eastern Vermont to l30s cpv.
Long term /Tuesday through Saturday/...
as of 337 PM EST Saturday...a weak disturbance will affect the
region Tuesday...followed by a potentially significant coastal
storm Wednesday into Thursday.
Clipper system tracks north of the area Tuesday morning and into
Canadian Maritimes during the afternoon. Northwest flow and some
lingering low level moisture will be enough to produce scattered
snow showers...especially over the higher terrain. In the
valleys...temperatures Tuesday will be marginal for snow/rain with highs
in the upper 30s and lower 40s. High pressure attempts to build in
for Tuesday night into early Wednesday...allowing for decreased
chance for precipitation and perhaps a period of clearing.
Problem part of the forecast continues to be Wednesday afternoon
into Thursday morning...due increasing potential for coastal system
to affect the area. Both GFS and European model (ecmwf) show upper trough digging
southeast across the central Great Lakes Wednesday...with southern
stream shortwave moving from Tennessee Valley to the middle Atlantic
coast. All 12z model solutions indicate more phasing of the two
streams than earlier model runs. GFS still further south with
surface low track and heavier quantitative precipitation forecast...with low track just inside the
40n 70w benchmark Wednesday night. European model (ecmwf) takes low up across Cape
Cod Wednesday night to Nova Scotia Thursday. Model blend of quantitative precipitation forecast
suggests amounts could range from 0.25 inches Saint Lawrence
valley to over an inch central/southern Vermont. Still some
uncertainty as to how upper streams will phase...so have limited
probability of precipitation to around 60 percent for now.
Drier conditions then 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
in the single numbers.
Another clipper system will race eastward across 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 sweeps across the area. Maximum temperatures Friday in the upper 20s
and lower 30s...then warming to the upper 30s and lower 40s
Aviation /03z Sunday through Thursday/...
through 00z Monday...VFR expected with light winds resulting from an
anticyclonic northerly flow of dry air behind a weak cold front
tonight. Satellite and surface observation show lower clouds at and behind
the front moving south out of the region. Some cirrus expected
through about 09z as seen on Sat also. Skies will be mainly clear
Sunday as a ridge of high pressure moves over the region with
north to west winds 5-10 kts. Middle level clouds around 10k feet will be
rolling in from the west northwest after 21z in New York and around 00z
Monday in Vermont.
Outlook 18z Sunday through Thursday...
00z Monday through 00z Wednesday...MVFR...tempo IFR in snow showers.
00z Wednesday through 18z Wednesday...mainly VFR under high pressure.
18z Wednesday through 12z Thursday...possible IFR/snow in NE coast storm.
12z Thursday through 00z Friday...improving to VFR.