Scientific Forecaster Discussion
fxus61 kbtv 101555
Area forecast discussion
National Weather Service Burlington Vermont
1055 am EST Sat Dec 10 2016
a cold and blustery day is expected with scattered snow showers.
Highs will only reach the teens mountains and 20s in the valleys
today. Our next system arrives on Sunday night into Monday with a
widespread accumulating snowfall expected. Total snow accumulations
will range from 3 to 7 inches by Monday afternoon. A slippery Monday
morning commute is expected.
Near term /through Sunday/...
as of 1052 am EST Saturday...cold air and cloudy skies is the
theme for the day. Persistent low to moderate cloud cover will
continue over Vermont while some breaks may show over northern
New York. Temps will be very slow to rise as cold air advection
continues. Current forecast is in good shape with no changes
Previous discussion...the coldest airmass of the season will be
parked over our region today into Sunday...as northwest flow
aloft continues. Forecast challenge today will be potential
areal coverage of snow showers...as several weak features are
showing up in water vapor and we have cold air moving over
relative Warm Lake Champlain water. Have bumped pops to chance
across the Champlain Valley and western slopes today...as water
vapor shows weak ribbon of mid level moisture dropping southeast
in the northwest flow aloft...along with weak 5h vort just
north of the Great Lakes. This energy/moisture...will combined
with low level cold air advection to produce scattered mainly
light snow showers across the Champlain Valley and western
slopes. Would not be surprised a few locations get a dusting to
maybe an inch or two given the synoptic and mesoscale setup. By
later this afternoon winds shift to more of a westerly direction
and this will limit fetch across Lake Champlain...resulting in
decreasing pops chances toward sunset. Progged 850mb temps drop
between -16c and -18c today with 925mb temps between -13c and
-15c...resulting in below normal readings. Thinking highs mainly
in the teens mountains to mid 20s warmer valleys.
For tonight...winds become light and variable as 1032mb high pres
builds overhead. Big question will be if skies can clear with drying
aloft and how temps are impacted. Soundings continue to show some
moisture between 925mb and 800mb overnight...which supports clouds
and slightly warmer temps. Low mainly in the single digits mountain
valleys with fresh snow pack to mid teens Champlain Valley. If more
clearing develops than anticipated...Northeast Kingdom and slk area
could see first night of below 0f of the winter season.
Sunday...relatively quiet and dry weather expected as we wait the
arrival of our next system. Have mention some chance pops southern
Saint Lawrence County as winds veer to the southwest
winds...thinking weakening lake effect snow band may impact this
region. Any accumulation would be light...given weak flow and
developing shear. Based on warm air advection pattern and progged
850 to 500mb rh>70% off the GFS...have increased pops to chance by
00z across our southwest cwa. Thinking precip will quickly expand
into our region...associated with strong developing low level
southerly jet after 00z Monday. Temps continue below normal with
highs mainly in the teens mountains to mid 20s valleys.
Short term /Sunday night through Monday night/...
as of 408 am EST Saturday...models continue to show clipper
type low moving across north central US and into the Great Lakes
region Sunday night. A warm front with strong isentropic lift
out ahead of the surface low will spread snow SW to NE across
the north country Sunday night into Monday morning. Models show
850mb jet stronger than previous runs, likely resulting in some
shadowing effects of precip amounts in the valleys and
enhancement on eastern/southeastern slopes. Heaviest precip
looks to occur between 08z-15z Monday and have mentioned
Impacts: snowfall of 2-4 inches by 12z Monday will affect the
morning commute, along with potential for wind gusts of 15-25
kts creating blowing snow and snow drifts. Snow continues
throughout the morning before dry slot begins to taper off
precip. Expect an additional 1-3 inches of snowfall with higher
amounts possible, especially in the high terrain during the day
Overall models have trended for a more northerly and quicker
track of the associated surface low. Therefore, expect precip to
taper off before warmer air has chance to affect ptype in most
areas. Immediate Champlain Valley could see rain mixing with
snow briefly. Cold front will move across the region late in the
day with 925mb temps falling to around -4c Monday night. Some
residual mountain snow possible Monday night.
Long term /Tuesday through Friday/...
as of 408 am EST Saturday...the theme for the long term is cold
with chances for more snow. Broad west to northwesterly flow
with periodic chances of snow showers expected as a large,
modified Arctic airmass persists across nearly the entire
northern tier of the lower 48. Models continue to show potential
for some energy to move across the northeast mid to late work
week, resulting in best chance for snow - although models still
differ on details. Temperatures trend colder throughout the
period with Friday Max temps possibly remaining in the teens.
Aviation /16z Saturday through Wednesday/...
through 12z Sunday...VFR conditions will prevail through 12z
Sunday at all taf sites. Cannot rule out a 10 to 20 minute
window of MVFR in -shsn at slk/btv/mpv. Otherwise...building
surface high pres will produce northwest winds 5 to 15 knots
this morning becoming light and variable overnight.
Outlook 12z Sunday through Wednesday...
VFR conditions thru 21z Sunday. Widespread light to occasional
moderate snow develops from southwest to northeast across our
taf sites on Sunday night. Expecting IFR vis between 03z-15z
with intervals of LIFR conditions possible...especially mpv/slk.
After 15z Monday...conditions will slowly improve with mainly
MVFR cigs/vis. Localized gusty southeast winds are possible on
Monday morning associated with low level jet of 35 to 45
knots...these winds will create areas of turbulence and wind
shear...especially near the terrain. Additional scattered snow
showers are possible Tuesday into weds with brief periods of