Area Forecast Discussion
Issued by NWS Burlington, VT-- Remove Highlighting --
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FXUS61 KBTV 100854
Area Forecast Discussion
National Weather Service Burlington VT
354 AM EST Sat Dec 10 2016
-- Changed Discussion --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.
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.NEAR TERM /THROUGH SUNDAY/...
-- Changed Discussion --As of 353 AM EST Saturday...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.
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.SHORT TERM /SUNDAY NIGHT/...
As of 218 PM EST Friday...By Saturday night into Sunday
generally quiet conditions are expected with surface high
pressure being the dominant driver of sensible weather. A
moderately moist, light westerly flow pattern argues for
persistence in this period with partly cloudy skies and perhaps
a few flurries or snow showers, especially across the higher
terrain and to the lee of Lake Ontario across the southern
SLV/western Dacks. Temperatures remain seasonably cold with lows
more or less in the 5 to 15 above range and subsequent highs on
Sunday in the 20s.
By Sunday night our next system is progged to arrive over time as
occluding cyclone across the upper Great Lakes drives strong
moisture and warm occlusion northeast into our region. Thermal
profiles solidly cold enough for all snow, which should arrive in
steady fashion from southwest to northeast over time as robust
isentropic lift in mid-levels interacts with the prime dendritic
snow growth layer. South to southeasterly 925-850 mb flow also
increases sharply during this time (30 to 50 knots) so valley
shadowing effects will be possible at least to some extent with
possible upslope enhancement along eastern facing slopes of the
Adirondacks and Greens. As we draw closer to the event finer scale
detail offered by the higher-resolution models should provide some
additional value. However, a general accumulation of 2-4 inches by
the Monday morning commute seems plausible at this point as
temperatures hold steady, or slowly climb through the 20s.
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 218 PM EST Friday...Best forcing for precipitation then
swings through and north/east of the area Monday morning through
early afternoon with best moisture advection/isentropic lift
associated with the occlusion. Precipitation will taper off to
very light snow/drizzle and/or freezing drizzle by afternoon as
a pronounced dry slot works in aloft. Some light icing will be
possible across portions of the area during the later part of
the day, mainly across the eastern portions of the Dacks and
eastern VT where sheltered sub-freezing air will be tough to
scour out. Snow totals for the event fairly typical for a strong
warm advective event - generally 3-7 inches with local
variation. Highs on Monday mainly in the upper 20s to lower 30s
in the Dacks and eastern Vermont, with lower to mid 30s in the
Champlain and St Lawrence Valleys.
The remainder of the forecast from Tuesday onward generally features
broad west to northwesterly flow with periodic chances of snow
showers as a large, modified arctic airmass persists across nearly
the entire northern tier of the lower 48. There remains some
disparity among solutions in regard to additional energy ejecting
from the plains states east/northeast along the polar front by mid
to late week and additional chances for steadier snows in our area.
The eventual solution seems to hinge on the degree this energy can
phase with a rather potent polar gyre dropping through central and
eastern Canada, and the extent to which moisture can be drawn back
north atop the polar boundary. Given the current uncertainty will
maintain persistence here capping pops in the chance category as
temperatures start seasonably cold and trend quite chilly by later
next week as modified arctic air continues to bleed south and east
from central Canada.
.AVIATION /09Z Saturday THROUGH Wednesday/...
Through 06Z Sunday...Looking at VFR to MVFR ceilings through
the forecast period. Scattered snow showers will exist through
about 12z on Saturday...but visibilities will generally be in
the VFR category. However...any snow showers will have the
potential to briefly reduce visibilities into the MVFR category.
West to northwest winds will continue to taper off early this
morning and will generally be under 10 knots for the remainder
of the period.
Outlook 06Z Sunday through Wednesday...
06z Sunday through 06Z Monday...VFR under high pressure.
06z Monday through 00z Tuesday...Widespread MVFR cigs and IFR
vsby in light snow.
00Z Tuesday through 00z Thursday...Mix of MVFR/VFR cigs with
scattered snow showers locally reducing vsby to IFR at times,
mainly at KSLK/KMPV.