Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
640 am EST Friday Nov 28 2014
light snow will end this morning as a weak area of low pressure
moves east of the area. Some clearing will then develop as high
pressure moves east from the Great Lakes. Temperatures will remain
cool through Saturday. A warm front will bring a light wintry mix
Saturday night...leading to milder weather Sunday into
Monday...along with breezy southwest winds. A few rain showers are
likely with a cold front on Monday...with cooler air returning by
Near term /until 7 PM this evening/...
as of 635 am EST Friday...light snow continues across much of
Vermont at this time...as shortwave and associated moisture move
eastward across the region. Conditions improving over northern New
York however. Clearing skies have moved into Saint Lawrence
valley and snow showers tapering off across the rest of northern
New York. Expect this improvement to occur from west to east
across the rest of the forecast area today as the shortwave
departs. Snow accumulations from this disturbance will generally
range from a dusting to around 2 inches. Snow will linger the
longest over the northern Green Mountains due northwest 850 mb
flow of 15 to 25 knots coupled with low level cold advection.
These same winds coupled with Warm Lake waters and blocked flow
will also help to keep a few light Lake Champlain snow showers
going across the Vermont side of the Champlain Valley and western
slopes this morning before drier air arrives.
With departure of trough this afternoon...upper flow becomes more
zonal and surface ridge will build east from Great Lakes/Ohio
Valley. This will allow for some clearing this afternoon with any
snow showers over the northern Green Mountains coming to an end.
Temperatures today will be well below seasonal norms with highs
only in the upper 20s and lower 30s.
Short term /7 PM this evening through Sunday/...
as of 425 am EST Friday..Ridge axis slides eastward across
forecast area tonight. This will allow for a period clear to
partly cloudy skies and light winds. With recent snows...this will
allow for a period of good radiational cooling. By morning
however...clouds will be returning to at least the western half of
the forecast area so min temperature forecast a challenging one.
Expect most locations to see Mercury dip to between 5 and
15f...and wouldn't be shocked to see a few subzero readings east
of The Greens.
Ridge axis moves east of the area Saturday allowing for return
southerly flow to develop. The warm advection coupled with increased
moisture will result in clouds and perhaps a few light snow showers
during the afternoon. Chances for precipitation increase Saturday
night due continued warm air advection and weak disturbance in
flow aloft. Problem becomes precipitation type...especially after
06z Sunday when model soundings indicate enough warming in middle
levels to allow for some sleet and freezing rain. Warm enough in
low levels by Sunday morning for just rain showers in Saint
Lawrence and Champlain Valley. Precipitation amounts Saturday
night will be quite light so not anticipating any appreciable
accumulation of snow or ice. Maximum temperatures Saturday still on the
chilly side with highs only in the upper 20s to middle 30s. Temperatures
will not fall all that much Saturday night due clouds and
increasing southerly flow. Look for lows mostly in the 20s.
Any mixed precipitation changes to a few scattered rain showers
Sunday morning as milder air continues to stream in on brisk
south to southwest winds. 850 mb temperatures climb to around +4c...which
should allow for maximum temperatures in the lower to middle 40s...despite
mainly cloudy skies.
Long term /Sunday night through Thursday/...
as of 349 am EST Friday...medium range guidance remains in good
agreement in regards to the overall synoptic pattern for the
extended forecast period with several weak systems to affect the
Low pressure tracking northeast through Quebec into
Newfoundland/Labrador will drag a surface cold front through the
region Sunday night into Monday. European model (ecmwf) and GFS have finally come
into agreement on frontal passage timing indicating front will be through
the btv County Warning Area by 18z Monday. Still looks like the available moisture
along the boundary is fairly narrow so not expecting much more
than some scattered rain showers transitioning to snow at the tail
end of the precipitation middle-day Monday. With the early frontal passage...expect
highs to occur during the morning hours with temperatures falling from
the 40s morning to 30s afternoon.
Behind the front...low level cold air advection develops as strong high pressure
builds eastward from the northern Great Plains into the Great
Lakes. The high tracks further east over the northeast Tuesday
before shifting offshore Tuesday night offering a cold but dry
stretch of weather to start the work week. Temperatures drop back below
seasonal normals falling into the teens and single numbers Monday
night and only rising in the 20s on Tuesday. Tuesday night will be
below normal as well but slightly warmer as the surface to middle-
level flow turn southerly as high pressure exits offshore and an
upper trough approaches to our west. Remnant moisture along a
stalled frontal boundary draped over the Tennessee River valley
pushes northward late Tuesday night into Wednesday and with
low/middle level ascent being enhanced by the approaching trough so
think a mix of rain and snow showers is likely through the day
Wednesday and into Wednesday night. Some minor accumulations look
Looking further out in the forecast towards the end of the
week...high pressure over the Ohio River valley builds eastward
Thursday centering over the northeast Thursday night. Look for
partly cloudy and dry conditions along with temperatures right
Aviation /12z Friday through Tuesday/...
through 06z Saturday...a weak upper disturbance moving through the
region has produced light snow at all terminals tonight with ceilings
varying from MVFR to VFR and visibility from MVFR to IFR. Current radar
shows snows lifting out of kmss/krut and will be east of kslk
within the next 2 hours. Slight downsloping northwest flow at kpbg will
keep conditions VFR there...but for kbtv and kmpv IFR visibility is
expected through the next 4-6 hours before trending towards VFR
by 12-13z. After 13z...visibility is VFR and any MVFR ceilings trend to VFR
as high pressure begins to build in.
Outlook 06z Friday through Tuesday...
06z Friday - 00z Sunday...sct-bkn VFR under high pressure.
00z Sunday - 18z Monday...generally VFR with scattered MVFR snow
showers possible Sunday...then MVFR/IFR snow likely Sunday night
into Monday morning along a cold front passage.
18z Monday - 00z Wednesday...conditions trend back to VFR as high
pressure builds overhead.