Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 261327

Area Forecast Discussion
National Weather Service Burlington VT
927 AM EDT Wed Oct 26 2016

The cyclonic flow that has produced cool temperatures and mainly
mountain snow showers will slowly weaken today...with some peeks
of sunshine possible by this afternoon. Temperatures will continue
to be below normal with lighter winds. The next system arrives
late Thursday into Friday with mainly a cold rain in the valleys
and mixed rain and snow in the mountains. A wet snow accumulation
of several inches is likely overnight Thursday.


As of 920 AM EDT Wednesday...With low Froude #`s (orographically
blocked NW flow), we`ve observed some increase in KCXX reflectivity
across the VT side of the Champlain Valley during the past hour.
Complex thermal profiles with PBL temps slightly above freezing at
lowest elevations, but mid 20s across the Green Mtn summits. Also,
saturated layer extends up to around 5-6kft, where temps are right
around -9C per RAP/NAM model soundings. This suggests about a 50%
chance of cloud getting reports of snow/snow pellets in
some areas, and also some light freezing drizzle as well with just
supercooled water aloft in some areas. BTV has had intervals of
1-2SM vsby during the past hour in snow, likely aided by some
diabatic (wet-bulb) type cooling near the surface with the
slight increase in precip intensity. Updated the forecast to
indicate a mix of snow/freezing drizzle next 2-3 hrs. Drier air
does eventually move in from the NW, so will trend partly sunny
and drier in valley locations by this aftn. Did maintain 20-30
pops for snow showers this aftn for far n-central into NERN VT.

Previous Discussion follows...Latest IR satl pics show clouds
increasing across portions of northern NY and eastern side of Lake
Champlain. Have updated grids to capture these trends through
15z...before clearing slowly develops first across northern NY
then VT by sunset. Western Champlain Valley will see some clearing
by mid morning due to downslope flow off the dacks.
Also...adjusted hourly temps up several degrees to match current
conditions. Still have chance pops thru the morning hours to
capture light upslope snow showers.

Deep cyclonic moist northwest flow which produced 4 inches of
snow atop Lincoln Peak per latest web cam will slowly breakdown
today as weak high pres builds into the region. The combination of
lingering mid level moisture...upslope flow...and some lake
enhancement may produce some additional scattered snow showers
along the western slopes this morning. Have continued to mention
chance pops...but any qpf/snowfall will be light. Hourly temps
continue to run several degrees above guidance because of
clouds/winds early this morning...making for a tricky afternoon
forecast. Have noted progged 925mb to 850mb temps are 1 to 2
degrees cooler today...with 850mb temps near -10c. Thinking highs
will generally be in the 30s mountains and lower 40s Champlain
Valley...some sun in the Saint Lawrence and western Champlain
Valley should help with surface heating.

Tonight...weak ridge of high pressure builds into the
region....between departing closed cyclonic circulation and
approaching energy and moisture from central Plains. Forecast
challenge will be amount of clouds and impacts on temps. Guidance is
very chilly with values near 10f SLK and mid teens northeast
kingdom...with lower 20s Saint Lawrence Valley and mid 20s Champlain
Valley. These values could be reached if skies are clear and winds
are light...but thinking lingering clouds and some wind will keep
temps several degrees warmer...mainly mid teens SLK/Northeast to
mid/upper 20s Saint Lawrence and Champlain Valley...except near
freezing by the lake.


As of 418 AM EDT Wednesday...Overall idea from the previous
forecast and mine before that remains in place for the end of the
work week as low pressure pulling out of the Eastern Great Lakes
and Ohio Valley will bring mixed precipitation mainly in the form
of rain and snow to the North Country. Main change with this
morning`s forecast is to offer a slower arrival time of the onset
of precipitation, and adjust temps warmer for the bulk of the
event. Consensus amongst the latest NWP guidance is that deeper
layer moisture doesn`t really arrive until at least mid-day as the
parent surface low tracks northeast through northern New York.
Precipitation at the onset will mainly be in the form of rain for
most locations with boundary layer temps in the 40s, but across
the Adirondacks temps will likely wet-bulb down to support snow.
As we move into Thursday evening and night, a developing 925/850mb
southeasterly jet of 40-50kts will usher in above freezing
temperatures aloft transitioning ptype to a rain/snow mix for the
Adirondacks and portions of eastern Vermont, and eventually all
rain area-wide after midnight. Thereafter, potent shortwave energy
rounding the base of an upper trough swinging to the area develops
a weak surface low along the frontal wave and eventually the
aforementioned parent low transitions its energy to this new low
over southern New England by Friday morning. Wrap- around moisture
combined with developing northwesterly flow on Friday will keep
precipitation going, especially across the upslope regions of the
Adirondacks and northern Greens but remains mainly rain as
surface/boundary layer temps remain mild.

All in all impacts from this event are very limited at the
surface, with any snow on the front side of the system only a
dusting to perhaps 2", and any downslope winds along the western
slopes Thursday night limited to 20-30 mph as the timing of max
winds aloft coincide with the heaviest precipitation occurring.
That said, it will be a different story across the higher peaks
above 2000 feet where thermal profiles still support storm total
accumulations in excess of 6" to up to as much as a foot of heavy
wet snow through Friday.


As of 418 AM EDT Wednesday...In general, the long term period
from the weekend into early next week has begun to trend more
quiet than what we`ve seen the past few days. Trends are for
another northern stream clipper to track north of the BTV CWA
Saturday offering a return to above normal temperatures and just
some light rain showers. Behind that, high pressure builds in and
dominates for Sunday and Monday before a strong low develops out
of the northern Plains and tracks well to our northwest on
Tuesday. A weak front traverses the forecast area Tuesday
afternoon, but with limited moisture to work with, we`re not
expecting a whole lot of precipitation. Temperatures though sky-
rocket well above freezing aloft supporting highs pushing back
into the mid-40s to low 50s on Monday, and further into the
mid/upper 50s for Tuesday.


.AVIATION /14Z Wednesday THROUGH Sunday/...
Through 12z Thursday...Clouds have increased and lowered to mvfr
conditions at several taf sites this morning. The combination of
upslope flow and lingering moisture around deep cyclonic flow will
continue to produce plenty of clouds with periods of mvfr cigs
through 15z at mss/btv and 17z at slk/mpv. Surface high pres will
result in developing vfr through tonight with northwest winds at 5
to 15 knots becoming light overnight. A few isolated to scattered
snow showers are possible this morning with summits obscured in

Outlook 12z Thursday through Sunday... An active pattern will
changeable flight conditions expected during this time period.
Clouds will quickly increase on Thursday with widespread
precipitation expected by Thursday Afternoon. Thermal profiles
suggest precip could start as a 1 to 3 hour period of snow with
ifr conditions at mpv/slk...before switching to rain. Mainly mvfr
cigs develop on Thursday into Friday...with some ifr cigs possible
at slk/mpv. In addition...strong low level jet of 50 knots around
5000 feet will produce areas of turbulence and wind shear during
this time period with localized gusts to 30 knots at RUT. Winds
shift to the northwest on Friday with some lingering upslope
precip and mvfr cigs likely at mpv/slk/btv/rut. Next system with
breezy southwest winds arrives late Saturday into Sunday with
additional precip and potential impacts to aviation.




NEAR TERM...Banacos/Taber
LONG TERM...Lahiff
AVIATION...Taber is the U.S. government's official web portal to all federal, state and local government web resources and services.