Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 200246
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
946 PM EST Thu Jan 19 2017

.SYNOPSIS...
A building ridge of high pressure both aloft and at the surface will
occur across our region...while plenty of low level moisture will
produce lots of clouds and patchy fog overnight. Given the depth of
moisture...expecting the higher summits to be above the low cloud
deck on Friday...with other areas of clearing also possible.
Temperatures will continue to be very mild with highs mainly in the
30s to near 40 and lows in the mid 20s to mid 30s. The next system
will impact our region late Monday into Tuesday with a wintry mix
likely.

&&

.NEAR TERM /UNTIL 11 AM FRIDAY MORNING/...
As of 946 PM EST Thursday...Overall forecast in good shape as
low level moisture persists in the form of low level clouds and
small temp-dewpoint spread. Light winds under the building high
pressure persists overnight. Given boundary layer moisture and
light winds...combined with additional snow melt...some areas of
patchy fog/br are possible overnight...especially Saint
Lawrence Valley and protected valleys. Cloud cover will inhibit
temperatures from falling much. Have mins generally in the mid
20s to mid 30s.

Friday...little change in overall pattern expected...except
soundings show shallower moisture. This will support more
clearing especially southern sections and summits. Expect clouds
to linger the longest over the Saint Lawrence and Champlain
Valleys on Friday...as light winds will limit mixing of boundary
layer moisture. Temps will be tricky with progged 925mb to
850mb values around 0C...but mixing will be limited with high
pres directly overhead. Thinking mainly near freezing summits to
lower 40s warmer valleys which experience some sun on Friday
afternoon...if more sun develops than expected highs will be 3
to 5 degrees warmer across the board.

&&

.SHORT TERM /11 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
As of 330 PM EST Thursday...Relatively quiet weather continues
into the Friday night/Saturday time frame. An upper level ridge
will be building into the North Country which should block some
of the energy that will be heading into the Great Lakes. The
strong inversion that will be trapping low level moisture will
become eroded on on Friday evening and so low level clouds begin
to move out of the area but a persistent mid deck will keep the
area mostly cloudy through the day. There will be some light
warm air advection that pushes into the region and so it
wont take much to generate some light stratiform rain/snow
especially in the higher terrain. Temperatures will remain above
normal in the  continue very mild with lows Friday night from
the lower 30s and Saturday highs in the upper 30s to lower 40s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 330 PM EST Thursday...The end of the weekend should remain
quiet before the weak upper level ridge breaks down. Then we
move into a more uncertain time period from Monday through
Wednesday. The one certainty is that we should be well above
normal for temperatures to start the week.

The most significant portion of the forecast is the potential
for a phased low pressure system that will impact us early in
the week. A southern stream upper level trough will dive south
of the mid-Atlantic region over the Carolinas while a surface
low develops over the DelMarVa peninsula. By Monday evening the
GFS and EC show the system phasing and increasing in intensity.
The trend in the guidance has been to bring the low close to the
coastline Monday Night into Tuesday sliding the surface low
inside of the benchmark. If that scenario plays out then we
would trend colder than previous runs and we will see a wintry
mix. I`m hesitant to go straight snow, however, because
1000-500mb thicknesses remain closer to 542-545 dam. So I chose
to use a thickness based approach for precip type for the event
leading to a mix of snow and sleet. The big take away is that
the trend was more from rain and freezing rain to more of a
wintry mix. This will be something continue to keep an eye on
moving forward.

I agree the previous forecaster in that there is some concern
based on the potential for gusty southeasterly downsloping
winds, especially along the western slopes of the Green
Mountains later Monday afternoon into Monday night as mean
925-850 mb flow may exceed 40 knots. This will eventually
predicate some adjustment of model qpf fields as valley/terrain
shadowing/enhancement effects will be magnified. Higher-res
guidance will certainly provide more detail as we draw closer in
time.

Variable conditions are expected behind that system as with
synoptic flow stays southwesterly. This results in no
significant change in our airmass through the mid week. Expect
several shortwaves to pass through the area but at this point
there isn`t a significant amount of confidence in timing. The
idea of a daily threat of scattered rain/snow shower activity
seems the way to go so I continued that from the previous
forecast. Temps will continue in the mid 30s to lower 40s during
the day time with overnight lows averaging in the upper 20s to
lower 30s.

&&

.AVIATION /03Z Friday THROUGH Tuesday/...
Through 00Z Saturday...This evening starts with MVFR conditions
outside the northern Champlain Valley and VFR conditions at
PBG/BTV. MVFR cigs will plague the North Country terminals with
IFR possible mainly after 05Z. With cross over temperatures
ranging from the upper 20s to low 30s, there a chance for
MVFR/IFR fog development in the light to calm winds high
pressure is providing overnight. Strong inversion will keep MVFR
cigs across the North Country, except RUT, through the late
Friday morning/early afternoon. BUFKIT models indicate inversion
breaks up in the afternoon, allowing for breaks in cloud cover
and cigs to lift.

Winds will continue to be light on Friday, generally 5 kts or
less.

Outlook 00Z Saturday through Tuesday...Areal coverage and cigs
heights associated with plenty of low level moisture continues
to be the aviation focus for Friday night into Saturday. A few
sprinkles or flurries possible Saturday with general mvfr
mountains to vfr valleys. Next system spreads a wintry mix
across our taf sites late Monday into Tuesday with widespread
mvfr to ifr conditions likely...along with breezy southeast
downslope winds possible at Rutland.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Taber
NEAR TERM...KGM/Taber
SHORT TERM...Deal
LONG TERM...Deal
AVIATION...KGM



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