Area Forecast Discussion
Issued by NWS Burlington, VT

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842
FXUS61 KBTV 181953
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
253 PM EST Wed Jan 18 2017

.SYNOPSIS...
Plenty of clouds will persist over the area tonight through
Friday. Some light precipitation is also possible tonight into
the first part of Thursday, mainly some light rain or light
snow...but there may also be some light freezing drizzle across
part of northern New York and northern Vermont. The clouds will
also keep above normal temperatures over the region through
Friday as well.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 157 PM EST Wednesday...Plenty of fine details for the
tonight through Thursday time period. For tonight...plenty of
low level moisture will exist over the region along with areas
of fog as satellite imagery shows plenty of clouds upstream
headed our way. The warmer temperatures over the fresh snowpack
should also enhance the potential for some fog and have included
for the entire area. Weak shortwave trough moves across eastern
Canada tonight and could see some light snow over the area later
tonight...mainly over the northern and central sections of
Vermont. Any accumulations would be less than an inch. Of note
however is the loss of ice in the clouds...especially over
northern New York tonight. This would set the stage for some
light freezing drizzle and have included in the forecast.

On Thursday...looking at plenty of cloud cover all day and with
upper ridge building in...low level inversion strengthens to
keep clouds and some fog in over the area. As will be the case
tonight...warmer air over fresh snowpack will also help enhance
the potential for low clouds and fog over the area. Will keep
the idea of areas of fog going for Thursday with highs in the
30s to around 40. In addition...areas over northern Vermont may
have a little light snow early...but ice goes away in the clouds
and some light freezing drizzle may occur in this area as well.
Drier air finally moves in during the afternoon hours on
Thursday.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 255 PM EST Wednesday...Large scale synoptic pattern shows mid/upper
level ridge directly overhead with building 1020mb surface high
pres. This results in a steepening subsidence inversion with
very light winds through the vertical profile and plenty of low
level moisture trapped below thermal inversion. Forecast
challenge will be determining if depth of moisture is enough to
produce areas of patchy drizzle/freezing drizzle...especially
Thursday Night...followed by any potential clearing on Friday
Afternoon.

Based on sounding profiles and available moisture thinking any
drizzle/freezing drizzle would occur above 1500 feet mainly Thursday
Night and again on Friday Night. Overall areal coverage will be
limited along with impacts...as temperatures will be holding in the
upper 20s to mid 30s for lows during this time period. Daytime
temperatures on Friday will be tricky with sharp
inversion...supporting higher temps in the mid/upper slopes and
cooler values in the deeper valleys like the CT River
Valley...Champlain and Saint Lawrence Valleys. Highs mainly in the
mid 30s deeper valleys to lower 40s, very difficult to place this
detail into the grids. Based on moisture depth of 2000 to 3000
feet...would not be surprised if summits breakout on Friday
Afternoon. Have continued with previous forecasters idea of trying
to show summits in the clear on Friday Afternoon.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 255 PM EST Wednesday...Pattern becomes more active by early next
week with large scale system expected to impact our forecast area.
Still plenty of uncertainty on impacts...timing...and thermal
profiles.

On Saturday...weak 5h vort and thin ribbon of dissipating mid/upper
level moisture tries to break down mid/upper level ridge across the
NE CONUS. Expecting very little fan fair associated with this
energy/moisture...as ridge holds in place. Increasing moisture
profiles may produce some very light rain or snow on Saturday with
temps mainly in the mid 30s to lower 40s.

Potent energy moving into CA on Fri/Sat will quickly eject into the
southern Plains by Sunday with a developing and closing off deep
full latitude trof taking shape across the eastern CONUS. This
system will have plenty of moisture from the pacific sub-tropical
jet and moisture advection from the Gulf of Mexico as pws climb
between 0.75 and 1.50 inches. A deep south flow aloft and strong
925mb to 850mb flow from the southeast will help to advect this
moisture into our region on Monday into Tuesday as surface low pres
is located over the mid Atlantic States. Have noted the nose of a 50
to 60 knot southeast 850mb jet angling into our region...resulting
in lots of downslope shadowing in the precip fields across the
western slopes/northeast Kingdom associated with this system. The
potential for gusty southeast downslope winds will need to be
watched...along with how much warm air can be advected into our
region. Given placement of 1030mb high pres over eastern
Canada...some low level cold air will linger to support a
snow/sleet/freezing rain threat initially...but this area of high
pres is not very cold...so threat is minimal at this time. Next
threat with warmer temps and rain...will be to watch area waterway
for potential rises and ice jams...all elements to monitor as we
move closer to this system. My initial thoughts are lots of items to
watch...with some potential impacts...stay tuned.

Thermal profiles continue to support much above normal temps through
the period...especially overnight lows. Over the weekend progged
925mb to 850mb thermal profiles hover around 0c...with limited
mixing supporting highs mainly in the mid 30s to l/m 40s. Lows with
clouds will hold mainly in the upper 20s to mid 30s...but if more
clearing develops than anticipated much cooler values can be
expected...especially in snow pack mountain valleys on Sunday Night.
early next week...highs continue to be in the 30s to near 40f with
lows mainly in the mid 30s.

&&

.AVIATION /20Z Wednesday THROUGH Monday/...
Through 18Z Thursday...A wide range of conditions exists across
the area this afternoon with MVFR to LIFR ceilings and IFR to
VFR visibilities. Unfortunately these conditions will continue
to be rather variable through about 00z and then there will be
an overall trend toward lower ceilings and visibilities during
the overnight and morning hours on Thursday. During this time
period were should see fairly widespread IFR and LIFR
ceilings and IFR to MVFR visibilities. Other than some brief
snow showers there may be some light freezing drizzle
tonight...especially at KMSS and KSLK. Winds will trend toward
light and variable at all locations through 00z and remain there
for the remainder of the period.

18z Thursday - 18z Friday - dry weather is expected but the
potential for low clouds and fog creating MVFR and IFR
conditions will exist during this period.

18z Friday through Monday - VFR conditions are expected through
the period.

&&

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

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Evenson
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...Evenson



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