Area Forecast Discussion
Issued by NWS Burlington, VT

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459
FXUS61 KBTV 261920
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
320 PM EDT Wed Apr 26 2017

.SYNOPSIS...
A building ridge of high pressure will result in much above normal
temperatures on Thursday with mostly sunny skies...except some
lingering clouds across central and eastern Vermont. Temperatures
will warm into the 70s with some lower 80s likely in the warmer
valleys. A weak front will produce scattered showers on Thursday
night into Friday with rainfall generally under a quarter of an
inch. Mild on Saturday with a chance of showers and cooler and drier
on Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 319 PM EDT Wednesday...Water vapor continues to show our cwa
between building heights and dry air to the west and cyclonic
circulation and deeper moisture to our east. As mid/upper level
ridge continues to develop overnight across our western/central
cwa...expecting some clearing skies...which combined with light
winds and plenty of low level moisture will aid in the
development of fog. Best opportunity for fog will be slv and
deeper/protected valleys of the dacks. Meanwhile...south to
southeast low level flow continues across central/eastern
vt...with additional low level moisture advecting from south to
north across this region. Expecting low clouds with areas of br
to redevelop across our eastern mtns tonight. Temps with some
clearing earlier western sections and high sfc dwpts in the 50s
will be challenging...but mainly 40s dacks to l/m 50s.

On Thursday...forecast focus will be low clouds especially
eastern/central sections associated with southeast 925mb to 850mb
flow of 15 to 25 knots. Soundings at mpv show some breaks developing
after 17z Thursday...with 2m temps only in the mid 60s.
Meanwhile...downslope drying off the greens with progged 925mb temps
between 17c and 19c support highs well into the upper 70s to lower
80s eastern cpv. Lake breeze will keep near Lake Champlain and
western cpv...much cooler with highs mainly in the mid 60s to lower
70s depending upon location away from the lake. Warmest readings on
Thursday will be across the dacks with lower 80s likely from
Edwards/Fine to Potsdam to Malone...with slightly cooler immediate
slv.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 310 PM EDT Wednesday...Models have come much more into
agreement with timing of a cold front Thursday night. Have used
a blend of hi-res models for better defining the hourly
progression of the front and associated precipitation. Models do
have a minimal amount of instability ahead of the front,
however dynamics are in short supply and with the overnight
timing, we don`t have daytime heating. Thus expect a broken line
of showers to trek eastward fairly quickly. Thinking late
evening in the St Lawrence Valley to about daybreak in the
Champlain Valley then by mid-morning exiting Vermont. Coverage
and intensity of precipitation will be diminishing as the front
moves east, so overall QPF will be less than 1/4". Given the
instability signals, can`t rule out a rumble of thunder, so have
maintained "slight chance" levels of thunder. All the clouds
will keep it very mild. Lots of 50s overnight, perhaps staying
above 60F in the Champlain Valley.

Friday isn`t looking all that bad. Westerly flow develops, with
drier air moving in. 925mb temperatures are still relatively
mild, ranging from about 18C far west to 23C or so far
southeast. This will support above normal highs from the
mid/upper 60s west to upper 70s across the lower CT River Valley
in southeast Vermont.

Friday night, pretty quiet, though clouds will start increasing
ahead of the next cold front, though lows will still be a good
10F degrees above normal.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 310 PM EDT Wednesday...Fairly changeable weather through
the period, however the longer term models are in pretty darn
good agreement. That raises the overall confidence of what is
expected. Taking it day by day...

Saturday: Cold front will be moving across the region during the
day. Not a lot of moisture or instability or dynamics with it,
but enough for a few spotty rain showers. We should still see
above normal temperatures despite the clouds and showers. Looks
like warmest temperatures will be south and east. Clears out for
Saturday night as a weak ridge of high pressure tries to build
in as the front stalls just to our south. Lows will be near
normal, and probably patchy frost around given clear skies and
relatively light winds.

Sunday: Seasonable temperatures, and dry for at least the first
part of the day. Clouds will increase during the afternoon with
initial push of warm air advection aloft associated with a
pretty big low well to the west. Can`t rule out a few spotty
light showers across western sections of northern NY during the
afternoon.

Monday/Tuesday: Looks like southerly flow will strengthen and
push a warm front through and north of the region Monday,
putting us into a mild warm sector. It`s possible we`ll get into
a solid dry slot for Monday afternoon, and if that happens we
could have enough sun to push temperatures well into the 70s.
Not confident enough about that right now, so stuck to model
blend for highs (still mid-upper 60s). Decent southerly jet with
40-45kt at 850mb that develops. Should be breezy in the
Champlain Valley at least. Tried to increase wind gusts a little
from raw model output (which tends to way underdo wind gusts).
Perhaps 25-35mph gusts. A front comes through Monday night into
early Tuesday. Models indicate some weak instability, so went
ahead and tossed in mention of slight chance of thunderstorms.
Should be a widespread rain event, perhaps 1/2" to 1" of rain,
which should not cause any significant hydro problems on rivers.
Residual clouds/showers around on Tuesday in a breezy westerly
flow, though not terribly cold as this storm system originated
in the southern Plains and isn`t really tapping into any very
cold air.

Wednesday: Still weak troffiness around along with plenty of low
level moisture, so chance level PoPs and at least partly cloudy
skies look good. Flow aloft turns more northwest and does start
to bring in cooler temperatures from Canada, so at this point it
looks like highs will be a few degrees below normal and
primarily in the 50s.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Through 18Z Thursday...Very challenging aviation forecast with
low confidence in overall flight categories and potential
impacts on TAFS overnight. Current obs show a wide range of
conditions from ifr at mpv in low clouds to vfr at btv/pbg/slk.
Thinking mainly mvfr/vfr this afternoon with another hour or two
of ifr at mpv. Winds generally light and variable...except
northeast at mss btwn 5 and 10 knots. Tonight...lots of low
level moisture is lingering with surface dwpts in the low to mid
50s...57 currently at slk...thinking with some clearing over
the SLV/northern NY areas...temps will drop below cross over
values with areas of fog/br possible after 04z. Have mention ifr
prevailing with lifr tempo btwn 07-11z at mss/slk.
Meanwhile...thinking southeast flow of low level moisture will
help advect ifr cigs back into MPV by midnight or so. Rest of
taf sites will remain between vfr/mvfr overnight. Winds shift to
the south/southeast on Friday with mvfr trending to vfr at all
sites by 15z.

Outlook...

Thursday Night: VFR. Chance SHRA.
Friday: VFR. Chance SHRA.
Friday Night: VFR. Slight Chance SHRA.
Saturday: VFR. Chance SHRA.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. Slight Chance SHRA.
Sunday Night: VFR. Chance SHRA.
Monday: VFR. Chance SHRA.

&&

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

&&

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



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