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272
FXUS61 KBTV 242341
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
741 PM EDT Mon Jul 24 2017

.SYNOPSIS...
An upper level low pressure system will keep showers and clouds
around through Tuesday morning. Drier weather moves in late
Tuesday with high pressure and remains in place for a day or
two. A cold front will bring a renewed threat of showers and
storms on Thursday. Fair weather then returns for Friday into
the weekend with temperatures near seasonal late summer norms.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 706 PM EDT Monday...Steady rainfall has shifted east of
VT early this evening. However, closed mid-level low - quite
evident on WV imagery east of Lake Ontario - will shift slowly
ewd overnight bringing additional UVV and bands of shower
activity. Abundant low-level moisture will also result in patchy
drizzle and/or fog, yielding a rather murky night. Winds will
generally be light. All those clouds won`t allow temperatures to
fall much overnight (maybe 5 degrees), with early AM lows in
the 50s for the entire area.

Tuesday, troughiness slowly gets pushed out to the southeast as
upper level ridging tries to build to our west. The good news
-- we should end the day with a good deal of sun and drier
conditions. However, the bad news is that I really mean the end
of the day. Up until mid/late afternoon, murky conditions with
lots of clouds and a few light showers will be around. The very
late day sun will allow temperatures to top out in the upper
60s, especially in northern areas where clearing happens first.

Tuesday night, high pressure builds over the region. Calm,
clear and drier airmass will allow for good radiational cooling,
especially outside of the larger valleys. We should see
temperatures drop into the 40s for many colder spots in eastern
VT and the `Dacks. The NAM MET guidance has Saranac Lake going
down to 36F (brrr) degrees. Don`t think it will be quite that
cold, but 39-41F is quite reasonable for that notoriously cold
location. With the wet ground, patchy dense fog is also expected
in the river valleys and sheltered valleys.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 320 PM EDT Monday..1025mb high pres directly overhead at
12z Weds morning will provide region with dry conditions and
near normal temps. Have continued with previous forecasters idea
of patchy valley fog thru 13z...before mixing increases and fog
dissipates. Otherwise...progged 850mb temps between 10-11c by
21z weds support highs lower 70s mtn towns to near 80 warmer
valley locations. With plenty of sun have trended toward the
warmer side of guidance. Weds night...mid/upper level clouds
increase as winds turn southerly ahead of our next surface
boundary. Best 1000 to 500mb rh fields and forcing stays west of
our cwa...so anticipating a mainly dry night. Temps fall
quickly early...but level off or increase slightly after
midnight with clouds and gradient flow increasing. Mainly mid
50s to l/m 60s depending upon location. Have mention schc/chc
pops nw sections by 12z Thursday. Clouds/winds should confine
fog/br to the immediate ct river valley on weds night.

Thursday...Mid/upper level trof digs across the northern Great
Lakes into the NE Conus with associated surface cold front.
Still some uncertainty on timing of system with gfs 3 to 6 hours
faster than the latest 12z NAM solutions. Timing of boundary
will play an important role on amount of instability and
magnitude of convection. Slower arrival would support greater
instability with CAPE values between 1200-1800 j/kg...combined
with 0 to 6 km shear of 35 to 45 knots...indicating a pre-storm
environment favorable for stronger storms with some
organization. Meanwhile...faster GFS shows less destabilization
with CAPE values of 400 to 800 j/kg...mainly over northern
NY...with plenty of clouds limiting sfc heating over VT. Both
solutions show favorable deep layer shear associated with 700 to
500mb wind max of 35 to 45 knots...in fast mid level
flow...just lacking instability with potential 5h energy. Some
of the stronger convective elements would be capable of
producing locally heavy rainfall given pws between 1.75 and 2.0
and the progged forcing associated with potent 5h energy.
Meanwhile...12z ECMWF is completely different with much slower
and deeper trof with 996mb low pres developing over central NY.
This scenario would support a general widespread rainfall with
embedded convective elements. Will continue with idea of chc to
likely pops for showers with isolated to scattered thunder
potential. Too much uncertainty for enhanced wording...but time
frame should be watched for potential stronger convective
elements. Temps on Thurs are tricky with potential for morning
showers followed by some sun...before more aftn showers/storms
arrive with progged 850mb temps climbing to near 14c. Will
mention highs l/m 70s mtns towns to lower 80s warmest valley
locations.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 320 PM EDT Monday...Mid/upper level trof continues to
influence our cwa on Thurs night into Friday and depending upon
timing...showers with embedded storms could linger into midday
Friday. Will continue to mention chc/likely pops during this
time period...as plenty of uncertainty with timing/magnitude of
trof and associated surface low pres/boundary continues to be
advertised in model solutions. Cooler and drier air eventually
returns by the weekend...as surface high pres builds into our
cwa. Progged 850mb temps between 9-11c Friday support highs
mainly 70s...but if ecmwf surface pres was to verify easterly
winds and much cooler temps would be possible...especially
eastern/central vt. Have played mid of the road with superblend
guidance and will fine tune as event become closer.

For the weekend...eventually 1020 mb high pres builds from the
Ohio Valley/Great Lakes...with building mid/upper level heights.
This will provide a mainly dry weekend with seasonable temps.
Highs mainly in the upper 60s to mid/upper 70s with lows mid 40s
to mid 50s and much lower humidity values. Expect some areas of
patchy fog in the deeper/protected valleys of northern NY and
parts of central/eastern VT.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Complex forecast with VFR to MVFR
conditions starting the period. Expect plentiful moisture in the
low levels and low level jet of 15-20kts to subside around 06Z
to allow for fog development. Expect MVFR conditions to
deteriorate to IFR and LIFR at KMPV and KSLK mainly between 06Z-
11Z. Rest of the terminals are expected to see MVFR conditions
with periods/TEMPO of IFR through Tuesday morning.

The mid-level trough will continue to affect the region,
putting the North Country in NE flow by Tuesday morning, expect
low level clouds to be slow and stubborn to scour out. Expect
MVFR cigs through most of Tuesday. Models indicate cig lifting
and clearing out in the mid to late afternoon.

Outlook...

Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Likely SHRA...Chance TSRA.
Thursday Night: VFR. Chance SHRA.
Friday: VFR/MVFR. Chance SHRA.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Nash
NEAR TERM...Banacos/Nash
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...KGM