544
FXUS61 KBTV 170428
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1228 AM EDT Tue Jul 17 2018

.SYNOPSIS...
After another hot and humid day across the North Country today,
relief is in sight as a cold front approaching from the west
tonight will bring periods of showers and a few embedded
thunderstorms to the region late tonight through Tuesday. A few
stronger storms are possible, containing heavy rainfall and
dangerous cloud to ground lightning. Once the front exits to the
east Tuesday evening, surface high pressure and ridging aloft
will keep the area mainly dry through Friday. Unsettled weather
returns for the weekend as the upper-level ridge overhead breaks
down.

&&

.NEAR TERM /UNTIL 1 PM THIS AFTERNOON/...
As of 1223 AM EDT Tuesday...Updated forecast to increase pops
across northern NY into parts of central/northern vt overnight
based on crnt radar trends. Radar shows areal coverage of
showers and storms increasing ahead of approaching cold front
and associated 5h vort in the southwest flow aloft. This
combined with soundings showing elevated instability above 850mb
of 500 to 1000 j/kg, have continued to mention thunder. Latest
radar analysis shows storm along the clinton/franklin county
border with some lightning and a solid 40 dbz core to 26,000
feet. Have mention likely pops for northern ny and expanded
these higher pops into parts of the cpv and central/northern vt
overnight. As of midnight our temp was still 83f, so have
adjusted hourly grids to match crnt obs, but holding overnight
lows in the 70s, as rain should cool air some, while increasing
the low level dwpts. Rest of forecast in good shape.

Previous Discussion...
Well, it`s another awful day across the North Country with
temps well into the upper 80s to mid 90s with a couple of
records broken or tied at KBTV and KMSS. Only saving grace to
this heat is that the humidity is comfortably low with areas
dewpoints generally in the 50s. Seeing a decent cumulus field
across northern New York and far southern Vermont this afternoon
as well, but overall we really haven`t been able to break the
cap to get any convection going.

Moving forward looking at the forecast for tonight, have backed
off on precip chances for much of the period with a lack of any
real forcing and models trending with a somewhat slower arrival
of precipitation associated with a cold front approaching from
the west. In addition, convection to our west and developing
southwest should throw plenty of debris clouds over the forecast
area tonight as well so while there could se a few isolated
showers, feel we`ll be waiting until better forcing arrives
towards daybreak. With increased cloud cover and light winds
overnight, it will be quite muggy with lows only in the upper
60s to low 70s and high humidity.

Tuesday continues to look rather active with a cold front
swinging through the region. Bulk of the precipitation is along
and ahead of the front, moving into northern New York during the
early morning hours, and through Vermont during the earl/mid
afternoon where the best chance for thunderstorms will exist.
12Z guidance wasn`t much different from 00Z showing only modest
0-3km shear 25-35kts and limited SBCAPE generally less than
1000 J/kg, but there is some favorable jet dynamics with the
forecast area located in the right entrance region of the
mid/upper level jet so SPC`s slight risk across eastern areas
does look good. Thinking though with an abundance of cloud
cover over the region it will be hard to get any severe
organized, and it might just be a bunch of SPS`s day. Primary
threat will be damaging winds but PWAT`s up towards 2" and warm
cloud depths up to 15kft supporting the idea of a heavy rain
threat. 1 hour FFG guidance is rather high though so the flash
flood threat will be isolated. Overall basin average QPF looks
to be in the 0.50-1" range which is well needed.

Tuesday night the front shifts east of the region with skies
gradually clearing and temps dropping down into 50s. It appears
boundary layer winds will be strong enough the inhibit fog
developing despite the rainfall, though can`t fully rule it out.

&&

.SHORT TERM /1 PM THIS AFTERNOON THROUGH WEDNESDAY NIGHT/...
As of 400 PM EDT Monday...Quiet weather conditions are
anticipated for the short-term. The longwave trough responsible
for Tuesday`s rain will slowly amble eastward with high pressure
slowly building in. North to northwesterly flow will allow
cooler and much drier air to advect across our area resulting in
highs generally in the 70s with higher elevations in the low to
mid 60s. Some fair weather cumulus is possible, especially in
the early afternoon.

The main question will be whether fog develops overnight
Wednesday into Thursday morning. High pressure should be just
south of our area overnight into Thursday morning. Pressure
gradients will begin to relax and dry, subsident air in the mid-
levels will aid the development of a strong nocturnal inversion.
Clear skies and light winds, in addition to the rains that will
have fallen Tuesday, will lend itself to the radiation fog
potential, mainly in protected river valleys of eastern and
south-central Vermont and the Adirondacks in New York. Lows will
be in the upper 40s to mid 50s across the St. Lawrence and
Champlain Valleys with lows in upper 30s to mid 40s across the
Northeast Kingdom and in the Adirondacks.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 400 PM EDT Monday...Quiet weather conditions will
continue for much of the long-term with a warming trend
expected. Thickness values quickly rebound from Wednesday under
high pressure with temperatures generally in low 80s across
lower elevations with 70s elsewhere. On Friday, conditions will
be warmer still as winds begin to come from the south with
temperatures well above seasonal norms, but still relatively
dry.

A slow-moving upper trough will begin to influence the general
weather pattern as it slowly progresses eastward in the Ohio
River Valley. A weak surface low or trough will develop along
the Eastern Seaboard while the upper trough weakens with vort
maxes passing in and around our area. The interaction of the
surface feature and the upper trough makes pinpointing the best
chances of precipitation challenging. Forecast trends indicate a
slower arrival of the better moisture until Sunday with
instability slow to return, so no mention of thunder until
Monday evening for now. Temperatures will remain above average
through the rest of the period.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...We start out with VFR conditions at all
sites through 06z and then we will see ceilings and visibilities
lowering into the MVFR category between 08z and 18z and showers
move across the area. There will also be some thunderstorms as
well. This activity is associated with a cold front which will
be moving from west to east across the area. Once the front
moves east of the area we will see winds go from south and
southwest to west and northwest...especially after 20z. Ceilings
and visibilities will also improve with the passage of the
front.

Outlook...

Tuesday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Patchy BR.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Lahiff/RSD
NEAR TERM...Lahiff/Taber
SHORT TERM...Haynes
LONG TERM...Haynes
AVIATION...Evenson/Lahiff