771
FXUS61 KBTV 072256
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
656 PM EDT Tue May 7 2024

.SYNOPSIS...
Idyllic spring weather is expected today. Early tomorrow
morning, showers and embedded thunderstorms will return to the
forecast. Following a cold frontal passage, we will observe cool
temperatures struggling to rise above 60 over the weekend with
lingering shower chances. Friday appears most likely to be the
wettest day. Temperatures will begin to moderate at the start of
next week.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 654 PM EDT Tuesday...Forecast is well on track this
evening with minimal updates needed. One slight tweak was to
increase winds on Lake Champlain for the next couple of hours
before these winds drop off into the late evening. Also adjusted
cloud cover slightly to account for some high clouds making
their way across the forecast area. Cloud coverage is still
expected to increase throughout the night. Temperatures
currently in the 60s and 70s will fall into the 40s for most by
early tomorrow morning. Previous discussion below:

Previous discussion...It doesn`t get much better than today
with respect to weather. The 60s and 70s under sunshine and
light north to northwest flow and low relative humidity is tough
to beat. High pressure will shift offshore tonight, and we`ll
see winds become southeast. This will keep temperatures from
falling quite as much as last night in addition to increasing
high clouds, mainly in the 40s to lower 50s, perhaps some spot
upper 30s in far eastern Vermont.

Pre-dawn into early Wednesday a warm front will move northeast
ahead of a compact surface low and an impressive-for-spring
upper jet of 120 knots at 250hPa. Strong frontal forcing and
elevated instability of 300-500 J/kg will produce widespread
moderate rain with embedded thunderstorms and locally heavy
downpours focused across the Adirondacks and the southern half
of Vermont. Mid-morning into early afternoon, there will be a
pocket of dry air that filters into the region, and this will
reduce shower activity for a time.

The point where models diverge is just how much dry air will be
in place by Wednesday afternoon. On one hand, dry air could
allow stronger surface heating and better near surface lapse
rates in conjunction with 7-7.5 C lapse rates due to cool mid-
level conditions associated with an upper trough pivoting east.
If it`s too dry though, only isolated convection will be able to
form and entrainment could prevent activity from getting too
strong. On the other hand, if it`s too wet, surface temperatures
will not become strong enough to break a subtle warm layer
around 600 hPa, but there would be more widespread
precipitation. Somewhere in between those two hands could be an
active convective day due to shear on the order of 0-6 km shear
at 40-50 knots. It`s a highly conditional potential for stronger
storms reliant on factors coming together just right, and thus,
the Storm Prediction Centers marginal risk outlook (Level 1 of
5) appears just right. If we can manage to destabilize, some
strong storms capable of gusty winds and hail will be possible,
mainly along the southern tier of our forecast area along the
Adirondacks and south-central Vermont.

A cold front will descend southwards overnight, with perhaps a
few scattered showers while backside of the upper trough swings
southeast before getting stretched out. Cool air behind the
front will result in 40s north, and a few 50s south.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 330 PM EDT Tuesday...Low pressure system tracks eastward
on Thursday and precipitation will spread northward into our
region, with chances continuing to increase during the overnight
period into Friday morning. This low will be very slow moving.
It will be a cool daytime period, with a mild overnight with
clouds and precipitation in place across our area. Maximum
temperatures will range from the upper 50s to lower 60s with
minimum temperatures ranging through the 40s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 345 PM EDT Tuesday...More of the same for the extended
portion of the forecast with upper level shortwave energy and
trough continuing to bring periodic chances for showers from
Friday through Monday night. Temperatures will start out cooler
than seasonal normals, then trend towards normal by early next
week. As previous forecaster mentioned, models continue to show
a consistent synoptic signal for a slow moving low pressure
system to approach from the southwest and produce isentropic
lift in our region. Variations in the storm track provide
uncertainty in both timing and intensity of precipitation.
Several members of the GEFS are particularly wet such that the
Otter Creek basin- average rainfall during this period could be
around an inch; on top of the rainfall from Wednesday, the
potential for minor flooding of this river remains low but non-
zero. Otherwise, a wider flood threat is not foreseen with lack
of tropical moisture or convective, intense precipitation with
this system. This consistent wet pattern will lead to some
modest rises on area rivers and streams.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...Mainly VFR conditions will prevail
through about 09z to 12z Wednesday. Mostly clear skies will give
way to high clouds beyond 00z. Northwest winds have ramped up
somewhat high than expected, ranging from 7 to 12 knots with a
few gusts to 18 knots at times. This should continue through
about 22z-00z before becoming light and variable. A warm front
will lift northeast about 09z-16z. Widespread rain with embedded
thunderstorms are possible. In thunderstorms, reductions in
visibility are likely, but given how far out this is, there are
no explicit mentions yet. Behind the warm front, ceilings should
lower to 1500-3000 ft agl and precipitation will scatter out
until additional showers develop towards 20-21z Wednesday.

Outlook...

Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA, Chance RA, Chance DZ, Patchy BR.
Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Thursday Night: Mainly VFR, with areas MVFR possible. Likely RA.
Friday: Mainly MVFR, with areas VFR possible. Likely RA.
Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Saturday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Storm
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Haynes