712
FXUS61 KBTV 080529
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
129 AM EDT Wed May 8 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 THURSDAY/...
As of 120 AM EDT Wednesday...No significant changes were needed
with this update. High clouds continue to stream into the
region this morning. Temperatures have cooled down into the 40s
to around 50F, with a few upper 30s being noted, but this should
slow as cloud cover increases. Convection can be seen moving
into western NY and Lake Ontario, and this should make it into
our forecast area by dawn. The forecast has this covered, so
just made some minor tweaks to sky cover and PoPs to match the
latest trends.

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 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 /06Z WEDNESDAY THROUGH SUNDAY/...
Through 06Z Thursday...VFR conditions will largely prevail
through the first half of the period, with brief MVFR likely.
Increasing mid/high clouds early this morning before ceilings
and visibility trend to MVFR after 12Z as showers move through
the region through the late morning hours. After 18Z, showers
end and conditions should return to VFR through about 00z, with
the exception of KMSS where northeasterly flow will maintain
MVFR ceilings. There will also be scattered
showers/thunderstorms 20z-00z, with MVFR or even IFR possible at
any affected terminal. Ceilings start to lower back to MVFR
after 00z, especially in northern areas. Winds will be light
and variable through this morning before trending SSE at
5-10 kt except locally northeast at KMSS. Gusts up to 25 kt
possible at KRUT this afternoon.

Outlook...

Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA,
Chance SHRA.
Thursday Night: Mainly VFR, with local MVFR possible. Likely
SHRA.
Friday: VFR. Likely SHRA.
Friday Night: VFR. Chance SHRA.
Saturday: VFR. Chance SHRA.
Saturday Night: VFR. Chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Hastings/Haynes
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Hastings/Lahiff