297
FXUS61 KBTV 261740
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
140 PM EDT Mon Aug 26 2024

.SYNOPSIS...
Scattered showers and isolated thunderstorms are expected
today, mainly across the higher terrain of central and southern
Vermont and the Adirondacks. Warmer and drier weather return for
Tuesday, with another round of rain likely Tuesday night into
Wednesday. Seasonably cool and dry conditions follow for the end
of the work week, with rising chances for showers again Friday
night into the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 132 PM EDT Monday...Monitoring convection for heavy rain
and possible small hail. Otherwise, no big changes to today`s
forecast. Previous discussion follows.

Isolated showers and thunderstorms across portions of Vermont
early this morning have finally dissipating as weak shortwave
energy that rounded the backside of an upper trough digging
through New England has weakened. Current water vapor imagery
shows another vort upstream across central Quebec, and when this
drops into the forecast area later this morning through the
afternoon additional scattered showers and isolated
thunderstorms are likely to develop, mainly across the higher
terrain of the Adirondacks and central/southern Vermont. Mean
short-range ensemble guidance and deterministic forecast
soundings show some modest instability developing upwards of
1200 J/kg, but low/mid-level sheer is quite weak, so despite the
SPC maintaining a marginal risk for severe thunderstorms across
our region, feel the likelihood is rather low. However, given
we saw upwards of 2" of rain from a slow- moving/backbuilding
thunderstorm this morning across Grand Isle County, think a
greater threat this afternoon will be isolated heavy rain with a
marginal risk of flash flooding given FFG is just under 2"/hr
and very light steering flow.

We should see convective activity rapidly wane after sunset
tonight with the loss of instability and upper level dynamic
support moving out of the region. Light winds and clearing skies
will lead to some dense river valley fog forming in the usual
places with lows close to normal across the region in the
mid-50s to low-60s. Quiet weather follows for Tuesday with temps
warming above seasonal norms as 925mb temps rising to around
+20C will support highs well into the low/mid 80s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 338 AM EDT Monday...A sharp frontal boundary is expected
to move through the North Country Tuesday night through
Wednesday night. Model output consensus has increased system
movement over the last 12-24hrs shifting the expected period of
highest chances earlier by 6 to 12 hours for precipitation from
mainly during the day on Wednesday to the early morning hours on
Wednesday with a fast exit by early Wednesday afternoon. CAMS
are favoring enough energy to close off a surface low pressure
and pushing it through by early afternoon while global models
and ensembles keep some chances going through Tuesday afternoon.
Opted to go between these two ideas on timing to keep some
consistency with previous forecasts, but acknowledge that rain
chances could be over earlier than Wednesday evening. Model CAPE
is largely lacking especially without added instability from
surface heating, but forcing and system speed may be sufficient
a few nocturnal thunderstorms; left these out for now, but will
reassess over subsequent runs.

Cooler, drier conditions are anticipated behind the front.
Adjusted temperatures down for northern locations which will
likely start the day behind the front or on the north side of a
SFC low if CAMS are correct. Highs ranging from low/mid 70s for
northern New York and northern Vermont are expected Wednesday
with mid/upper 70s to low 80s for central/southern Vermont.
Northerly flow will continue overnight with lows dipping into
the 40s for many locations and 50s for broader valleys. southern
Vermont.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 338 AM EDT Monday...High pressure is favored Thursday
through Friday with dry conditions and seasonably cool to mild
temperatures. Flow will return southerly early Friday with model
disagreement increasing in timing of the next system`s approach
to the North Country. GFS is more delayed than other suites
favoring a full meridional presentation of the trough while
consensus is not as deep with the parent low and subsequent
trough. Sticking with consensus, chances likely increase Friday
afternoon with potential for wet conditions to persist through
Saturday night.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Through 18Z Tuesday...Conditions across the region will
primarily be VFR through the day with the exception being brief
MVFR/IFR in isolated to scattered showers and thunderstorms this
afternoon, mainly from KSLK eastward. Any convective activity
will diminish after sunset with another night of LIFR fog likely
at KSLK, KMPV, and KEFK after 06Z. Winds will be 6kts or less
through the period mainly from the NNW except locally SE at KPBG
during the day, and SE at KRUT tonight. May also see some fog
at KBTV and KPBG.

Outlook...

Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA.
Wednesday: Mainly MVFR, with areas VFR possible. Chance SHRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. Chance SHRA.
Friday Night: Mainly VFR, with local MVFR possible. Chance SHRA.
Saturday: Mainly MVFR, with areas VFR possible. Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Lahiff/Neiles
SHORT TERM...Boyd
LONG TERM...Boyd
AVIATION...Neiles