520
FXUS61 KBTV 191116
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
716 AM EDT Sun May 19 2024

.SYNOPSIS...
Unseasonably warm temperatures will continue through the middle of
the upcoming week as high pressure builds into the region with dry
conditions persisting. Temperatures warm well into the 70s today and
upper 70s to mid 80s by Monday. Building heat will continue for
Tuesday and Wednesday, along with a chance of afternoon showers and
thunderstorms.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 716 AM EDT Sunday...A building mid/upper level ridge
oriented from southwest to northeast from the Ohio Valley into
the Northeast will provide mainly dry conditions to the region
for the next 36 hours. Variable cloud cover exists across the
region this morning associated with a weak surface trough and
low pressure off the eastern seaboard pulling a marine stratus
cloud layer into portions of eastern Vermont on southeasterly
flow. It will take some time for these clouds to lift this
morning, and will lead to a fairly widespread cumulus deck this
afternoon with a mix of sun and clouds expected. 925mb temps
rise a couple of degrees from yesterday to +14-16C east to west
supporting highs a little warmer than yesterday in the low/mid
70s east of the Green Mountains, and mid/upper 70s with a few
spot 80s elsewhere. A mild night follows with lows in the 50s to
around 60 and some river valley fog possible, mainly across
eastern VT.

For Monday the main story will be the heat as 925mb temps warm
several degrees more to around +18C area-wide supporting high temps
in the low/mid 80s for most locations. Partly sunny and dry
conditions will generally prevail, but there are signs of the ridge
shifting slightly south allowing the mid/upper flow to turn more
westerly along the international border. Weak shortwave energy
riding along this flow and modest instability from surface heating
could support the development of an isolated shower and maybe a weak
thunderstorm along the lake breeze over the Adirondack coast and/or
higher terrain of the Adirondacks, so will maintain some 10-20% PoPs
introduced by the previous forecast.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
As of 327 AM EDT Sunday...It does look there is the potential for
thunderstorms across the region on Tuesday. Within the building H5
ridge, there is an embedded weak shortwave trough that swings across
the northern half of the CWA. With temperatures getting into the low
to mid 80s and dew points reaching the upper 50s to low 60s, there
is the potential for a few stronger storms with 500 to 1000 J/kg of
surface based CAPE and 25 kt of shear. Mid level lapse rates are not
that impressive, but any stronger storm is capable of producing
large hail and locally strong wind gusts. With PWAT values at 1.5
standard deviations above normal, locally heavy downpours are also
possible. So despite 925mb temperatures rising reaching +21C to
+24C, we are currently forecasting highs to generally top out in the
low to mid 80s range due to the chance for rain and thunderstorms. A
potential limiting factor for the thunderstorm coverage is that the
wind field is generally westerly, so the moisture profile might be a
little lacking for updrafts to develop efficiently despite good
instability and speed shear.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 327 AM EDT Sunday...At this time, it looks like Wednesday would
be warmer than Tuesday due to lower shower and thunderstorm coverage
as well as slightly higher temperatures aloft. 925mb temperatures
reach +22 to +25C, or around 2 to 2.5 standard deviations above
normal. Expect highs in the mid to upper 80s on Wednesday, with 90
degrees not out of the question. With dew points in the upper 50s to
mid 60s, some locations in the lower Champlain valley might
experience apparent temperatures or heat index values in the mid 90s
range on Wednesday afternoon. Whether or not heat advisories are
needed, people should pay attention to heat risk associated with
this early season warm weather owing to the lack of acclimatization.
Cold water safety should also be exercised due to water temperatures
still only in the mid to upper 50s.

Surface cold front crosses the region sometime on Thursday. There
remains considerable differences between the models on the frontal
passage timing, as is expected at this time frame. Showers and
thunderstorms are once again on the table, but whether they can tap
into the best daytime heating is questionable. But if the timing
checks out, it looks like we have the most favorable combination of
ingredients for more widespread organized convection on Thursday.
Ensemble-based scenarios do show CAPE values exceeding 1000 J/kg,
along with 35 kt shear and a southwesterly wind component helping to
advect a more moist 1000-500mb moisture profile. Overall, given the
uncertainty in timing of the frontal passage, have only kept a
generic mention of thunderstorms. Temperatures wise, best
probability of low to mid 80s would be across Vermont. Behind the
cold front, we do get a reprieve from the early season heat, with
seasonable highs in the upper 60s to mid 70s expected on Friday and
Saturday. It will also be quite refreshing with dew points in the
40s along with dry weather.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Through 12Z Monday...VFR conditions will largely persist
through the period with variable cloud cover across the region
this morning lifting into a SCT-BKN cumulus deck from late-
morning through the afternoon, then clearing out after sunset.
Light winds this morning will trend SSW at 5-10kts through the
day, returning the light and variable after sunset. Tonight, the
chance for IFR fog is once again present, with the best chances
being across eastern VT at KMPV and KEFK, with lesser chances
elsewhere.

Outlook...

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

&&

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

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Lahiff
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Lahiff