580
FXUS61 KBTV 191739
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
139 PM 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 1021 AM EDT Sunday...No real changes made with the AM update.
Skies have cleared in the Champlain Valley allowing temperatures
to climb. We are starting to see some of the fair weather Cu
forming as expected. PoPs remain at or near zero for the vast
majority of the CWA.


Previous Discussion...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 SUNDAY/...
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 /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions continue through the TAF period, with the only
possible exception of MPV developing fog overnight. Currently seeing
widespread Cu deck that will clear off when diurnal heating shuts
down. Low level winds could die off in the vicinity of MPV allowing
for creation of FG near sunrise, but conditions aren`t favorable for
more than short duration IFR.

Outlook...

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: MVFR. Chance SHRA, Slight chance TSRA.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Friday: VFR. Slight chance SHRA.

&&

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

&&

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