-- Discussion containing changed information from previous version are highlighted. --
942
FXUS61 KBTV 201721
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
121 PM EDT Mon May 20 2024

.SYNOPSIS...
Unseasonably warm temperatures remain on track for much of this week
with near record highs in the mid 80s to around 90 expected on
Wednesday. Dry conditions are expected today, but chances for
afternoon showers and thunderstorms exist Tuesday through Thursday,
some of which could be strong to severe. Cooler and drier weather
returns for Friday into the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --
As of 113 PM EDT Monday...No changes made to aftn fcst as all
elements are within thresholds. Temps have warmed into the mid
70s to lower 80s with some fair wx cumulus clouds developing
over the trrn. LAPS analysis shows CAPE values have increased
into the 1200-1800 J/kg range over the Dacks as sfc heating and
dwpts near 60F have helped to contribute to the instability.
Mid/upper lvl forcing is limited, so not anticipating much to
develop, but we will continue to watch closely for an isolated
shower or two acrs the trrn. Highs warm into the upper 70s to
l/m 80s by mid aftn with southerly winds.

Previous discussion below:
The main story for today continues to be the beginning of a
stretch of unseasonably warm temperatures that will last through
Thursday. A mid/upper level ridge over the forecast area will
provide mainly dry conditions to the region today, though an
isolated shower or two can`t be ruled out over the Adirondack
coast and/or higher terrain of the Adirondacks this afternoon.
Morning clouds over eastern Vermont and clearer skies elsewhere
will give way to increasing fair weather clouds through the
afternoon with mean 925mb temps around +20C supporting highs
well above normal in the low/mid 80s. Winds will be light from
the south-southwest generally less than 10 mph. Another quiet
night follows with skies clearing through the evening, but will
increase after midnight from west to east ahead of an
approaching shortwave trough which will keep min temps mild in
the mid 50s to low 60s.

The forecast for Tuesday continues to be very tricky in regard to
the convective potential associated with the aforementioned
shortwave. The feature has roots in ongoing convection this morning
over the Midwest, and as it moves through the Great Lakes and Ohio
Valley this afternoon and tonight, it`s questionable whether it
holds together, or if models are suffering from convective feedback.
The latest NAM is certainly overdone with modeled dewpoints in the
upper 60s and progged SBCAPE of nearly 3000 J/kg, but there is
greater consensus between other CAMs and the HREF indicating up to
around 1000 J/kg with DCAPE accounting for the majority of it. This
instability seems reasonable considering max temps will once again
be in the 80s and dewpoints will rise to the lower 60s. The severe
threat is certainly conditional with uncertainty in the strength and
track of the upper level support and potential for mid/upper level
blowoff clouds from upstream convection, and SPC agrees with a new
day 2 marginal risk across the area. We`ll likely see some storms
develop but exactly when, where, and how strong remains in question.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
As of 345 AM EDT Monday...Shower and thunderstorm activity wane with
the loss of daytime heating. There is no air mass change so it will
be a very mild and muggy night. The NWS experimental heat risk
indicates rather widespread moderate heat risk for our region on
Wednesday. Heat index values are expected to stay generally in the
mid 80s to low 90s and therefore below Heat Advisory criteria on
Wednesday. However, the lack of acclimatization given the early
season heat as well as lack of nighttime cooling overnight Tuesday
does suggest a somewhat heightened risk for sensitive individuals as
well as those without access to effective cooling. Additionally,
area waters remain cold with Lake Champlain water temperatures still
around 60 degrees. The public is encouraged to exercise cold water
safety and wear a life jacket if recreating on the waters.

With upper ridging building into the region and 925mb temperatures
reaching +22 to +25C or 2 to 2.5 standard deviations above normal,
have utilized the 75th percentile of model guidance to yield
forecast highs in the 85 to 91F range. An embedded weak shortwave
trough within the building ridge could spark a few showers and
garden variety thunderstorms in the afternoon, but no severe weather
is expected on Wednesday at this time. So have kept with a chance
for showers (30 to 40%) and a slight chance for thunder (15 to 24%)
across our area.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
As of 345 AM EDT Monday...As alluded to in the short term discussion,
showers and thunderstorms chances do increase heading into the
Wednesday evening hours. Models are suggesting a pre-frontal trough
crossing the area overnight Wednesday, with another possible round
of showers and thunderstorms on Thursday. The severe setup looks
more favorable than on Tuesday, with ensemble-based scenarios
showing 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 into the region. However, the timing of
the surface cold front remains in question, which reduces confidence
on how widespread and organized the convection could get on
Thursday. 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. The
next chance for showers and thunderstorms look to arrive for the
second half of Memorial Day weekend.

&&

.AVIATION /17Z MONDAY THROUGH SATURDAY/...
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Through 18Z Tuesday...VFR conditions prevail at all taf sites
for the next 6 to 12 hours with just some mid/upper lvl clouds
and south winds 5 to 10 knots. Have noted slightly higher bl
dwpts in the SLV again today, which could help produce very
localized and shallow fog/br near MSS btwn 07-11z on Tues. Also,
some localized patchy fog/br is possible near KMPV, but
confidence is too low, so have just mentioned VCFG for now at
both sites. A few scattered showers are possible toward 12z acrs
the northern NY taf sites with additional showers/storms
developing after 18z on Tues.

Outlook...

Tuesday Night: VFR. Slight chance SHRA.
Wednesday: VFR. Slight chance SHRA, Slight chance TSRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, Slight chance TSRA.
Thursday: VFR. Chance SHRA.
Thursday Night: VFR. Slight chance SHRA.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
-- End Changed Discussion --

&&

.CLIMATE...
Record High Temperatures:

May 22:
KBTV: 93/1977
KMPV: 90/1994
KMSS: 89/1977
KSLK: 91/1911


Record High Minimum Temperatures:

May 22:
KBTV: 70/1911
KPBG: 65/1975
KSLK: 63/1921

May 23:
KPBG: 65/1964

&&

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

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Lahiff/Taber
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Taber
CLIMATE...Team BTV