-- Discussion containing changed information from previous version are highlighted. --
409
FXUS61 KBTV 140207
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1007 PM EDT Thu Jun 13 2024

.SYNOPSIS...
A cold front moving through the Great Lakes this afternoon will
bring a period of showers and possibly thunderstorms to our region
late tonight into Friday with localized stronger storms possible in
far southern Vermont early Friday afternoon. Cool and dry air
filters in for the weekend, but by Monday, warm and moist air will
shift back into the region. Temperatures warming into the upper 80s
to mid 90s is expected by the middle of next week. In conjunction
with high dewpoints and warm overnight conditions, heat impacts are
likely next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
As of 1003 PM EDT Thursday...A line of showers and thunderstorms
is rapidly approaching from the west. This line is expected to
move into the St. Lawrence Valley right around 11 PM, give or
take a few minutes, and will likely accelerate eastward as it
moves through the North Country. The latest TYX data shows a
50-60 knot jet art around 15,000 ft which should help push this
line eastward at a faster pace. The 00Z HRRR and RAP data
suggest we have decoupled with the loss of daytime heating which
should keep the stronger winds elevated since the convection
won`t be rooted at the surface. However, DCAPE values close to
800 J/kg exist so it`s still possible we could see a brief burst
of gusty winds along several portions of the approaching line.
All guidance has this line falling apart quickly through the
overnight hours but should be able to produce overnight rumbles
of thunder and brief heavy rain as it quickly moves eastward. We
will be watching the line closely should any warnings be
necessary although it currently looks unlikely.

Previous Discussion...The forecast remains on track for tonight
through Friday night with the main feature of interest being a cold
front currently moving through the Great Lakes region. CAMs have
been very consistent showing showers and embedded thunder associated
with the front won`t move into the St. Lawrence Valley until close
to midnight, then become fragmented and scattered as it moves
eastward through the remainder of the night into Friday morning.
With the loss of daytime heating and precip arrival time, along with
the best dynamics and cold pool shifting north of the region, the
threat for strong storms is low during the overnight hours despite a
strong low-level jet of 40-50kts moving across the region. As such,
gusty winds are likely the biggest threat which will continue up to
25 mph in the broader valleys overnight with the potential for brief
gusts greater than 35 mph along the frontal passage, mainly across
northern New York.

As the front shifts through Vermont during the daylight hours
Friday, a short window will exist in the early to mid-afternoon
hours for some stronger storms to develop across central and
southern zones where up to 1000 J/kg of CAPE and about 40-45 knots
of 0-6km shear may exist. As the previous forecaster mentioned, the
intensity of storms will be conditional on clearing, and SPC`s
depiction of a slight risk outlook south of our forecast area and a
marginal risk across Rutland and Windsor Counties of Vermont
continues to be reasonable. Any activity that does develop will wane
after sunset with the loss of surface heating and the front shifting
away from the region, and a quiet and cool night is on tap with lows
falling into the 40s and 50s.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
As of 326 PM EDT Thursday...The weekend weather will be gorgeous,
featuring highs in the 60s and 70s, and low humidity. There will
also be abundant sunshine and relatively light winds. Clear skies
and calm winds overnight will allow temperatures to drop quickly.
Lows Saturday night will mostly be in the 40s, but temperatures
should reach the 30s in the coldest hollows. Enjoy the cooler
weather while it lasts because significant heat will build in next
week.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 326 PM EDT Thursday...The first major heat event of the year
looks to occur next week, starting Tuesday and continuing for the
rest of the week. High temperatures above 90 degrees and increasing
humidity will likely cause apparent temperatures to be well in the
90s, particularly in the broad valleys. The region will be on the
northern periphery of an unusually strong ridge. Some model guidance
brings the center of it to 600 dm at 500 mb. Southwest flow will
prevent any cooling marine impacts from the Atlantic and increased
humidity will help lows stay elevated overnight. Temperatures in the
valleys will likely not fall out of the 70s Tuesday night onward,
preventing much overnight relief from the heat. While there is high
confidence of very warm temperatures, the exact magnitude of the
heat is still uncertain. It looks like there will be a couple of
shortwaves that will ride along the top of the ridge. With
sufficient instability from the airmass, it would not take much to
initiate some convection to keep afternoon temperatures a little
lower. Also, with westerly flow aloft from being on the northern
edge of the ridge, it is possible that debris from upstream
convection over the Great Lakes could stream into the area provide
some cloud cover. While this would limit high temperatures, it would
also increase overnight lows. However, despite these uncertainties,
there is high confidence in a significant heat event and the NBM
seems very reasonable in giving an 80-90 percent probability of
highs exceeding 90 in the broad valleys. However, the higher end
probabilities where it gives the Burlington area a 40-50 percent
chance of reaching 100 are likely unrealistic. Overall, this looks
to be a relatively long- duration significant heat event and it would
beneficial to take precautions early.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Through 00Z Saturday...VFR conditions are expected to continue
through about 09Z-10Z for most sites, with winds being the main
concern over the next 24 hours. Currently, wind across sites is
decreasing, but surface flow generally remains out of the south
3-9 knots. Winds will increase again tonight into tomorrow as a
cold front crosses the forecast area, bringing gusts to 10-30
knots at various sites. Winds will turn southwesterly and
eventually northwesterly by the end of the 24 hour period. By
around 18Z-22Z we may see another drop in the wind gusts. LLWS
is expected with the frontal passage, primarily 04Z-13Z.

As for ceilings and precipitation associated with the front, we
are not particularly concerned as models show the precipitation
weakening and falling apart as it crosses the forecast area.
Most likely chance of rain showers will be from 08Z-14Z, though
site MSS could experience a couple showers early, over the next
few hours. There is the potential for thunderstorms embedded in
any of these showers, but confidence is not high enough to
include any thunder in TAFs at this time. There is also the
potential for visibilities to drop in heavier showers/storms,
but again, ability to pinpoint when and wear this will occur is
not of high accuracy or confidence. Ceilings will likely drop to
MVFR at MSS and SLK, but as the front continues eastward,
ceilings are looking less likely to break VFR levels at all.

Outlook...

Friday Night: VFR. Slight chance SHRA.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.

&&

.MARINE...
As of 326 PM EDT Thursday...A brief period of wind gusts up to
25 knots is expected across the broad lake waters tonight
prompting the issuance of a lake wind advisory. Waves will
likely build to 1 to 3 feet, and caution is urged for small
craft venturing out overnight.

&&

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

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Clay/Lahiff
SHORT TERM...Myskowski
LONG TERM...Myskowski
AVIATION...Storm
MARINE...Lahiff