620
FXUS61 KBTV 092321
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
721 PM EDT Sun Jun 9 2024

.SYNOPSIS...
Showers and thunderstorms will continue this afternoon and evening
before tapering off this evening. Additional showers will be
possible on Monday but we are trending back toward drier conditions
with surface high pressure expected to build into the region on
Tuesday.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
With no to minimal forcing present this evening, thunderstorms
have ended across the forecast area, leaving behind some
scattered to isolated showers as chance of precipitation
decreases overnight tonight. Some tweaks to increase winds and
decrease hourly temperatures were made with this update as well,
but otherwise the forecast remains on track. Many spots that
experienced showers and thunderstorms today experienced drastic
temperature drops and didn`t fully recover. We continue to
expect lows in the upper 40s to mid 50s tonight. Previous
discussion below:

Previous discussion...Widespread showers with isolated
thunderstorms have developed across the region this afternoon in
response to modest low level heating coupled with a weak
shortwave rotating around an upper low north of the
International Border. Our 850 mb and 500 mb heights are close to
four standard deviations below normal with respective
temperatures around 2 standard deviations below normal. Even
with just modest heating, the lower heights/cooler temperatures
aloft have allowed for multiple reports of pea sized hail across
the region. The thermodynamics will remain modest, at best,
with SBCAPE values generally less than 1000 J/kg with mixed
layer shear of only 20 knots. These should be limiting factors
in updraft strength which should preclude any longer lived cells
capable of producing larger hail. We will see these showers and
thunderstorms continue into the evening hours but will begin to
dwindle in coverage as we lose our heating and see the
atmosphere begin to stabilize. Rainfall amounts this afternoon
should generally be a quarter of an inch or less but could
exceed a half inch in thunderstorms.

High res guidance suggests we could see a few showers linger in the
mountains overnight but we should be between shortwave energy which
should really limit the areal coverage. We will be in store for a
cloudy night with a strong nocturnal inversion trapping in a lot of
the low level moisture as a result of the showers and storms this
afternoon. As of 705 PM EDT Sunday. This inversion will mix out
after sunrise on Monday. Additional showers appear possible on
Monday but less shortwave energy should limit the coverage and
intensity of showers.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 326 PM EDT Sunday...Mid/upper lvl trof wl cont to linger acrs
the region during the short term, with general drying trend toward
mid week. Still cool 500mb temps btwn -16C and -18C associated with
trof and some weak s/w energy may produce a few isolated to widely
scattered showers (15-25%) on Tues. These showers wl have a diurnal
cycle with areal coverage with highs pops when instability is the
greatest during the mid aftn hours. Soundings indicate limited
instability with sfc based CAPE values in the 200-400 J/kg range and
very weak flow with trof axis nearby, so have just kept showers for
now. Did note a little difference btwn the latest synoptic scale
models with regards to thermal profiles with 12z GFS about 2 to 3C
warmer than the NAM progged 925mb temps associated with subsidence
type profile. Have used compromise of NAM/GFS and NBM and have temps
upper 60s to mid 70s. Areal coverage of precip quickly wanes on Tues
night with some clearing possible. Temps wl be highly dependent upon
clearing, so have stayed close to guidance with values in the lower
40s SLK/NEK to upper 50s CPV.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 326 PM EDT Sunday...The long term wl feature warming thermal
profiles and generally drier conditions as mid/upper lvl trof is
replaced by westerly flow aloft. GFS is now showing some lingering
qpf acrs NEK of VT on Weds, for now have not included in the fcst,
but something to monitor as we head toward the new week. Next
challenge wl be warming temps on Weds thru Friday with some valley
locations approaching 90F possible by Friday. Progged 925mb temps
are 16-18C on Weds, 18-20C on Thurs and 20-22C by Friday, supporting
highs upper 70s to mid 80s Weds, lower to mid 80s Thurs, and mid 80s
to near 90F for Friday. As southerly flow develops and dwpts slowly
climb, so wl the overnight lows from the 40s to mid 50s into the mid
50s to mid 60s by Friday. Similar to yesterday timing of s/w energy
and associated cold frnt along with chances for shower/storms
becomes the challenge for late week. Have kept pops in the 20 to 35%
range for now with highest probs on Friday. Did note the GFS/ECMWF
are more aggressive with potent s/w energy and showing sfc
convergence with boundary, but run to run consistency in these
scenarios has been limited, resulting in minimal confidence with
regards to pop timing and convective potential. As temps warm well
into the 80s and dwpts climb back into the 60s, would anticipate
some instability wl be kicking around to support convection on
Friday aftn/evening. For next weekend sfc high pres rebuilds back
into our region with less humidity and temps cooling back closer to
normal. As with any fcst out 7 days, timing of building high pres
and clearing wl continue to be adjusted and fine tuned this week.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
Through 00Z Tuesday...Coverage of showers is diminishing, but
scattered showers will continue overnight with several weak
troughs moving around the upper low. While these will be more
miss than hit, cannot rule out VIS decreasing to MVFR at times.
CIGs will be the main limiter to aviation with a mix of IFR/MVFR
across the North Country. SLK/MSS stand the best chances of
having IFR CIGs after 06Z with most other spots dropping to MVFR
in the same time frame. After 14Z, instability will aid in
lifting CIGs, but some increase in shower activity will occur.
Thunderstorms are looking less likely overnight and Monday, but
can`t completely rule them out.

Outlook...

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

&&

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

&&

$$
SYNOPSIS...Clay
NEAR TERM...Clay/Storm
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...Boyd