-- Discussion containing changed information from previous version are highlighted. --
126
FXUS61 KBTV 210537
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
137 AM EDT Fri Jun 21 2024

.SYNOPSIS...
Our hot streak will come to an end with temperatures returning
to seasonable levels to end out the week. Additional
thunderstorm chances are expected over the weekend with the best
chances occurring Sunday.

&&

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
As of 127 AM EDT Friday...Main concern for the rest of the
overnight/early morning hours will be patchy dense fog. Other
than a few lingering showers across northern VT/Northeast
Kingdom, precipitation has pretty much ended across the region.
Clouds have thinned out as well, especially over
central/southern regions. Sky cover`s been a bit more persistent
along the international border, but still seeing some breaks
further upstream. Lots of low-level moisture and little to no
flow combined with clearing has allowed patchy fog to develop,
especially in the favored valley locations across central and
southern VT. With variable cloud cover, expect fog may be a bit
variable in nature. Temperatures will generally remain in the
60s through daybreak, with a few locations possibly dipping
into the 50s. Overall the forecast has this covered, but did
expand fog coverage a bit, along with making tweaks to sky cover
and PoPs to match the latest trends. No other changes were
needed.

Previous discussion...High pressure located in the Atlantic
Ocean continues to draw warm, moist air into the forecast area
from the west/southwest this afternoon and evening, and mid
level westerly winds will be strongest across the international
border where deep layer shear is most significant. A cold
frontal boundary will be dropping through this evening from
north to south, continuing to trigger showers and thunderstorms
as well as putting an end to our three day heat wave. As the
front clashes with our warm, humid air mass in place, this will
be the focus of convection this evening. Deep layer shear as a
whole is meager, but precipitable water values are impressive,
up to around 2 inches in some spots. Modeled MLCAPE values are
2000-3000 J/kg. The main concern with these storms will be
damaging wind gusts and hail, which has already been reported
across portions of the forecast area this afternoon. In addition
to severe concerns, we are also monitoring the thunderstorms
for heavy rain over the same area, as this could result in
isolated flash flooding. The storms are expected to be slow
moving along the stalling front, which would allow a heavy storm
to drop an impressive amount of rain in one spot before moving
on under high pwat conditions. Expected rainfall amounts will
vary depending on where thunderstorms occur, but generally
thinking 0.20-1.00". Thunderstorm threat should end around 8 PM
this evening as we lose daytime heating and instability.

Low temperatures will fall into the 60s for most tonight, which
will be much cooler than it has been the last few nights, but
still a good 5-10 degrees above average. Thick moisture at the
surface will result in patchy fog in the classic valley
locations and those that received plenty of rain from the
showers and storms today. Tomorrow will be cooler than today,
returning our highs back to around seasonable levels in the
upper 70s to mid 80s. Showers and thunderstorms are expected to
return tomorrow, mainly for the southern half of the forecast
area along the frontal boundary. Severe weather is not
anticipated tomorrow. Rainfall amounts should be up to a half an
inch. Tomorrow night, this frontal boundary will be stalled out
just to our south, which again will be where most showers set
up. Lows will fall even farther tomorrow night into the mid 50s
to mid 60s, still about 5 degrees above climatological normals.
Once again, there is the potential for some fog with the
stationary boundary and low level moisture.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY NIGHT/...
As of 410 PM EDT Thursday...Active weather with showers and
thunderstorms continues on Saturday, with potential impacts more
towards excessive rainfall than strong thunderstorms with
limited instability. Temperatures have trended a bit cooler for
Saturday associated with northerly low level flow, clouds, and
showers. Highs may be only in the upper 60s to low 70s in much
of northern New York and Vermont. However, south of a surface
front a chance of thunderstorms is indicated. In this region,
which may include much of south central Vermont into portions of
the Adirondacks, daytime heating and moist boundary layer air
would support tall skinny CAPE that could result some showers
that can produce frequent lightning along with torrential rain.
However, even showers on the cool side of the front will be
capable of torrential rain with high precipitable water, deep
cloud layer depths in a very moist air mass. Given suddenly
wetter antecedent conditions, potential for flash flooding may
be elevated. The orientation of the front, largely draped west
to east, will likely act as a focus for additional showers and
thunderstorms back across the eastern Great Lakes Saturday night
while the front bulges northward in our region. As such,
despite relatively cool air on Saturday, it may not cool off
much overnight.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 410 PM EDT Thursday...Sunday is set up to be potentially
a significant severe weather day as a strong cold front
approaches from the west. Most model guidance brings upper level
support through our region during the afternoon hours
coincident with an unseasonably strong surface low lifting
through the St. Lawrence Valley, putting our region in the
system`s warm sector. Amongst the global model clusters, three
of the four scenarios for Sunday produce ingredients for severe
weather Sunday afternoon, which would include organized
thunderstorms given the deep layer shear and moderately high
CAPE expected. The one scenario that does not suggest an active
day, driven by many GEFS members, shows very little instability
due to a lot more ongoing showers. Mid level flow looks to be
southwesterly near 40 knots at 700 millibars, with increases in
upper level winds coinciding with peak heating as heights fall.

After this cold front crosses the region, humidity should trend
downward to more comfortable conditions on Monday. The next
opportunity for severe weather then may follow for Wednesday as
another strong cold front may pass through the region. Below
normal temperatures finally may arrive for Thursday following
that frontal passage.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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Through 06Z Saturday...Variable conditions expected through 12z
Friday due to patchy fog, then trending toward VFR thereafter.
Ample low level moisture, light winds, and partly to mostly
clear skies have allowed patchy dense fog to develop. Overall
expect this to be transient as cloud cover will be variable, so
have gone with TEMPO groups at all terminals. KMPV/KSLK/KRUT
will have the best chances of visibility dropping below 1SM and
ceilings AOB 900 ft, but just about all sites have a chance of
IFR or LIFR conditions through 12z. Scattered showers develop
after 15z, mainly over southern VT, and have gone with -SHRA at
KRUT through much of the afternoon. MVFR visibility possible in
any showers. Otherwise, VFR to prevail through the remainder of
period from 12z onward, though patchy fog may once again develop
as we head toward 06z Sat. Light to calm winds will become
north/northwest around 5 kt 14z-00z, then trending toward calm.

Outlook...

Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA,
Slight chance TSRA.
Saturday Night: Mainly MVFR, with local IFR possible. Chance
SHRA, Slight chance TSRA.
Sunday: Mainly MVFR, with local VFR possible. Definite SHRA,
Chance TSRA.
Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHRA,
Slight chance TSRA.
Monday: Mainly MVFR, with areas VFR possible. Likely SHRA, Slight
chance TSRA.
Monday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Tuesday: VFR. NO SIG WX.
-- End Changed Discussion --

&&

.EQUIPMENT...
Our radar KCXX is currently down. Time of return is unknown at
the moment.

&&

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

&&

$$
SYNOPSIS...Storm
NEAR TERM...Hastings/Storm
SHORT TERM...Kutikoff
LONG TERM...Kutikoff
AVIATION...Hastings/Neiles
EQUIPMENT...Team BTV