419
FXUS64 KHUN 191955
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
255 PM CDT Wed Jun 19 2024

...New NEAR TERM, SHORT TERM...

.NEAR TERM...
(Tonight)
Issued at 255 PM CDT Wed Jun 19 2024

A large area of high pressure is currently centered off the
eastern seaboard and extends west into the Mid-Atlantic area.
This continues to bring the worst of the heat over the eastern
U.S. to northeastern portions of the country. Further south, quite
a bit of mid/high cloud cover is helping to keep conditions a bit
cooler. Here over the Tennessee Valley, this cloud cover has
become more widespread over the last few hours and has kept
temperatures in the lower to mid 80s.

Not sure we will see more breaks in cloud cover later this
afternoon, so will lower highs a bit to keep forecast closer to
what observations would suggest later today. Likely highs will
only reach the mid to upper 80s.

Most guidance suggest that the surface high doesn`t move much
overnight. This should keep enough of a pressure gradient over
the area to keep winds around 5 mph, except in sheltered valley
locations (could be light and variable there). Given prevalent
low level advection from the east, not expecting dewpoints to
change much. Guidance continues to show cloud cover dissipating
later tonight. Winds should help keep low temperatures up a bit
though. This should allow temperatures to only drop into the 65
to 70 degree range (lower valeus likely in spots that are
sheltered valley locals).

&&

.SHORT TERM...
(Thursday through Saturday)
Issued at 255 PM CDT Wed Jun 19 2024

During the day on Thursday, the center of the upper level ridge
associated with the surface high shifts southwest into the
Tennessee Valley. Not confident models are handling cloud cover
caught up in this ridge, but kept with low sky coverage guidance
is presenting at this time. It should get hotter again in response
to the building upper ridge Thursday afternoon, but how much is
the question. Given the uncertainty with cloud cover, the forecast
only included highs in the 90 to 95 degree range mostly. This
should keep heat index values 95 to 100 degrees.

The upper ridge drops further southwest and sets up right over the
area late Thursday night through Saturday. With that feature
right over the area and little cloud cover expected Friday and
Saturday, these may be our hottest days during that period. Highs
on one or both of those days could climb into the mid to upper
90s. However, kept temperatures and heat index on the lower side
on Friday again given uncertainty with cloud cover. By Saturday
though, heat index values could climb just over 100 degrees again.

&&

.LONG TERM...
(Sunday through Wednesday)

Issued at 355 PM CDT Wed Jun 19 2024

Guidance from the 12Z suite of global models suggests that a
strong mid-level high will continue to be centered across the TN
Valley at the beginning of the extended forecast period.

Although this evolution will result in a gradual increase in NW
flow aloft for the TN Valley. Given the a continued increase in
925 mb temperatures, thinking highs still could reach the mid to
upper 90s again in some areas. However, confidence is low this
will happen given some of the model guidance as subsidence
weakens and possibly a weak shortwave approaches the area on
Sunday. Thus, low chances of afternoon/evening showers and
thunderstorms were introduced into the forecast. If highs do reach
the mid/upper 90s, then heat index values could climb to between
the 98-102F range with dewpoints in the 65 to 70 degree range.

There is reasonably good agreement among the models that a weak cold
front (attached to the northern stream trough) will drop southward
through the region on Monday, and we have indicated our highest POPs
for the extended period on this day. Frontal convection will likely
end south of the TN River Monday evening, with the front expected to
decelerate and become increasingly oriented in a NW-SE fashion to the
west of the forecast area on Monday night/Tuesday. Although a
slightly drier airmass may spread into the northeastern portion of
the region, there is some uncertainty regarding precisely where the
front will lie, and we have kept a low (~20% POP) intact for Tuesday.
High temperatures will change little (if at all) in the wake of the
front, but may be a couple of degrees cooler due to an increase in
cloudiness both days.

&&

.AVIATION...
(18Z TAFS)
Issued at 122 PM CDT Wed Jun 19 2024

VFR conditions are expected throughout the TAF period with on and
off mainly high cloud cover over the next 24 hours. Wind gusts
from the east will drop off this evening, but remain around 5
knots much of the night. This should keep fog at bay.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&

$$

NEAR TERM...KTW
SHORT TERM....KTW
LONG TERM....70
AVIATION...KTW