364
FXUS64 KHUN 141927
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
227 PM CDT Wed Aug 14 2024

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

.NEAR TERM...
(Tonight)
Issued at 226 CDT Wed Aug 14 2024

Aside from shower activity affecting NW AL this afternoon, much of
the forecast for tonight revolves around humid conditions coming
back to the area after a brief reprieve from it over the last few
days. What convection is ongoing now will dissipate shortly after
sunset this evening, with morning lows falling into the lower 70s.
Some patchy fog is possible tomorrow morning, especially in
locations that received some light rainfall today.

&&

.SHORT TERM...
(Thursday through Saturday)
Issued at 226 PM CDT Wed Aug 14 2024

Low chances (10-20%) for showers and storms exist again on
Thursday, with hit or miss convection around the area. The bigger
story for tomorrow will be daytime highs and potential heat index
values. Daytime highs tomorrow will top out in the middle 90s with
HI values in the low 100s. The area is highlighted on the HeatRisk
maps with a Moderate Heat Risk for Thursday, but this threat ramps
up Friday ahead of the convection that may/may not impact Northern
AL and Southern Middle TN. A Heat Advisory will likely be needed
Friday (ahead of storms) for areas along/W of Interstate 65 with
the HeatRisk map advertising Major impacts with daytime highs in
the upper 90s and Heat Index Values at/above 105F (Heat Advisory
Criteria).

The bulk of the focus on the forecast package this afternoon
revolves around this potential for strong/severe storms on Friday
afternoon/evening (despite the threat for dangerous heat earlier
in the day). There is some uncertainty of storms forming to the N
of the local area ahead of a cold front sprawled across the OH
Valley. Models indicate an outflow boundary from a remnant MCS
pushing SE toward the area during Friday afternoon/evening. While
the CAMS are notorious for dissipating MCS activity too
prematurely, the atmosphere does have decent thermodynamic
support for the threat of strong/severe storms during this time.
MUCAPE north of 3000 J/kg combined with lapse rates approaching
8C/km should allow for anything that develops along the outflow
boundary to grow rapidly, and with higher PW values in the 90th
percentile for climatology, this poses a gusty/damaging wind and
heavy rainfall threat. For this reason, we`ve messaged this to
partners and in the public graphics this afternoon. Can`t discount
a hail threat either during this time, but the thinking is that
with the high moisture content in the atmosphere, this should
enhance melting before it reaches the ground.

Storms will move through the area into Friday evening, making way
for a muggy start to the day Saturday. Morning lows will start out
in the 72-76F range, climbing into the lower 90s (a few degrees
lower than Thu/Fri thanks to cloud cover from recent convection).
A cold front will be approaching the area at the end of the short
term portion of the forecast, slated to enter the area Sat night.
More details to follow in the Long Term section of the AFD from
the midnight shift crew below...

&&

.LONG TERM...
(Saturday through Tuesday)
Issued at 156 AM CDT Wed Aug 14 2024

An upper shortwave trough is shown to traverse the Ohio and
Tennessee valleys to begin the long term. At the surface,
anticipating the passage of a cold front overnight on Saturday, with
high pressure moving into the region through early next week. There
are some discrepancies with regards to the evolution of the upper
trough (how far south the trough digs) and how quickly it moves east
through the weekend and into early next week. This would affect how
much the upper ridge to the west pushes into the Southeast. A drier
forecast is anticipated with a more eastward nudge of the ridge.
Otherwise, we`d be more under the influence of northwest flow aloft,
which would be conducive for potential MCS activity (increased
chances for showers/storms). Overall, we`ll continue to monitor model
trends, but the forecast currently calls for low to medium chances
(20-45%) of showers and storms on Saturday ahead of the cold front,
with some low chances (20-30%) of showers and storms lingering into
Sunday. We`ll need to keep an eye on Saturday, as models indicate
that there will be sufficient instability and increasing bulk shear
from the afternoon into the evening (ahead of the cold front) for
stronger storm development. At this point, drier weather is then
expected to take hold for early next week.

Highs will generally hover between the upper 80s to lower 90s each
day, with lows decreasing into the mid to upper 60s by Sunday night.
The warmest day of the long term will be Saturday, as moisture
remains elevated (dew points in the lower to mid 70s) for most
locations during the day. While Heat Advisory criteria is not likely
to be reached, it`ll still be warm. Heat indices are expected to
reach the upper 90s to around 102 degrees and NWS HeatRisk outlooks
our local area in a minor to moderate risk of heat-related illness.
Ultimately, please make sure to stay hydrated and take frequent
breaks in the shade if you have outdoor plans next Saturday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1239 PM CDT Wed Aug 14 2024

VFR conditions are expected at both KMSL and KHSV thru the TAF
period. A few showers are in the vicinity of KMSL, but its a very
low chance that one directly impacts the terminal. For this
reason, retained the PROB30 for the afternoon, but confidence is
low in this scenario. Patchy fog is possible at KMSL tomorrow
morning with the rain in the local area today, but will reassess
this with the 00Z TAF cycle.

&&

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

$$

NEAR TERM...12
SHORT TERM....12
LONG TERM....26
AVIATION...25