938
FXUS64 KHUN 131605
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1105 AM CDT Sat Jul 13 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 850 AM CDT Sat Jul 13 2024

The day has begun slightly hazy but mostly sunny. We do expect a
cumulus deck to form as heating increases as the shallow inversion
is breaking down. Steep low level lapse rates and the southern
extent of a passing shortwave through the lower OH valley may be
just enough to produce isolated showers or thunderstorms this
afternoon. Will not vary from the previous forecast here.
Otherwise, expect a near persistence temperature forecast today
with highs in the middle to upper 90s.

&&

.SHORT TERM...
(Tonight through Monday night)
Issued at 417 AM CDT Sat Jul 13 2024

Any showers/thunderstorms which manage to develop during peak
heating this afternoon should quickly dissipate around or shortly
after sunset this evening, with lows expected to fall into the
u60s-l70s Sunday morning and a similar coverage of patchy
mist/fog. Little change in the synoptic pattern is anticipated on
Sunday/Sunday night, and with this in mind, we have included a
very low (~15%) chance for development of high-based convection
during the afternoon hours, as temps warm into the m-u 90s once
again. On Monday/Monday night, the position of the low-level ridge
will shift southeastward, inducing a SSW flow across the region
as a deepening surface low tracks east-northeastward along the US-
Canadian border and into southern Ontario. A notable increase in
dewpoints (into the lower 70s) is anticipated as this occurs, and
this may allow afternoon heat index readings to reach the 100-105F
range for many locations. The resultant increase in CAPE may also
support a slightly greater coverage of afternoon showers and
storms, but in the absence of synoptic scale forcing for ascent we
will keep POPs in the 20-30% range. Locally heavy rainfall could
occur in a few locations, as steering currents will collapse due
to development of a broad weakness in the height field over the TN
Valley. Convection should dissipate shortly after sunset Monday
evening, with a warmer and more humid night in store, featuring
lows in the l-m 70s.

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 417 AM CDT Sat Jul 13 2024

The most recent suite of global models suggests that conditions
on Tuesday will be very similar to Monday, with highs in the m-u
90s, heat indices in the 100-105F range and a 20-30% coverage of
afternoon showers and storms (which will likely be slow-moving and
capable of producing heavy rainfall in localized areas). By
Wednesday, however, our region will experience increasing
influence from an amplifying northern stream trough, which is
predicted to spread northeastward from Ontario into the Canadian
Maritime provinces by Thursday night/Friday morning. The cold
front related to this trough is expected to advance southeastward
during the middle portion of the week, with the prefrontal wind
shift axis expected to slowly cross the TN Valley at some point
Wednesday night or Thursday. A higher (60-80%) POP for showers
and thunderstorms is warranted as early as Wednesday afternoon
given the position of the front to our north and strengthening WNW
flow aloft. The greater coverage of convection will likely
continue on Wednesday night/early Thursday morning, before
becoming focused to the south/east of the wind shift (across our
southeastern zones) on Thursday afternoon. Due to some uncertainty
regarding the location of the front before it eventually stalls,
we will maintain a medium chance POP in the southeastern portion
of the CWFA on Thursday night and Friday. Fortunately, a modest
coverage of clouds and precipitation should keep highs in the
u80s-l90s from Wednesday-Friday, lowering the heat risk region-
wide.

&&

.AVIATION...
(18Z TAFS)
Issued at 1105 AM CDT Sat Jul 13 2024

VFR flight weather conditions will prevail for most areas during
the period. There is a 10-20% of SHRA or TSRA from 18-00Z, but this
is too low to include at KHSV or KMSL. However, variable and
gusty winds will occur with any TSRA that develops. Patchy BR with
visibility of 3-5SM (MVFR) is possible from 09-12Z, but
confidence remains too low to include at either KHSV or KMSL.

&&

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

$$

NEAR TERM...17
SHORT TERM....70
LONG TERM....70
AVIATION...17