314
FXUS64 KHUN 151925
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
225 PM CDT Thu Aug 15 2024

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

.NEAR TERM...
(Tonight through midday Friday)
Issued at 203 PM CDT Thu Aug 15 2024

The forecast for Northern AL and Srn Middle TN hasn`t changed much
in the past 24hrs; we still have a stalled sfc frontal boundary
draped from the ArkLaMiss SE into the Nrn GOMEX, with high pressure
in control aloft across the area. This ridge will set the stage for
the change in pattern expected for our area as it retrogrades W,
allowing our area to be in more NW flow. This will allow MCS
activity upstream to divert SE toward the local area on Friday and
again on Saturday.

Before we get to that just yet, the rest of today will be warm but
heat index values will remain below Advisory criteria this
afternoon. Any convection today will be relegated to our far Ern
zones on the edge of the ridge. Tomorrow ahead of the developing
storms, a Heat Advisory will be issued from 11am to 5pm for Heat
Index values in the 105-107F category along and west of a Lincoln
TN/Madison/Morgan/Cullman AL Counties line. The impacts from the
heat will dissipate when the storms arrive toward the end of that
timeframe. Daytime highs will top out in the 95-98F range.

&&

.SHORT TERM...
(midday Friday through Sunday)
Issued at 203 PM CDT Thu Aug 15 2024

The threat for storms tomorrow is the big question, and moreso where
convection will develop. An MCS ongoing upstream of us tonight will
dive SE tonight and eventually dissipate. This will throw an outflow
boundary toward N AL/Srn Middle TN. The uncertainty in this portion
of the forecast is precisely where this boundary ends up, and
therefore, pinpoints the area that will have convective initiation
first tomorrow. Most HIRES models show a wide range of time of
arrival of the storms; as early as 14z or as late as 21/22z. The
best consensus shows convection firing up right on top of us between
18-20Z and then scooting off to the SE thru the evening. Like
yesterday, thermodynamic elements support a gusty to damaging wind
threat (50-60mph) with these storms, combined with low level lapse
rates between 7-8C/km. When these storms form, they`ll rapidly grow
with the potential to produce wind gusts quickly. Heavy rainfall is
another threat tomorrow with PWats in the 90th percentile for
climatology. Widespread 1-1.5" rainfall amounts seem reasonable,
with isolated higher amounts in excess of 2" less likely, but
possible in areas where storms slowly move. Hail is also a
possibility, but I think with the excess moisture in the atmosphere,
enhanced melting will help keep this threat at bay.

Saturday now holds another shot at strong/severe storms and heavy
rainfall. Like Friday, an MCS upstream of the local area will dive
SE Friday night into early Saturday morning. Unlike Friday, some
light rain may overspread the area as the MCS decays early Saturday
morning. This will delay any redevelopment until later in the
afternoon/early in the evening on Saturday, making for storms more
likely after ~21z the most probable scenario then. Regarding the
thermodynamics Saturday, a similar atmosphere will be in place with
perhaps a bit more shear (30-35kts) and instability (with the later
arrival time/peak heating), translating to a 50-60mph wind threat
and more locally heavy rainfall. This activity should linger through
midnight or a little after before the same scenario is repeated
Sunday, though thankfully south of our CWFA (Birmingham and points
south).

The cold front will push through our CWFA overnight Saturday into
Sunday, with rain chances finally dwindling and more calm and dry
weather expected to start the new work week.
&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 419 AM CDT Thu Aug 15 2024

The upper trough centered just to our east will continue to dig
south through the second half of the weekend, and will lead to a
cooler, drier pattern to start the work week. Will keep low
chances (20-30%) for showers/storms Sunday with the cold front
expected to push south through the area Sunday afternoon/evening.
By then, expect the better strong/severe thunderstorm environment
to be to our south where the axis of better moisture lies. Dry
weather will return by late Sunday, and northerly flow will begin
to advect cooler temperatures into the area. The remainder of the
long term forecast looks very nice for mid to late August, with
daily highs in the 80s and lows in the low to mid 60s. High
pressure will help us maintain a dry forecast through Wednesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1236 PM CDT Thu Aug 15 2024

VFR conditions will prevail through the duration of the TAF
period. After sunrise tomorrow winds will shift from SE to SW with
a slight increase in winds speed to around 6 KTS. There is a low
chance of rain and storms from 12-18Z tomorrow however confidence
was too low to include in the TAF. In confidence increases rain
and thunder will be added to the TAF during additional issuances.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from 11 AM to 5 PM CDT Friday for ALZ001>007-016.

TN...Heat Advisory from 11 AM to 5 PM CDT Friday for TNZ096.

&&

$$

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