156
FXUS64 KHUN 201705
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1205 PM CDT Sat Jul 20 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 940 AM CDT Sat Jul 20 2024

A broad cluster of showers, along with a few embedded tstms, is
currently spreading NE across parts of north central/NE AL this
Sat morning. This activity is being driven by a weak shtrwv
embedded within a broad upper trough axis over much of the region,
coupled with a weak frontal boundary located from east TN WSW into
the lower MS Valley. Increased latent heating coupled with a
continued influx of Gulf moisture out of the south will translate
into sct/perhaps num showers/tstms later today. While deep layer
shear remains minimal at best, SBCAPE values increasing near 2K
J/kg, along with PW`s around 1.80in, will allow for brief heavy
rainfall/gusty outflow winds with a few of the stronger storms.
Afternoon highs may also struggle to surpass the mid/upper 80s,
given a persistent cloud deck.

&&

.SHORT TERM...
(Tonight through Monday night)
Issued at 136 AM CDT Sat Jul 20 2024

A nocturnal decrease in showers and thunderstorms will occur this
evening and tonight. Once again, low clouds and patchy fog will
develop overnight with lows in the upper 60s to around 70.

Another similar scenario is expected Sunday with another shortwave
rounding the trough axis through the mid MS into the TN and OH
valleys. The trough axis remains ever present through Monday and
Monday night, keeping a southwesterly flow through a deep layer
into our region. Thus, will keep similar medium chances of showers
and thunderstorms during the day, which decreases after loss of
daytime heating. The models continue to be a bit too widespread
with categorical/high chances, so have brought those down a
category Sunday and Monday. Highs are forecast in the middle to
upper 80s, with lows in the upper 60s to around 70. QPF forecasts
are for 0.5-1.0 inch, but again, totals will likely be uneven with
smaller higher maxes and lower minimums in spots.

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 136 AM CDT Sat Jul 20 2024

A deep upper low currently over the eastern Hudson Bay, by next Tue
should be weaker and moving off of the Canadian coast. Rather strong
troughing this low produced (extending to the Gulf Coast) did help
put an end to the relentless heat of late, and brought much needed
rainfall to the region. This upper troughing pattern should persist
into the middle of next week, with strong upper ridging over much of
the north Atlantic basin. A southerly flow rounding this high (aloft
and at the surface) will return lots of lower level moisture from a
very warm Gulf of Mexico (sea temperatures in the mid/upper 80s) well
inland. Some of the guidance, especially the GFS has around 2" or
higher of precipitable water moisture content in this period.

Overall QPF mainly from WPC are showing .10" to .25", but with
amounts upwards to .50" in the afternoon. But with such high precip
water values, it would very easy for stronger showers or storms
produce much higher amounts. Although the area is still in a long
term drought, rainfall amounts exceeding say 1-2" an hour, or heavy
showers repeatedly impact an area could produce water ponding as well
as instances of flash flooding. Larger scale stream/river flooding
look more unlikely at this time, unless more widespread heavy
rainfall occurs.

Daytime heating of this moisture and resultant instability, will
yield daily chances of showers and thunderstorms, especially in the
afternoon and evening. Have stayed on that track this issuance. The
blends show this well, but think the PoPs are too high (going into
the categorical 75-100%) range for much of the period without a real
focusing mechanism or organized system. Thus have trimmed back into
the likely 55-74% range for maximum values in the afternoon hours.
With a mix of clouds and sun, plus good rain chances, forecasting
high temperatures is a little more challenging. More sun breaking
through would result in even more unstable environment and
potentially stronger and wetter showers. Will raise the lower end of
the high temperatures up a degree or two. Low temperatures look to be
okay.

&&

.AVIATION...
(18Z TAFS)
Issued at 1205 PM CDT Sat Jul 20 2024

Other than a few shra/tsra invof the two main terminals, VFR conds
will prevail into the afternoon hrs this Sat. Additional shra/tsra
are possible later today and a tempo group has been added to for
any MVFR cigs/vis due to heavier precip. Lingering shra/tsra will
then begin to diminish with the onset of the evening period, with
some -br/reduced vis possible early Sun morning. Any -br will then
diminish going into the daytime hrs Sun, with VFR conds prevailing
thru the remainder of the TAF period.

&&

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

$$

NEAR TERM...09
SHORT TERM....17
LONG TERM....RSB
AVIATION...09