Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 281139

Area Forecast Discussion
National Weather Service Huntsville AL
639 AM CDT Wed Jul 28 2021

For 12Z TAFS.


.NEAR TERM...(Today)
Issued at 406 AM CDT Wed Jul 28 2021

With an exception of eastward moving higher altitude clouds south of
the Tennessee River, clear skies prevailed across the area. Area
temperatures have cooled into the 70s with light winds. The clear
skies and lower level moisture has resulted in the development of
patchy fog over parts of the Tennessee Valley. The night-time
microphysics view and a few surface observations indicted fog forming
in DeKalb County with Ft Payne already having dense fog. Other fog
was forming in some of the valleys across the region. We may need an
advisory for dense fog should it become more prevalent during the
remainder of the night.

Upper level high pressure situated over the central Great Plains will
become the dominate feature controlling the weather for the remainder
of the work week. Under generally sunny skies, another very warm to
hot day is forecast. High temperatures later today should warm into
the low/mid 90s. NBM dewpoints in the mid/upper 70s this morning
continued a trend into the lower 70s this afternoon. This keeps most
areas apparent temperatures less than 105 degrees. So will hold off
on a Heat Advisory this go around. Although we are just below
advisory criteria, those outdoors need to take appropriate measures
to minimize heat related health issues. Drier air moving into the
region, courtesy of the upper high to our west will effectively
minimize shower chances today.

.SHORT TERM...(Tonight through Friday night)
Issued at 406 AM CDT Wed Jul 28 2021

Dry weather will continue into Friday evening, as upper ridging
remains to our west. Somewhat drier air filtering in tonight should
help minimize fog issues tonight across the area. Low temperatures
otherwise should cool into the lower 70s with light winds.

Thursday, slightly higher heights will move over the region, as the
upper ridge, maintaining upper 590s decameter heights over the
Central Plains brings even warmer conditions. High temperatures again
will range in the mid 90s. This time, dewpoint values should remain
in the mid 70s, boosting heat index values above 105 degrees for much
of the forecast area. Heat Advisory conditions look likely on Thu for
most of the greater Huntsville forecast area. Lows Thu night should
remain a tad warmer, only cooling into the mid 70s. Friday looks to
be even hotter with high temperatures in the mid/upper 90s. Dewpoints
in the low/mid 70s will result in more of the area above 105 degrees,
continuing a Heat Advisory conditions. A few pixels in the apparent
temperatures rise to 110 degrees on Fri, that would warrant
Excessive Heat Warnings if more of the area was to be impacted by
such warmth. A continued dry trend in the mid troposphere should keep
a damper on shower chances through Fri night.

.LONG TERM...(Saturday through Tuesday)
Issued at 406 AM CDT Wed Jul 28 2021

The overall pattern across much of the region becomes more unsettled
heading into the weekend period. The latter half of the global model
suites continue to suggest more of a NW flow regime setting up over
much of the SE region starting Sat, as a weak frontal boundary moves
into much of the area from the north. This will translate into a
favorable pattern for MCS activity traversing NW to SE into the first
half of the new week. In fact, latest model runs are still suggesting
Sun as the more active day for any potential MCS, with enhanced deep
layer shear hinting at the potential for some strong/marginally svr
tstms capable of damaging wind gusts. Timing though is uncertain at
this point, in addition to the number/strength of any possible MCS.
The active wx continues into Mon before diminishing Tue, as the weak
frontal boundary moves south of the area.

Much of the unseasonably hot/humid wx conditions will linger into
Sat, as afternoon highs climb into the lower/mid 90s and max heat
indices trend near the 100-105F range. The increase in clouds/rain
will then allow some cooler temps from Sun into Tue, with highs more
in the mid/upper 80s for most spots. Overnight lows early Sun will
start out in the lower 70s/near 70F, before trending more in the
mid/upper 60s Mon/Tue mornings.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 639 AM CDT Wed Jul 28 2021

At daybreak, patchy fog was affecting parts of the Tennessee Valley,
especially across NE AL and adjacent TN/GA. MVFR fog was also present
at KMSL. The fog should dissipate over the next couple hours as
resultant daytime heating and mixing dominates. VFR weather otherwise
is forecast, as high pressure at the surface and aloft control the
weather. Calm winds should become NE around 5kt in late morning and
afternoon. Winds will become light/variable this evening under clear


AL...Dense Fog Advisory until 8 AM CDT this morning for ALZ005>010-016.

TN...Dense Fog Advisory until 8 AM CDT this morning for TNZ076-096-097.




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