Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 270534

Area Forecast Discussion
National Weather Service Huntsville AL
1234 AM CDT Tue Jul 27 2021

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 840 PM CDT Mon Jul 26 2021

Showers and storms have come to an end, for the most part, with the
loss of daytime heating. Cannot rule out an isolated shower or two
overnight but decreased PoPs during the overnight period. The latest
CAMs support the dry conditions overnight as well. The boundary layer
remains saturated with dewpoints in the mid to upper 70s. After a
decent coverage of precipitation today and some areas of clear skies
overnight, expect fog will form late tonight and into Tuesday
morning. Therefore, increased the coverage of fog in the forecast to
mention patchy fog for most of the Tennessee Valley. Overnight lows
will be mild again in the low to mid 70s for most locations.

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 317 PM CDT Mon Jul 26 2021

Morning fog across the Tennessee Valley should dissipate with
daytime heating and mixing. Another very warm to hot day is in the
forecast, with highs rising to around 90. Forecast dewpoints in the
mid 70s will create heat indices in the 100-104 degree range.
With plenty of moisture in an increasingly unstable atmosphere,
daytime heating will bring scattered to numerous showers and
thunderstorms mainly in the afternoon. Areas mainly east of I-65 and
near/south of the Tennessee River will have the higher rain chances,
with lower chances more to our NW. Shower activity should fade
Tuesday evening with a loss of daytime heating and a more stable
atmosphere. More muggy conditions with lows in the lower 70s.

Drier air moving in aloft will make for a partly sunny skies, with
very warm to hot conditions for the midweek. Highs on Wednesday
should rise into the low/mid 90s, with heat index values in the
100-106 range. A Heat Advisory may be required Wed if more of the
area goes into the greater than 105 degree range. Although an
isolated shower or storm cannot be totally ruled out, continued with
a dry forecast.

.LONG TERM...(Thursday through Sunday)
Issued at 317 PM CDT Mon Jul 26 2021

Despite a drier air column, near sfc moisture will keep hot and
humid conditions in place over the Tennessee Valley through the end
of the work week. The upper ridge/high will center over the Ozarks on
Thursday, and abundant sunshine will allow for efficient diurnal
heating. Because of this, have bumped high temps up a degree from NBM
guidance with the realization that they may need to be bumped up
more if this trend holds. The high should begin to retrograde into
the weekend, and a sfc front will drift south over the Appalachians.
Models have been struggling with the evolution of this front, and now
it looks like it will not drift into the area until the Sunday-
Monday timeframe. Have stuck with blended guidance with temps through
the weekend, and kept chance PoPs in the forecast due to the close
proximity of the front and sufficient low level moisture in place.
After Thursday, temps look to cool by a degree or two each day, but
afternoon heat indices will still rise near or above 100 degrees.
Overnight lows will be in the low to mid 70s each night.

For those tired of the heat, some relief might be in sight toward the
beginning of next week when a pattern change occurs. Northwest flow
will settle in aloft, at least temporarily, which usually means a
little cooler but a bit more active in the way of storms. Something
to keep our eyes on as the week goes on.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1234 AM CDT Tue Jul 27 2021

No changes from previous aviation forecast reasoning, with VFR
conditions currently across the terminals. The main concern will be
fog overnight. MVFR conditions are forecast with a period of IFR
visibilities possible near sunrise. Highest confidence in IFR is at
MSL after getting widespread rainfall earlier this afternoon. Fog
should mix out around 14z. Scattered showers and storms will be
possible again tomorrow afternoon but confidence is too low at this
time to include in the TAFs.






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