Area Forecast Discussion
Issued by NWS Huntsville, AL
FXUS64 KHUN 241633 AAC
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
1133 AM CDT SUN JUL 24 2016
For 18Z TAFs.
(Issued 1047 AM CDT SUN JUL 24 2016)
A very warm and humid start to the day with temperatures already at
10 AM between 85 and 88 degrees near and west of Interstate 65 and
heat index values between 95 and 98 degrees. The biggest question for
the day will be whether enough cloud cover can form to keep high
high temperatures and heat index values below heat advisory criteria.
Currently, a weak area of low level/surface convergence can be seen
in observations extending from central/southern Georgia to near
Auburn to near the MS/AL state line. This will likely be the focus
for scattered shower and storm activity today, with less upper level
forcing available to assist convection. Another limiting factor for
convection today, especially east of Interstate 65 will be low level
subsidence produced by the surface high developing over eastern
Alabama eastward into Georgia. Despite this, a very unstable
atmosphere will likely be in place this afternoon with CAPE values
likely between 2500 and 3500 J/KG and DCAPE values around 1000 J/KG.
Although activity will be a bit more sparse than yesterday, kept 20
pop in east due to thermodynamics in place. Further west added a
gradient to more scattered convection with highest chances south of
the Tennessee River and in northwest Alabama (30% to 40% chance of
precipitation). Stronger wind gusts to between 40 and 50 mph,
frequent lightning, and heavy downpours with stronger storms look
reasonable given thermodynamic parameters expected.
Mesoscale models differ a good bit on how much cloud cover forms
this afternoon and how long it stays more widespread across the
Tennessee Valley. Regardless, believe we will see fairly widespread
mostly cloudy conditions develop around noon or 1 pm in most
locations. These conditions will likely hold on east of Interstate
65 through 3 or 4 pm. Further west near the AL/MS state line expect
more widespread cloudiness to hold on the remainder of the
afternoon. This along with some mixing late, especially east of
Interstate 65 should keep heat index values below 102 or 103 degrees.
Highs should still climb into the lower to mid 90s in most locations.
For 18Z TAFs: Scattered thunderstorms will occur this afternoon into
early evening. These may affect both KMSL and KHSV vicinities through
~01Z. Gusty winds up to 35kt, heavy downpours reducing visibility to
the IFR category for a brief period, and frequent cloud to ground
lightning can be expected with the stronger thunderstorms. These
thunderstorms should diminish or dissipate after 01Z. Outside of
thunderstorms, VFR conditions are anticipated during the period.
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