Heat in Alabama, July 16, 2024

Area Forecast Discussion
National Weather Service Huntsville AL
950 AM CDT Tue Jul 16 2024

...New NEAR TERM...

.NEAR TERM...
(Rest of Today)
Issued at 950 AM CDT Tue Jul 16 2024

A cluster of showers and thunderstorms continue to move east
across northeastern Alabama producing heavy rainfall and some
frequent lightning at times. 0.5 to 1.5 inches of rainfall has
fallen over the last 3 hours in western DeKalb into Marshall
county so far this morning. Luckily this whole cluster of activity
is moving east a enough of a clip that flash flooding should not
be a major concern. However, some backbuilding may occur and this
may eventually cause some isolated flash flooding concerns.

RAP13 seems to have the best handle on this activity so far. This
and other models forecast this activity to fall apart around noon.
However, RAP13 seems to be picking up on an outflow boundary that
is moving south into north central Tennessee. This may push
southeast and enhance low level convergence in southern middle
Tennessee and further south in northern Alabama during the
afternoon hours. This matches satellite trends in respect to the
arrival of this outflow boundary.

Based on current radar and expected movement of the current
precipitation, have raised chances of precipitation this morning
to between 40 and 60 percent in northeastern Alabama. Also, kept a
30 to 40 percent chance of additional shower and thunderstorm
development in the forecast in the afternoon with the arrival of
the outflow boundary. Mostly cloudy conditions were added across
much of the area after 1 pm and in northeastern Alabama this
morning. This will keep highs a tad cooler than previously thought
(89-96 degrees). Despite the cooler temperatures, believe pooling
ahead of the outflow boundary of higher dewpoints will still
allow heat index values to climb to between 105 and 107 degrees
this afternoon for locations west of Cullman to Lincoln counties.

&&

.SHORT TERM...
(Tonight through Friday)
Issued at 405 AM CDT Tue Jul 16 2024

Tonight, low temperatures drop into the low to mid 70s. Both MSL
and HSV are forecast to drop to the mid 70s which could be close
to breaking their record for high minimum temperatures for July
17th. HSV's record is 77 degrees (set in 1932) while MSL's record
is 78 degrees (set in 1980). Therefore, it is safe to say these
temperatures are above-normal.

Dry weather is forecast overnight before high rain chances
(70-80%) return Wednesday and continue through Thursday as a cold
front approaches the Tennessee Valley from the northwest. Low-
medium chances of showers/storms (30-60%) continue into Friday.
During this time, several rounds of showers are forecast to bring
a potential for moderate to heavy rainfall, frequent lightning,
and gusty winds. PWATs are forecast to be in the 1.7-1.9 range in
HREF solutions, nearing the 90th percentile per BMX sounding
climatology. Therefore, a low flooding threat is a concern as
these continue both throughout the daytime as well as overnight.
The Weather Prediction Center (WPC) has placed portions of our
area in a Marginal (threat level 1/4) Excessive Rainfall Outlook
Wednesday morning through Thursday morning, meaning there is at
least a 5% risk of rainfall exceeding flash flood guidance.

The forecast rainfall and surplus of cloud cover will allow
temperatures to cool off for the remainder of the work week,
capping high temperatures in the 80s Thursday and Friday. On
Wednesday, high temperatures in the 90s are still forecast with
heat indices in the 99-104 range, however, we will be monitoring
how early rainfall develops which may mitigate the need for any
Heat Products as temperatures would be cooler than currently
forecast. Be sure to check back in for the latest forecast
information.

&&

.LONG TERM...
(Friday night through Monday)
Issued at 405 AM CDT Tue Jul 16 2024

Medium-high shower/storm chances continue through the weekend as
the aforementioned front is forecast to stall to our southeast,
allowing higher rain chances in our southeastern counties
(Cullman, Marshall, Dekalb, Jackson) Friday before lifting back
northward due to high pressure off the east coast of Florida. High
temperatures in the 80s continue during this time and the need for
any Heat Products is not expected.

&&

.AVIATION...
(12Z TAFS)
Issued at 550 AM CDT Tue Jul 16 2024

VFR conditions continue through the TAF period at both KMSL and
KHSV, however, a PROB30 group exists this afternoon at KHSV for
potential MVFR conditions due to lowered visibilities as a result
of showers. There is a low chance (20% or less) of showers
impacting KMSL this afternoon, however, confidence is too low to
include any mention in the official TAF package. Therefore,
amendments may be needed.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory until 8 PM CDT this evening for ALZ001>007-016.

TN...Heat Advisory until 8 PM CDT this evening for TNZ096.

&&

NEAR TERM...KTW
SHORT TERM....HC
LONG TERM....HC
AVIATION...HC