515
FXUS64 KMEG 220926
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
426 AM CDT Sat Jun 22 2024

...New SYNOPSIS, DISCUSSION...

.SYNOPSIS...
Issued at 425 AM CDT Sat Jun 22 2024

A ridge of high pressure will bring mainly rain free weather and
very hot temperatures in the middle 90s to the Mid-South this
afternoon. Increasing humidity combined with temperatures rising
into the upper 90s may result in heat index values at or above 105
degrees for portions of the area Sunday through Tuesday. A cold
front will bring the best potential for showers and thunderstorms
followed by slightly cooler air for mid to late week.

&&

.DISCUSSION...
(Today through Friday)
Issued at 425 AM CDT Sat Jun 22 2024

Surface and upper-level ridging remain in place across the Lower
Mississippi and Tennessee Valleys early this morning. This is
resulting in rain free weather across the Mid-South. A warm and
humid airmass is present across the region with 4 AM CDT temperatures
in the 70s with surface dewpoints in the upper 60s to lower 70s.

Another warm and mainly dry day is expected across the Mid-South
today as 925 mb temperatures rise to around 26C, translating into
afternoon temperatures into the middle to upper 90s. Heat index
values are anticipated to rise to around 100 degrees. The upper-
level ridge will begin to retrograde west to the Southern Plains
tonight with rain free weather expected to persist across the
forecast area.

Some timing discrepancies persist with the operational short-term
models as a weak back door cold front is expected to drop into
portions of the Tennessee Valley Sunday night into Monday. The NAM
continues to be the most aggressive of the models bringing the
potential for showers and thunderstorms into the area as early as
Sunday morning. Meanwhile, the GFS, ECMWF, and CMC lean towards
potential Sunday afternoon/Sunday night isolated to scattered convection.
HREF Grand Ensemble members show surface-based instability
increasing to around 2000 J/kg with overall shear remaining around
20 kts. This weakly sheared environment will present challenges
for short-term CAMs to resolve the overall convective
coverage/potential. Strong instability and a weakly sheared
environment would favor pulse-type thunderstorms mainly during
the afternoon and evening hours. However, mid-level lapse rates
will remain poor (< 6 C/km) and this may help to mitigate the
overall severe thunderstorm potential. Gusty winds would be the
main threat if a strong thunderstorm or two were to occur.

Confidence is higher with the potential for a Heat Advisory for
portions of the Mid-South, especially for areas around and
southwest of Memphis on Sunday. Very hot temperatures in the upper
90s combined with surface dewpoints in the lower to middle should
yield heat index values at or slightly above 105 degrees. Very
hot and humid conditions are expected to continue into Tuesday
with a better potential for Heat Advisories to encompass a larger
portion of the forecast area.

Long-term operational and ensemble model solutions indicate a
gradual increase in shower and thunderstorm chances by Wednesday
as the upper-level ridge moves to the Southwest United States, and
placing the Lower Mississippi Valley on the eastern periphery of
the ridge. This will allow for a cold front to move through the
area on Wednesday, bringing a temporary break in the very hot
temperatures. Temperatures will begin to increase by next weekend
as mid-level heights increase back across the region.

CJC

&&

.AVIATION...
(06Z TAFS)
Issued at 1138 PM CDT Fri Jun 21 2024

VFR. Light and variable winds will become SSW by late morning.
Guidance is hinting at isolated to scattered -SHRA at JBR at the
end of the period. Not enough confidence to add at this time.

ACH/AC3

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$

PUBLIC FORECAST...CJC
AVIATION...AC3