737
FXUS64 KJAN 151727
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1227 PM CDT Thu Aug 15 2024

...New AVIATION...

.MESOSCALE UPDATE...
Issued at 902 AM CDT Thu Aug 15 2024

A few showers and storms have popped up this morning along a
boundary in the vicinity of I-55 and should continue to increase
this afternoon and evening, especially south of I-20. Morning
sounding analysis and microburst checklist yield a chance for
microbursts this afternoon, so isolated severe wind gusts could be
possible. Additionally, hot and humid conditions will persist and
should yield heat indices in the 105 to 112 range. This has
prompted the issuance of a heat advisory for eastern areas and an
excessive heat warning for central MS, SE AR and NE LA, as well as
the HWY 98 corridor. That said, there has been a downtrend of
dewpoints this morning, and dewpoints will play an important role
in both hazards today, so will have to continue to monitor this
for future updates./SAS/

&&

.DISCUSSION...
Issued at 500 AM CDT Thu Aug 15 2024

Through the End of This Week:

Heat and Humidity. Hard to say it is good for much, but in this case
the increased humidity is at least enough to bring rain chances to
our forecast area. That`s a positive for sure. The disturbance which
moved south across the area yesterday is still in the region and may
provide some enhanced rain chances farther south toward the Gulf
Coast this afternoon and evening. A pool of 2.0+ PW air will be
located south of Interstate 20 today, but even the drier air farther
north should still have enough moisture (PW > 1.6-1.7) today to
support some isolated showers or storms. The influence of the ridge
aloft will be felt as temperatures climb into the mid and upper 90s
before most shower or storm activity gets going. Forecast soundings
show possibility of greater than 2000-3000 J/kg of SBCAPE and around
1000 J/kg of DCAPE, so some strong storms with gusty winds cannot be
ruled out. Given the observed heat index values yesterday and the
forecast for today/tomorrow/Saturday, felt it was reasonable to
upgrade the western and southern portions of the forecast area to an
Excessive Heat Warning and advertise "Extreme" dangerous heat
impacts on the local HWO graphics to account for multi-day threat of
110+ heat indices especially west of Interstate 55 and down into the
Pine Belt. Pop up showers or storms may provide some localized
relief, but it appears we are in for a multi-day heat wave with the
ridge centered to our west bringing the heat and surface ridging
centered to our east keeping the humidity in place.

A low pressure system pivoting over the Great Lakes will nudge a
cold front toward the Mid-South/Interstate 40 corridor by Saturday
afternoon, with increased jet stream winds accompanying the front
southward. The increased flow and wind shear is expected to support
severe storm development in the vicinity of the front Friday into
Saturday, with storms then possibly moving southward into better
instability either day. There is a Marginal Risk for organized
severe storms Friday afternoon into evening for far northern parts
of our area, and then across more of the CWA by Saturday afternoon
and evening as the front moves into the area.

Sunday into Next Week:

Model guidance shows the front to get a better push southward toward
the Gulf Coast Sunday into Monday. Main differences behind the front
will be drier air and slightly cooler mornings (upper 60s vs mid
70s). Afternoons will feel cooler too, though mainly because of the
lost humidity. /NF/

&&

.AVIATION...
(18Z TAFS)
Issued at 1223 PM CDT Thu Aug 15 2024

VFR conditions will prevail through the period with scattered
clouds building this afternoon and into tonight. A few popup
showers and storms are possible this afternoon, particularly I-20
and south. These should clear later this evening. Visibilities
could lower to 6SM at southern sites tomorrow morning, with patchy
fog possible, not likely to impact overall air travel. Winds will
prevail from the southwest around 3 to 5kts./SAS/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       76  97  77  97 /  20  50  10  40
Meridian      75  97  74  97 /  10  50  10  50
Vicksburg     77  97  77  97 /  20  30  10  20
Hattiesburg   76  96  75  97 /  30  50  10  40
Natchez       76  96  75  96 /  30  30  10  20
Greenville    77  99  77  98 /  10  20  10  20
Greenwood     77  99  77  97 /  10  30  20  30

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Excessive Heat Warning until 8 PM CDT this evening for MSZ018-
     019-025>027-034>036-040>043-047>049-053>055-059>064-072>074.

     Heat Advisory until 8 PM CDT this evening for MSZ028>033-037>039-
     044>046-050>052-056>058-065-066.

LA...Excessive Heat Warning until 8 PM CDT this evening for
     LAZ007>009-015-016-023>026.

AR...Excessive Heat Warning until 8 PM CDT this evening for ARZ074-
     075.

&&

$$

NF/NF/SAS20