730
FXUS64 KJAN 201451 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
951 AM CDT Wed Aug 20 2025

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 938 AM CDT Wed Aug 20 2025

Local radars showed a narrow line of thunderstorms along a
prefrontal boundary that extended from Columbus, MS to Rayville,
LA. As temperatures become hot this afternoon and the prefrontal
trough sags into central Mississippi, the storms will become more
vigorous and isolated severe storms capable of damaging wind gusts
will be possible. The storm motions will be to the south southwest
again so the severe threat will be across the southern half of our
CWA. This early start to convection and the scattered to numerous
storms expected today will likely knock temperatures down in spots
but heat and humidity remain a concern today. The area along and
just east of the Mississippi river will see the highest heat
indices today and is under am Extreme Heat Warning. Much of the
remainder of our CWA remains under a Heat Advisory. Other than to
increase pops along the prefrontal trough the next several hours,
no significant changes were needed to the forecast. /22/

&&

.DISCUSSION...
Issued at 308 AM CDT Wed Aug 20 2025

Through Thursday: A summertime front will begin to make southward
progress into the region later today. Unfortunately, our area
will remain ahead of the front during the warmest part of the day
meaning we have at least one more day of heat and humidity to cope
with. With increasing moisture convergence and compressional
heating ahead of the front, it seems likely that some areas,
mainly across the MS Delta and near the MS River, will once again
see enough overlay of heat and humidity for heat index values
surpassing 110F. An Extreme Heat Warning has been posted for this
area. A Heat Advisory remains in effect for most areas
surrounding the warning, except parts of east MS.

The front is likely to help incite greater convective coverage
today, though this is unlikely to lower max heat indices as
development most likely holds off until closer to mid-afternoon.
Given the forecast steep low level lapse rates due to the heat
and humidity, we could some of these storms become severe with a
damaging wind threat, similar to what transpired across parts of
AR, northwest MS, and north LA yesterday. Latest SPC Day 1 outlook
has added a marginal risk, and ML guidance supports this, so we
will highlight this potential as well. CAMs indicate most
convection will taper off by 2z, but a few rogue storms could
persist into the night.

The front will continue a slow southward push and begin to stall
into Thursday. This will bring somewhat drier conditions mainly
north of I-20 and daytime temperatures regressing closer to
seasonal averages. The farther south you are in the area,
particularly across the Pine Belt and south MS, it will still be
rather warm and muggy on Thursday, with heat indices potentially
approaching critical thresholds especially if afternoon convective
development doesn`t interfere with daytime heating. The HRRR
shows good chances for afternoon convection roughly south of
I-20, but latest RRFS runs are more less aggressive with
development in our area.

Friday through Tuesday: As the front stalls and falls apart
across our south, the north-south split in conditions will remain
into the beginning of the weekend. Farther south in the area, the
humidity will persist with better potential for diurnal
convection. Though heat stress may approach critical thresholds,
greater prevalence of clouds and rain may prevent conditions from
being quite as hot and humid as we`ve seen in recent days. Farther
north, there will be a more noteworthy decrease in deep layer
moisture, yielding a decrease in rain chances, especially across
AR and north MS, and dewpoints are expected to fall into the more
tolerable 60s in that area as well. The daytime periods will
still be seasonably warm but yet more tolerable owing to the drier
conditions.

By the beginning of next week, a reinforcing front will push
southward across the area. This should further lower daily rain
chances even into southern portions of the area, with high temps
potentially failing to touch the 90s in many areas by Tuesday.
/DL/

&&

.AVIATION...
(12Z TAFS)
Issued at 622 AM CDT Wed Aug 20 2025

Brief patchy fog is possible over the next few hours. Later
today, redevelopment of convection is expected mainly this
afternoon into early this evening, potentially resulting in brief
categorical reductions in TSRA or brief strong convective wind
gusts. Otherwise, VFR conditions will prevail through the TAF
period with mainly light wind. /DL/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       98  74  92  71 /  50  40  40  20
Meridian      97  73  92  71 /  40  30  50  20
Vicksburg     97  74  92  71 /  50  40  40  10
Hattiesburg   98  74  95  73 /  30  30  60  30
Natchez       97  73  91  71 /  40  40  50  20
Greenville    97  73  93  70 /  50  30  10   0
Greenwood     98  73  94  70 /  60  20  10   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory until 8 PM CDT this evening for MSZ026-028>033-037-
     044-049-050-055-056-059>066-072>074.

LA...Heat Advisory until 8 PM CDT this evening for LAZ007>009-015-023-
     024-026.

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

&&

$$

22/DL/