796
FXUS64 KJAN 291524
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1024 AM CDT Sat Jun 29 2024

...New AVIATION...

.MESOSCALE UPDATE...
Issued at 946 AM CDT Sat Jun 29 2024

Several updates were made to the forecast to better reflect
current conditions and expectations. Isentropic ascent beneath
building ridging aloft has lead to isolated to scattered showers
and cloudcover holding on longer than expected. This has
introduced some uncertainty regarding the temperature forecast.
Current thinking is greater low level moisture and cloudcover will
keep temperatures lower than anticipated southeast of the Natchez
Trace. As such, ticked down temps in this area a few degrees.
Conditions will continue to be monitored and the forecast will
adjusted accordingly. In addition to the lower than expected
temps, the dewpoints are holding higher. Regardless, it is going
to be quite a muggy afternoon.

Have also opted to cut back on PoPs to better reflect a more
isolated to scattered nature. Further north, little changes were
made. GLH already has a heat index of 105, and clearing is
visible on satellite in this area. This area should feel more
influence of the ridge, which should act to suppress cloudcover as
opposed to areas further south and east. Thinking it will still
be quite a hot day in the Delta./SAS/

&&

.DISCUSSION...
Issued at 420 AM CDT Sat Jun 29 2024

Today and Tonight:

Dangerous heat conditions will continue to be the primary hazard in
the short term period as early morning global guidance continues to
show upper ridging building over the southeast CONUS. Southwesterly
low level flow will continue across the forecast area today. This
will allow for dewpoints to hold in the upper 70s across our CWA,
with a few spots across the Delta seeing dewpoints in the 80s. This
combination will yield heat indices well into the 105-115 F deg
range areawide. For this reason, an excessive heat warning remains
in effect from 10 am this morning to 8 pm Sunday evening, including
the Delta, southeast Arkansas, and northeast Louisiana. Elsewhere, a
heat advisory remains in effect mainly for areas along and east of
the I-55 corridor. Later in the afternoon, it is possible that some
of the counties currently under heat advisory could see slightly
higher dewpoints. If this trend holds, it is possible that several
counties could see an upgrade to excessive heat warning. Rain
chances will be fairly low across northwest portions of our area
with the best rain chances (between 60- 70%) across the Pine Belt.
No changes were made to the heat graphic for today and we maintained
a "Significant" heat risk for areas where the excessive heat warning
remains in effect. Rain chances will begin to diminish heading into
the evening hours. Nighttime temperatures will drop into the mid to
upper 70s across the area providing very little relief heading into
the overnight period. /CR/

Sunday through Friday:

Heat is still going to be the main message for the week ahead. As
the subtropical ridge moves east over the Gulf Coast region through
the week, subsidence below the core of the ridge will limit rain
chances and support mostly above normal temperatures. This isn`t to
say rain is impossible, but just that rain chances increase more
around the periphery of the ridge.

A "cold front" moving south into the area Sunday night into Monday
will arrive in advance of the ridge`s passage, with the week`s best
areawide chances for showers and thunderstorms Sunday afternoon.
Temps on Monday will even be knocked down a few degrees north of
Interstate 20, but as the front washes out temps should quickly
rebound for the rest of the week. Daily rain chances will be focused
in the afternoon with peak heating and mainly in the south
and southeast with possible sea breeze activity and better moisture
availability. Flow trajectories around the high will bring drier air
generally from the east through most of the period. Guidance
looks to be trending a little drier for Thursday July 4th, though a
slight chance to chance for showers and storms cannot be ruled out
at this time. Friday into the weekend, the ridge shifting farther
east will allow for troughing to more influence the central and
southern US. Another cold front moving into the region will likely
bring another focus for rain during the weekend.

Will continue to evaluate Heat products for this Sunday, but current
forecast temp/dew point values yield similar values for current
Advisory/Warning configuration. Monday`s heat will be mainly in the
southern half of the area, and an extension of the Heat Advisory is
possible for those areas. Headlines likely to continue into the
Independence Day holiday as well if trends continue as they are. /NF/

&&

.AVIATION...
(18Z TAFS)
Issued at 1022 AM CDT Sat Jun 29 2024

MVFR ceilings continue to prevail longer than anticipated. Have
increased cloudcover and added BKN MVFR ceilings. Isolated to
scattered showers will continue to be possible across central and
southeastern sites./SAS/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       92  76  93  76 /  40  20  60  20
Meridian      90  74  95  73 /  50  20  80  20
Vicksburg     95  77  95  76 /  30  20  40  20
Hattiesburg   89  76  95  77 /  50  30  80  20
Natchez       94  75  93  76 /  30  20  40  20
Greenville    97  79  96  76 /  10  20  50  20
Greenwood     96  77  96  73 /  20  20  60  20

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Excessive Heat Warning until 8 PM CDT Sunday for MSZ018-019-
     025>027-034>036-040>042-047-053-059-060.

     Heat Advisory until 8 PM CDT Sunday for MSZ028>033-037>039-
     043>046-048>052-054>058-061>066-072>074.

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

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

&&

$$

CR/NF/SAS20