173
FXUS64 KJAN 031733
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1233 PM CDT Wed Jul 3 2024

...New AVIATION...

.MESOSCALE UPDATE...
Issued at 1110 AM CDT Wed Jul 3 2024

Mesoscale Update: The forecast remains on track, thus no major
updates were made to the package. Earlier this morning a few showers
popped up just east of the Jackson metro area dropping a quick 2-3in.
This will likely be the trend for today, very weak deep layer flow
will allow the possibility for any storms that pop up to move very
slow potentially causing locally high rainfall amounts. Today we can
expect storm coverage to be generally scattered in nature with the
greatest chances across the SE half. However, due to instability in
excess of 4000J/kg of SBCAPE and temps reaching into the upper 90s,
a storm or two has the possibility to be strong with the main threat
being strong wind gusts. For heat impacts, the "Excessive Heat
Warning" will remain in effect for most areas today with a "Heat
Advisory" in effect elsewhere. High temperatures will be dangerously
hot with temps climbing into the mid to upper 90s mixed with the
high humidity will lead to heat indices to range from 110-120
degrees./KP/

&&

.DISCUSSION...
Issued at 435 AM CDT Wed Jul 3 2024

Today and Tonight:

Taking a look at regional METAR obs - or stepping out into the early
morning air - confirms that the warm tropical air mass has indeed
spread back north across our forecast area. Dew point values at this
hour range from about 72 in southeast AR/northwest MS to a balmy 78-
79 in southeast MS and central LA. Overnight showers are festering
at the Gulf Coast, and we expect coverage of showers and
thunderstorms to increase over more of our forecast area as the day
wears on. Before rain becomes too widespread, temperatures climbing
into the mid and upper 90s will combine with the humid air to
produce heat index values mostly near 110 up to 115-120. Confidence
was lowest in the Interstate 59 corridor where rain chances are
expected to start earliest in the day, so stuck with a Heat Advisory
in those areas. The remainder of the forecast has a greater chance
to hit the 110+ heat index values before rain moves in, so an
Excessive Heat Warning is in place through the evening.

High PWAT values of 2+ inches driven by increased lower level
humidity and dry air aloft associated with upper-level ridge over
the region will yield steep vertical Theta-E differences and
approximately 3000-4000 J/kg of SBCAPE. Flow aloft is very weak and
easterly, and the lack of shear will limit storm updraft
organization or longevity. Organized severe storms are not expected,
but there will be some threat for damaging wind gusts with any of
the stronger pulse thunderstorms that develop today. /NF/

Thursday through next Tuesday:

High pressure will continue to gradually slide east through the
region, where it`ll remain centered and overall remain in control
of our weather during the forecast period. At the surface, high
pressure will likewise slide further east of the CWA, wedging
itself into the region from the east. As this happens, copious
amounts of deep moisture will feed into the CWA through early next
week. This`ll maintain high humidity levels across the forecast
area. Not only that, it will also result in increasing chances for
showers and storms each afternoon. These better rain chances will
be further aided by a frontal boundary that will drop south into
the region Friday afternoon. Over the weekend and into early next
week, this boundary is advertised to stall and eventually washout
out over the forecast area.

As far as temperatures are concerned, dangerous heat stress will
continue across much of the forecast area Thursday into Friday.
Temperatures will warm into the low and middle 90s both days. This,
coupled with the aforementioned high humidity levels over the area,
will result in afternoon heat index values climbing above the
century mark across the CWA. This will especially be the case
Thursday, when indices will be more in the 106-115 range areawide.
As a result, a "Heat Advisory" and an "Excessive Heat Warning" have
now been hoisted for portions of the CWA for Thursday, i.e.
Independence Day.

As the frontal boundary sinks into the region Friday afternoon,
relief from the heat will come in the way of scattered to numerous
showers and storms over the CWA. This frontal boundary is again
forecast to stall and washout over the forecast area Saturday into
early next week.  With some slightly drier air filtering into mainly
far northern parts of the area over the weekend, and the better
coverage of convection over the CWA, relief from the oppressive heat
is expected to be more widespread across the area as highs range
from the upper 80s to middle 90s Saturday through Tuesday. However
with the boundary washing out early next week, deep moisture will
again engulf the entire forecast area ahead of another frontal
boundary that`s currently forecast to impede upon the forecast area
from the northwest Tuesday night. /19/

&&

.AVIATION...
(18Z TAFS)
Issued at 1233 PM CDT Wed Jul 3 2024

VFR flight conditions across the area for the start of the TAF
period. Shower/thunderstorm potential will increase this afternoon
and into the early evening. Southeasterly winds near 6kts are
expected. Near 08-09Z Thursday, patchy fog will be possible
especially near central and southern TAF sites, reducing flight
conditions to MVFR/possible IFR. Any developed fog will diminish
after sunrise, bringing flight conditions to VFR. /SW/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       77  93  77  92 /  10  50  10  70
Meridian      75  94  76  94 /  20  60  10  80
Vicksburg     78  94  78  92 /  10  30  10  60
Hattiesburg   78  94  77  96 /  20  70  10  70
Natchez       77  93  76  93 /  20  40  10  60
Greenville    79  96  78  93 /  10  20  10  60
Greenwood     78  94  78  92 /  10  30  10  70

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Excessive Heat Warning until 8 PM CDT this evening for MSZ018-
     019-025>045-047>050-053>056-059>065-072.

     Excessive Heat Warning from 10 AM to 8 PM CDT Thursday for
     MSZ018-019-025>027-034>036-040>042-047-053.

     Heat Advisory from 10 AM to 8 PM CDT Thursday for MSZ028>033-
     037>039-043>046-048>052-054>066-072>074.

     Heat Advisory until 8 PM CDT this evening for MSZ046-051-052-057-
     058-066-073-074.

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

     Excessive Heat Warning from 10 AM to 8 PM CDT Thursday for
     LAZ007>009-015-016-023>026.

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

     Excessive Heat Warning from 10 AM to 8 PM CDT Thursday for
     ARZ074-075.

&&

$$

KP/19/SW