-- Discussion containing changed information from previous version are highlighted. --
759
FXUS64 KJAN 260028 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
728 PM CDT Tue Jun 25 2024

...New MESOSCALE UPDATE, AVIATION...

.MESOSCALE UPDATE...
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Issued at 700 PM CDT Tue Jun 25 2024

Weak moisture convergence and steep lapse rates supported isolated
showers and a few thunderstorms around the forecast area this
afternoon, but more robust convection has been limited today by
weaker deep-layer wind shear to sustain updrafts. Expecting
lingering showers or storms to diminish by 8-10 pm this evening,
and temps falling into the mid 70s at most locations by morning.
These values will be slightly above normal for late June, but
could be near record warm low temperatures especially in the
Delta. Looking into tomorrow, the various high-res models present
a few varying solutions. But general consensus is still for
organized convection in the Midwest tonight to make a run
southward into tomorrow with an MCS possibly moving into our
forecast area during the daytime. If it holds off until midday or
so, better instability south of the MCS would support a better
threat for severe weather. The Marginal Risk for severe
thunderstorms tomorrow remains in place for this potential -
mainly for damaging winds. /NF/
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&&

.DISCUSSION...
Issued at 336 PM CDT Tue Jun 25 2024

Tonight and Wednesday: Afternoon surface analysis had a high
centered northeast of our CWA and a slightly stronger high centered
over the central Gulf coast. As the high to our northeast continues
shifting farther to the northeast we will come more under the
influence of the surface high to our south. This will help maintain
high humidity over our CWA through Wednesday. Temperatures have
climbed into the upper 90s this afternoon. This has led to Excessive
Heat Warning criteria over our delta and Heat Advisory criteria over
the remainder of our CWA. These oppressive conditions will linger
into the evening before gradually diminishing. Visible satellite
imagery shows a rather suppressed cu field across our CWA and the
potential for microbursts look to remain limited.

The large upper level ridge that has led to the recent heat wave
across our CWA has shifted west and mid afternoon satellite
imagery/RAP analysis showed a shortwave trough over the central
Plains that will drop around the high and over our CWA Wednesday.
This is expected to lead to a greater coverage of convection over
our CWA that will lower the heat stress. The timing of the
convection is in question with the most likely time during prime
heating but several models suggest an MCS development that moves
into our CWA during the morning hours. Later convection would limit
heating so peak heat index values would be limited to 105F or less.
A later onset of convection would allow for greater heating and a
possible Heat Advisory for portions of the CWA. In addition, the
environmental parameters look adequate for damaging wind gusts with
the storms. An MCS would bring a broader area of damaging winds. For
now, isolated severe storms capable of damaging wind gusts and hail
to the size of quarters during the afternoon into the evening, as
far south as the Highway 84 corridor look possible. /22/

Wednesday Night through Friday....

Shower and thunderstorm potential will continue as a cold front
continues to moves through northern portions of the ArkLaMiss region
Wednesday night. With a slightly unstable airmass (bulk shear around
20-30 kts and dewpoints in lower/mid 70s), a "Marginal" risk for
severe weather will continue for areas north of I-20. Damaging
winds/hail up to quarter-size are the primary hazards of concern. As
the frontal boundary shifts southward Thursday,
showers/thunderstorms will be possible with best rain chances near
the I-20 and I-59 corridor. A few strong thunderstorms can`t be
ruled out and organized convection is not expected. along/south of
the boundary. Post-frontal passage, a less oppressive hot/humid
airmass will filter in and bring slight relief to the hot
temperatures. Expect post frontal high temperature in the upper
80s/lower 90s and low temperatures in the lower 70s.

Saturday through Monday....

The relief from hot temperatures will be short-lived as an upper-lvl
high amplifies over TX and an upper-lvl ridge builds over the
southeast. As a result, oppressive heat and humidity will return to
the area Saturday and continues through the weekend. As the weekend
progresses and into next week, the aforementioned high pressure
center is expected to migrate eastward, bringing a hot airmass into
the area and increasing heat stress and danger across the CWA. High
temperatures are expected to be in the mid/upper 90s and heat
indices reach 105-110F degrees. With heat indices in the 105-110F
degree range, an "Elevated" heat threat HWO graphic was introduced
for Saturday through Monday. Heat related warnings and advisories
may be needed as the weekend gets closer but will hold off for now.
Take precautions to prevent heat-related illnesses and stay
hydrated. A frontal boundary is expected to push towards the
southeast, increasing shower/thunderstorm potential Sunday afternoon
and Monday. Severe weather is not anticipated but will continue to
monitor as the forecast progresses. /SW/

&&

.AVIATION...
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(00Z TAFS)
Issued at 700 PM CDT Tue Jun 25 2024

VFR conditions are expected to prevail at the TAF sites through
the period, however the chance for SHRA or TSRA (mainly after 18Z
Wednesday) could bring variable conditions and gusty winds near
any storms. /NF/
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Jackson       77  94  73  90 /  20  50  50  70
Meridian      75  96  72  91 /  10  80  60  70
Vicksburg     77  94  73  90 /  20  40  40  40
Hattiesburg   77  95  74  92 /  30  70  40  80
Natchez       75  94  73  89 /  20  30  40  60
Greenville    78  95  72  92 /  20  60  40  20
Greenwood     78  95  72  91 /  20  70  50  30
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&&

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

     Heat Advisory until 8 PM CDT this evening for MSZ028>033-037>039-
     043>046-048>066-072>074.

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

     Heat Advisory until 8 PM CDT this evening for LAZ023>026.

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

&&

$$

22/SW/NF