Severe Thunderstorm Warning 520, NWS Jackson, MS

Area Forecast Discussion
National Weather Service Jackson MS
1151 AM CDT Sat Jul 22 2023

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 1151 AM CDT Sat Jul 22 2023

Rest of today...

Morning 12Z upper/water vapor analysis indicates longwave trough
centered over the Great Lakes with the axis extending to the south,
with the trough axis just to the west of the region.
Favorable upper jet dynamics/diffluence in advance of another
perturbation progged to move into the Mid-South this afternoon in
northwest flow will help increased ascent persist across the
southern half of the area. Earlier morning shortwave has departed to
the east, with decreased ascent & rain chances across the northern
half of the region. Morning sfc analysis indicates frontal zone
draped south of Interstate 20, with continued convergence & pooling
moisture along & south of the boundary. This is evident in
increased agitated cumulus field south of Interstate 20. This is
combined with nearly 2 inch PWs for rain & storm potential into
early to mid afternoon. Severe storm potential will persist into the
afternoon hours. Unidirectional shear profiles & mean bulk shear
around 25-30kts in the low-mid levels combined with some steep lapse
rates/vertical totals around mid-upper 20s degree C & moderate
destabilization will favor efficient cold pool development & some
hail up to quarter size. Main concerns will be for multicell
clusters or bowing segments, especially any that propagate east-
northeast more orthogonal to the low-level flow. SPC added a Slight
area, which seems reasonable. Morning sfc modified soundings
indicate deeply unstable air favorable of microburst wind potential
& this looks to be realized in regional mesoanalysis of nearly 5000
J/kg SBCAPE. Timing will be early afternoon into the evening hours.
In addition, HREF indicates potential for some heavy rain &
increased neighborhood probs/max of > 3 inches in the Hwy 84 to I-59
corridor. Added a "Limited" in the HWO in southeast MS along &
southeast of a line from southern Lawrence County to central Clarke
County. Backbuilding doesn't look to be a concern but efficient
heavy downpours/training look probable.

Highs will remain less oppressive north of I-20 but compressional
warming & continued warm thermo south of I-20 will help aid in
temperatures peaking into the mid 90s especially in the Hwy 84
corridor. With high PWs & limited mixing, sfc dewpoints remain the
mid-upper 70s. Dangerous heat stress remain a concern into the
afternoon, with some areas in the Pine Belt currently reaching Heat
Advisory criteria. Heat Advisory/HWO look on track & no changes were
needed at this time. /DC/

&&

.DISCUSSION...
Issued at 359 AM CDT Sat Jul 22 2023

Today through tonight: A cold front pushing south across the area
will bring a marginal risk for severe weather, and it will help
suppress the significant heat stress conditions to along/south of
the Highway 84 corridor where a heat advisory will continue for
today. A weak shortwave trough is helping to generate numerous
showers and thunderstorms over mainly north central Mississippi
early this morning. The convective rainfall will continue for the
next several hours before diminishing later this morning as the
minor trough exits. Then expect redevelopment of storms this
afternoon for locations mainly south of the I-20 corridor, where
most unstable CAPE > 3000 j/kg combined with ~30 kt mid level flow
will support a few severe multicell storm segments. Storms should
diminish early this evening with cooler and less humid air
conditions expected overnight. /EC/

Sunday through Friday: On Sunday, the cold front associated with
a upper level trough will stall out along the Gulf Coast. Rain
chances will remain along the Gulf Coast through Sunday night as
the trough gradually makes its way east. Temperatures will be
relatively cooler during this period as highs will be in the low
90s and lows with be in the upper 60s across the area. By Tuesday,
the trough will have made its way east of the area and the upper
level high that was giving us problems earlier this week will make
its back eastward. 500mb heights will increase, bring warmer
conditions back to the region by midweek. High temperatures during
this period will be in the mid 90s. Dew points in the high 60s
will suppress some of those extreme heat indices we experienced
earlier this week, but heat indices ranging from 100-105 can still
be expected in some areas. By Thursday, ridging from the high
pressure system will begin to weaken off to our west. The chance
for scattered diurnally driven storms will increase areawide
heading into the weekend. /LCP/

&&

.AVIATION...
(12Z TAFS)
Issued at 645 AM CDT Sat Jul 22 2023

Convective precip continues along/ahead of a cold front, and this
will likely continue for the next few hours in northern portions
of the area. IFR/LIFR category stratus has developed and could
impact most sites early this morning before lifting/dissipating by
late morning. Expect another round of SHRA/TS to develop this aftn
across southern portions of the area. Otherwise, VFR conditions
and light surface wind will prevail through this evening. Another
round of low stratus may impact the area late tonight into early
Sunday morning. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       91  71  91  69 /  50  20  10   0
Meridian      89  70  90  68 /  70  40  10   0
Vicksburg     89  69  90  70 /  40  10   0   0
Hattiesburg   95  73  91  70 /  80  80  40  10
Natchez       91  72  90  70 /  60  40  10   0
Greenville    87  67  89  69 /  20   0   0   0
Greenwood     87  67  90  69 /  30   0   0   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory until 7 PM CDT this evening for MSZ060>066-072>074.

LA...Heat Advisory until 7 PM CDT this evening for LAZ024-026.

AR...None.
&&

DC/LCP/EC

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