Severe Thunderstorm Warning 203, NWS Jackson, MS

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1013 AM CDT Wed Jun 26 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 947 AM CDT Wed Jun 26 2024

Satellite imagery showed only a few clouds across the CWA and
temperatures were warming up nicely. Portions of the delta were
already to 90F resulting in heat index values of 105F. Heat stress
conditions will continue to increase into the afternoon warranting
the Heat Advisory but, regional radars showed vigorous convection
over central Arkansas. This activity was being driven by a
shortwave trough topping the ridge to our west and will continue
to track toward our CWA. This will support the convective activity
that will continue to approach our CWA this morning and drop into
our CWA this afternoon. Considering the environment over our CWA
that the convection will be moving into, severe storms capable of
damaging wind gusts and hail up to quarter size. The severe threat
potential is expected to begin in our northwest by noon and
progress to the south southeast through the afternoon and into the
evening across our southern most zones. /22/

&&

.DISCUSSION...
Issued at 455 AM CDT Wed Jun 26 2024

Today through tonight...

Early this morning, water vapor/synoptic analysis indicate 596DM
500mb mean ridge over West TX & northern Mexico while deepening
longwave trough/jet energy diving into the northern Plains to
Great Lakes, while stronger shortwave is diving southward out of
the Mid West. This is helping deep ascent/storm development
across the Mid West, with cooling cloud tops in GOES East water
vapor imagery. Increased convergence & high moisture pooling
ahead of the boundary, well above 90th percentile, near or in
excess of the climatological maxima around 2.25 inches, will help
rain & storm development to increase, with potential MCS diving
down into the Delta by midday & spreading south to southeast
through the day into the evening hours. Rain & storm coverage
becoming more scattered-numerous during this time. Seasonably
warm highs in the low-mid 90s are expected preceding any MCS, with
dangerous heat stress now expected to peak between 105-110F
degrees. With recent convective allowing models (CAMs) indicating
timing being mainly after midday through the evening, heat indices
could peak above criteria before midday. Earlier addition of the
heat advisory looks good & there was enough confidence to expand
eastward along the I-20 corridor & southward into the I-59
corridor as well. Even though there will be some earlier
development, there should be a window from 10AM-2PM where heat
headlines would be warranted. Added an "Elevated" in the HWO for
these areas & expanded the Heat Advisory. With a potential MCS
moving into dangerous heat environment, these are usually
conducive for severe storms. Mean bulk shear is favorable for
organization, nearly 15-20kts in the 0-2/0-3km layer & even up to
30kts in the 0-6km layer & some lapse rates/vertical totals in the
25-27 deg range. Recent convective outlook from SPC was upgraded
to a "Slight", which mostly looked good but made expansion
southward along I-20 to include Richland & Madison Parishes in LA
& more of Warren & Hinds in MS. Recent trends in CAMs look
supportive of a more southward expansive MCS. Damaging wind gusts
of 60-70mph & quarter size hail remain the main concerns. Expect
most of the severe potential to wind down by 9-10PM & some rain
chances to persist through daybreak, mainly south of I-20 into the
Hwy 84 corridor. Near to slightly seasonably warm lows in the
low 70s are expected. /DC/

Thursday through Friday...

Early morning global guidance highlight a cold front moving
southward across the forecast area starting on Thursday. With the
increase in moisture head of the front, showers and thunderstorms
will be possible, with higher storm chances (around 70-90%) near the
I-20 and I-59 corridor. A few strong thunderstorms cannot be ruled
out, and both the GFS and the Euro show a lack of organized
convection along/south of the boundary. Heading into Thursday
evening, rain chances will begin to diminish across southern
portions of our forecast area as the boundary pushes further south
out of our CWA. With this boundary pushing further south, a less
oppressive airmass/decreased heat stress will filter in some relief
to the recent hot and humid conditions on Thursday. As high pressure
ridge builds in late week, dangerous heat stress will become the
primary concern on Friday. Afternoon highs are expected to peak in
the low/mid 90s with dewpoints climbing into the mid/upper 70s. This
will yield heat indices in the 105 F - 110 F deg range. An
"Elevated" heat risk was introduced for southeast AR, northeast
Louisiana and portions of northwest, central and southern MS. Heat
headlines may be needed as we get closer.

Saturday through Tuesday...

The short break from the hot temperatures will unfortunately come to
an end on Saturday as global guidance highlights an upper-level high
amplifying over Texas. At the same time, an upper-level ridge will
build over the southeast CONUS. This will bring oppressive heat and
humidity across the area through the weekend. As we head into the
new work week, global guidance shows the high pressure weakening,
due to height falls from upper level system across the Great Lakes
to northeast states. Heat will persist from the weekend into early
next week, but increased rain and storm chances make areal
configuration more uncertain. We maintained an "Elevated" heat in
the HWO graphic areawide Sunday and Monday. Expect further updates
to the heat graphics as we get closer to the weekend. Heat related
warnings and advisories may be continue to be needed as we get
closer. A frontal boundary is expected to push towards the
southeast, increasing shower/thunderstorm potential Sunday afternoon
and Monday. The potential for severe weather is low around this
timeframe, but there are signals in CSU machine learning probs for
marginally severe storms late weekend into early next week. Rain
chances will start to increase especially for areas east of I-55
heading into Tuesday. /CR/DC/

&&

.AVIATION...
(12Z TAFS)
Issued at 704 AM CDT Wed Jun 26 2024

VFR conditions are expected to prevail at the TAF sites through
the period, however the chance for SHRA or TSRA (mainly after
26/18Z Wednesday - 27/01 Thursday) could bring variable conditions
& gusty winds near any storms. Expect light winds in the wake,
before some lowered ceilings, potentially down to MVFR, are
possible near the end of the TAF period in central, eastern &
southern sites. /NF/DC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       93  73  90  74 /  50  50  60  10
Meridian      96  71  90  72 /  70  60  60  20
Vicksburg     94  73  90  74 /  50  50  30  10
Hattiesburg   95  75  90  74 /  70  50  80  20
Natchez       93  73  89  73 /  40  50  60  10
Greenville    94  73  90  74 /  70  40  10   0
Greenwood     94  72  90  74 /  70  40  20   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory until 8 PM CDT this evening for MSZ018-019-025>027-
     034>036-040>043-047>066-072>074.

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

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

&&

DC/CR/DC

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