Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 301128 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
628 AM CDT Fri Jul 30 2021

...EXTREMELY DANGEROUS HEAT WAVE EXPECTED TO CONTINUE THROUGH EARLY
WEEKEND...

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
MVFR vis restrictions are ongoing or intermittent & will remain
just after daybreak at GLH, GWO, GTR, JAN, MEI & PIB, with
IFR/LIFR cigs/vis ongoing at MEI. VFR flight cats will return
after 30/13Z. Other than 4-5kft cigs, area will stay VFR through
aftn. Another round of aftn isolated SHRA/TSRA psbl near or S of
HBG & PIB. Timing will begin around 30/20-22Z & wind down around
31/00Z. Light W-NW winds are expected today, generally less than
10mph. Persistence fcst for brief MVFR vis &/or isolated IFR cigs
can`t be ruled out, mainly after midnight through daybreak
Saturday. However, low confidence remains for radiation fog
potential so left out of current 12Z TAF cycle. /DC/

&&

.DISCUSSION...

Today & tonight...

Today: Extremely dangerous heat wave & stress continues to grip the
region. Stout 597DM mean ridge axis remains parked over central
Plains/Ozarks & building into the ArkLaTex & ArkLaMiss while mean
trough & frontal zone remains off to the NE. A significant MCS is
ongoing across the Tennessee Valley but cloud tops are beginning to
warm. This is not expected to cause any aftn convection issues in
our NE. With mean ridge axis nosing E-SE, this will keep broad
subsidence & warming in low-levels. PWs will remain around an inch &
a half & slight aftn mixing could tamper down dewpoints a touch.
However, this should not hamper dangerous heat stress for the aftn.
Kept a persistence fcst to lean on previous afternoon high temps &
bumped up a couple of degrees or so & slightly less aggressive. A
couple of areas could again reach near 100 degrees this afternoon &
get into the top 5 for high temp records.

Heat stress will be downright dangerous as heat indices will be
widespread above 105-110 deg. F & some exceeding 115 deg. F,
especially in the ArkLaMiss Delta & portions of south-central to
western MS where the advertised "Significant" & "Extreme" in the HWO
remains valid. Main adjustments were to expand the "Significant"
into NE LA & SW MS & upgrade these areas to an Excessive Heat
Warning as well & added Smith/Jones into the "Significant"/Excessive
Heat Warning to the E. Otherwise, inherited areas remain mostly
intact. Heat stroke will be increasingly likely with prolonged
outdoor activity. Stay cool, hydrated & take your safety precautions
in this extremely dangerous heat wave.

A subtle shortwave over the Gulf Coast could bring some very
isolated showers & storms by late aftn across the Hwy 98 corridor,
but rain chances will remain extremely sparse & confined to the Pine
Belt. Strong subsidence & limited forcing will keep most areas dry
today.

Tonight: The synoptic & sfc pattern will persist, with a front
dropping S into Mid-South & Lower MS Valley but no discernible
changes to our ongoing pattern. With limited rain cooled air, expect
lows to struggle to fall below 80 degrees. A few record warm low
temps are possible overnight again. /DC/

Saturday through Thursday...

Hot and humid weather will continue into the first part of the
weekend...and tomorrows temperature/heat index forecast looks very
similar to todays. The possible break in the heat may come in the
form of a stormy Sunday/Monday.  At 500mb, a trough digs in over the
eastern half of the country, sending a surface front southward with
a relatively drier and cooler airmass behind it. The cold air does
not quite make a quick appearance...and Sunday will be a race to see
how warm it can get before the cloud cover/showers cut off the
heat...and for now, the heat indices are in the 100F to 110F range.
However, by Monday, the precip should be more widespread as the
front slows...and max temps are limited to 10 degrees or so below
Sundays. The rain will keep the area muggy, more than likely, but
cooler overall. As the front pushes south into Tuesday...the focus
for the pops does as well. Temperatures at 850mb drop from the 21C-
23C with the heat in the short term...to 15C-16C by Wednesday...and
surface temps settle into the upper 80s/lower 90s with dewpoints
down in the mid 60s. By the end of the forecast, can see the 70
dewpoints creeping back northward from the Gulf. /HJS/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       98  78  98  77 /   4   2  24   5
Meridian      99  77  99  76 /   5   4  25   8
Vicksburg    100  78  99  78 /   5   2  17   3
Hattiesburg   98  77  98  76 /  21  11  42  14
Natchez       96  77  96  76 /  11   7  26   5
Greenville    98  77  99  77 /   1   0  10   4
Greenwood     98  77  99  77 /   2   1  12   5

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Excessive Heat Warning until 7 PM CDT Saturday for MSZ018-019-
     025>043-047>049-053>056-059>066-072>074.

     Heat Advisory until 7 PM CDT Saturday for MSZ044>046-050>052-057-
     058.

LA...Excessive Heat Warning until 7 PM CDT Saturday for LAZ007>009-
     015-016-023>026.

AR...Excessive Heat Warning until 7 PM CDT Saturday for ARZ074-075.


&&


$$

DC/HJS


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