119
FXUS64 KJAN 131550 AAB
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1050 AM CDT Sat Jul 13 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 1034 AM CDT Sat Jul 13 2024

Previous forecast largely on track. Heat and humidity continue to
creep upwards, with analyzed PWAT values currently at 1.5 inches
or greater south of a Bastrop, LA to Meridian, MS line. A
positively-tilted upper-level trough over the central CONUS is
keeping southwesterly flow aloft over our region and is resulting
in about 15-20 kts of deep-layer wind shear over the area. Mid-
level ridge over the southeastern U.S. will limit instability from
northeast MS eastward into AL, but increasing moisture and even
minimal instability will support a chance for isolated showers or
a thunderstorm into northern Mississippi today. Have added
isolated showers and storms to the forecast for all zones this
afternoon, with better chances south of Interstate 20 with the
better instability and moisture. With some flow aloft, precip
chances will linger into the evening especially in the south. A
Heat Advisory remains in place today and tomorrow where heat index
values are expected to top out in the 105 to 110 range. /NF/

&&

.DISCUSSION...
Issued at 336 AM CDT Sat Jul 13 2024

Today and tonight...

Southwest flow regime will persist this weekend, with moist Gulf
air building northward. Look for increasing dewpoints through the
period. This along with surface temperatures in the upper 90s to
near 100 will result in heat indices around 105, thus a heat
advisory has been hoisted for the southwestern half. Further
northeast, drier air lingers, allowing for deeper mixing, keeping
dewpoints in the 60s, limiting greater heat stress today. This
area will eventually get their share though early next week.
Mostly diurnal convection should be confined to along and south of
the I-20 corridor this afternoon where greater moisture is
available. A few showers could linger after sunset as heating
wanes leading to an otherwise quiet night./SAS/

Sunday through Wednesday: Mid level ridging over the Southeast
and a surface high over the northern Gulf will serve as primary
influences over the first half of the new week. Thanks to the
ridge, daytime temps in the mid 90s to near 100 will remain common
across the area. As we remain just on the western side of the
ridge axis, low level trajectories will maintain a seasonably
moist airmass across the region. This will provide the fuel for
mainly diurnally driven convection over the first half of the
week. In most areas, development will occur too late in the day to
disrupt heating before heat indices reach crucial levels, so heat
stress will remain a concern during this time frame. A Heat
Advisory will likely be needed for at least some portion of the
area each day, barring some change in precip timing. We have gone
ahead and extended the current Heat Advisory into Sunday, and some
expansion in area is possible at a later time.

Thursday and Friday: A pattern change is in the offing for the
latter half of the week as an upper trough over the Upper Midwest
dips further southward across the country. This will bring a cold
front southward into the Mid South around Friday. Much like the
other weak summertime cold fronts we have seen in recent weeks,
this one will likely stall near or just north of the area as it
loses upper level support. However, it would likely still serve as
a forcing mechanism for greater rain chances at the end of the
week, resulting in some downward trend in daytime high temps and
heat stress. A brief intrusion of slightly drier air is also
possible mainly over the northern half of the area. This time of
year, we`ll take what we can get. /DL/

&&

.AVIATION...
(12Z TAFS)
Issued at 622 AM CDT Sat Jul 13 2024

VFR conditions prevail across the majority of the area, but patchy
transient fog has reduced visbys at a few sites. Categorical
reductions should be short lived, with VFR conditions returning
shortly after sunrise. Scattered SHRA and TS are possible mainly
across south MS and central LA this afternoon, which could result
in brief sub-VFR conditions. Otherwise, VFR conditions are
expected through the TAF period with light wind. /DL/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       97  76  95  76 /  20  10  50  20
Meridian      99  74  98  74 /  20  20  50  20
Vicksburg     95  75  94  75 /  20  10  40  10
Hattiesburg   97  76  97  76 /  50  30  70  10
Natchez       94  74  93  75 /  30  20  50  10
Greenville    96  76  94  76 /  20  10  30  10
Greenwood     97  76  96  75 /  20  10  30  10

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory until 7 PM CDT this evening for MSZ040-041-047>049-
     053>057-059>066-072>074.

     Heat Advisory from 10 AM to 7 PM CDT Sunday for MSZ040-041-
     047>049-053>057-059>066-072>074.

LA...Heat Advisory until 7 PM CDT this evening for LAZ007>009-015-016-
     023>026.

     Heat Advisory from 10 AM to 7 PM CDT Sunday for LAZ007>009-015-
     016-023>026.

AR...None.
&&

$$

NF/DL/SAS20