535
FXUS64 KJAN 061743 AAC
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1243 PM CDT Sat Jul 6 2024

...New AVIATION...

.MESOSCALE UPDATE...
Issued at 916 AM CDT Sat Jul 6 2024

A tropical air mass remains in place over the Gulf Coast region
this morning. A weak cold front which had dipped into the area
yesterday brought slightly drier air to far northern parts of our
forecast area, but by and large PWAT values are still 2+ inches
south of a line from Monroe, LA to Columbus, MS per latest
mesoanalysis. Though not strong, there is also some southwesterly
deep-layer shear across the region as the right entrance region of
the jet stream sits over the Ozarks and as upper-level outflow
from what is currently Tropical Storm Beryl overspreads the
central Gulf Coast. 0-6km shear vectors of 15-25 kts may support
some level of organization for any stronger storms that develop
today. In the axis of deepest moisture and greatest instability,
we`ve already seen a cluster of showers and storms develop in
East Mississippi this morning, and the expectation is for greater
coverage of storms focused between the Interstate 20 and US
Highway 84 corridors this afternoon with daytime heating. A
microburst composite parameter of 5 derived from this morning`s
KJAN sounding suggests there is a chance for several strong to
severe storms with damaging wind gusts through the course of this
afternoon and evening. The main limiting factor is the tropical
nature of the atmosphere and lapse rates aloft near moist
adiabatic values, but with enough daytime heating there should
still be the potential for downdrafts to incorporate some of the
drier, cooler air aloft. Given the southwesterly shear aloft, the
northern and eastern sides of any outflow boundaries will be
favored for wind potential. Expected peak heat index values near
105 degrees in the Pine Belt continue to warrant "Limited" heat
stress messaging on our current heat graphic. /NF/

&&

.DISCUSSION...
Issued at 428 AM CDT Sat Jul 6 2024

Today through tonight: The most impactful weather, including
thunderstorm potential and the risk for dangerous heat, will
generally be for locations along/south of the I-20 corridor as we
begin the weekend. A weak west-to-east oriented frontal boundary
will meander over the forecast area this weekend, and the hottest
and most humid conditions should generally exist along and south
of the boundary, where we expect the development of numerous
showers and storms this afternoon. Poor lapse rates will continue
to limit updraft/storm intensity, but very moist air with
precipitable water (PW) up to 2.4 inches and H850 dewpoints up to
16 deg C will support very efficient and locally heavy rainfall
if slow-moving storms become focused. As we go into the evening,
storms should diminish quickly and then mostly quiet and humid
conditions are expected for the overnight. /EC/

Sunday through Friday night:

To begin the forecast period, very moist tropical airmass will
continue to flow into the area around weakening high pressure
stationed over the southeastern states. The increase in tropical
flow will combat the drier air associated with the stalled
boundary in the northern portions of the CWA throughout the day
eventually pushing the front northward out of the area. With this
moist tropical airmass, we can expect to see surface dewpoints in
the mid to upper 70s and PWs in the 2 to 2.5 inch range. This
tropical airmass will help maintain areawide rain chances
throughout the day with the greatest chances being in the
southeast. Increasing cloud cover and convection will likely limit
daytime temps Sunday for a majority of the CWA, however the
southern portions of the CWA will have the opportunity for some
early heating allowing for heat indices to approach dangerous heat
criteria. Thus the limited heat stress HWO graphic will remain in
effect for Sunday.

Going into next week: Upper level troughing will continue its track
eastward through the central states into the mid MS valley on
Monday. Southwesterly flow will persist allowing for continuous deep
layer moisture to flow into the area keeping scattered to isolated
diurnal convection constant each day of the period. By Tuesday we
will see increasing chances for showers and storms along the western
edges of the CWA as TC Beryl continues its track. NHC guidance
now show the cyclone turn more to the northeast across eastern
Texas as it weakens to a depression. This track will help to
increase rain chances Tuesday and Wednesday for our area,
especially over the ArkLaMiss Delta region where there could end
up being a risk for heavy rainfall. As we go through the
remainder of the week, we can expect diurnally driven rain and
storm chances to continue through end of the period. /KP/

&&

.AVIATION...
(18Z TAFS)
Issued at 1243 PM CDT Sat Jul 6 2024

Patchy MVFR ceilings are hanging on from the morning across south
and east MS and central LA, but these are in the process of
lifting and breaking up. Scattered SHRA and TS will be possible
this afternoon, mainly along and south of I-20, decreasing early
this evening. Another round of scattered low stratus and
localized fog is expected to develop Sunday morning near daybreak
and lasting through mid to late morning. It is possible not all
sites will be impacted, but those that are may see IFR or LIFR
conditions. /DL/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       74  91  75  94 /  20  50  20  60
Meridian      73  93  73  95 /  20  60  30  70
Vicksburg     74  90  75  92 /  10  40  20  50
Hattiesburg   76  94  76  95 /  30  70  20  60
Natchez       74  90  74  93 /  20  50  20  50
Greenville    73  91  75  92 /  10  20  20  50
Greenwood     74  91  75  93 /  10  20  20  50

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&

$$

NF/EC/KP/DL