878
FXUS64 KJAN 290356
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1056 PM CDT Sun Apr 28 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 1056 PM CDT Sun Apr 28 2024

Rest of tonight...

Ongoing MCS is somewhat waning as it moves into the area, with
the forward propagation component of this MCS more focused towards
central-eastern AR. A tornado watch was issued for southeast AR,
northeast LA & extreme northwest MS & continues through 2AM.
GOES-East infrared imagery & regional radar mosaic indicate
somewhat warming cloud tops aloft & convection somewhat waning in
radar presentation on the leading edge of this MCS. More vigorous
deep convection/intense cloud tops over southern portions of the
ArkLaTex. Evening synoptic analysis remains across the Carolinas
to Appalachians while subtropical sfc high remains right off the
Atlantic seaboard. 1005mb sfc low is moving into the Mid West. As
the trough swings east-northeast, strong southern stream
shortwave, indicated by stout drying over the southern Plains,
will continue to eject to the east overnight through the morning
hours. This will provide the impetus for more convective
development, especially in the areas along the ArkLaTex & expected
to slide to the east-southeast a MCS. For areas south of the
ongoing complex & cold pool moving into northeast LA & southeast
AR, low-level jet around 30-40kts, low-level instability &
somewhat favorably aligned low-level flow for organized MCS to
remain likely into the overnight hours. SPC earlier added an
"Enhanced" for areas west of the MS River & kept it confined to
this zone, with the most likely area of seeing the higher wind
probs of up to 70mph along & south of the I-20 corridor from
Rustin, LA to Natchez, MS area through the overnight hours. Main
hazards remain damaging winds 60-70mph, with best chances west of
MS River, spinup tornadoes & large hail in any deeper core that
could develop. Timing has been tricky, as guidance earlier
indicated some of this convection could precede a later MCS, but
have now congealed into one definitive MCS propagating southeast,
with the southern half along & south of I-20 corridor becoming the
most concerning. Main updates were to add the "Enhanced" to the
HWO graphics for west of the MS River, tweak an earlier start
timing for the western timing slot & speed up timing slightly
along & east of the I-55 corridor. Heavy rain looks to be confined
for the southwestern half of the area, with most confident area
along & southwest of a line from Bolivar to Lincoln county in MS.
No other major changes were needed. Updates are out. /DC/

&&

.DISCUSSION...
Issued at 253 PM CDT Sun Apr 28 2024

As anticipated, weaker inhibition today is allowing for warm
advection showers to develop and spread north across the forecast
area today. Isolated thunderstorms are embedded with this
activity as well, but deep layer shear is not favorable for
organized updrafts. Expect quick moving, and short-lived storms
where they do develop. Regional radar mosaic showed the remnants
of last night`s convective line were all but washed out across
North Texas into Arkansas, but an organized cluster of storms has
re-fired east of Waco and Killeen in Texas this afternoon. High
res guidance has struggled with how to transition from last night
to today`s activity, but but they all generally get to the point
of one or more MCS segments drifting east through Louisiana and
Arkansas toward Mississippi late tonight. 06Z and 12Z HRRR were previous
fast outliers, but 18Z run has come into a little closer agreement
with consensus of HREF members regarding timing.

Southerly low-level jet winds and greatest instability located to
the south of any MCS activity will favor southward propagating
MCS activity by morning (or at least most intense MCS activity
farther south along any broken line). Forecast MLCAPE values over
1000 J/kg seem to favor MCS trajectory to be along or southwest
of a diagonal line roughly from Ruston, LA down Natchez, MS or so.
Depending on timing and placement of overnight storms, the
potential for severe storms could extend farther east to around
the Interstate 55 corridor. Bowing segments along any line could
lead to increased potential for damaging wind gusts and possible
spinup tornadoes. The Slight Risk for severe storms was expanded
to account for this wind and isolated tornado potential -
including southeast Arkansas, northeast and central Louisiana, and
far southwestern Mississippi. The Marginal Risk area extends
south through Mississippi generally along Interstate 55. In
addition to any severe threat, heavy rainfall could cause
localized flash flooding concerns. End timing is a little
uncertain, but an organized line will probably clear out earlier
in the day than anything disorganized. /NF/

Monday Night through Sunday:

A fairly progressive split flow regime sets up over the CONUS
through the rest of next week, driving a few potential periods of
showers and thunderstorms as shortwave troughs moving east and
interact with spring-like humid and unstable air masses across the
South. Nothing at this point looks to fully scour out the decent
moisture in the region, and PWAT values over 1.3 inches should
support air mass thunderstorms on any given day. When not
raining, afternoon high temperatures should push the upper
80s/lower 90s range. Glimpses of summertime are coming into view.
/NF/

&&

.AVIATION...
(00Z TAFS)
Issued at 826 PM CDT Sun Apr 28 2024

Southeasterly sfc winds will continue through early evening. MVFR
stratus should develop at all TAF sites, with onset between
29/04-7Z & earlier onset at southern-central TAF sites.
TSRA ongoing across northern LA into southwestern AR will
propagate northeastward, with more SHRA & TSRA expected overnight.
Some gusts in these storms could bring 40-50kts at times &
variable ceilings/vsby. Expect a gradual decrease in coverage from
west-east overnight & some improvement to VFR flight categories in
spots. SHRA & TSRA will decrease from west-east into the morning
hours, mainly after 29/15-20Z. /DC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       69  78  63  83 /  10  80  60  20
Meridian      64  81  63  84 /   0  70  80  30
Vicksburg     67  77  63  84 /  40  90  40  20
Hattiesburg   67  81  64  84 /  10  70  70  40
Natchez       67  76  63  85 /  40  90  40  30
Greenville    69  75  63  82 /  60  90  40  10
Greenwood     68  76  63  83 /  20  90  60  10

&&

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

$$

DC/NF/DC