-- Discussion containing changed information from previous version are highlighted. --
097
FXUS64 KMEG 050245
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
945 PM CDT Sat May 4 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 929 PM CDT Sat May 4 2024

Fairly quiet this evening as mid level shortwave ridging spreads
into the region ahead of the next disturbance moving toward the
Arklatex. Fog is the main concern once again this evening. Best
chances appear to be across the TN River Valley and NE MS where
dewpoint depressions are already 1 degree or less. Confidence is
not quite as high as last evening since the HRRR has not really
jumped on board yet. Ongoing forecast handles it well and we will
monitor fog development for potential Dense Fog Advisory later
tonight. The next disturbance will swing through on Sunday
afternoon with numerous showers and thunderstorms. A few severe
storms are possible with gusty winds and large hail.
-- End Changed Discussion --

&&

.SYNOPSIS...
Issued at 326 PM CDT Sat May 4 2024

Warm and humid conditions will support scattered to numerous
showers and thunderstorms through the middle of next week. A few
severe thunderstorms will possible on Sunday, as an upper level
disturbance lifts from Texas into the lower Mississippi River
Valley. Severe thunderstorm chances will increase by midweek,
ahead of a deep upper level low pressure system moving through the
Great Plains and mid-Mississippi River Valley.

A cold frontal passage on will bring cooler and less humid conditions
to the Midsouth by next weekend.

&&

.DISCUSSION...
(This evening through next Friday)
Issued at 326 PM CDT Sat May 4 2024

An active weather pattern is ahead for the Midsouth through the
middle of next week.

A convectively- enhanced shortwave will lift from west central
Texas into the western Ozarks by midday Sunday. Mixed layer CAPE
over the Midsouth will increase to 1000-1500 J/kg. 0-6km bulk
shear will prevail at 20-30kt, relatively modest but about double
that of today. This will support a marginal severe threat by
midmorning Sunday. Damaging winds, hail and heavy rainfall appear
to be the primary threats. Given the projected timing of the
shortwave, storms should exit and/or diminish by Sunday evening.
Monday should be relatively quiet under shortwave ridging. But the
ridge axis will be east of the area Monday evening, opening the
door for storms to enter the Midsouth from southern AR, aided by a
40kt low level jet.

Severe thunderstorms are appearing more likely Tuesday and
Wednesday, aided by height falls associated with a deepening northern
branch longwave trough over the western two-thirds of the CONUS.
Low level return flow will strengthen in response, driving surface
dewpoints to around 70F over the Midsouth. The increased low
level moisture will drive surface-based CAPE in excess of 2500
J/kg Tuesday afternoon, accompanied by 0-6km bulk shear around
45kt north of I-40.

With strong southerly flow continuing, the lower atmosphere should
recover Wednesday from Tuesday night storms. An upper level
trough axis, pendant from a closed low over eastern Nebraska, will
pivot through the Ozarks Wednesday afternoon and evening, driving
height falls and enhancing frontal convergence over the lower
Ohio River Valley and Midsouth. Surface-based CAPE will peak
around 3000 J/kg Wednesday afternoon, before moderating below a
still impressive 1500-2000 J/kg Wednesday evening. GFS and ECMWF
mean 700-500mb lapse rates are progged at an impressive 8 C/km
Wednesday afternoon and evening. Given the projected CAPE, this
would be supportive of very large hail, at least during the
afternoon. Given the tendency for prefrontal veering of low level
winds, convection may transition to a linear mode Wednesday
evening, perhaps reducing the large hail and tornado threat, but
enhancing the flash flooding threat. Projected PWAT is around 2
inches, about as high as it gets this time of the year.

Quieter weather should prevail Thursday, following the passage of
the convectively-reinforced cold front. Another cold frontal
passage appears likely on Friday, as a deep longwave trough
sets up briefly over the eastern CONUS. This should bring relatively
cool and dry conditions to the Midsouth next weekend.

PWB

&&

.AVIATION...
(00Z TAFS)
Issued at 710 PM CDT Sat May 4 2024

Near term aviation concerns pertain to the development of reduced
visibilities, ceilings, and possible fog overnight as winds go
calm and variable. High resolution CAM guidance depicts a line of
showers and thunderstorms that will move through the airspace
sometime tomorrow afternoon. Have elected to use a PROB30 for now
with respect to this situation until further details can be
resolved.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$

PUBLIC FORECAST...SJM
AVIATION...JPR