110
FXUS64 KMEG 260301
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1001 PM CDT Sat May 25 2024

...New UPDATE...

.UPDATE...
Issued at 924 PM CDT Sat May 25 2024

Fairly quiet across the Mid-South with a few showers that are
slowly dissipating. Overnight a shortwave rotating through the
Mid MS Valley will kick off a cluster of storms that will track
along the northern border of the Mid-South. A few severe storms
are possible across mainly the northern tier of counties with
this complex as SBCAPES of nearly 3000 J/kg continue and 0-6km
shear values climb above 50 kts with the approach of the
shortwave. There is a tornado threat with this round along the
MO/AR and KY/TN borders. This first round will push east of the
area in the morning. The interesting thing will be to see where
the outflow boundaries from this cluster end up during the
afternoon.

Expect at least isolated convection to develop along the outflow
boundary wherever it ends up by Sunday afternoon. The latest CAMs
are less aggressive with Sunday afternoon development but it still
bears monitoring. HRRR model soundings across much of the area are
impressive by 21z. For example at Memphis expect SBCAPES around
3500 J/kg, 0-6km shear values greater than 50 kts and 0-1km
helicity values of 175 m2/s2. If convection can get going Sunday
afternoon it will likely be severe with damaging winds, large hail
and perhaps a tornado. There does seem to be a cap around 750mb
that may be a result of some shortwave ridging between the
departing morning shortwave and the next one approaching Sunday
evening. This may inhibit convection Sunday afternoon until it
breaks, if it does.

As the next shortwave rotates into the area and lift ramps up expect
coverage to quickly increase resulting in a few broken line
segments that eventually form a line of strong to severe storms
Sunday evening trekking SE across the Mid-South. The line will
exit into central MS and northern AL by 10z or so. Expect damaging
winds, large hail and a perhaps some quick spin up tornadoes.

&&

.SYNOPSIS...
Issued at 342 PM CDT Sat May 25 2024

Enhanced severe weather chances return Sunday with multiple
rounds of storms possible through early Monday morning. The main
concern at this time remains potential for afternoon supercells to
develop and produce all hazards of severe weather. In addition,
flooding chances remain elevated as efficient rainfall rates
accompany storms. Unsettled weather should come to an end on
Monday, when dry conditions return to the Mid-South.

&&

.DISCUSSION...
(This evening through next Friday)
Issued at 342 PM CDT Sat May 25 2024

Shortwave ridging aloft has precluded shower and thunderstorm
chances this afternoon, with only a few pop-up storms present on
radar as of 3PM. Isolated storms may continue to develop over the
next few hours, with a few possibly reaching severe limits. If
storms do form, the main concerns will be damaging winds and large
hail.

Greater severe weather chances will materialize on Sunday, with
multiple rounds of storms possible. The first round will be driven
by a shortwave trough pushing into the Midwest late tonight.
Several CAMs depict an MCS developing over Missouri, pushing
eastward into Kentucky by 7AM. The main question regarding this
round of storms lies in the southern extent of the MCS. The 18Z
HRRR keeps storms along the Kentucky / Tennessee border. However,
all other CAMs support storms pushing well into northeast Arkansas
and the Missouri Bootheel. Regardless of which scenario
materializes, severe weather chances will be possible as dewpoints
surge to the low 70s by 7AM. The main threats with this batch of
storms will be damaging winds and large hail.

A secondary round of convection may materialize in the mid
afternoon hours along a remnant outflow boundary from the
aforementioned MCS. At this time, hodographs become more favorable
for tornadic development with 0-3 km SRH increasing to 250 m2/s2
in portions of northwest Tennessee. In addition, mid-level lapse
rates on the order of 7.5 C/km will support strong updrafts
capable of producing large hail. Any storms that develop at this
time will likely be discrete and pose the greatest tornadic
threat, with a few significant tornadoes possible. As such, the
Storm Prediction Center has extended portions of the Enhanced Risk
to areas of northwest Tennessee. Important note: confidence for
this round of storms remains low due to uncertainties in exact
track of Sunday morning`s MCS. The bottom line: if storms do form
in the afternoon, they will be capable of all hazards.

A third, and final round of storms will occur late Sunday evening
into the overnight hours. Convection is expected to form along a
cold front that pushes southeast across Missouri in the evening
hours. By the time this line impacts the Mid-South, a QLCS
structure will be evident with damaging winds the primary concern.
A few CAMs decrease lapse rates to around 5.5 - 6.0 C/km
overnight, which should hamper large hail development. However,
brief spin-up tornadoes will remain possible as the LLJ
strengthens and SRH values remain around 150 - 200 m2/s2. The main
areas of concern for this round of storms will be northeast
Arkansas and west Tennessee. By 4AM Sunday, the severe weather
threat will wane with dry conditions returning Monday.

In addition to severe weather concerns, flooding potential remains
elevated as precipitable water values approach the 99th
percentile. Any storms that do develop will likely be prolific
rainfall producers, resulting in rises of rivers and streams. The
Flood Watch has been adjusted to include areas north of the
Tennessee / Mississippi state border now through 7AM Monday.
Additional rainfall totals of 1-2 inches with locally higher
amounts are possible.

ANS

&&

.AVIATION...
(00Z TAFS)
Issued at 650 PM CDT Sat May 25 2024

Main story this TAF issuance is the timing and intensity of TSRA
across each terminal tomorrow afternoon and into the overnight
hours. Latest CAMs have two lines of convection: the first looks
to form along a few shortwaves out ahead of the second main line
associated with a cold front. TSRA is expected to begin impacting
JBR/MEM/MKL beginning around 21Z tomorrow afternoon through the
TAF period as these lines of convection move across the Mid-South.
South/southwest look to gust up to 30 kts tomorrow morning
through the TAF period as this cold front passes. VFR conditions
are expected to prevail, though each terminal could see a brief
lowering to MVFR with onset convection.

AEH

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Flood Watch through Monday morning for ARZ009-018-026>028-035-
     036-048.

MO...Flood Watch through Monday morning for MOZ113-115.

MS...None.
TN...Flood Watch through Monday morning for TNZ001>004-019>022-
     048>055-088>092.

&&

$$

PUBLIC FORECAST...SJM
AVIATION...AEH