Mesoscale Discussion 571

Issued

May 9, 2021, 3:23 PM CDT (20:23 UTC)

Expired

May 9, 2021, 5:30 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Nashville radar (KOHX), 78 km from the middle of the area, began a volume at 20:26 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

355 
ACUS11 KWNS 092023
SWOMCD
SPC MCD 092023 
TNZ000-KYZ000-GAZ000-ALZ000-092230-

Mesoscale Discussion 0571
NWS Storm Prediction Center Norman OK
0323 PM CDT Sun May 09 2021

Areas affected...Northern Alabama into central Tennessee

Concerning...Severe potential...Watch unlikely 

Valid 092023Z - 092230Z

Probability of Watch Issuance...20 percent

SUMMARY...Ongoing thunderstorms may pose a brief severe threat as
they continue to move east across northern Alabama and central
Tennessee. However, the longevity of these storms is uncertain. A
watch is not expected.

DISCUSSION...A convective line across northern TN and a cluster of
semi-discrete cells over northern AL have shown somewhat surprising
persistence over the past hour as they continue to move away from
the region of better instability and into a drier air mass. GOES IR
imagery continues to show periodic cloud top cooling with these
storms, indicating that robust updrafts remain supported, likely the
result of a combination of strong deep-layer shear (effective bulk
shear values near 50 knots are noted over the region) and a slow
eastward progression of a mid-level moist axis. KOHX and KHTX VWP
observations show 40 knot 0-3 km shear over the region, and recent
RAP analyses suggest lapse rates within this layer have steepened to
near 7 C/km ahead of these clusters. This environment may support
organizing cold pools and a damaging wind threat as the storms
continue east over the next 1-2 hours. However, it is not clear how
much longer this activity will maintain its current intensity as it
continues to move into the drier air to the east. Given the
uncertainty in the duration of this threat and the low probability
of further intensification, a watch is not expected.

..Moore/Thompson.. 05/09/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MRX...JKL...FFC...LMK...OHX...BMX...HUN...

LAT...LON   36258678 36788622 37038528 36918426 36228407 35228455
            34538532 34318682 34298767 34838759 35798696 36258678

Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Kentucky, 2021Mesoscale Discussions in Alabama, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.