Mesoscale Discussion 307

Issued

Mar 31, 2021, 1:55 AM CDT (06:55 UTC)

Expired

Mar 31, 2021, 4:00 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

Counties Blount County, AL, Cullman County, AL, Fayette County, AL, Franklin County, AL, Lamar County, AL, Lawrence County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Walker County, AL, Winston County, AL, Calhoun County, MS, Chickasaw County, MS, Itawamba County, MS, Lee County, MS, Monroe County, MS

The Columbus AFB radar (KGWX), 70 km from the middle of the area, began a volume at 06:54 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.

497 
ACUS11 KWNS 310655
SWOMCD
SPC MCD 310655 
ALZ000-MSZ000-310900-

Mesoscale Discussion 0307
NWS Storm Prediction Center Norman OK
0155 AM CDT Wed Mar 31 2021

Areas affected...Parts of northeastern Mississippi through northern
Alabama

Concerning...Severe potential...Watch unlikely 

Valid 310655Z - 310900Z

Probability of Watch Issuance...20 percent

SUMMARY...Vigorous thunderstorm development may persist and continue
to spread east-northeastward across the region through 4-6 AM CDT,
with at least some continuing risk for potentially damaging surface
gusts and, perhaps, an isolated, brief tornado.

DISCUSSION...An eastward advancing zone of low/mid-level warm
advection (mostly in the 850-700 mb layer) continues to support a
developing area of thunderstorm activity across northern Mississippi
into Alabama.  Ascent is being enhanced by high-level divergence
downstream of the base of amplified large-scale troughing, which is
forecast to spread toward the southern Appalachians through 11-12Z. 

This convection includes a small, but organizing cluster of storms
(currently north of Columbus, MS), preceded by an isolated
supercell, supported by inflow of weak to moderate CAPE on the order
of 500-1000 J/kg.  Stronger convection probably has become rooted
close to the surface, where hodographs within the inflow layer may
be moderately large and clockwise curved beneath a 30-40
southwesterly 850 mb jet.  Otherwise, activity appears mostly rooted
above weakly unstable to neutral near surface lapse rates which
trend at least a bit more stable with eastward extent into the
southern Appalachians.  This seems likely to continue to inhibit
tornado potential, although an isolated, brief tornado may not be
completely out of the question.  However, with weak mid-level lapse
rates expected to continue to minimize the potential for severe
hail, locally damaging wind gusts appears the primary potential
severe hazard, aided by heavy precipitation.

..Kerr/Guyer.. 03/31/2021

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

ATTN...WFO...BMX...HUN...MEG...JAN...

LAT...LON   33928958 34578832 34548687 34498601 34138597 33698635
            33708703 33658864 33928958

Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Mississippi, 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.