Mesoscale Discussion 484

Issued

May 2, 2021, 11:45 PM CDT (04:45 UTC)

Expired

May 3, 2021, 1:45 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

The Columbus AFB radar (KGWX), 93 km from the middle of the area, began a volume at 04:50 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.

506 
ACUS11 KWNS 030445
SWOMCD
SPC MCD 030445 
ALZ000-MSZ000-030645-

Mesoscale Discussion 0484
NWS Storm Prediction Center Norman OK
1145 PM CDT Sun May 02 2021

Areas affected...Portions of northern MS into northwestern AL

Concerning...Severe potential...Watch possible 

Valid 030445Z - 030645Z

Probability of Watch Issuance...40 percent

SUMMARY...An isolated tornado threat may persist overnight. Watch
issuance is possible, but will depend on signs on increasing storm
intensity.

DISCUSSION...A long-lived, low-topped supercell that produced a
tornado earlier in Tupelo MS has weakened somewhat as it has moved
northeastward into northwestern AL and encountered a less unstable
airmass, but it is still showing signs of occasional low-level
rotation. Additional low-topped convection has formed in the past
hour across parts of northern MS in a continued strong low-level
warm advection regime. A low-amplitude shortwave trough is moving
over the Mid-South now per recent water vapor satellite imagery.
Ascent associated with this upper trough and the low-level warm
advection will probably continue to support convection across
northern MS and parts of northwestern AL through the early overnight
hours. Deep-layer shear remains adequate for storm organization.
Recent VWPs from KGWX show some veering of the 0-1 km flow in the
past hour or so, and this trend should continue as the core of the
low-level jet shifts eastward into AL/TN overnight. Still, low-level
shear is expected to remain more than adequate for updraft rotation,
with effective SRH around 200-300 m2/s2 likely to remain in place
over this region for at least several more hours. Isolated tornadoes
may occur if any of this ongoing low-topped convection can
strengthen further. However, this potential appears uncertain given
the weak instability in place and the stabilizing effects of earlier
storms. Tornado Watch issuance is possible in the next couple of
hours, but will largely be dependent on radar and observational
trends.

..Gleason/Thompson.. 05/03/2021

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

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

LAT...LON   33599090 34389054 34958895 34948781 34718762 33958774
            33708846 33329073 33599090

Mesoscale Discussions in Mississippi, 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.