Mesoscale Discussion 210

Issued

Mar 17, 2021, 2:56 PM CDT (19:56 UTC)

Expired

Mar 17, 2021, 4:30 PM CDT

In force

94 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 32

The Jackson/Brandon,MS radar (KDGX), 86 km from the middle of the area, began a volume at 19:56 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.

• Tornado Watch 36Mar 17, 6:45 PM CDT

551 
ACUS11 KWNS 171957
SWOMCD
SPC MCD 171956 
ALZ000-MSZ000-ARZ000-LAZ000-172130-

Mesoscale Discussion 0210
NWS Storm Prediction Center Norman OK
0256 PM CDT Wed Mar 17 2021

Areas affected...Northeast Louisiana...southeast Arkansas and much
of Mississippi.

Concerning...Tornado Watch 32...

Valid 171956Z - 172130Z

The severe weather threat for Tornado Watch 32 continues.

SUMMARY...The tornado threat is expected to increase late this
afternoon/evening.

DISCUSSION...Most of Mississippi is in a relative lull for
convective coverage/intensity with more intense convection to the
east with the stronger low-level jet and to the west near the
surface trough. Within this area, significant clearing has allowed
temperatures to warm into the low 80s with dewpoints in the upper
60s yielding MLCAPE of 1500 to 2000 J/kg per SPC mesoanalysis. This
strong surface heating has led to deep boundary layer mixing (as
evident on the 18Z JAN RAOB) and as a result, surface flow has
veered southwesterly across much of Mississippi which has reduced
low-level directional shear significantly. However, despite this
veered low-level flow, a widespread and potentially intense tornado
threat is still expected late this afternoon/evening as the surface
trough approaches. 

Low-level flow in proximity to this surface trough has started to
back across southeast Arkansas and Louisiana. Expect this trend to
continue as the boundary tightens in response to the ejecting upper
trough. Evidence of this ejecting trough and the corresponding
increase to the flow field can be seen on the KLCH VWP where 1km
flow has strengthened by 20 kts (to near 60 knots) within the last
hour. Expect this stronger low-level jet to overspread much of the
warm sector by 22-00Z which should elongate low-level hodographs
substantially.

Expect multiple supercells to develop along this surface boundary in
the next few hours and track northeastward through the late
afternoon and into the evening hours. In response to the
aforementioned instability and strengthening low-level shear, the
12Z HREF shows widespread 4+ STP across much of Mississippi this
afternoon/evening with some areas in excess of 6. This environment
will support the potential for intense/long-track tornadoes through
the late afternoon and evening hours.

..Bentley.. 03/17/2021

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

ATTN...WFO...HUN...MEG...JAN...LIX...LZK...LCH...SHV...

LAT...LON   31629262 32439230 33559193 34139085 34558968 34618884
            34478814 33798826 32818859 31788974 31409097 31249198
            31629262

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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.