Mesoscale Discussion 275

Issued

Mar 27, 2021, 2:05 AM CDT (07:05 UTC)

Expired

Mar 27, 2021, 4:00 AM CDT

In force

115 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Columbus AFB radar (KGWX), 126 km from the middle of the area, began a volume at 07:06 UTC, the scan nearest the moment this went out.

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277 
ACUS11 KWNS 270706
SWOMCD
SPC MCD 270705 
TNZ000-ALZ000-MSZ000-ARZ000-270900-

Mesoscale Discussion 0275
NWS Storm Prediction Center Norman OK
0205 AM CDT Sat Mar 27 2021

Areas affected...Parts of northern Mississippi...adjacent eastern
Arkansas...northern Alabama and southern/middle Tennessee

Concerning...Severe potential...Watch unlikely 

Valid 270705Z - 270900Z

Probability of Watch Issuance...20 percent

SUMMARY...Intensifying thunderstorm development is expected by 4-6
AM CDT.  Some of these storms may, at least initially, pose a risk
for severe hail, with some potential to organize into a cluster
which could pose a risk for strong surface gusts toward daybreak.

DISCUSSION...Convection is initiating within a narrow, rough
east-west corridor across northern Mississippi into Alabama.  This
appears to be occurring in response to lift associated with
lower/mid tropospheric warm advection, along the northern edge of
the plume of higher precipitable water which is forecast to continue
slowly surging northward/north-northeastward through daybreak.  Also
on the northern periphery of mid-level subtropical ridging, the
leading edge of this moisture return is initially in mid levels, but
forecast soundings indicate that this will deepen into lower levels
through 9-12Z.  As it does, beneath fairly steep mid-level lapse
rates, increasing CAPE likely will support intensifying thunderstorm
development.  

While these storms probably will remain rooted above at least a
shallow near surface dry/stable layer, hodographs within to just
above the inflow layer are forecast to become characterized by
modest clockwise curvature and speeds increasing from 30 to 50+ kt
with height.  This probably will become supportive of low to
mid-level updraft rotation, with stronger storms becoming capable of
producing severe hail.  Closer to daybreak and beyond, it might be
possible that consolidating and upscale growing convection could
eventually evolve into an organizing cluster posing a risk for
strong surface gusts.  However, this potential remains a bit unclear
at the present time.

..Kerr/Guyer.. 03/27/2021

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

ATTN...WFO...OHX...HUN...MEG...JAN...LZK...

LAT...LON   35089013 35668851 36198602 35538562 34868625 34578783
            34308896 33999127 35089013

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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.