Mesoscale Discussion 212

Issued

Mar 17, 2021, 5:49 PM CDT (22:49 UTC)

Expired

Mar 17, 2021, 7:15 PM CDT

In force

86 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 29...33

The Birmingham radar (KBMX), 138 km from the middle of the area, began a volume at 22:49 UTC, the scan nearest the moment this went out.

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• Tornado Watch 36Mar 17, 6:45 PM CDT
• Tornado Watch 37Mar 17, 7:10 PM CDT

896 
ACUS11 KWNS 172249
SWOMCD
SPC MCD 172249 
GAZ000-ALZ000-MSZ000-LAZ000-180015-

Mesoscale Discussion 0212
NWS Storm Prediction Center Norman OK
0549 PM CDT Wed Mar 17 2021

Areas affected...Much of southeastern Mississippi and central
Alabama

Concerning...Tornado Watch 29...33...

Valid 172249Z - 180015Z

The severe weather threat for Tornado Watch 29, 33 continues.

SUMMARY...The risk for tornadoes, a couple of which could become
strong and particularly damaging, is expected to continue to
increase through mid to late evening as an organizing squall line
overspreads the region.  This may also be accompanied by more
general strong to severe surface gusts.  A new tornado watch will be
needed by 7 PM CDT.

DISCUSSION...Large-scale ascent, aided by lower/mid tropospheric
warm advection beneath difluent high-level flow, continues to
support discrete thunderstorm development within a relatively broad
warm sector.  Areas of the warm sector not substantially impacted by
prior convection remain characterized by CAPE of 1000-2000 J/kg, and
wind profiles across the region exhibit strong deep-layer shear and
sizable, clockwise-curved low-level hodographs.  This environment
remains potentially conducive to long-lived supercells with strong
low-level mesocyclones posing a risk for tornadoes.

While the onset of diurnal cooling could result in at least some
decrease in instability by 00-01Z, favorable large-scale forcing for
ascent seems likely to maintain discrete storm development across
central Alabama, as a linear convective system continues to evolve
upstream, across southeastern Louisiana through southern and eastern
Mississippi.  This is occurring ahead of a vigorous short wave
trough turning east-northeast of the southern Great Plains.  As this
feature progresses into the lower/middle Mississippi Valley through
mid/late evening, south-southwesterly 850 mb flow is forecast to
strengthen in excess of 50 kt in a corridor along/ahead of the
evolving squall line.  

Further enlargement of low-level hodographs will maintain the risk
for tornadoes with both the discrete supercells preceding the the
squall line and those forming within the squall line.  This will
include the potential for strong tornadoes.  Otherwise, corridors of
potentially damaging wind gusts will probably begin to increase as
the evolving squall line continues to organize and accelerate
northeastward.

..Kerr.. 03/17/2021

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

ATTN...WFO...FFC...BMX...HUN...MOB...JAN...LIX...

LAT...LON   31958982 33108866 34018760 34198650 33098473 32388488
            31968596 31388687 30858797 30398875 30648987 31958982

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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.