Mesoscale Discussion 294

Issued

Mar 28, 2021, 1:25 AM CDT (06:25 UTC)

Expired

Mar 28, 2021, 3:30 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The Knoxville radar (KMRX), 111 km from the middle of the area, began a volume at 06:28 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 66Mar 28, 2:05 AM CDT
• Severe Thunderstorm Watch 67Mar 28, 5:10 AM CDT

801 
ACUS11 KWNS 280625
SWOMCD
SPC MCD 280625 
NCZ000-TNZ000-VAZ000-KYZ000-GAZ000-ALZ000-280830-

Mesoscale Discussion 0294
NWS Storm Prediction Center Norman OK
0125 AM CDT Sun Mar 28 2021

Areas affected...Eastern Tennessee and adjacent portions of the
Cumberland Plateau/southern Appalachians

Concerning...Severe potential...Watch possible 

Valid 280625Z - 280830Z

Probability of Watch Issuance...60 percent

SUMMARY...A squall line appears likely to overspread much of eastern
Tennessee and adjacent portions of the Cumberland Plateau into
southern Appalachians through 5-7 AM EDT, accompanied by a risk for
damaging wind gusts and perhaps a couple of brief tornadoes.

DISCUSSION...A squall line segment appears to be advecting with the
deep-layer ambient mean flow, east-northeastward at up to 50 kt,
into and across middle Tennessee.  This appears to be occurring just
to the south of a possible evolving mesoscale convective vortex,
aided by lower/mid tropospheric warm advection along a remnant
convectively generated or reinforced surface frontal zone.  Although
the boundary layer remains stable to the cool side of this front,
across the Cumberland Plateau, Rapid Refresh forecast soundings
suggest that weak destabilization is possible ahead of the
convective system in response to thermal and moisture advection
during the next few hours.  As this occurs, the vigorous convective
system probably will be maintained with continuing, or perhaps
increasing, risk for damaging wind gusts and/or tornadoes, aided by
momentum/shear associated with forecast pre-frontal strengthening of
south-southwesterly flow around 850 mb in excess of 50 kt.

..Kerr/Guyer.. 03/28/2021

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

ATTN...WFO...RNK...GSP...MRX...JKL...FFC...OHX...HUN...

LAT...LON   36328594 36608424 36698295 36258162 35378277 34898383
            34728470 34688590 35008688 36328594

Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in North Carolina, 2021Mesoscale Discussions in Georgia, 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.