Mesoscale Discussion 383

Issued

Apr 14, 2021, 4:24 PM EDT (20:24 UTC)

Expired

Apr 14, 2021, 6:30 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Raleigh/Durham radar (KRAX), 95 km from the middle of the area, began a volume at 20:26 UTC, the scan nearest the moment this went out.

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107 
ACUS11 KWNS 142024
SWOMCD
SPC MCD 142024 
VAZ000-NCZ000-142230-

Mesoscale Discussion 0383
NWS Storm Prediction Center Norman OK
0324 PM CDT Wed Apr 14 2021

Areas affected...Parts of southern Virginia and northern North
Carolina

Concerning...Severe potential...Watch unlikely 

Valid 142024Z - 142230Z

Probability of Watch Issuance...20 percent

SUMMARY...Intensifying thunderstorm development is possible near the
central Virginia and North Carolina state border vicinity by 7-8 PM
EDT, with the potential for this activity to organize and pose a
risk for small hail and strong surface gusts.  It still appears that
the severe weather threat will remain isolated and marginal enough
that a severe weather watch will not be required.  However, trends
will continue to be monitored.

DISCUSSION...Ahead of a cold front approaching the southern
Appalachians, low-level moisture is rather modest across the
Carolina Piedmont into the Blue Ridge.  But this has allowed for
seasonably strong surface heating and deep boundary-layer mixing. 
Mixed-layer CAPE appears on the order of 250 J/kg, with somewhat
larger CAPE for most unstable surface parcels across much of the
Piedmont, and as far west as the Blue Ridge.  

This destabilization has been accompanied by deepening convective
development north of Hickory into areas near/northwest of
Greensboro, which appears to be supported by lift associated with
low-level warm advection, on the northeastern periphery of the more
strongly heated/deeply-mixed air mass.  Within 30-40 kt westerly
deep-layer ambient mean flow, in advance of the base of mid-level
troughing to the south of the broad mid-level low slowly turning
southeast of the upper Great Lakes region, this forcing and
associated convective development will continue to develop eastward
through early evening.

As convection begins to encounter better low-level moisture return
(including mid 50s to near 60F surface dew points) near the
Virginia/North Carolina state border vicinity, north of Raleigh
through the Roanoke Rapids area, there appears increasing potential
for substantive intensification by 15/00Z, if not before.  CAPE of
500-1000 J/kg is possible across at least a localized area, with
thermodynamic profiles becoming increasing conducive to
thunderstorms.  Coinciding with strengthening southwesterly flow
near the 850 mb level to 30+ kt, wind profiles may support the
evolution of a supercell structure or two, with the potential to
produce small hail and a few strong surface gusts.

..Kerr/Thompson.. 04/14/2021

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

ATTN...WFO...AKQ...RAH...RNK...

LAT...LON   36068025 36628030 37297837 37027697 36297686 36027856
            36068025

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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.