Mesoscale Discussion 225

Issued

Mar 18, 2021, 5:57 PM EDT (21:57 UTC)

Expired

Mar 18, 2021, 7:00 PM EDT

In force

63 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 42...43

The Raleigh/Durham radar (KRAX), 40 km from the middle of the area, began a volume at 22:01 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.

913 
ACUS11 KWNS 182157
SWOMCD
SPC MCD 182157 
VAZ000-NCZ000-SCZ000-182300-

Mesoscale Discussion 0225
NWS Storm Prediction Center Norman OK
0457 PM CDT Thu Mar 18 2021

Areas affected...far northern South Carolina...much of North
Carolina...and southern/southeastern Virginia

Concerning...Tornado Watch 42...43...

Valid 182157Z - 182300Z

The severe weather threat for Tornado Watch 42, 43 continues.

SUMMARY...Tornadoes and damaging wind gusts are possible with
clusters of ongoing convection.  This threat will persist for at
least the next couple of hours.

DISCUSSION...Convection initially over north-central North Carolina
has organized and acquired rotation while favorably interacting with
a warm frontal zone over far southern Virginia.  These storms are in
a strongly sheared environment with lingering instability upstream
from an undisturbed environment along/south of the front containing
1000-1500 J/kg MLCAPE.  The general clustered nature of the
convection suggests potential for several cell interactions, though
the combination of shear, localized vorticity ingest along the
front, and moderate instability suggests that the tornado threat
will exist for at least the next couple hours.  Hail is also
possible near supercellular convection exhibiting stronger updrafts.

Farther upstream, another quasi-linear segment was located very near
the Greensboro, NC area and has also exhibited occasionally strong
rotation on radar.  Brief tornadoes and wind damage are likely as
this area of convection migrates/propagates east-northeastward along
the remnant frontal boundary in that area.

More isolated cells farther southwest into north-central South
Carolina may also exhibit a hail/wind and isolated tornado risk
given the strong shear and weak instability downstream, although
slightly veered low-level flow may temper the tornado threat in this
area compared to farther downstream.

..Cook/Guyer.. 03/18/2021

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

ATTN...WFO...AKQ...MHX...RAH...ILM...RNK...CAE...GSP...

LAT...LON   36487971 36897935 37167841 37527744 37627672 37357586
            36617574 36037597 35527667 35137773 34697891 34467989
            34448040 34708075 35308087 35978039 36487971

Mesoscale Discussions in North Carolina, 2021Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in South Carolina, 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.