Mesoscale Discussion 1122

Issued

Jun 28, 2021, 2:21 PM EDT (18:21 UTC)

Expired

Jun 28, 2021, 4:15 PM EDT

In force

114 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

5%

Counties Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Colleton County, SC, Dorchester County, SC, Georgetown County, SC, Williamsburg County, SC

The Charleston,SC radar (KCLX), 118 km from the middle of the area, began a volume at 18:23 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.

755 
ACUS11 KWNS 281822
SWOMCD
SPC MCD 281821 
SCZ000-282015-

Mesoscale Discussion 1122
NWS Storm Prediction Center Norman OK
0121 PM CDT Mon Jun 28 2021

Areas affected...Coastal South Carolina

Concerning...Severe potential...Watch unlikely 

Valid 281821Z - 282015Z

Probability of Watch Issuance...5 percent

SUMMARY...A brief tornado or two will be possible this afternoon
across the South Carolina coastal region as Tropical Depression Four
moves onshore. A watch is not likely due to low confidence in a more
robust tornado threat.

DISCUSSION...A few weak thunderstorms associated with the outer
bands of Tropical Depression Four have been moving across coastal
areas of SC over the past hour with only transient signs of
intensification. This is likely due to weak low and mid-level lapse
rates as sampled by the 12Z CHS sounding. However, temperatures are
warming into the low to mid 80s where cloud cover is minimal, which
may locally augment instability through the afternoon and lead to
some storm intensification. GOES visible and IR imagery show a
couple of additional convective towers developing inland as well as
offshore, suggesting that lift and instability remain adequate for
new development at least for the near term. Recent hi-res guidance
supports this idea, suggesting that another round of storms is
possible along the coast by mid afternoon, though confidence in this
scenario is low. The KCLX VWP sampled veering winds in the lowest
1-2 km, which is supporting around 100 m2/s2 ESRH along the coast.
The combination of sufficient instability and low-level shear will
support a low-end tornado threat through the afternoon. This threat
will likely be conditional on sustained mature convection, but the
transient nature of storms thus far and limited potential for
widespread convection point to low confidence in a robust tornado
threat. Trends will be monitored, but a watch is unlikely.

..Moore/Thompson.. 06/28/2021

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

ATTN...WFO...ILM...CHS...CAE...

LAT...LON   32178052 32448089 33028060 33438017 33777953 33887887
            33717858 33077890 32677937 32407979 32298008 32178052

Mesoscale 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.