Mesoscale Discussion 1543

Issued

Aug 17, 2021, 8:22 AM EDT (12:22 UTC)

Expired

Aug 17, 2021, 10:15 AM EDT

In force

113 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 443

The Greer radar (KGSP), 111 km from the middle of the area, began a volume at 12:24 UTC, the scan nearest the moment this went out.

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• Tornado Watch 444Aug 17, 10:40 AM EDT

441 
ACUS11 KWNS 171223
SWOMCD
SPC MCD 171222 
SCZ000-GAZ000-171415-

Mesoscale Discussion 1543
NWS Storm Prediction Center Norman OK
0722 AM CDT Tue Aug 17 2021

Areas affected...Parts of northeast and east central Georgia into
western South Carolina

Concerning...Tornado Watch 443...

Valid 171222Z - 171415Z

The severe weather threat for Tornado Watch 443 continues.

SUMMARY...The development of isolated supercell structures with the
potential to produce short-lived tornadoes remains possible to the
northeast of the weakening remnants of Fred.  This may gradually
spread across the remainder of northeastern Georgia into Upstate
South Carolina by 10 am-12 pm EDT.  Trends are being monitored for
the possibility of a new watch, but it is also possible that the
threat may become marginal and/or isolated enough that a new watch
may not be needed.

DISCUSSION...More substantive central pressure rises have been
occurring the past few hours as Fred migrates northward.  A
corresponding weakening of low-level wind fields has also been
observed, and these trends are likely to continue as the depression
progresses north-northeast of the Auburn, AL vicinity, toward the
Greater Atlanta metro through 14-16Z.  

Mid-level subsidence warming nosing northeastward around the
southern through eastern periphery of the circulation aloft is
contributing to diminishing convective potential across the Warner
Robins/Macon vicinity into the Greater Atlanta area, and this is
forecast to continue spreading toward the Savannah River through mid
to late morning.  This also corresponds with a weak surface wind
shift, and the onset more unidirectional shear in the near surface
layer.

Ahead of the wind shift, strongest mid/upper forcing for ascent,
low-level convergence and largest clockwise-curved low-level
hodographs will generally be focused in an area overspreading
northeastern Georgia into Upstate South Carolina through 14-16Z. 
Although wind fields are gradually weakening, southerly 850 mb flow
on the order of 30+ kt may still contribute to sufficiently large
low-level hodographs to maintain at least some risk for the
development of supercell structures with the potential to produce 
tornadoes.  This probably will be aided by at least some further
increase of surface dew points through the lower to mid 70s F across
parts of the Piedmont.

..Kerr.. 08/17/2021

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

ATTN...WFO...CAE...GSP...FFC...

LAT...LON   34458355 34918266 34188175 33458189 32948238 33708311
            34068367 34458355

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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.