Mesoscale Discussion 121

Issued

Feb 18, 2021, 11:35 AM EST (16:35 UTC)

Expired

Feb 18, 2021, 1:30 PM EST

In force

115 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 11

Counties Gadsden County, FL, Jefferson County, FL, Leon County, FL, Liberty County, FL, Wakulla County, FL, Berrien County, GA, Brooks County, GA, Colquitt County, GA, Cook County, GA, Grady County, GA, Irwin County, GA, Lowndes County, GA, Mitchell County, GA, Thomas County, GA, Tift County, GA, Worth County, GA

The Tallahassee radar (KTLH), 53 km from the middle of the area, began a volume at 16:38 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.

222 
ACUS11 KWNS 181636
SWOMCD
SPC MCD 181635 
GAZ000-FLZ000-181830-

Mesoscale Discussion 0121
NWS Storm Prediction Center Norman OK
1035 AM CST Thu Feb 18 2021

Areas affected...the central through eastern Florida Panhandle
through southern Georgia

Concerning...Tornado Watch 11...

Valid 181635Z - 181830Z

The severe weather threat for Tornado Watch 11 continues.

SUMMARY...The threat for severe storms will probably remain marginal
through about 18Z, followed by a gradual increase during the
afternoon. The primary risk will be a couple of tornadoes and
locally strong wind gusts.

DISCUSSION...As of late morning a band of scattered showers and a
few embedded thunderstorms continue from the central FL Panhandle
through southwest and south central GA. Activity is developing along
the warm conveyor belt associated with a southwesterly 40-50 kt
low-level jet. A cold front extends southwestward into the northern
Gulf from a weak surface low in southwest GA. A warm front resides
across southern GA and should continue slowly north during the day.
Widespread clouds, mostly in the form of anvil debris, have spread
across the western portion of the warm sector, slowing boundary
layer warming. Mid level lapse rates are very weak (less than 6
C/km), but as the surface layer warms, MLCAPE from 600-1200 J/kg is
expected. As the atmosphere destabilizes, a gradual increase in
thunderstorm intensity may occur this afternoon. Tendency will be
for the low-level winds to veer with time, which will result in a
decrease in low-level hodograph size and 0-1 km storm relative
helicity generally from 150-250 m2/s2, with the larger hodographs in
vicinity of the warm front. Effective bulk shear from 40-45 kt will
remain supportive of some updrafts to develop rotation. 

The marginal thermodynamic environment and tendency for the
low-level winds to veer with time should serve as limiting factors
for a more robust severe threat. Nevertheless, the environment may
still become supportive of supercells and a couple of tornadoes
along with a few locally strong wind gusts this afternoon.

..Dial.. 02/18/2021

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

ATTN...WFO...JAX...FFC...TAE...

LAT...LON   30158506 31098439 31568386 31788299 31338289 30548348
            29878463 30158506

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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.