Mesoscale Discussion 671

Issued

May 18, 2021, 1:18 PM CDT (18:18 UTC)

Expired

May 18, 2021, 3:15 PM CDT

In force

117 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

The Ft Hood radar (KGRK), 83 km from the middle of the area, began a volume at 18:21 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.

• Tornado Watch 188May 18, 2:30 PM CDT

225 
ACUS11 KWNS 181818
SWOMCD
SPC MCD 181818 
TXZ000-182015-

Mesoscale Discussion 0671
NWS Storm Prediction Center Norman OK
0118 PM CDT Tue May 18 2021

Areas affected...Portions of south-central into east-central/coastal
TX

Concerning...Severe potential...Watch possible 

Valid 181818Z - 182015Z

Probability of Watch Issuance...60 percent

SUMMARY...A threat for large hail, damaging wind gusts, and perhaps
a couple of tornadoes should increase this afternoon. Watch issuance
will probably be needed.

DISCUSSION...As of 1815Z an outflow boundary from earlier convection
extends from parts of south-central into east-central TX. Recent
visible satellite imagery shows this boundary has slowed, and it may
not make much more southeastward progress this afternoon. Mostly
clear skies ahead of the outflow boundary have allowed robust
diurnal heating to occur, with surface temperatures generally
warming into the low to mid 80s. A rather moist low-level airmass
characterized by surface dewpoints in the mid to upper 60s also
exists across this region. Continued heating of this moist airmass
coupled with somewhat steepened mid-level lapse rates will likely
support MLCAPE of 1500-2500 J/kg by late afternoon. Around 25-35 kt
of southwesterly mid-level flow associated with an upper low over
the southern/central High Plains should foster similar values of
deep-layer shear. Current expectations are for storms to gradually
increase in both coverage and intensity along/near the outflow
boundary this afternoon as convective inhibition continues to erode.
A mixed mode of supercell and multicell structures appears likely,
with both large hail and damaging wind gusts possible. Storms may
have a tendency to congeal into a bowing cluster with time, and
severe/damaging winds may eventually become the main threat. Some
risk for a couple of tornadoes could also exist with storms near the
outflow boundary where low-level flow and shear may be modestly
enhanced. A watch will probably be needed in the next couple of
hours, dependent on convective trends.

..Gleason/Guyer.. 05/18/2021

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

ATTN...WFO...HGX...FWD...CRP...EWX...

LAT...LON   29149642 28379788 28399855 29379916 29929899 30189823
            30589726 31129664 31679593 31689546 31359503 30959481
            29919537 29149642

Mesoscale Discussions in Texas, 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.