Mesoscale Discussion 864

Issued

Jun 7, 2021, 1:37 AM CDT (06:37 UTC)

Expired

Jun 7, 2021, 3:00 AM CDT

In force

83 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 240

The Dyess AFB radar (KDYX), 122 km from the middle of the area, began a volume at 06:39 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 241Jun 7, 2:45 AM CDT

115 
ACUS11 KWNS 070637
SWOMCD
SPC MCD 070637 
TXZ000-OKZ000-070800-

Mesoscale Discussion 0864
NWS Storm Prediction Center Norman OK
0137 AM CDT Mon Jun 07 2021

Areas affected...Parts of the Texas South Plains and Big Country
into southwestern Oklahoma

Concerning...Severe Thunderstorm Watch 240...

Valid 070637Z - 070800Z

The severe weather threat for Severe Thunderstorm Watch 240
continues.

SUMMARY...At least scattered thunderstorms posing a risk for locally
strong surface gusts and marginally severe hail will overspread and
develop across the much of the Texas Big Country and adjacent
portions of the Red River Valley through 3-5 AM CDT.  It is not
certain that another watch is needed, but trends are being monitored
for this possibility.

DISCUSSION...Widely scattered ongoing strong storms are propagating
southeastward around 20 kt, a bit faster than than the 10-15 kt
deep-layer westerly mean ambient wind field in which they are
embedded.  This is likely being supported by a modest (20-30 kt)
southerly 850 mb jet across the Edwards Plateau into the South
Plains and Big Country, which is contributing to relatively strong
southeasterly low-level storm-relative inflow.  

The downstream boundary layer is seasonably moist, with steep
lower/mid tropospheric lapse rates associated with elevated
mixed-layer air contributing large CAPE as high as 3000-4000 J/kg. 
This provides potential for substantive further thunderstorm
intensification and upscale growth along the leading edge of
southeastward advancing, consolidating cold pools.  However, the
inhibition associated with the elevated mixed-layer air also appears
strong, and as the low-level jet gradually veers from southerly to
southwesterly through 08-10Z, weakening convergence may result in
diminishing convective intensity on the forward propagating flank of
the cold pools.

Even if ongoing storms do weaken/dissipate, warm advection above the
cold pools, in the wake of this activity, could support renewed
vigorous thunderstorm development, with the potential to produce
marginally severe hail and locally strong surface gusts.

..Kerr.. 06/07/2021

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

ATTN...WFO...FWD...OUN...SJT...LUB...MAF...

LAT...LON   32540107 32890112 33230082 33690070 34060042 34430058
            34779986 34549876 32889842 31849890 31900093 32540107

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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.