Mesoscale Discussion 463

Issued

Apr 28, 2021, 9:19 PM CDT (02:19 UTC)

Expired

Apr 28, 2021, 11:15 PM CDT

In force

116 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 121

The Western Arkansas radar (KSRX), 181 km from the middle of the area, began a volume at 02:18 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.

483 
ACUS11 KWNS 290220
SWOMCD
SPC MCD 290219 
ARZ000-TXZ000-OKZ000-290415-

Mesoscale Discussion 0463
NWS Storm Prediction Center Norman OK
0919 PM CDT Wed Apr 28 2021

Areas affected...Eastern Oklahoma...western Arkansas...northeast
Texas...and northwest Louisiana

Concerning...Tornado Watch 121...

Valid 290219Z - 290415Z

The severe weather threat for Tornado Watch 121 continues.

SUMMARY...The risk for severe weather continues across WW 121.
Thunderstorms are expected to increase in coverage across the
Arklatex region over the next few hours. Isolated severe storms are
expected to continue across portions of central Oklahoma and
north-central Texas.

DISCUSSION...Recent regional radar trends have shown an increase in
storm coverage across the Arklatex region, likely the result of
increasing isentropic ascent between 850-700 mb. Storms will
gradually become organized as they begin to mature in an environment
characterized by 1000-1500 J/kg MLCAPE and 50-60 knots of effective
bulk shear. Despite some boundary-layer stabilization, effective SRH
values remain elevated between 200-400 m2/s2 from northeast TX into
eastern OK/western AR. KSRX VWP observations support this idea with
nearly 500 m2s2 0-1 km SRH noted, and a nearby supercell has taken
on transient low-level rotation. As such, the tornado potential
should continue over the next few hours for all of WW 121. 

To the west, isolated supercells have developed along a weak cold
frontal boundary from central OK into northern TX. Hail up to 2
inches has been reported with some of this activity (particularly in
the OKC metro area). This activity will likely persist as it
translates eastward into a most unstable air mass, and will continue
to pose a severe hail and wind risk. While one or two additional
cells are possible, storm coverage should remain isolated enough to
negate the need for an new watch.

..Moore.. 04/29/2021

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

ATTN...WFO...LZK...SHV...TSA...FWD...OUN...

LAT...LON   32869769 34189677 35079594 35939476 35929388 35619356
            34829339 33999367 33199398 32749444 32489522 32339672
            32429744 32869769

Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Oklahoma, 2021Mesoscale Discussions in Arkansas, 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.