Mesoscale Discussion 511

Issued

May 3, 2021, 8:38 PM CDT (01:38 UTC)

Expired

May 3, 2021, 10:45 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

95%

The Little Rock radar (KLZK), 59 km from the middle of the area, began a volume at 01:40 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.

• Severe Thunderstorm Watch 137May 3, 9:10 PM CDT

388 
ACUS11 KWNS 040138
SWOMCD
SPC MCD 040138 
MOZ000-ARZ000-LAZ000-TXZ000-OKZ000-040345-

Mesoscale Discussion 0511
NWS Storm Prediction Center Norman OK
0838 PM CDT Mon May 03 2021

Areas affected...Portions of northeast TX...far southeastern
OK...extreme northwestern LA...much of AR...and far southern MO

Concerning...Severe potential...Watch likely 

Valid 040138Z - 040345Z

Probability of Watch Issuance...95 percent

SUMMARY...The severe threat will increase this evening as storms
approach from the west. Damaging winds should become an increasing
concern. Isolated large hail and a couple tornadoes may also occur.
Watch issuance is very likely.

DISCUSSION...The OOZ sounding from LZK showed a very unstable
airmass is present across much of AR to the south of a front, with
around 3800 J/kg of MLCAPE observed. Robust, severe storms ongoing
across north-central TX and eastern OK are expected to move eastward
this evening into parts of northeast TX, much of AR, and eventually
far southern MO later this evening. With generally upper 60s to mid
70s surface dewpoints and steep mid-level lapse rates in place
across these areas, moderate to strong instability will likely
persist through much of the evening and early overnight hours, even
with the loss of daytime heating. Enhanced mid-level flow associated
with a shortwave trough over the southern Plains will overspread
this region, with around 35-45 kt of effective bulk shear supporting
continued storm organization and intensity.

An ongoing cluster of storms in eastern OK has recently produced a
measured severe wind gust to 71 mph. Current expectations are for
this cluster to continue growing upscale this evening as it moves
into AR, with additional severe storms potentially developing from
north-central into northeast TX. Both large hail and damaging wind
gusts will be a concern given the large reservoir of buoyancy
available. But, scattered to numerous severe/damaging winds will
likely become the primary concern as the storm mode becomes
increasingly linear across AR this evening. Given the steep lapse
rates aloft, there may be some potential for significant severe wind
gusts (75+ mph) if storms form into a bowing complex. Finally, even
though low-level flow is not forecast to be very strong, a couple
tornadoes also appear possible with any embedded circulations given
around 100-150 ms/s2 of effective SRH forecast. With the overall
severe threat expected to increase in the next couple of hours,
watch issuance will be needed.

..Gleason/Thompson.. 05/04/2021

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

ATTN...WFO...PAH...MEG...LZK...SGF...SHV...TSA...

LAT...LON   32939518 34359493 34459440 35439435 36159450 36639325
            36879169 36879078 36749009 36518976 36068982 34949053
            34359109 33579225 32739413 32289497 32169540 32939518

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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.