Mesoscale Discussion 894

Issued

May 28, 2017, 2:53 AM CDT (07:53 UTC)

Expired

May 28, 2017, 5:00 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

The Western Arkansas radar (KSRX), 169 km from the middle of the area, began a volume at 07:53 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.

299 
ACUS11 KWNS 280754
SWOMCD
SPC MCD 280753 
LAZ000-ARZ000-TXZ000-OKZ000-281000-

Mesoscale Discussion 0894
NWS Storm Prediction Center Norman OK
0253 AM CDT Sun May 28 2017

Areas affected...portions of northern Texas east across the Arklatex
region...and north into eastern Oklahoma

Concerning...Severe Thunderstorm Watch 289...

Valid 280753Z - 281000Z

The severe weather threat for Severe Thunderstorm Watch 289
continues.

SUMMARY...Severe risk continues in and near WW 289.

DISCUSSION...Latest radar loop shows convective outflow sagging
south across north Texas, in advance of a west-to-east band of
storms extending from the Montague/Jack/Wise County vicinity
eastward, roughly along the Red River.  Meanwhile, a somewhat
disorganized bowing segment on the eastern fringe of the
aforementioned Red River band of storms continues moving east across
southwest AR.  

Convection continues moving generally eastward across southwest
Arkansas, but has been more hesitant to expand southward, likely due
to capping -- evident on both FWD and SHV 00Z RAOBs.  While ascent
associated with the convective outflow is likely acting to gradually
weaken the cap, diurnal diabatic cooling of the boundary layer is
acting in opposition, i.e. providing an at least somewhat-offsetting
increase in inhibition for surface-based parcels.

Overall, CAM guidance suggests the capping issue, with little hint
of appreciable southward spread of storms over the next few hours. 
Though largely not modeling the existing convection well, the lack
of convection south of the Red River vicinity within the model
solutions add some credence to the idea that the southward spread of
storms into Louisiana, and additional expansion of severe risk
across north Texas, will likely be slow to occur, with an overall
decrease in convective intensity likely to gradually manifest over
the next several hours.  Where storms are ongoing however, and
immediately to the south and east, risk for large hail and locally
damaging winds persists.

Farther north into east central OK, a few elevated storms developed
earlier, posing isolated large-hail risk, but this convection has
trended downward over the past hour and additional increases in this
activity appear unlikely at this time.

..Goss.. 05/28/2017

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

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

LAT...LON   32929773 33289801 33599795 33759717 33829656 34139607
            34569608 34889614 35319609 35709590 35599494 35579419
            35069413 34349409 33919329 33079196 32619218 32559397
            32929773

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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.