Mesoscale Discussion 899

Issued

Jun 9, 2021, 3:22 PM CDT (20:22 UTC)

Expired

Jun 9, 2021, 4:15 PM CDT

In force

53 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

5%

The Western Arkansas radar (KSRX), 87 km from the middle of the area, began a volume at 20:21 UTC, the scan nearest the moment this went out.

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248 
ACUS11 KWNS 092023
SWOMCD
SPC MCD 092022 
ARZ000-OKZ000-092115-

Mesoscale Discussion 0899
NWS Storm Prediction Center Norman OK
0322 PM CDT Wed Jun 09 2021

Areas affected...eastern OK...western into central AR

Concerning...Severe potential...Watch unlikely 

Valid 092022Z - 092115Z

Probability of Watch Issuance...5 percent

SUMMARY...A few storms are possible this afternoon.  Updrafts that
root in the boundary layer and become sustained/surface-based, will
likely pose at least an isolated risk for large hail/severe gusts. 
The overall coverage of potential severe weather will likely
preclude the need for a severe thunderstorm watch.

DISCUSSION...Visible satellite imagery shows a few thunderstorms
initiating over north-central and central AR with another attempt at
CI over eastern OK.  This region was subjectively analyzed with 12z
raob data and model data as having higher 700 mb moisture content
compared to central OK and southwest MO.  Surface temperatures as of
20z are in the upper 80s with mid-upper 70s deg F dewpoints.  The
airmass is characterized as extremely unstable with 4000 J/kg MLCAPE
over central AR to around 5000 J/kg over eastern OK.  Large-scale
forcing for ascent is considered weak, but a weak upper-level trough
noted on water-vapor imagery and RAP-analyzed 250-mb PV, appears to
be associated with the initial attempts at CI over eastern OK, and
this forcing influence perhaps extends as far east as north-central
AR.  

Both the Tulsa, OK and Fort Smith, AR WSR-88D VAD show
east-southeasterly surface flow veering to northwesterly at 20 kt
around 3 km ARL.  The latest RAP model forecast soundings show 25-30
kt effective shear across eastern OK into central AR.  

It remains unclear whether sustained storms will evolve across
north-central AR westward into eastern OK.  However, given the
magnitude of CAPE/shear, any sustained storm would pose at least
some risk for large hail/severe gusts.

..Smith/Guyer.. 06/09/2021

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

ATTN...WFO...LZK...TSA...

LAT...LON   34299231 35109520 35579563 36049521 35909257 35639220
            34649191 34299231

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