Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 272152
SWOMCD
SPC MCD 272151
OKZ000-TXZ000-272215-

Mesoscale Discussion 0873
NWS Storm Prediction Center Norman OK
0451 PM CDT Sat May 27 2017

Areas affected...the eastern half of Oklahoma

Concerning...Tornado Watch 279...

Valid 272151Z - 272215Z

The severe weather threat for Tornado Watch 279 continues.

SUMMARY...An extremely unstable airmass is in place across the
eastern half of Oklahoma.  Once surface-based convective initiation
begins, explosive thunderstorm development will lead to rapid
supercell evolution with isolated storm coverage expected.

DISCUSSION...Visible-satellite imagery shows a bubbling cumulus
field across the eastern half of Oklahoma with a mid-level ACCAS
field across central OK into the greater Tulsa metro.  Eroding
convective inhibition will gradually prove more favorable for a
couple of thunderstorms to develop over the next several hours.  20Z
NSSL mobile soundings in Stephens County, OK and in Ardmore, OK
showed extreme buoyancy with 6317 J/kg and 6474 J/kg MLCAPE,
respectively.  The Ardmore 20Z sounding displayed a negligible
remaining capping inversion.  Effective shear of 48-kt was sampled
with both soundings.  In summary, explosive thunderstorm development
is expected with giant hail an initial risk with the updrafts.
Middle to upper 70s degrees F dewpoints and forecast 100-200 m2/s2
0-1 km SRH around 00Z and thereafter will yield a tornado risk
(perhaps intense) once established supercells are present.

..Smith.. 05/27/2017

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

ATTN...WFO...TSA...FWD...OUN...

LAT...LON   33959755 35909752 36929633 36919465 33949645 33959755




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