Severe Storm Outlook Narrative (AC)
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106
ACUS11 KWNS 221955
SWOMCD
SPC MCD 221954
OKZ000-TXZ000-NMZ000-222230-

Mesoscale Discussion 1553
NWS Storm Prediction Center Norman OK
0254 PM CDT Tue Aug 22 2017

Areas affected...Portions of OK...north TX...the TX Panhandle/South
Plains...eastern NM

Concerning...Severe potential...Watch unlikely

Valid 221954Z - 222230Z

Probability of Watch Issuance...5 percent

SUMMARY...An isolated severe-thunderstorm risk is expected to exist
into the late afternoon and early evening hours. Watch issuance will
be unlikely.

DISCUSSION...The following zones will be focus areas for convective
deepening into the late afternoon hours:
(1) an outflow boundary arcing from east-central OK toward the Tulsa
area,
(2) differential-heating-induced baroclinicity on the warm-side
fringes of a multi-layered cloud band from the Wichita Falls and
Lawton areas toward Norman and Tulsa,
(3) modest synoptic frontal convergence from east-central NM into
west-central OK (convectively influenced in NM), and
(4) deeper baroclinicity along a stronger-frontal segment just south
of the northeast OK/southeast KS border.

Modifications to the 17Z and 18Z observed soundings across the area
suggest that capping aloft continues to erode as pockets of at least
filtered insolation continue on the warm sides of the aforementioned
zones of convective initiation. Related convective inflow is
becoming increasingly buoyant, with MLCAPE increasing to
1000-2500 J/kg -- highest magnitudes where insolation has been
strongest. While pockets of ongoing clouds are locally muting
diabatic surface-layer heating in parts of OK, eventually
strengthening/expanding cold pools will likely breed growing
convective coverage/intensity during the next few hours across the
entire area, amid DCAPE upwards of 1000-1250 J/kg. Sporadic severe
wind gusts may accompany collapsing convective cores into the
evening hours, though weak effective shear will limit convective
organization and severe coverage. The isolated severe risk will tend
to spread southward with time owing to preferential growth of
incipient updrafts into the more buoyant air with southward extent
across the region.

..Cohen/Elliott/Grams.. 08/22/2017

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

ATTN...WFO...SHV...TSA...FWD...OUN...SJT...LUB...AMA...MAF...
ABQ...

LAT...LON   33840383 34620356 34940281 34960169 35349935 36539704
            36589615 36359557 35749487 34939453 34069472 33379632
            33029946 33230259 33840383




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