Severe Storm Outlook Narrative (AC)
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919
ACUS11 KWNS 232016
SWOMCD
SPC MCD 232015
ARZ000-OKZ000-TXZ000-232245-

Mesoscale Discussion 1410
NWS Storm Prediction Center Norman OK
0315 PM CDT Sun Jul 23 2017

Areas affected...Portions of central and southern
Oklahoma...Arkansas...north Texas

Concerning...Severe potential...Watch unlikely

Valid 232015Z - 232245Z

Probability of Watch Issuance...5 percent

SUMMARY...The risk for thunderstorm downbursts producing sporadic
severe wind gusts will exist through the early evening hours. Watch
issuance will not be necessary.

DISCUSSION...Convergence along a composite front -- composed of
synoptic baroclinicity augmented by convective outflow and
differential heating -- will focus continued isolated to scattered
convective development from parts of west-central OK to the Mid
South. Additional convective development continues amidst the
uncapped, moist boundary layer farther south toward the Red River.
Low-level lapse rates on the warm/hot side of the front have
appreciably steepened -- e.g., 8-9 C/km in the lowest 3 km. This has
contributed to the development of 2000-3000 J/kg of MLCAPE amidst
surface dewpoints holding in the upper 60s to middle 70s in many
areas.

The aforementioned magnitude of buoyancy will likely support a few
intense updrafts, strengthening through late afternoon and
continuing into the early evening. Weak effective shear --
i.e., around 20 kt -- will contribute to poorly organized convective
modes. However, a few loosely organized multicell clusters could
evolve from far east-central OK to the Mid South region -- on the
edge of a band of cyclonic mid-level flow surrounding a Great Lakes
area trough. The most intense convection may produce isolated severe
wind gusts, owing to DCAPE breaching 1500 J/kg in many areas,
especially with collapsing cells and where small-scale cold-pool
amalgamation enhances storm-scale vertical circulations.

Cells/clusters will spread eastward to southward, with preferential
cell development focusing along southern-flanking outflow where
unperturbed buoyancy will be greatest. The isolated severe-wind risk
will continue into the early evening.

..Cohen/Grams.. 07/23/2017

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

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

LAT...LON   35249964 35419771 35469477 35589218 35699042 34919051
            34299139 33859329 33759554 33789760 34239938 34659988
            35249964




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