SPC Sep 18, 2017 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1120 AM CDT Mon Sep 18 2017

Valid 181630Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
WEST TEXAS....

...SUMMARY...
A few strong storms are possible today from west Texas to Missouri,
with isolated severe storms possible mainly over parts of west
Texas.

...West Texas...
A lead short wave trough moving into the central Plains is
associated with several clusters of diminishing thunderstorms from
central Oklahoma into the lower Missouri Valley.  In the wake of
this activity, visible imagery indicates generally clearing skies
over western/central Kansas into western parts of Oklahoma and
Texas.  Oklahoma convection has generated an outflow boundary
extending from extreme southeast Oklahoma westward across north
central Texas into the south plains, with stable low wave clouds
noted across the Panhandle and southwest Oklahoma.  

12Z area soundings at AMA and MAF indicate continuing steep
mid-level lapse rates near 8C/km over west Texas, above a moist PBL
where surface dew points are in the low-mid 60s F.  Strong diabatic
heating in cloud-free areas will contribute to some mixing of the
low-level moisture, but sufficient instability is likely with MLCAPE
reaching 1000-2000 J/kg this afternoon and evening.

Forcing for ascent is expected to be limited, however, water vapor
imagery indicates a weak short-wave perturbation over the
Colorado-New Mexico border region that will move eastward over the
high plains late this afternoon and evening.  Although the 12Z
parent NAM does not develop convection over this area, the 00Z
ECMWF, 12Z GFS and nearly all morning CAMs/HREFv2 initiate
convection over parts of west Texas late this afternoon.  Given the
favorable thermodynamic environment coupled with veering winds with
height /effective shear of 30-35 kt/, isolated severe storms capable
of producing strong wind gusts and hail will be possible during the
21-03Z period.

..Weiss/Leitman.. 09/18/2017

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