Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 190522
SWODY3
SPC AC 190521

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1221 AM CDT Thu Oct 19 2017

Valid 211200Z - 221200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS OK AND
PARTS OF NORTH TX...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHWEST TX
TO EASTERN KS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TX
TO SOUTHWEST IA...

...SUMMARY...
Severe thunderstorms, including large hail and damaging winds, will
develop late Saturday afternoon across eastern Kansas into western
Oklahoma. Severe squall line will progress into the
lower/mid-Mississippi Valley during the overnight hours.

...Texas to Iowa...

Short-range model guidance supports earlier thoughts regarding the
evolution of a strong trough as it progresses across the western US
into the Plains Saturday night. As the trough approaches the Plains,
LLJ will strengthen markedly ahead of a pronounced cold front, and
higher-PW plume will surge north across TX into portions of the
eastern central Plains where values could approach 1.5". Latest data
suggests a sharp front will extend from western MN, southwest across
central KS into the northern TX Panhandle at 18z, then into eastern
KS-central OK-northwest TX by 22/00z. This boundary will be the
focus for organized severe thunderstorms as it surges southeast.

Early-day capping will suppress convection along the front until mid
afternoon across eastern KS/western IA where inhibition will weaken
sufficiently for frontal convection, most likely by 21z. Farther
southwest along the boundary into western OK, strong surface heating
should contribute to steeper low-level lapse rates as temperatures
warm into the upper 70s/lower 80s. Substantial SBCAPE (2500-3000
J/kg) is forecast across western OK prior to convective initiation
and strengthening shear profiles suggest initial convection across
this region could be supercellular in nature. However, strong
large-scale forcing for ascent will contribute to a rapidly maturing
squall line that should encompass the frontal zone from eastern KS
into southwest OK by 22/00z. Elongated MCS, with possible bow-type
structures, should surge east-southeast toward AR and northeast TX
during the overnight hours. While a tornado or two can not be ruled
out given the forecast shear, damaging winds may ultimately be the
greatest risk with this convection. Additionally, very large hail
could accompany supercells that develop early in the convective
cycle over the southern Plains.

..Darrow.. 10/19/2017

$$


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