Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 211254
SWODY1
SPC AC 211252

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT TUE APR 21 2015

VALID 211300Z - 221200Z

...THERE IS A MRGL RISK OF SVR TSTMS W TX TO SRN PORTIONS KS/MO...

...SUMMARY...
A FEW THUNDERSTORMS MAY PRODUCE HAIL AND/OR GUSTS NEAR SEVERE LIMITS
THIS AFTERNOON AND EVENING OVER SOME OF SOUTHERN KANSAS AND
MISSOURI.  ISOLATED STRONG TO SEVERE HAIL AND THUNDERSTORM GUSTS ARE
ALSO POSSIBLE THIS AFTERNOON THROUGH TONIGHT OVER THE SOUTHERN HIGH
PLAINS AND INTO WESTERN OKLAHOMA.

...SYNOPSIS...
UPPER-AIR PATTERN IS CHARACTERIZED BY SPLIT FLOW OVER WRN NORTH
AMERICA AND LARGE AREA OF CYCLONIC FLOW E OF ROCKIES.  LATTER FLOW
FIELD IS RELATED TO MID/UPPER-LEVEL LOW INITIALLY LOCATED OVER WRN
LS.  CYCLONE IS FCST TO MOVE SLOWLY ENEWD ACROSS LS AND PARTS OF ONT
TO ITS NE THROUGH REMAINDER PERIOD...ORBITED BY SEVERAL SHORTWAVE
PERTURBATIONS AND ACCOMPANYING VORTICITY MAXIMA.  HIGH-AMPLITUDE
RIDGING NOW OVER INLAND PAC NW AND WRN CANADA IS FCST TO SHIFT EWD
AS TROUGH NOW OVER NERN PAC MOVES ASHORE BC AND AMPLIFIES SEWD OVER
PAC NW COAST.  AS THIS OCCURS...WEAK SRN-STREAM LOW -- NOW NEAR CA
CHANNEL ISLANDS -- WILL MOVE SLOWLY INLAND/NEWD AND REACH SRN SIERRA
BY 12Z.  FOREGOING SHORTWAVE RIDGE -- CURRENTLY LOCATED FROM NRN AZ
SEWD ACROSS CHIHUAHUA -- WILL MOVE NEWD TO SRN HIGH PLAINS BY END OF
PERIOD.  VORTICITY MAX ASSOCIATED WITH WEAK SHORTWAVE TROUGH --
EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER PAC NEAR 28N125W -- WILL
PIVOT CYCLONICALLY AROUND SRN SEMICIRCLE OF CA PERTURBATION THEN
MOVE OVER NWRN MEX AFTER 00Z...REACHING NM/MEX BORDER AROUND 12Z.

AT SFC...LEADING COLD FRONT HAS MOVED OFFSHORE MID ATLC AND EXTENDS
SWWD OVER NC OUTER BANKS REGION TO NRN FL AND N-CENTRAL/W-CENTRAL
GULF S BRO.  COLD FRONT SHOULD MOVE SEWD ON FL PENINSULA WHILE
WEAKENING/DECELERATING.  GULF PORTION OF COLD FRONT LIKEWISE WILL
WEAKEN...WITH WRN SEGMENT SOON RETURNING NWD ACROSS S TX AS DIFFUSE
WARM FRONT.  SECONDARY COLD FRONT -- NOW DEVELOPING OVER NRN PLAINS
-- IS EXPECTED TO STRENGTHEN AND MOVE SEWD TO NRN MO...SRN NEB AND
CENTRAL WY BY 00Z...REACHING KY...SRN MO/NRN AR OZARKS...AND WRN OK
BY 12Z.  OVERNIGHT...WEAK SFC LOW IS EXPECTED TO DEVELOP OVER TX
PANHANDLE...IN ZONE OF WARM FRONTOGENESIS EXTENDING ESEWD ACROSS SRN
OK.  THIS LOW MAY LINK WITH WRN SEGMENT OF SECONDARY COLD FRONT BY
12Z.  AS MOISTURE RETURNS NWD THROUGH TX...DRYLINE SHOULD DEVELOP
FROM S-N ACROSS W TX.

...KS/MO AREA...AFTN/EARLY EVENING...
DIABATIC SFC HEATING...STEEP MIDLEVEL LAPSE RATES...AND PW
INCREASING INTO MRGL .5-INCH TO .75-INCH RANGE WILL SUPPORT
DEVELOPMENT OF WEAKLY INHIBITED MLCAPE IN 250-500 J/KG RANGE THIS
AFTN AHEAD OF SECONDARY COLD FRONT...NEAR PREFRONTAL
TROUGH/CONFLUENCE LINE.  THOUGH BUOYANCY WILL BE LIMITED BY LACK OF
GREATER MOISTURE...FAVORABLE DEEP SHEAR AND ELONGATED/NEARLY
STRAIGHT-LINE HODOGRAPHS MAY SUPPORT BRIEF SVR POTENTIAL WITH ANY
SUSTAINED TSTMS.  ONSET OF NOCTURNAL LLJ AND IMPINGEMENT OF COMBINED
COLD-FRONTAL ZONE AND WARM-FRONTOGENETIC REGIME MAY HELP TO CONTINUE
SOME TSTMS ON WRN LIMB OF THIS PROCESS INTO EVENING OVER SRN
KS...PERHAPS MERGING INTO INITIALLY SEPARATE NOCTURNAL CONVECTIVE
REGIME DESCRIBED BELOW.

...SRN HIGH PLAINS...LATE AFTN THROUGH OVERNIGHT HOURS...
ISOLATED TSTMS MAY FORM OVER HIGHER TERRAIN OF ERN NM AND MOVE EWD
INTO INCREASING MOISTURE...AND/OR INVOF SHARPENING DRYLINE.  ANY
ACTIVITY THAT DOES DEVELOP WILL OCCUR ATOP WELL-MIXED SUBCLOUD
LAYERS THAT WILL SUPPORT MAINTENANCE TO SFC OF ANY HAIL/GUSTS
GENERATED ALOFT..INCLUDING SOME DOWNDRAFT ACCELERATION.  DESPITE
INCREASE IN PW...SUPPORT FOR CONVECTION WILL BE MRGL WITH ONLY 40S
TO LOWER 50S SFC DEW POINTS REALIZED BEFORE DUSK.  LACK OF MORE
ROBUST MOISTURE AND OF SUBSTANTIAL UPPER-LEVEL SUPPORT WILL LIMIT
ORGANIZED SVR POTENTIAL.

LATE IN PERIOD...PROBABLY AFTER 06Z...TSTMS ROOTED ABOVE SFC SHOULD
DEVELOP AROUND ERN TX PANHANDLE OR NWRN OK.  THIS AREA WILL RESIDE
NEAR JUXTAPOSITION OF SEVERAL IMPORTANT SOURCES OF LIFT AT VARIOUS
SCALES--COLD FRONT...ELEVATED WARM FRONT...AND NRN RIM OF 30-40 KT
LLJ ASSOCIATED WITH SUBSTANTIAL LOW-LEVEL WAA AND INCREASING
MOISTURE.  THIS ACTIVITY MAY CONTINUE SEWD OVER OK INTO DAY-2 PERIOD
AND INFLUENCE DEVELOPMENT/EVOLUTION OF MORE WIDESPREAD/SFC-BASED/SVR
MCS DISCUSSED IN THAT OUTLOOK.

..EDWARDS/PICCA.. 04/21/2015



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