Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS11 KWNS 181853
SWOMCD
SPC MCD 181852
OKZ000-TXZ000-KSZ000-182045-

MESOSCALE DISCUSSION 0355
NWS STORM PREDICTION CENTER NORMAN OK
0152 PM CDT SAT APR 18 2015

AREAS AFFECTED...PORTIONS OF SOUTH-CENTRAL KS...WESTERN AND CENTRAL
OK...NORTHERN TX

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181852Z - 182045Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...THE SEVERE THREAT IS INCREASING FROM SOUTH-CENTRAL KS
ACROSS WESTERN AND CENTRAL OK INTO NORTH TX. LARGE HAIL WILL BE THE
MAIN THREAT AS SUPERCELLS STORMS TRACK EASTWARD ACROSS THE MCD AREA.
HOWEVER...A TORNADO OR TWO CANNOT BE RULES OUT. A WATCH WILL LIKELY
BE NEEDED IN THE NEXT HOUR OR TWO.

DISCUSSION...THE SEVERE THREAT ACROSS THE MCD AREA IS INCREASING
THIS AFTERNOON AND A WATCH WILL LIKELY BE NEED WITHIN THE NEXT HOUR
OR SO. A SURFACE DRYLINE WAS ANALYZED FROM THE EASTERN OK/TX
PANHANDLES SOUTH/SOUTHWEST TO THE TX BIG BEND AREA. FURTHER
EAST...AN OUTFLOW BOUNDARY WAS LOCATED FROM PARTS OF SOUTH-CENTRAL
KS INTO CENTRAL OK. SOME STRONG THUNDERSTORMS HAD DEVELOPED ALONG
THE BOUNDARY...BUT THIS IS NOT EXPECTED TO BE THE MAIN FOCUS OF
SEVERE THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND EVENING.
THUNDERSTORMS ARE EXPECTED TO DEVELOP NEAR THE DRYLINE BY 22Z AND
QUICKLY BECOME SEVERE AS THEY TRACK EASTWARD INTO SOUTH-CENTRAL
KS...WESTERN OK AND NORTH TX. HIGH RESOLUTION MODELS SUGGEST THE
CURRENT SOUTHWESTERLY LOW LEVEL WINDS ACROSS WESTERN OK INTO WESTERN
NORTH TX BECOME BECOME SOUTHEASTERLY BEFORE CONVECTIVE INITIATION
OCCURS. IN FACT...18Z SURFACE OBS AT SPS AND GAG HAVE BECOME
SOUTHEASTERLY AT AROUND 5-15 KT. THIS IS LIKELY DUE TO WEAK
CYCLOGENESIS JUST AHEAD OF THE DRYLINE DUE TO WEAK HEIGHT FALLS
RESULTING FROM A BRANCH OF VORTICITY EJECTING ACROSS THE TX SOUTH
PLAINS INTO WESTERN OK. AS A RESULT...A NARROW CORRIDOR MAY EXIST
WHERE THE TORNADO THREAT WILL BE ENHANCED BRIEFLY ACROSS
SOUTHWESTERN OK. THIS MAY RESULT IN THE NEED FOR A SMALL TORNADO
WATCH ACROSS THIS AREA...WITH A SEVERE THUNDERSTORM WATCH FROM
SOUTH-CENTRAL KS THROUGH CENTRAL OK INTO NORTH TX.

OTHERWISE...MODERATE INSTABILITY NEAR 2000+ J/KG SBCAPE COUPLED WITH
STEEP MIDLEVEL LAPSE RATES WILL LEAD TO A SEVERE HAIL THREAT.
ALTHOUGH LOW LEVEL FLOW IS MODEST...STEEPENING LOW LEVEL LAPSE RATES
WITH ADDITIONAL HEATING COULD ALSO AID IN SOME STRONG TO LOCALLY
DAMAGING WINDS WITH THE STRONGEST STORMS.

..LEITMAN/HART.. 04/18/2015

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ICT...FWD...OUN...DDC...SJT...LUB...

LAT...LON   34429764 32819763 32089785 31939811 31779864 31679941
            31940036 32360061 33280005 34009994 35869996 37880002
            38079936 37799877 36699810 35469762 34429764



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