Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 261957
SWODY1
SPC AC 261955

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT SAT JUL 26 2014

VALID 262000Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID MO
VALLEY...MID TO UPPER MS VALLEY...OH VALLEY AND SRN GREAT LAKES...

...SUMMARY...
SEVERE STORMS...SOME ACCOMPANIED BY LARGE HAIL...DAMAGING GUSTS AND
A COUPLE OF TORNADOES ARE EXPECTED LATER THIS AFTERNOON THROUGH THIS
EVENING FROM THE MID MISSISSIPPI VALLEY EASTWARD ACROSS THE OHIO
VALLEY. OTHER SEVERE STORMS WILL BE POSSIBLE ACROSS SOUTHEASTERN
NEBRASKA SOUTHEASTWARD INTO NORTHERN MISSOURI WHERE HAIL AND
ISOLATED DAMAGING WIND GUSTS WILL BE POSSIBLE.

SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THIS ISSUANCE DUE
TO LACK OF CONFIDENCE CONCERNING THE DEVELOPMENT OF AN ORGANIZED
SEVERE PRODUCING MCS. THE FIRST CHANGE IS TO REMOVE THE MODERATE
RISK AREA FROM THE UPPER MIDWEST AND OH VALLEY. A VORTICITY MAX IS
EVIDENT ON WATER VAPOR OVER NRN MO. THIS FEATURE IS ASSOCIATED WITH
THUNDERSTORM ACTIVITY THAT HAS YET TO BECOME ORGANIZED. AS THIS
CONVECTION MOVES EWD ACROSS SCNTRL IL AND INTO SRN IND OVER THE NEXT
2 TO 4 HOURS...WIND DAMAGE AND ISOLATED LARGE HAIL MAY OCCUR WITH
THE CELLS THAT CAN INTENSIFY. HOWEVER...THE INITIATION OF SFC-BASED
STORMS TO THE WEST OF THE ORIGINAL MODERATE RISK AREA HAS NOT
MATERIALIZED. THE CURRENT THINKING IS THAT A CLUSTER OF SEVERE
STORMS WILL MOVE EWD ACROSS CNTRL IL INTO SCNTRL IND AND SW OH WHERE
AN ENHANCED WIND DAMAGE THREAT MAY OCCUR...JUSTIFYING A 30 PERCENT
WIND DAMAGE PROBABILITY. THE SECOND CHANGE TO THE OUTLOOK IS TO
REMOVE THE SLIGHT RISK AREA FROM NE NEB AND CNTRL IA IN THE WAKE OF
A PLUME OF CONVECTION IN THE VICINITY OF OMAHA NEB. THE THIRD CHANGE
TO THE OUTLOOK IS TO ADD A 15 PERCENT HAIL PROBABILITY OVER PARTS OF
CNTRL AND NRN OH FOR A CLUSTER OF SEVERE THUNDERSTORMS THAT IS
CURRENTLY IN NW OH AND FAR NE IND. THE FINAL CHANGE TO THE OUTLOOK
IS TO REMOVE THE SLIGHT RISK AREA FROM PARTS OF CNTRL MO WHERE AN
AXIS OF WEAK INSTABILITY IS ANALYZED ASSOCIATED WITH EXTENSIVE CLOUD
COVER FROM AN EXITING VORTICITY CENTER.

..BROYLES.. 07/26/2014

.PREV DISCUSSION... /ISSUED 1153 AM CDT SAT JUL 26 2014/

...POTENTIAL FOR MULTIPLE SEVERE THUNDERSTORM COMPLEXES TO AFFECT
PARTS OF MID/UPPER MS VALLEY INTO OH VALLEY TODAY AND TONIGHT...

MORNING WATER VAPOR LOOPS SHOW THE PRIMARY BAND OF WESTERLIES
EXTENDING ACROSS THE NORTHERN PLAINS INTO THE GREAT LAKES REGION.  A
STRONG UPPER LOW OVER SASK/MANITOBA WILL DEVELOP
SOUTHEASTWARD...WHILE SEVERAL SMALLER SHORTWAVE TROUGHS TRAVEL
ACROSS THE MID/UPPER MS VALLEY INTO THE GREAT LAKES.  THE RESULT
WILL BE SEVERAL POTENTIAL AREAS OF CONCERN FOR SEVERE STORMS
TODAY...AND HIGHER-THAN-USUAL UNCERTAINTY REGARDING WHICH CLUSTER
WILL BE OF GREATEST RISK.

...SD/NEB/WESTERN IA THIS AFTERNOON...
AN INTENSE THUNDERSTORM CLUSTER HAS FORMED THIS MORNING OVER
SOUTHEAST SD.  THESE STORMS ARE EXPECTED TO TRACK SOUTHEASTWARD
THROUGH THE LATE MORNING AND AFTERNOON ACROSS EASTERN NEB AND
WESTERN IA.  THE STORMS HAVE NOT SHOWN ANY SIGNS OF WEAKENING...BUT
IT REMAINS UNCERTAIN IF THIS CLUSTER IS THE START OF A LARGER
LONG-LIVED BOW ECHO EVENT...OR IF THE OUTFLOW FROM THESE STORMS WILL
EVENTUALLY LEAD TO UPSCALE GROWTH LATER TODAY. REGARDLESS...VERY
LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE THROUGH THE
AFTERNOON.

...MO/IL THIS AFTERNOON...
A WEAK REMNANT MCV IS NOTED IN VISIBLE SATELLITE IMAGERY OVER
NORTHEAST KS.  SCATTERED SHOWERS AND THUNDERSTORMS HAVE BEGUN TO
FORM AHEAD OF THIS FEATURE OVER WESTERN MO.  12Z MODEL SOLUTIONS
LEND LESSENED CONFIDENCE THAT THIS GROUP OF CONVECTION WILL BECOME
AN ORGANIZED SEVERE-PRODUCING SYSTEM.  HOWEVER...AMPLE MOISTURE/CAPE
AND INCREASING WINDS ALOFT INDICATE THE RISK OF UPSCALE-GROWTH DOES
EXIST.  IF THESE STORMS MATURED...THEY WOULD LIKELY POSE A RISK OF
SEVERE WIND AND HAIL ACROSS MO INTO IL.

...NORTHERN IL INTO OH THIS AFTERNOON...
A SMALL-SCALE VORTICITY MAX IS SHOWN IN MOST 12Z INITIALIZATIONS
OVER SOUTHERN MN.  THIS FEATURE IS EXPECTED TO TRACK SOUTHEASTWARD
ACROSS NORTHERN IL THIS AFTERNOON AND EVENTUALLY INTO THE OH VALLEY
THIS EVENING.  STRONG INSTABILITY IS DEVELOPING AHEAD OF THIS
SYSTEM...AND IT APPEARS LIKELY THAT SCATTERED THUNDERSTORMS WILL
DEVELOP BY MID AFTERNOON.  IF THIS SCENARIO OCCURS...ISOLATED SEVERE
STORMS INCLUDING DAMAGING WINDS AND HAIL COULD OCCUR IN THIS REGION
THROUGH THE EVENING.

...MO/IL/IND THIS EVENING...
MODELS SOLUTIONS ARE QUITE DIVERSE REGARDING THE LOCATION AND TIMING
OF STRONG CONVECTION BY THIS EVENING.  HOWEVER...GIVEN THE MESOSCALE
ORGANIZATION OF THE SYSTEM OVER NEB...IT APPEARS PROBABLE THAT THIS
CLUSTER OR A REMNANT OUTFLOW WILL CONTINUE TO BE A RISK OF SEVERE
WIND AND HAIL THROUGH THE EVENING.  ITS UNCLEAR WHICH OF THE
AFOREMENTIONED CONVECTIVE CLUSTERS WILL BECOME A DOMINANT RISK
TODAY...BUT THIS SCENARIO WOULD LIKELY POSE THE GREATEST RISK OF
WIDESPREAD DAMAGING WINDS THIS EVENING AND TONIGHT ACROSS THE
MODERATE RISK AREA.




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