Moderate Risk for Iowa, Nebraska and Kansas

   SPC AC 121611

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1111 AM CDT MON MAY 12 2014

   VALID 121630Z - 131200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER GREAT LAKES TO
   TX...

   ...SUMMARY...
   CLUSTERS OF STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE TODAY FROM
   WISCONSIN AND LOWER MICHIGAN SOUTHWARD ACROSS PARTS OF THE MID-
   MISSISSIPPI VALLEY INTO THE SOUTHERN PLAINS.

   ...SYNOPSIS...

   A HIGH-AMPLITUDE AND ONLY SLIGHTLY PROGRESSIVE PATTERN WILL PERSIST
   OVER NORTH AMERICA THROUGH THE DAY ONE PERIOD WITH THE PRIMARY
   FEATURE OF INTEREST BEING A FULL-LATITUDE TROUGH WHICH WILL EDGE EWD
   FROM THE ROCKIES INTO GREAT PLAINS. WITHIN THIS LARGE-SCALE
   PATTERN...A 70-80 KT MIDLEVEL JET STREAK OBSERVED OVER THE CNTRL/SRN
   PLAINS THIS MORNING WILL PROGRESS NEWD INTO THE UPPER MS VALLEY BY
   TONIGHT.

   AT THE SURFACE...LOW PRESSURE OVER CNTRL IA WILL DEEPEN SLIGHTLY
   PRIOR TO UNDERGOING OCCLUSION AS IT DEVELOPS NNEWD INTO WRN ONTARIO.
   AN ASSOCIATED COLD FRONT WILL ADVANCE EWD INTO THE UPPER GREAT LAKES
   AND MID MS VALLEY WITH THE SRN EXTENSION OF THIS BOUNDARY MOVING
   SEWD THROUGH THE OZARK PLATEAU AND MUCH OF THE SRN PLAINS. THIS COLD
   FRONT WILL SERVE AS THE PRIMARY FOCUS FOR STRONG TO SEVERE TSTM
   DEVELOPMENT THIS AFTERNOON INTO TONIGHT.

   ...UPPER GREAT LAKES INTO MIDWEST/OH VALLEY THIS
   AFTERNOON/EVENING...

   MULTIPLE CLUSTERS OF TSTMS ARE ONGOING AS OF MID MORNING FROM ERN IA
   INTO WI/LOWER MI/OH...AIDED BY CONVECTIVELY GENERATED VORTICITY
   MAXIMA AND A BROAD ZONE OF WAA WITHIN THE EXIT REGION OF A NOCTURNAL
   LLJ. A SUBSET OF THESE EARLY-DAY STORMS WILL LIKELY CONTINUE INTO
   AFTERNOON WITH ADDITIONAL STORMS FORMING ALONG THE SYNOPTIC COLD
   FRONT AND RESIDUAL OUTFLOW BOUNDARIES. 12Z OBSERVED SOUNDINGS
   INDICATE THAT THE WARM SECTOR AIR MASS HAS BECOME QUITE MOIST WITH
   LOWEST 100-MB MEAN-MIXING RATIOS AS HIGH AS 13-14 G/KG. THIS
   MOISTURE WILL COMBINE WITH DAYTIME HEATING AND STEEPENING MIDLEVEL
   LAPSE RATES TO YIELD AFTERNOON MLCAPE VALUES APPROACHING 1500-2500
   J/KG.

   THE STRONGEST VERTICAL SHEAR WILL RESIDE ACROSS MN/IA INTO WI/NRN IL
   WHERE A NWD-MIGRATING 30-40 KT SLY LLJ WILL ALIGN WITH THE MIDLEVEL
   JET STREAK PROGRESSING NEWD FROM THE CNTRL PLAINS. WHERE STRONGER
   HEATING/DESTABILIZATION CAN OCCUR...THE ENVIRONMENT WILL SUPPORT
   BOWING AND SUPERCELL STRUCTURES WITH A RISK FOR DAMAGING
   WINDS...LARGE HAIL AND PERHAPS A COUPLE OF TORNADOES.

   FARTHER TO THE E INTO LOWER MI AND THE OH VALLEY...VERTICAL SHEAR
   WILL DECREASE OWING TO THE PROXIMITY OF THE MIDLEVEL RIDGE AXIS.
   HOWEVER...GIVEN AT LEAST MODESTLY STRONG DEEP SWLY FLOW AND THE
   POTENTIAL FOR MODERATE AFTERNOON INSTABILITY...SOME ORGANIZED LINE
   SEGMENTS AND/OR MULTICELL CLUSTERS APPEARS POSSIBLE WITH DAMAGING
   WINDS AND LARGE HAIL BEING THE PRIMARY HAZARDS.

   ...OZARK PLATEAU TO TX THIS AFTERNOON/EVENING...

   WHILE LARGE-SCALE FORCING FOR ASCENT WILL REMAIN MINIMAL ACROSS THE
   REGION...LOW-LEVEL UPLIFT ALONG THE SYNOPTIC COLD FRONT AND A
   PROMINENT GRAVITY WAVE PROPAGATING THROUGH AR AND CNTRL/ERN TX WILL
   FOSTER SCATTERED TSTM DEVELOPMENT. THE AREA WILL REMAIN ON THE
   SERN/ERN PERIPHERY OF STRONGER MID AND HIGH-LEVEL FLOW ATTENDANT TO
   THE CNTRL U.S. TROUGH...EFFECTIVELY LIMITING THE POTENTIAL FOR
   HIGHER-ORDER STORM MODES. NONETHELESS...THE CO-LOCATION OF ABUNDANT
   BOUNDARY-LAYER MOISTURE AND STEEP MIDLEVEL LAPSE RATES /AND
   RESULTING IN MLCAPE OF 1500-3000+ J PER KG/ WILL PROMOTE
   STRONG-SEVERE STORMS WITH THE POTENTIAL FOR UPSCALE GROWTH INTO A
   BROKEN BAND WITH AN ATTENDANT RISK FOR DAMAGING WIND GUSTS AND HAIL.

   ..MEAD/MOSIER.. 05/12/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z