SPC AC 160559

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 AM CDT SAT MAY 16 2015

   VALID 161200Z - 171200Z

   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SOUTHERN
   NEBRASKA..WESTERN AND CENTRAL KANSAS...THE WESTERN HALF OF
   OKLAHOMA...AND A SMALL PORTION OF WESTERN NORTH TEXAS...

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM CENTRAL NEB SWD TO N TX...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN PLAINS SWD TO
   CENTRAL TX...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE PLAINS FROM THE
   U.S./CANADA BORDER TO THE RIO GRANDE...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SRN NY AND ROUGHLY THE
   NRN HALF OF PA INTO NRN NJ...

   ...SUMMARY...
   AN OUTBREAK OF SEVERE THUNDERSTORMS IS EXPECTED ACROSS THE PLAINS
   STATES SATURDAY INTO SATURDAY NIGHT...FROM PARTS OF NEBRASKA
   SOUTHWARD TO TEXAS.  RISKS WILL INCLUDE VERY LARGE HAIL...DAMAGING
   WIND GUSTS...AND SEVERAL TORNADOES -- WITH A FEW LIKELY TO BE
   SIGNIFICANT/LONG-LIVED.

   ...SYNOPSIS...
   A LARGE UPPER TROUGH CROSSING THE INTERIOR WRN U.S. AT THE START OF
   THE PERIOD IS FORECAST TO SHIFT INTO THE PLAINS THROUGH THE
   DAY...TAKING ON AN INCREASINGLY NEGATIVE TILT WITH TIME AS AN
   EMBEDDED VORT MAX SHIFTS QUICKLY ACROSS THE SRN ROCKIES INTO THE
   CENTRAL/SRN HIGH PLAINS BY EARLY AFTERNOON.  DOWNSTREAM...RIDGING
   WILL PREVAIL ACROSS MOST OF THE U.S. E OF THE MS RIVER.

   AT THE SURFACE...LOW PRESSURE IS FORECAST TO GRADUALLY CONSOLIDATE
   INVOF THE CENTRAL HIGH PLAINS...WHILE A PACIFIC COLD FRONT CROSSES
   THE SRN HIGH PLAINS INTO THE AFTERNOON.  BY THE END OF THE
   PERIOD...A FAIRLY DEEP LOW IS FORECAST ACROSS NEB...WITH THE
   TRAILING FRONT EXTENDING SWD ACROSS CENTRAL KS/CENTRAL OK AND INTO
   NRN/WRN TX.  THE EMERGENCE OF THIS POTENT STORM SYSTEM INTO THE
   PLAINS SHOULD SUPPORT WIDESPREAD/SUBSTANTIAL SEVERE STORMS FROM
   EARLY AFTERNOON INTO THE OVERNIGHT HOURS.

   ...CENTRAL AND SOUTHERN PLAINS...
   THUNDERSTORMS ARE FORECAST TO BE UNDERWAY ACROSS PORTIONS OF THE
   PLAINS STATES AT THE START OF THE PERIOD...AND EVOLUTION OF THIS
   CONVECTION AND ASSOCIATED CLOUD COVER THROUGH THE DAY MAY HAVE
   SUBSTANTIAL INFLUENCE OVER SUBSEQUENT AFTERNOON DESTABILIZATION --
   AND OVERALL DEGREE OF SEVERE RISK.  WITH THAT SAID HOWEVER...THE
   SYNOPTIC/KINEMATIC ENVIRONMENT ACROSS THE CENTRAL PLAINS AND SWD
   ACROSS OK INTO N TX APPEARS OTHERWISE HIGHLY SUGGESTIVE OF POTENTIAL
   FOR A SEVERE WEATHER OUTBREAK.  THEREFORE -- DESPITE THE
   UNCERTAINTIES...AN UPGRADE TO MODERATE RISK APPEARS WARRANTED AT
   THIS TIME.

   LATEST RUNS OF BOTH THE NAM AND GFS AS WELL AS NUMEROUS HIGH-RES
   CAMS SUGGEST -- TO VARYING DEGREES -- THAT THE EARLY/ONGOING
   CONVECTION WILL DIMINISH SIGNIFICANTLY THROUGH THE MORNING AS IT
   SPREADS EWD ACROSS NEB/KS/OK.  THIS SHOULD ALLOW AT LEAST SOME
   AFTERNOON HEATING OF THE MOIST BOUNDARY LAYER...PARTICULARLY OVER
   WRN PORTIONS OF THE AREA -- INVOF THE ADVANCING PACIFIC
   FRONT/DRYLINE AND LIKELY TO THE W OF MOST OF THE MORE RECENT
   PRECIPITATION AND ASSOCIATED CLOUD COVER. 

   GIVEN STRENGTH OF THE UPPER SYSTEM EMERGING INTO THE PLAINS AND
   ASSOCIATED UVV FOCUSED INVOF THE FRONT/DRYLINE...IT APPEARS THAT
   EARLY REDEVELOPMENT/INTENSIFICATION OF STORMS WILL OCCUR -- LIKELY
   IN THE 19-20Z TIME FRAME.  ALONG WITH DEVELOPMENT NEAR THE SURFACE
   BOUNDARY FROM THE ERN TX PANHANDLE/WRN OK NWD INTO THE WRN KS
   VICINITY...SOME OF THE REMNANT STORMS FARTHER E MAY ALSO REINTENSIFY
   AS DESTABILIZATION OCCURS AROUND THE PERIPHERY ONGOING CONVECTION.

   AS MENTIONED...THE BACKGROUND KINEMATIC FIELD IS EXPECTED TO BECOME
   INCREASINGLY FAVORABLE FOR THE DEVELOPMENT OF INTENSE/LONG-LIVED
   SUPERCELLS.  THUS...STORMS DEVELOPING INVOF THE FRONT ARE LIKELY TO
   RAPIDLY ORGANIZE...WITH RISK FOR VERY LARGE HAIL AND DAMAGING WINDS
   EXPECTED.  AS STORMS MATURE AND THE LOW-LEVEL SHEAR INCREASES
   THROUGH THE AFTERNOON AS SLY H8 FLOW INCREASES TO IN EXCESS OF 40
   KT...RISK FOR SIGNIFICANT TORNADOES IS ALSO EXPECTED.

   SEVERE RISK WILL CONTINUE THROUGH THE EVENING AND INTO THE OVERNIGHT
   HOURS...AS STORMS EVOLVE INTO AN ARCING BAND WITH TIME WHICH IS
   EXPECTED TO ADVANCE EWD ACROSS NEB/KS/OK...AND THEN SEWD ACROSS TX
   AS STORMS DEVELOP SWD ALONG THE PACIFIC FRONT AFTER DARK.  

   ...NRN PLAINS/UPPER MS VALLEY AREA...
   A RATHER COMPLEX SCENARIO IS LIKELY TO UNFOLD ACROSS THE N CENTRAL
   U.S. THIS PERIOD...WITH AN EARLY/ONGOING AREA OF CONVECTION
   SPREADING NWD ACROSS THE DAKOTAS/MN.  THE RESIDUAL
   CLOUDS/PRECIPITATION CAST UNCERTAINTY WITH RESPECT TO DEGREE OF
   AFTERNOON DESTABILIZATION -- AND THUS SEVERE POTENTIAL ACROSS THIS
   REGION.

   ATTM...IT APPEARS THAT POCKETS OF AMPLE DESTABILIZATION WILL DEVELOP
   BY LATE AFTERNOON NEAR AND S OF THE WARM FRONT -- PROGGED TO ARC
   FROM SERN MT ENEWD ACROSS NWRN SD/ND AND THEN SEWD INTO CENTRAL MN
   DURING THE AFTERNOON -- SUCH THAT SCATTERED STORM REDEVELOPMENT
   APPEARS LIKELY TO OCCUR.  WITH STRONGEST SHEAR EXPECTED FROM THE ERN
   HALF OF THE DAKOTAS INTO MN /WITH FLOW BACKING FROM SELY AT LOW
   LEVELS TO SLY/SSWLY AT MID LEVELS/...RISK FOR ISOLATED
   ROTATING/SEVERE STORMS EVOLVING THROUGH LATE AFTERNOON/EARLY EVENING
   IS APPARENT.  PRIMARY RISKS WILL BE HAIL AND LOCALLY DAMAGING
   WINDS...THOUGH SOME TORNADO RISK IS ALSO APPARENT -- PARTICULARLY
   NEAR AND JUST TO THE COOL SIDE OF THE NWD-MOVING WARM FRONT.

   ...SRN NY/NRN PA/NRN NJ VICINITY...
   AS OVERNIGHT CONVECTION LINGERING ACROSS THE AREA SHIFTS EWD INTO
   SRN NEW ENGLAND...WEAK DIURNAL DESTABILIZATION IS EXPECTED ACROSS
   THE PA/NY VICINITY.  AS A WEAK VORT MAX SHIFTS EWD ACROSS SRN
   ONTARIO AND THE LOWER GREAT LAKES THROUGH THE AFTERNOON...SHOWERS
   AND SCATTERED THUNDERSTORMS SHOULD REDEVELOP ACROSS THE AREA. 
   THOUGH WEAK CAPE EXPECTED ACROSS THE AREA SHOULD LIMIT ANY SEVERE
   RISK...AN ISOLATED STRONGER CELL OR TWO -- AIDED BY AMPLY STRONG
   FLOW ALOFT -- COULD PRODUCE GUSTY WINDS OR MARGINAL HAIL THROUGH
   EARLY EVENING.

   ..GOSS/GLEASON.. 05/16/2015

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z