SPC AC 270450

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1150 PM CDT THU SEP 26 2013

   VALID 281200Z - 291200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SYNOPSIS...
   A POTENT SHORTWAVE TROUGH WILL EJECT RAPIDLY NEWD ACROSS THE NRN
   PLAINS AND UPPER MS VALLEY DURING THE DAY...AND WILL BE LOCATED OVER
   ONTARIO BY SUNDAY MORNING. AT THE SURFACE...A LOW WILL DEEPEN FROM
   NRN MN INTO WRN ONTARIO...WITH A SHARP COLD FRONT EXTENDING SWD INTO
   WI AND UPPER MI. FORCING WILL BE STRONG WITH THE FRONT BUT
   INSTABILITY FOR THUNDERSTORMS WILL BE EXTREMELY LIMITED. TO THE
   S...THE TAIL END OF THE COLD FRONT WILL MOVE SLOWLY ACROSS OK AND
   INTO NWRN TX BY AFTERNOON...WHERE MORE SUBSTANTIAL MOISTURE AND
   INSTABILITY WILL EXIST BUT WEAKER SHEAR.

   ACROSS THE PACIFIC NW...A SIGNIFICANT STORM SYSTEM WILL BRING STRONG
   WINDS AND HEAVY PRECIPITATION ALONG THE W SLOPES OF THE WA CASCADES
   AND INTO COASTAL WA AND OREGON.

   ELSEWHERE...AWAY FROM THE AFOREMENTIONED COLD FRONT...HIGH PRESSURE
   WILL KEEP CONDITIONS DRY.

   ...WA...
   A VERY STRONG TROUGH WILL ARRIVE MAINLY AFTER 00Z AND WILL BRING
   STRONG WINDS AND A LONG DURATION OF HEAVY RAIN. FORECAST SOUNDINGS
   INDICATE THAT EXTREME SHEAR PROFILES WILL MATERIALIZE...WITH
   SUBSTANTIAL LOW LEVEL VEERING WITH HEIGHT/LOOPING LOW LEVEL
   HODOGRAPHS ALONG WITH SPEED SHEAR ALOFT. STRONGLY
   FORCED...LOW-TOPPED LINES OR SMALL BOWING SEGMENTS WILL BE POSSIBLE
   ALONG COASTAL WA AND OREGON DURING THE LATE AFTERNOON/EVENING WHEN
   THE MAIN FRONTAL FORCING ARRIVES AND COOLING BELOW 500 MB OCCURS.
   WITH SUCH STRONG SHEAR...SOME OF THESE ELEMENTS COULD ENHANCE WIND
   POTENTIAL AT THE SURFACE...ALTHOUGH LIGHTNING PRODUCTION COULD BE
   LIMITED.

   ...UPPER MS VALLEY...
   INSTABILITY AHEAD OF THE COLD FRONT WILL BE QUITE WEAK DUE TO POOR
   LOW TO MIDLEVEL LAPSE RATES. IT IS DIFFICULT TO FIND ANY NAM
   FORECAST SOUNDING WITH MORE THAN 15 J/KG MLCAPE OVER THE WARM
   SECTOR...DESPITE BOUNDARY LAYER DEWPOINTS IN THE UPPER 50S/LOWER
   60S. THEREFORE...WHILE WINDY CONDITIONS WILL OCCUR WITH THE COLD
   FRONT PASSAGE...SEVERE THUNDERSTORMS ARE NOT EXPECTED. 

   ...OK INTO NWRN TX...
   MORE SUBSTANTIAL LOW LEVEL MOISTURE WILL EXIST ACROSS THE SRN PLAINS
   WITH A PLUME OF UPPER 60S F DEWPOINTS AHEAD OF THE FRONT. WITH
   HEIGHT RISES BEHIND THE EJECTING UPPER TROUGH...FORCING WILL BE WEAK
   OVERALL...BUT HEATING NEAR THE FRONT COULD RESULT IN A REJUVENATION
   OF STORM VIGOR. A FEW LOCALLY STRONG WIND GUSTS WOULD BE
   LIKELY...BUT WITH THE FILLING SURFACE TROUGH AND WEAKENING SHEAR
   WITH SRN EXTENT...SEVERE APPEARS UNLIKELY.

   ..JEWELL.. 09/27/2013

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z