SPC AC 150601

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0101 AM CDT FRI MAY 15 2015

   VALID 151200Z - 161200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PORTIONS OF SRN SD/WRN
   AND CENTRAL NEB AND VICINITY...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN WY/NERN CO/SRN SD/NEB
   SWD TO THE TX/OK PANHANDLE VICINITY...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM SD SWD TO THE TX BIG
   BEND...AND FROM THE PLAINS EWD ACROSS THE MIDWEST TO THE LOWER GREAT
   LAKES...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE EXPECTED ACROSS PARTS OF NEBRASKA AND
   SOUTHERN SOUTH DAKOTA FRIDAY AFTERNOON AND EVENING.  MORE ISOLATED
   STRONG/SEVERE STORM DEVELOPMENT IS POSSIBLE SOUTHWARD INTO THE
   SOUTHERN HIGH PLAINS BY FRIDAY EVENING.  A FEW STRONG TO PERHAPS
   SEVERE STORMS ARE ALSO POSSIBLE FRIDAY FROM PARTS OF THE MIDDLE
   MISSISSIPPI VALLEY EASTWARD ACROSS THE MIDWEST REGION TO THE LOWER
   GREAT LAKES.

   ...SYNOPSIS...
   WHILE RIDGING ALOFT IS EXPECTED TO PREVAIL OVER THE SOUTHEAST
   CONUS...A LARGE UPPER LOW/TROUGH WILL ADVANCE EWD ACROSS THE WRN
   THIRD OF THE COUNTRY FRI.  AT THE SURFACE...A PACIFIC COLD FRONT
   SHOULD ADVANCE ACROSS THE INTERMOUNTAIN W...WHILE A WEAK LEE LOW
   OVER THE CENTRAL HIGH PLAINS DRIFTS NWD WITH TIME.  THIS LOW --
   ALONG WITH A WARM FRONT EXTENDING EWD ACROSS THE NEB VICINITY AND A
   DRYLINE MIXING EWD ACROSS WRN PORTIONS OF THE PLAINS -- WILL PROVIDE
   THE PRIMARY FOCI FOR SEVERE STORM DEVELOPMENT THIS PERIOD.

   ...PORTIONS OF THE CENTRAL AND NRN PLAINS...
   WITH HEIGHT FALLS ASSOCIATED WITH THE MAIN UPPER TROUGH TO REMAIN
   LARGELY W OF THE CENTRAL AND SRN PLAINS THROUGH THE DAY...ANY MORE
   THAN ISOLATED STORM DEVELOPMENT REMAINS QUESTIONABLE FROM WRN KS SWD
   ACROSS W TX INVOF THE DRYLINE.  ANY STORM WHICH COULD BECOME
   SUSTAINED ACROSS THIS AREA WOULD LIKELY POSE SOME SEVERE
   RISK...GIVEN THE UNSTABLE ENVIRONMENT FORECAST ALONG/E OF THE
   DRYLINE AND AMPLE FLOW FIELD ALOFT.  

   GREATER SEVERE RISK HOWEVER SHOULD EXIST ACROSS WRN AND CENTRAL NEB
   AND INTO SRN SD...AS A SURFACE LOW PROGGED TO RESIDE ACROSS THE
   CENTRAL HIGH PLAINS DRIFTS NWD TOWARD THE NEB PANHANDLE THROUGH THE
   AFTERNOON.  STORMS SHOULD INITIATE ACROSS NRN CO/SERN WY AS A
   WEAK/LEAD IMPULSE AHEAD OF THE MAIN TROUGH ROTATES NNEWD ACROSS THIS
   AREA...WITH STORMS THEN SPREADING NEWD ACROSS WRN NEB/SWRN SD IN AN
   INCREASINGLY UNSTABLE AFTERNOON AIRMASS.  BACKED LOW-LEVEL FLOW
   NEAR/NE OF THIS LOW AND EWD ALONG THE WARM FRONT BENEATH INCREASING
   SSWLYS AT MID LEVELS WILL RESULT IN SHEAR PROFILES FAVORABLE FOR
   SUPERCELLS...AND THUS EXPECT STORMS TO STRENGTHEN TO SEVERE LEVELS
   -- WITH HAIL/LOCALLY DAMAGING WINDS POSSIBLE ALONG WITH A FEW
   TORNADOES.  GREATEST RISK WILL EXIST THROUGH EARLY EVENING...AFTER
   WHICH A GRADUAL DECREASE IN STORM INTENSITY/SEVERITY SHOULD BEGIN --
   CONTINUING INTO THE OVERNIGHT HOURS.

   ...MID MS VALLEY/MIDWEST...
   A RATHER BROAD ZONE OF CONVECTION IS FORECAST TO EVOLVE WITHIN A
   BACKGROUND LOW-LEVEL WARM ADVECTION REGIME...AS GRADUAL MOISTENING
   OF THE LOW-LEVEL AIRMASS COMBINES WITH SOME AFTERNOON HEATING TO
   RESULT IN AN AMPLY UNSTABLE ENVIRONMENT.  STRONGEST FLOW ALOFT
   ACROSS THE REGION WILL LIKELY REMAIN CONFINED TO THE LOWER GREAT
   LAKES REGION -- WHERE WEAKEST INSTABILITY IS EXPECTED.  FARTHER
   W...GREATER MOISTURE/INSTABILITY BUT WEAKER FLOW ALOFT SHOULD -- IN
   AN OVERALL SENSE -- GREATLY LIMIT ORGANIZATION POTENTIAL/SEVERE
   WEATHER RISK.  STILL...WITH A STRONGER WIND GUST OR MARGINALLY
   SEVERE HAILSTONE NOT OUT OF THE QUESTION...WILL OPT TO MAINTAIN A
   LARGE AREA OF LOW /5%/ SEVERE WEATHER RISK ACROSS THIS REGION.

   ..GOSS/GLEASON.. 05/15/2015

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