Jul 26, 2011 1300 UTC Day 1 Convective Outlook
Updated: Tue Jul 26 12:22:07 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the northern plains this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20110726 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110726 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20110726 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20110726 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
   SPC AC 261217
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0717 AM CDT TUE JUL 26 2011
   
   VALID 261300Z - 271200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF SD AND ND THIS
   AFTERNOON AND EVENING...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE CENTRAL AND
   NORTHERN PLAINS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTHEAST
   STATES...
   
   BROAD RIDING CONTINUES TO DOMINATE THE WEATHER OVER MUCH OF THE
   UNITED STATES TODAY.  HOWEVER...TWO AREAS WILL SEE RISKS OF SEVERE
   STORMS LATER THIS AFTERNOON AND EVENING.  ONE OVER THE NORTHERN
   PLAINS...AND ONE OVER THE NORTHEAST STATES.
   
   ...DAKOTAS/MN...
   A RATHER STRONG UPPER TROUGH IS CURRENTLY MOVING ACROSS THE NORTHERN
   ROCKIES...AND WILL BEGIN AFFECTING THE NORTHERN PLAINS BY LATE
   AFTERNOON.  A WEAK SURFACE BOUNDARY OVER SD WILL SERVE AS THE FOCUS
   FOR LOW LEVEL CYCLOGENESIS LATER TODAY.  THIS WILL RESULT IN
   STRENGTHENING LOW LEVEL WINDS AND VERTICAL SHEAR PROFILES FOR SEVERE
   STORMS.  FULL SUNSHINE WILL STEEPEN THE LOW LEVEL LAPSE RATES AND
   EVENTUALLY BREAK THE CAP OVER CENTRAL SD NEAR THE SURFACE LOW THIS
   AFTERNOON.  THE INITIAL STORMS WILL LIKELY BE SUPERCELLULAR AND WILL
   TRACK NORTHEASTWARD WITH THE LOW INTO SOUTHEAST ND.  THE COMBINATION
   OF HIGH CAPE VALUES...LARGE SCALE FORCING...AND FAVORABLE LOW/DEEP
   LAYER VERTICAL SHEAR WILL PROMOTE A RISK OF A FEW TORNADOES
   /POTENTIALLY STRONG/ THIS AFTERNOON AND EVENING.  VERY LARGE HAIL
   WILL ALSO BE POSSIBLE IN THE STRONGEST STORMS.  DURING THE
   EVENING...STORMS ARE LIKELY TO INCREASE IN COVERAGE AND SPREAD
   EASTWARD INTO WESTERN MN WITH AN INCREASING RISK OF DAMAGING WINDS.
   
   ...CENTRAL HIGH PLAINS...
   HOT TEMPERATURES ARE EXPECTED THIS AFTERNOON OVER PARTS OF
   SD/NEB/KS/CO WITH NEARLY DRY ADIABATIC LAPSE RATES FROM THE SURFACE
   TO 550MB.  SUFFICIENT LOW/MID LEVEL MOISTURE ARE FORECAST ALONG AN
   AXIS FROM NORTHEAST CO INTO WESTERN SD TO PROMOTE THE DEVELOPMENT OF
   SCATTERED THUNDERSTORMS.  VERTICAL SHEAR WILL ONLY BE MARGINALLY
   SUFFICIENT FOR CONVECTIVE ORGANIZATION.  HOWEVER...IT APPEARS LIKELY
   THAT THE STRONGER STORMS ALONG THIS CORRIDOR WILL POSE A THREAT OF
   LOCALLY DAMAGING WINDS.
   
   ...NORTHEAST STATES...
   WATER VAPOR IMAGERY SHOWS BROAD CYCLONIC FLOW OVER THE NORTHEAST
   STATES TODAY.  A SHORTWAVE TROUGH IS DIGGING SOUTHEASTWARD ACROSS
   LOWER MI AND WILL AFFECT PARTS OF PA/NY AND NEW ENGLAND BY THIS
   AFTERNOON.  EARLY VISIBLE SATELLITE IMAGERY SHOWS MOSTLY CLEAR SKIES
   OVER NY/PA WHERE SCATTERED THUNDERSTORMS ARE LIKELY TO FORM BY LATE
   MORNING.  STORMS WILL THEN SPREAD EASTWARD ACROSS MOST OF NEW
   ENGLAND DURING THE DAY.  COOLING TEMPERATURES ALOFT AND 50-70 KT
   MID/UPPER LEVEL WINDS WILL AID IN THE DEVELOPMENT OF A FEW SEVERE
   STORMS CAPABLE OF DAMAGING WINDS AND LARGE HAIL.
   
   ..HART/HURLBUT.. 07/26/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z