Categorical Graphic
Probabilistic Tornado 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
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
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 220558
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1258 AM CDT SUN MAY 22 2011
   
   VALID 221200Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SRN PLAINS
   THROUGH THE MID MS VALLEY...GREAT LAKES ...AND OH VALLEY...
   
   ...SYNOPSIS...
   
   CLOSED UPPER LOW OVER THE NRN PLAINS WILL DRIFT SLOWLY EWD INTO THE
   UPPER MS VALLEY SUNDAY...WHILE UPSTREAM TROUGH AMPLIFIES ALONG THE
   WRN U.S. COAST. IN BETWEEN THESE TWO FEATURES WEAK SHORTWAVE RIDGING
   WILL SHIFT INTO THE CNTRL AND SRN ROCKIES. AT THE SURFACE AN
   OCCLUDED LOW WILL ACCOMPANY UPPER LOW CIRCULATION. ATTENDANT FRONT
   WILL TRAIL SWWD THROUGH THE UPPER-MID MS VALLEY AND ERN KS. DRYLINE
   WILL EXTEND FROM THE BIG BEND AREA OF TX THROUGH CNTRL OK INTO KS
   WHERE IT WILL INTERSECT THE FRONT. WARM FRONT SHOULD CONTINUE TO
   LIFT NWD THROUGH THE OH VALLEY INTO THE GREAT LAKES.
   
   ...SRN PLAINS...
   
   OVERNIGHT CONVECTION IS IN PROCESS OF DIMINISHING ACROSS TX AND THE
   LOWER MS VALLEY. RICH GULF MOISTURE WITH LOW 70S DEWPOINTS WILL
   PERSIST BENEATH STEEP LAPSE RATES ASSOCIATED WITH EML PLUME AND WILL
   LIKELY ADVECT FARTHER NWD INTO SERN KS AND SWRN MO. THE WARM SECTOR
   IS EXPECTED TO BECOME VERY UNSTABLE AS THE BOUNDARY LAYER WARMS
   DURING THE AFTERNOON WITH 3000-4000 J/KG MLCAPE. WEAK HEIGHT RISES
   AND WEAKENING LOW LEVEL FLOW WILL OCCUR OVER THE SRN PLAINS DURING
   THE DAY AS UPPER LOW DRIFTS TOWARD THE GREAT LAKES. THESE FACTORS
   ALONG WITH PRESENCE OF CAP ATTENDING THE EML COULD POTENTIALLY LIMIT
   STORM COVERAGE. NEVERTHELESS...AT LEAST ISOLATED STORMS SHOULD
   DEVELOP AS THE DRYLINE MIXES EWD ESPECIALLY FROM NWRN TX INTO
   CNTRL/ERN OK INTO SERN KS WHICH WILL RESIDE WITHIN EXIT REGION OF
   UPPER JET. GIVEN THE MAGNITUDE OF INSTABILITY WITH HIGH VALUES OF
   NORMALIZED CAPE AND EFFECTIVE SHEAR SUPPORTIVE OF SUPERCELLS...VERY
   LARGE HAIL WILL BE LIKELY. LOW LEVEL SHEAR WILL ALSO IMPROVE TOWARD
   EVENING AS SRN BRANCH OF LLJ STRENGTHENS. THE SHEAR AND INSTABILITY
   PARAMETER SPACE WILL ALSO SUPPORT POTENTIAL FOR ISOLATED STRONG
   TORNADOES FROM LATE AFTERNOON INTO THE EVENING. A MODERATE RISK MAY
   BE NEEDED FOR A PORTION OF THIS AREA IN LATER OUTLOOKS ONCE STORM
   COVERAGE CONCERNS HAVE BEEN MITIGATED.
   
   
   ...MID MS VALLEY THROUGH TN AND OH VALLEYS AND GREAT LAKES...
   
   ONGOING MCS FROM NRN MO INTO EXTREME ERN IA EARLY THIS MORNING IS
   EXPECTED TO GRADUALLY DIMINISH...BUT REMNANT OUTFLOW BOUNDARY MAY
   PLAY A ROLE IN STORM EVOLUTION LATER TODAY. A 40-45 KT SSWLY LLJ
   SHIFT NEWD THROUGH THE MID MS VALLEY AND GREAT LAKES MAINTAINING
   INFLUX OF RICHER MOISTURE BENEATH COOL AIR ALOFT AND LIKELY
   CONTRIBUTING TO 2000-3000 J/KG MLCAPE WHERE DIABATIC WARMING OCCURS.
   SEVERAL VORTICITY MAXIMA WILL CONTINUE TO ROTATE THROUGH UPPER LOW
   CIRCULATION...AND STORMS WILL LIKELY ONCE AGAIN DEVELOP ALONG AND
   EAST OF PACIFIC FRONT. VERTICAL SHEAR WILL BE SUPPORTIVE OF
   SUPERCELLS WITH VERY LARGE HAIL AND ISOLATED TORNADOES THE INITIAL
   THREATS ESPECIALLY OVER THE MID-UPPER MS VALLEY INTO WRN PORTION OF
   THE GREAT LAKES WHERE REMNANT OUTFLOW BOUNDARY COULD AUGMENT LOW
   LEVEL SHEAR. SOME OF THE STORMS MAY EVENTUALLY EVOLVE INTO ONE OR
   MORE MCSS AS THEY DEVELOP TOWARD THE OH AND TN VALLEYS WITH A
   CONTINUED THREAT FOR MAINLY ISOLATED DAMAGING WIND AND LARGE HAIL
   INTO THE EVENING. PORTIONS OF THE MID MS VALLEY WILL ALSO BE
   MONITORED FOR A POSSIBLE MODERATE RISK IN LATER OUTLOOKS.
   
   ..DIAL/GARNER.. 05/22/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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