Apr 21, 2010 0600 UTC Day 1 Convective Outlook
Updated: Wed Apr 21 05:31:19 UTC 2010
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20100421 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20100421 1200 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20100421 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20100421 1200 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 210528
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1228 AM CDT WED APR 21 2010
   
   VALID 211200Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
   PORTIONS OF THE CNTRL AND SRN HIGH PLAINS...
   
   ...SYNOPSIS...
   
   AN INTENSE MID AND UPPER-LEVEL LOW CURRENTLY DIGGING SSEWD ALONG THE
   CA COAST WILL UNDERGO FURTHER STRENGTHENING WHILE PROGRESSING SEWD
   INTO THE GREAT BASIN AND LOWER CO VALLEY.  THIS SYSTEM WILL BE
   ACCOMPANIED BY A 100+ KT UPPER-LEVEL JET STREAK AND SIGNIFICANT
   HEIGHT FALLS WHICH WILL SPREAD EWD THROUGH THE GREAT BASIN AND LOWER
   CO VALLEY INTO THE CNTRL AND SRN ROCKIES THROUGH THE DAY ONE 
   PERIOD.
   
   AT THE SURFACE...BROAD LEE CYCLOGENESIS IS FORECAST OVER THE CNTRL
   AND SRN HIGH PLAINS TODAY...PRIOR TO CONSOLIDATION INTO A MORE
   CONCENTRATED LOW CENTER OVER ERN CO TONIGHT.  AS THIS PROCESS
   OCCURS...A NW-SE ORIENTED BAROCLINIC ZONE IS EXPECTED TO STRENGTHEN
   FROM SERN CO THROUGH THE OK/TX PNHDLS INTO THE RED RIVER VALLEY.  A
   WEAK DRYLINE OR LEE TROUGH WILL THEN EXTEND FROM THE INTERSECTION
   WITH THIS FRONT SWD THROUGH WRN TX.
   
   FARTHER W...A SURFACE LOW INITIALLY OVER WRN UT WILL DEEPEN WHILE
   DEVELOPING NWD AND THEN NWWD INTO THE SNAKE RIVER VALLEY IN
   CONJUNCTION WITH A STRONG VORTICITY MAXIMUM ROTATING AROUND THE
   PARENT UPPER SYSTEM.  MEANWHILE...TRAILING PACIFIC FRONT WILL SURGE
   EWD THROUGH THE GREAT BASIN AND LOWER CO VALLEY INTO THE CNTRL AND
   SRN ROCKIES.
   
   ...CNTRL AND SRN HIGH PLAINS...
   
   THE DEEPENING LEE CYCLONE WILL ALLOW FOR THE NWD/NWWD FLUX OF AN
   INCREASINGLY MOIST BOUNDARY LAYER WITH DEW POINTS INCREASING THROUGH
   THE 50S FROM THE LOWER RIO GRANDE VALLEY INTO OK AND THE ERN OK/TX
   PNHDLS.  WHEN COUPLED WITH THE PRESENCE OF STEEP LAPSE RATES...THE
   AFTERNOON AIR MASS OVER THE SLIGHT RISK AREA WILL BECOME MODERATELY
   UNSTABLE WITH MLCAPE RANGING FROM AROUND 1000 J/KG OVER SERN CO TO
   1500-2000 J/KG ACROSS THE ERN TX PNHDL AND NWRN TX INTO WRN OK.
   
   00Z MESOSCALE MODEL GUIDANCE SUGGESTS THAT THE REGION WILL INITIALLY
   RESIDE UNDER GRADUALLY BUILDING MIDLEVEL HEIGHTS DOWNSTREAM FROM
   AMPLIFYING UPPER-LEVEL SYSTEM.  HOWEVER...BY LATE AFTERNOON AND MORE
   SO THIS EVENING...THE LEADING EDGE OF MORE MEANINGFUL HEIGHT FALLS
   WILL BEGIN TO OVERSPREAD THE AREA FROM THE W. THIS PROCESS IN
   CONJUNCTION WITH OROGRAPHIC UPSLOPE FLOW OVER SERN CO AND
   CONVERGENCE ALONG THE ABOVE-MENTIONED SURFACE BOUNDARIES SHOULD
   ALLOW FOR THE DEVELOPMENT OF ISOLATED TO SCATTERED DIURNAL STORMS
   ACROSS THE SLIGHT RISK AREA.
   
   SELY SURFACE WINDS VEERING TO WLY AT 25-35 KT IN THE MIDLEVELS WILL
   RESULT IN 35-45 KT OF DEEP-LAYER SHEAR...SUFFICIENT FOR SUPERCELLS
   GIVEN THE DEGREE OF INSTABILITY.  SEVERE HAIL WILL BE THE PRIMARY
   HAZARD WITH THESE STORMS AS THEY MATURE AND SLOWLY MOVE EWD/SEWD.  A
   TORNADO OR TWO IS POSSIBLE...ESPECIALLY WITH ANY SUPERCELLS THAT CAN
   FAVORABLY INTERACT WITH PRE-EXISTING SURFACE BOUNDARIES -- MESOSCALE
   OR SYNOPTIC.  A MORE ROBUST TORNADO THREAT WILL LIKELY BE LIMITED BY
   THE MARGINAL MOISTURE QUALITY WHICH WILL LEAD TO A STRENGTHENING CAP
   LATER THIS EVENING WHEN THE LLJ AND NEAR-GROUND SHEAR ARE RAPIDLY
   INTENSIFYING.
   
   CLUSTERS OF MAINLY ELEVATED STORMS WILL LIKELY CONTINUE OVERNIGHT
   ACROSS PARTS OF KS AND OK WITHIN A STRENGTHENING WAA REGIME
   COINCIDENT WITH THE LLJ AXIS.  THE STRONGER STORMS WILL BE CAPABLE
   OF SOME HAIL WHICH MAY APPROACH SEVERE LEVELS.
   
   ...SNAKE RIVER VALLEY AND ERN PARTS OF THE GREAT BASIN INTO THE
   CNTRL ROCKIES...
   
   SIMILAR TO TUESDAY...STEEP LAPSE RATES...STRONG DYNAMIC FORCING AND
   VERTICAL SHEAR MAY YIELD A FEW ORGANIZED STORMS ALONG THE PACIFIC
   FRONT WITH THE PRIMARY SEVERE THREAT BEING DAMAGING WIND GUSTS. 
   THIS THREAT SHOULD BEGIN TO DIMINISH BY LATE EVENING AS THE BOUNDARY
   LAYER COOLS AND STABILIZES.
   
   ..MEAD/SMITH.. 04/21/2010
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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