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    Day 2 Outlook >
May 22, 2010 1300 UTC Day 1 Convective Outlook
Updated: Sat May 22 12:48:17 UTC 2010  (Print Version)
Probabilistic to Categorical Outlook Conversion Table
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SPC Day1 1300Z Outlook Categorical
  
  
 Forecast Discussion
   SPC AC 221245
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0745 AM CDT SAT MAY 22 2010
   
   VALID 221300Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN PLAINS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CAROLINAS...
   
   ...SYNOPSIS...
   UPPER AIR PATTERN THIS PERIOD WILL BE DOMINATED BY A BELT OF FAST
   SWLY FLOW FROM THE LOWER CO RIVER VALLEY TO THE DAKOTAS/MN ON THE
   ERN FLANK OF A LARGE SCALE TROUGH ESTABLISHED OVER THE WRN U.S. THIS
   STRONGER FLOW WILL COINCIDE WITH A SLOW-MOVING DEEP-LAYER FRONTAL
   ZONE ALONG WHICH THE MOST SIGNIFICANT PERTURBATION WILL TRACK OUT OF
   THE INTERMOUNTAIN REGION AND OVER THE DAKOTAS LATER TODAY.
   
   DOWNSTREAM FROM THE WRN U.S. TOUGH...UPPER RIDGE WILL BUILD ACROSS
   THE MS VALLEY AND GREAT LAKES AS A WEAKENING UPPER TROUGH IS SHUNTED
   EWD ACROSS THE APPALACHIANS/MID ATLANTIC.
   
   ...NRN PLAINS...
   POTENT LOW LEVEL JET OF 50-60KT WAS CONTINUING TO TRANSPORT HIGH
   THETA-E AIR NWD ACROSS THE GREAT PLAINS THIS MORNING BENEATH
   WELL-DEFINED CAP/ELEVATED MIXED LAYER EMANATING FROM THE HIGHER
   TERRAIN UPSTREAM /REF LBF RAOB WITH OBSERVED 8.6C PER KM 700-500MB
   LAPSE RATE...0.84 INCH PW...AND 14C TEMP AT 700MB/.
   
   ONGOING MCS ACROSS ERN SD WAS BEING FUELED BY THIS PLUME OF ELEVATED
   INSTABILITY AND SUSTAINED BY MASS AND MOISTURE INFLUX ON THE NOSE OF
   60KT LOW LEVEL JET. ADDITIONAL/RECENT DEVELOPMENT HAS OCCURRED ON
   THE EDGE OF THE CAP ACROSS ERN NEB AND IS FORECAST TO DRIFT INTO IA
   THIS MORNING PERHAPS POSING A THREAT FOR ISOLATED LARGE HAIL /REF
   SWOMCD NUMBER 660/.
   
   ANOTHER ROUND OF ROBUST CONVECTIVE DEVELOPMENT IS EXPECTED LATER
   TODAY ACROSS PARTS OF ERN WY AND THE ADJACENT HIGH PLAINS AS A
   LOW-AMPLITUDE SHORT WAVE TROUGH EMERGES ACROSS THE HIGH PLAINS AND
   ACTS ON WARM AND VERY UNSTABLE AIR MASS FROM NEB NWD ACROSS THE
   DAKOTAS. BY LATE AFTERNOON EXPECT MLCAPE VALUES IN THIS AREA TO
   EXCEED 3000 J PER KG. WHILE CAP WILL LIKELY HOLD ACROSS MUCH OF THE
   PLAINS SOUTH OF NEB...COMBINATION OF SURFACE HEATING AND WEAK HEIGHT
   FALLS WITH APPROACHING SHORT WAVE SHOULD BE SUFFICIENT TO OVERCOME
   REMAINING INHIBITION AND SUPPORT THUNDERSTORM INITIATION IN STRONGLY
   SHEARED DEEP-LAYER FLOW.
   
   THUNDERSTORMS WILL OCCUR COINCIDENT WITH WEAK FRONTAL WAVE TRACKING
   NEWD ALONG THE SURFACE FRONT...AND A DRY LINE NOSING ENEWD NEAR THE
   SD/NEB BORDER. MODEST LOW LEVEL HODOGRAPH CURVATURE AND MAGNITUDE OF
   INSTABILITY SUGGEST THAT A COUPLE OF TORNADOES AND VERY
   LARGE/DAMAGING HAIL WILL BE POSSIBLE WITH DISCRETE
   STORMS/SUPERCELLS. THIS ACTIVITY MAY STRUGGLE TO BECOME MORE
   WIDESPREAD INITIALLY DUE TO STRONG CAPPING AND TENDENCY FOR STORMS
   TO TAKE ON MORE LINEAR CHARACTERISTICS AND BE UNDERCUT ALONG THE
   FRONTAL ZONE WHERE STRONGEST MESOSCALE FORCING CAN ACT TO FURTHER
   ERODE THE CAP.
   
   FORCING ALONG THE EDGE OF THE CAP THROUGH THE EVENING AND THEN
   STRENGTHENING NOCTURNAL LOW LEVEL JET SHOULD CONTRIBUTE TO SEVERE
   MCS EVOLVING ACROSS SD...AND PERHAPS PARTS OF ND...AND THEN
   SPREADING ENEWD INTO MN THROUGH EARLY SUNDAY MORNING.
   
   ...NC PIEDMONT TO SC MIDLANDS...
   MODEST NW FLOW OF 20-30KT AND GRADUAL DIURNAL DESTABILIZATION...WITH
   SBCAPE RANGING FROM 1000 TO 2000 J PER KG BY AFTERNOON...MAY SUPPORT
   INCREASING SEVERE STORM POTENTIAL THESE AREAS. FORCING FOR LARGER
   SCALE ASCENT WILL BE SUBTLE BUT IT APPEARS REGION WILL COME UNDER
   THE INFLUENCE OF WEAK HEIGHT FALLS FROM THE TROUGH PASSING NORTH OF
   THE AREA AND LEE-TROUGH WILL BECOME COINCIDENT WITH AXIS OF GREATEST
   FORECAST DESTABILIZATION. 
   
   EFFECTIVE BULK SHEAR ON THE ORDER OF 30KT WILL FURTHER AID STORM
   PERSISTENCE AND ORGANIZATION WITH A FEW HAILSTONES POSSIBLY
   EXCEEDING ONE INCH ALONG WITH LOCALLY DAMAGING WIND GUSTS.
   
   ...WEST TX...
   HOT TEMPERATURES EXCEEDING 90F...TERRAIN INFLUENCES...AND DRY LINE
   MIXING MAY PROVE SUFFICIENT TO OVERCOME WARM EML AND RESULT IN
   ISOLATED STORM DEVELOPMENT LATE THIS AFTERNOON AS INDICATED IN SOME
   NUMERICAL GUIDANCE. CHANCES FOR NUMEROUS STORMS APPEAR LOW BUT
   ABUNDANT CAPE AND ADEQUATE SHEAR THIS REGION SUGGEST A CONDITIONAL
   LOW PROBABILITY OF SEVERE HAIL/WIND IS WARRANTED.
   
   ..CARBIN/ROGERS.. 05/22/2010
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
   CURRENT UTC TIME: 1337Z (6:37AM), RELOAD THIS PAGE TO UPDATE THE TIME
        
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Page last modified: May 22, 2010
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