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

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