SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0300 PM CDT SUN APR 29 2012 VALID 292000Z - 301200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND CENTRAL HIGH PLAINS ACROSS OK...SRN/ERN KS INTO MO... ...SERN-E CENTRAL KS INTO WRN/CENTRAL MO... EARLY AFTERNOON SURFACE ANALYSIS SHOWED AN AREA OF RELATIVELY LOWER PRESSURE CENTERED BETWEEN ICT-EMP WITH A BOUNDARY EXTENDING ESEWD THROUGH CENTRAL MO TO FAR SRN IL/IND. ANOTHER BOUNDARY EXTENDED SSWWD FROM THE ICT/EMP LOW TO A SECOND LOW OVER SOUTH CENTRAL KS. MEANWHILE...THE BOUNDARY EXTENDING SWWD THROUGH CENTRAL OK HAS WEAKENED/BECOME ILL-DEFINED...GIVEN SURFACE STREAMLINE ANALYSES SHOWING DIFFLUENCE...ESPECIALLY INTO WRN OK. INCREASING DESTABILIZATION ACROSS THE SERN QUARTER OF KS INTO NERN OK IS SUPPORTING MLCAPE OF 1000-2000 J/KG. THIS COMBINED WITH EFFECTIVE BULK SHEAR OF 40-50 KT IS MORE THAN ADEQUATE FOR ORGANIZED STORMS...INCLUDING SUPERCELLS. GIVEN THE DEVELOPMENT OF THE MORE UNSTABLE WARM SECTOR WITH NWD EXTENT...THE SLIGHT RISK AREA HAS BEEN EXPANDED NWD TO INCLUDE MORE OF EAST CENTRAL KS INTO WEST CENTRAL MO. STORMS DEVELOPING IN THIS ENVIRONMENT...ESPECIALLY WITH A SURFACE WIND HAVING AN ELY COMPONENT WILL HAVE ENHANCED LOW LEVEL SHEAR...AND THUS A TORNADO THREAT CANNOT BE RULED OUT. GIVEN THESE FACTORS...A 5 PERCENT TORNADO PROBABILITY HAS BEEN INTRODUCED ACROSS SERN-E CENTRAL KS INTO PARTS OF WRN/CENTRAL MO FOR THIS AFTERNOON AND EVENING. THIS SLIGHT RISK EXPANSION IS SUPPORTED BY MODEL GUIDANCE FROM THE 12Z 4KM WRF-NMM/WRF-NSSL AND 16Z HRRR. HOWEVER...CONSIDERABLE UNCERTAINTY REMAINS REGARDING CONVECTIVE INITIATION ACROSS THIS AREA. ...SRN HIGH PLAINS... VISIBLE SATELLITE AND RADAR IMAGERY SHOWED A BOUNDARY EXTENDING FROM 50 NW ABI-20 NW BGS-25 NNE HOB. THE AIR MASS HAS BECOME MODERATELY UNSTABLE IN THIS REGION AND THE 16Z HRR AND 12Z 4KM WRF-NMM SUGGESTS ISOLATED TSTM DEVELOPMENT ACROSS THIS AREA. THUS...THE SLIGHT RISK AREA HAS BEEN EXPANDED SWD. ..PETERS.. 04/29/2012 .PREV DISCUSSION... /ISSUED 1136 AM CDT SUN APR 29 2012/ ...SRN PLAINS FROM NW ACROSS CNTRL OK TO MO... A WEAKENING BAROCLINIC ZONE/INVERTED TROUGH AXIS EXTENDS FROM WEST TX NEWD ACROSS CNTRL OK...AND THEN EAST AS A WARM FRONT FROM MO TO THE LOWER THE OH VALLEY THIS MORNING. THIS FRONTAL ZONE LIES WITHIN A BROAD BELT OF DEEP-LAYER CYCLONIC FLOW ON THE SERN FLANK OF A LARGE SCALE TROUGH CURRENTLY SITUATED OVER THE INTERMOUNTAIN WEST AND NRN PLAINS. THE LARGE SCALE TROUGH AXIS IS FORECAST TO TRANSLATE NEWD ACROSS THE CNTRL/NRN PLAINS TO THE UPPER MS VALLEY WHILE UNDERGOING DEAMPLIFICATION THROUGH MONDAY MORNING. AS THIS OCCURS...LOW LEVEL FRONTAL ZONE FROM TX TO MO MAY GRADUALLY LIFT/REFORM NWD WHILE REMAINING SITUATED WITHIN/BENEATH A SWATH OF 40-50KT SWLY FLOW AT MID LEVELS. SUBSTANTIAL CONVECTIVE OVERTURNING AND LOCAL REINFORCEMENT OF THE BAROCLINIC BOUNDARY OCCURRED OVERNIGHT FROM PORTIONS OF WEST TX INTO OK AND CONTINUES ACROSS MO THIS MORNING WHERE AN MCS WAS BEING SUSTAINED NORTH OF THE FRONT. A WARM/MOIST AIRMASS WILL PERSIST ALONG AND SOUTH OF THE FRONT TODAY WHERE WARMER TEMPERATURES ALOFT SHOULD SUBSTANTIALLY LIMIT CONVECTIVE DEVELOPMENT POTENTIAL WITH SWD EXTENT. SBCAPE NEAR THE BOUNDARY IS FORECAST TO INCREASE TO AROUND 2000 J/KG WITH HEATING OF THE DAY AND EXPECT THAT FOCUSED AND PERSISTENT LOW LEVEL CONVERGENCE ALONG THE BOUNDARY...IN CONCERT WITH POCKETS OF STRONGER HEATING...WILL PROMOTE TSTM DEVELOPMENT FROM NWRN TX NEWD ACROSS OK AND INTO SERN KS AND MO THROUGH THE LATE AFTERNOON. MODEST EFFECTIVE SHEAR WITHIN THIS ZONE WILL LIKELY SUPPORT STORM ORGANIZATION WITH MULTICELL TO WEAK SUPERCELL STORM STRUCTURES POSSIBLE. HOWEVER...FORECAST PROFILES INDICATE THAT MID LEVEL SWLY FLOW COINCIDENT WITH STRONGEST INSTABILITY WILL WEAKEN WITH TIME...PERHAPS RESULTING IN AN EVOLUTION TOWARD MORE MULTICELLULAR STORMS. SOME INCREASE IN CONVECTIVE VIGOR AND COVERAGE MAY OCCUR INTO THE EVENING AS INITIAL ACTIVITY TAPS PEAK IN DIURNAL INSTABILITY AND RESULTANT COLD POOLS ACT TO REINFORCE THE LOW LEVEL BAROCLINIC ZONE COINCIDENT WITH AN INCREASE IN THE LOW LEVEL JET AND SUBSEQUENT ISENTROPIC ASCENT ACROSS THE BOUNDARY. EXPECT THIS CONVECTIVE SCENARIO TO RESULT IN A FEW HAIL AND WIND EVENTS FROM NRN TX TO MO THROUGH THE PERIOD. ...SRN HIGH PLAINS FROM ERN NM/CO ACROSS WRN KS AND TX/OK PNHDLS... THE COMBINATION OF POST-FRONTAL OROGRAPHIC LIFT AND STRONG SURFACE/BOUNDARY LAYER HEATING ACROSS THE FRONT RANGE AND ADJACENT HIGH PLAINS WILL AID IN BOOSTING CONVECTIVE INSTABILITY ACROSS THESE AREAS THROUGH THE AFTERNOON. DESPITE GENERALLY MEAGER LOW LEVEL MOISTURE CURRENTLY ACROSS THE REGION... EVAPOTRANSPIRATION AND INCREASE IN LOW LEVEL MOISTURE ADVECTION WILL COMBINE WITH STEEPENING LAPSE RATES AND CONTRIBUTE TO SBCAPE IN THE RANGE OF 500-1000 J/KG. WEAK DPVA WITH APPROACHING SHORT WAVE TROUGH NOW ACROSS SRN UT SHOULD ARRIVE COINCIDENT WITH MAXIMUM IN DIURNAL HEATING AND AID AT LEAST ISOLATED TSTM DEVELOPMENT. SUFFICIENT SHEAR WILL EXIST TO AID UPDRAFT PERSISTENCE/ROTATION WITH A COUPLE OF SUPERCELLS POSSIBLE. HAIL AND STRONG WINDS APPEAR POSSIBLE WITH THIS ACTIVITY AS IT DEVELOPS EAST INTO PARTS OF WRN KS AND THE PNHDLS OF TX/OK INTO THE EVENING.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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