SPC AC 060546
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT SAT JUN 06 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM IA TO SWRN TX...
...SYNOPSIS...
LARGE SCALE PATTERN WILL BECOME A BIT MORE TYPICAL OF EARLY JUNE
OVER THE NEXT FEW DAYS AS STRONGER MID LEVEL FLOW BEGINS TO SAG
SOUTH ACROSS THE MIDDLE OF THE CONUS. WITH TIME BOUNDARY LAYER WILL
GRADUALLY MOISTEN AND INCREASING INSTABILITY WILL CONTRIBUTE TO AN
EXPANDING THREAT OF STRONG-SEVERE THUNDERSTORMS...PRIMARILY ALONG
SYNOPTIC FRONTAL ZONE...AND AT TIMES NEAR THE DRYLINE OVER THE
SRN/CNTRL PLAINS.
...CENTRAL PLAINS/MID MS VALLEY...
00Z MODELS ALL SUGGEST ONGOING MCS WILL SPREAD EAST ACROSS NEB INTO
IA BY SUNRISE AS LLJ VEERS A BIT OVER CNTRL KS. IF THIS ACTIVITY
CONTINUES TO EXPAND...A DEVELOPING COLD POOL COULD SURGE SEWD AND
BECOME THE EFFECTIVE BOUNDARY FOR LATE AFTERNOON CONVECTION.
RESULTANT SEVERE RISK WOULD THEN SHIFT TO THE SRN OUTFLOW WHICH
COULD BECOME ORIENTED NEAR THE IA/MO BORDER...ARCING INTO SERN NEB.
AT THIS TIME IT APPEARS BOUNDARY LAYER WILL RECOVER ALONG WRN
PERIPHERY OF EARLY MORNING MCS OVER SCNTRL NEB WHERE STEEP LAPSE
RATES WILL ALLOW SFC PARCELS TO REACH THEIR CONVECTIVE TEMPERATURES
BY LATE AFTERNOON. NAM IS MORE AGGRESSIVE WITH THUNDERSTORM
DEVELOPMENT ALONG PERCEIVED OUTFLOW WHILE GFS ALLOWS FOR RECOVERY
ALONG SYNOPTIC FRONT ACROSS ERN NEB. IT/S NOT ENTIRELY CLEAR HOW
INFLUENTIAL EARLY MORNING MCS WILL BE...BUT IT DOES APPEAR STRONG
HEATING OVER SCNTRL NEB/NCNTRL KS WILL AID IN SEVERE THUNDERSTORM
INITIATION BY LATE AFTERNOON. FORECAST SHEAR PROFILES ARE MORE THAN
ADEQUATE FOR SUPERCELLS WITH H5 FLOW ON THE ORDER OF 50KT AND
VEERING LOW LEVEL FLOW FROM THE SE INTO THE SW AT MID LEVELS. FOR
THIS REASON IT APPEARS A CLUSTER OF SEVERE THUNDERSTORMS...SOME
SUPERCELLULAR WILL EVOLVE BY EARLY EVENING...MOST LIKELY OVER SERN
NEB INTO WCNTRL IA. THIS ACTIVITY WILL THEN PROPAGATE EAST ACROSS
THE MID MS VALLEY AS LLJ VEERS TOWARD NRN IL LATE.
...SRN HIGH PLAINS...
VERY STRONG BOUNDARY LAYER HEATING WILL CONTRIBUTE TO A SLIGHT EWD
MIXING OF THE DRYLINE ACROSS WRN KS INTO THE TX PANHANDLE SATURDAY
AS SFC TEMPERATURES SOAR WELL INTO THE 90S. NEEDLESS TO SAY
CONVECTIVE INHIBITION WILL BECOME NILL BY LATE AFTERNOON AND DRYLINE
SHOULD PROVE CONVERGENT ENOUGH FOR ISOLATED THUNDERSTORM
DEVELOPMENT. ALTHOUGH SHEAR PROFILES WILL BE CONSIDERABLY WEAKER
THAN ACTIVITY OVER THE CNTRL PLAINS...SLOW MOVING MULTICELL OR
PERHAPS SUPERCELLS SHOULD BE NOTED ACROSS WRN OK INTO THE EDWARDS
PLATEAU OF SWRN TX.
...NRN ME...
STRONG MID LEVEL JET MAX WILL INCREASE TO SPEEDS IN EXCESS OF 90KT
AT 500 MB AS IT EJECTS ACROSS ME. LATEST MODEL GUIDANCE INDICATES
FAVORABLE LEFT EXIT REGION OF UPPER JET WILL OVERSPREAD NRN NEW
ENGLAND...COINCIDENT WITH FRONTAL PASSAGE IN THE 00Z-03Z TIME FRAME.
VERY COLD H5 TEMPERATURES NORTH OF JET AXIS WILL CONTRIBUTE TO
STEEP LAPSE RATES WITHIN STRONGLY SHEARED WLY FLOW REGIME. AT THIS
TIME IT APPEARS BOUNDARY LAYER MOISTURE/INSTABILITY WILL BE A BIT
TOO LOW TO WARRANT MORE THAN LOW PROBABILITIES FOR HAIL AND DAMAGING
WINDS. HOWEVER...GIVEN THE STRENGTH OF THIS SYSTEM A SLIGHT RISK
MAY BE ADDED IF IT BECOMES APPARENT THAT BUOYANCY WILL BE GREATER
THAN MODELS SUGGEST.
..DARROW/JEWELL.. 06/06/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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