SWODY2
SPC AC 060658
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CST FRI MAR 06 2009
VALID 071200Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTH CENTRAL PLAINS
AND LOWER/MIDDLE MO VALLEY...
...SYNOPSIS...
AN INITIALLY NEUTRAL TILT UPPER TROUGH IS EXPECTED TO STEADILY
TRANSITION EAST-NORTHEASTWARD FROM THE EASTERN GREAT BASIN/FOUR
CORNERS REGION EARLY SATURDAY...TO THE CENTRAL PLAINS/MIDDLE MO
VALLEY BY EARLY SUNDAY WHERE IT IS EXPECTED TO TAKE ON MORE OF A
NEGATIVE TILT. AT THE SURFACE...FRONTAL BOUNDARY IS EXPECTED TO
STALL/BECOME ESTABLISHED IN A GENERAL WEST-EAST CORRIDOR FROM KS TO
THE MIDWEST/OHIO VALLEY. LEE-SIDE SURFACE CYCLOGENESIS WILL OCCUR
DURING THE DAY ACROSS THE HIGH PLAINS...WITH A GRADUALLY DEEPENING
SURFACE LOW AND SHARPENING COLD FRONT/DRYLINE EXPECTED TO DEVELOP
EASTWARD ACROSS PORTIONS OF KS/OK/TX SATURDAY AFTERNOON/NIGHT. IN
THE PREFRONTAL WARM SECTOR...BOUNDARY LAYER MOISTURE WILL REMAIN
MODEST...WITH RETURN LIMITED IN THE WAKE OF LAST WEEKENDS DEEP
FRONTAL PENETRATION INTO THE GULF OF MEXICO.
...MIDDLE MO VALLEY TO IL/INDIANA SATURDAY MORNING...
SIMILAR TO THE LATE DAY 1 SCENARIO...SCATTERED ELEVATED
STRONG/POTENTIALLY SEVERE TSTMS WILL BE ONGOING AT THE BEGINNING OF
THE PERIOD SATURDAY MORNING VIA A 50 KT LOW LEVEL JET AIDED WARM
ADVECTION/ELEVATED MOISTURE TRANSPORT REGIME. AMIDST AMPLE SHEAR
THROUGH THE CLOUD BEARING LAYER FOR UPDRAFT ROTATION...A STEEP LAPSE
RATE ENVIRONMENT AND ELEVATED MUCAPE TO 500-1000 J/KG WILL SUPPORT A
CONTINUED HAIL RISK DURING THE MORNING ACROSS NORTHERN MO/SOUTHERN
IA INTO IL/INDIANA. THESE TSTMS AND ANY ASSOCIATED HAIL THREAT
SHOULD GRADUALLY SHIFT EAST-NORTHEASTWARD DURING THE MORNING ALONG
THE SURFACE-850 MB BAROCLINIC ZONE...WITH THE HAIL THREAT EXPECTED
TO WANE THROUGH MID/LATE MORNING AS THE LOW LEVEL JET WEAKENS/VEERS
WESTERLY.
...KS/OK/MO SATURDAY AFTERNOON/EVENING...
AHEAD OF THE UPPER TROUGH CROSSING THE ROCKIES...KS/OK SHOULD REMAIN
CAPPED MUCH OF THE DAY. HOWEVER...SUFFICIENT HEATING AND ONSET OF
LARGE SCALE HEIGHT FALLS COULD BE SUFFICIENT FOR ISOLATED SURFACE
BASED TSTM DEVELOPMENT AS EARLY AS MID AFTERNOON...BUT IT MUCH MORE
LIKELY SATURDAY EVENING ACROSS CENTRAL/EASTERN KS INTO OK
ALONG/AHEAD OF THE ADVANCING SURFACE LOW AND COLD FRONT/DRYLINE.
WARM SECTOR SURFACE DEWPOINTS WILL LIKELY TO BE LIMITED TO THE
LOWER/MIDDLE 50S F ACROSS THE SOUTH CENTRAL PLAINS/MO VALLEY
SATURDAY AFTERNOON/EVENING...AND THIS WILL BE THE PRIMARY LIMITING
FACTOR FOR A MORE APPRECIABLE SEVERE RISK. REGARDLESS...INCREASINGLY
STEEP MID LEVEL LAPSE RATES ATOP MODEST BOUNDARY LAYER MOISTURE
SHOULD RESULT IN 500-800 J/KG OF MLCAPE BY LATE AFTERNOON. BENEATH
50+ KT OF SOUTHWESTERLY MID LEVEL FLOW...STRONG SHEAR/AMPLE VEERING
WOULD SUPPORT A RISK OF WELL-ORGANIZED TSTMS INCLUDING
SUPERCELLS...WITH THE PRIMARY RISK OF SEVERE HAIL. IN SPITE OF A
RATHER DYNAMIC SCENARIO WITH STRONG SHEAR...THE LIMITED MOISTURE
SHOULD FAVOR A QUICKLY DECOUPLING BOUNDARY LAYER WITHIN AN HOUR OR
TWO OF SUNSET...WITH A NOCTURNAL TENDENCY FOR TSTMS TO BE BASED
ABOVE A SHALLOW STABLE LAYER.
...SOUTHERN OK/NORTH TX SATURDAY AFTERNOON/EVENING...
AS THE SOUTHERN PERIPHERY OF THE APPROACHING UPPER TROUGH/LARGE
SCALE HEIGHT FALLS...TSTM POTENTIAL/COVERAGE AND ANY ASSOCIATED
SEVERE THREAT BECOMES MUCH MORE CONDITIONAL WITH SOUTHWARD EXTENT
ACROSS SOUTHERN OK INTO PORTIONS OF NORTH CENTRAL TX. IF/WHERE TSTMS
DEVELOP SATURDAY LATE AFTERNOON/EARLY EVENING...MODEST INSTABILITY
AND FAVORABLE SHEAR PROFILES WOULD CONDITIONALLY SUPPORT A RISK OF
SUPERCELLS WITH MAINLY A SEVERE HAIL RISK.
...NORTHEAST KS/SOUTHEAST NEB TO IA/NORTHERN MO/IL LATE...
AS THE UPPER TROUGH REACHES THE CENTRAL PLAINS...AN INTENSIFYING LOW
LEVEL JET /50-55 KT/ AND ASSOCIATED WARM ADVECTION REGIME SHOULD
AGAIN INCREASE HAIL POTENTIAL ACROSS THE MIDDLE MO VALLEY/MIDWEST
SATURDAY NIGHT INTO EARLY SUNDAY.
..GUYER.. 03/06/2009
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