SPC AC 220600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SAT MAY 22 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE CNTRL AND
NRN PLAINS AND UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE CNTRL
CAROLINAS...
...SYNOPSIS...
SHORTWAVE TROUGH NOW OVER THE OH VALLEY/GREAT LAKES WILL WEAKEN AS
IT ADVANCES SLOWLY EAST TOWARD THE MID ATLANTIC AND NERN STATES.
BROAD UPPER TROUGH OVER THE WRN U.S. WILL UNDERGO FURTHER
AMPLIFICATION. AN UPPER JET MAX NOW MOVING THROUGH THE BASE OF THE
UPPER TROUGH AND INTO THE GREAT BASIN REGION WILL EJECT NEWD INTO
THE CNTRL AND NRN HIGH PLAINS THIS AFTERNOON. LEE CYCLONE INITIALLY
OVER WRN SD EARLY SATURDAY WILL LIFT NWD DURING THE DAY IN
ASSOCIATION WITH IMPULSE EJECTING THROUGH ERN PERIPHERY OF UPPER
TROUGH. IN THE PROCESS A COLD FRONT WILL ADVANCE EWD THROUGH THE
CNTRL AND NRN PLAINS. DRYLINE WILL EXTEND NWD THROUGH THE SRN AND
CNTRL PLAINS WHERE IT WILL INTERSECT THE COLD FRONT ACROSS NEB.
...CNTRL AND NRN PLAINS AREAS...
A STRONG 50+ KT SLY LOW-LEVEL JET EAST OF LEE CYCLONE WILL RAPIDLY
ADVECT 60+ F DEWPOINTS NWD THROUGH PRE-FRONTAL WARM SECTOR ACROSS
THE CNTRL AND NRN PLAINS BENEATH STEEP LAPSE RATES. AN AXIS OF
2000-3000 J/KG MLCAPE WILL BECOME LIKELY AS THE BOUNDARY LAYER
WARMS. A WARM EML WITH TEMPERATURES UP TO 14C AT 700 MB WILL LIKELY
CAP THE WARM SECTOR MUCH OF THE DAY. HOWEVER...MESOSCALE FORCING
WILL INCREASE DURING THE LATE AFTERNOON INTO THE EARLY EVENING IN
ASSOCIATION WITH EJECTING IMPULSE...ACCELERATING COLD FRONT AND
STRENGTHENING LOW-LEVEL JET. STORMS WILL LIKELY DEVELOP ALONG THE
FRONT FROM PARTS OF NEB NWD INTO THE DAKOTAS. EFFECTIVE VERTICAL
SHEAR OF 40-45 KT AND STRONG INSTABILITY WILL SUPPORT SUPERCELLS.
WINDOW OF OPPORTUNITY WILL EXIST FOR ISOLATED VERY LARGE HAIL AND
ISOLATED TORNADOES FROM CNTRL NEB INTO THE CNTRL/ERN DAKOTAS INTO
THE EARLY EVENING. HOWEVER...STORMS WILL LIKELY GROW UPSCALE INTO A
LINEAR MCS DURING THE EVENING WITH AN INCREASING THREAT FOR DAMAGING
WIND AS STORMS MOVE NEWD TOWARD THE UPPER MS VALLEY.
...SRN PLAINS...
THE ATMOSPHERE WILL BECOME QUITE UNSTABLE EAST OF THE DRYLINE ACROSS
THE SRN PLAINS. A STRONG CAP RESULTING FROM A WARM EML AND WEAKER
FORCING IN THIS REGION SHOULD LIMIT STORM COVERAGE. HOWEVER...VERY
ISOLATED STORMS MAY DEVELOP BY LATE AFTERNOON WITHIN THE ZONE OF
DEEPER MIXING IN VICINITY OF THE DRYLINE AS WELL AS FARTHER SOUTH
OVER THE MOUNTAINS OF SWRN TX. VERTICAL SHEAR WILL SUPPORT
SUPERCELLS WITH A THREAT FOR MAINLY ISOLATED LARGE HAIL AND PERHAPS
A TORNADO. ANY STORMS THAT MANAGE TO DEVELOP SHOULD DISSIPATE
RAPIDLY WITHIN AN HOUR OR TWO AFTER SUNSET.
...CAROLINAS...
POTENTIAL WILL EXIST FOR STORMS TO DEVELOP OVER THE HIGHER TERRAIN
AND IN ASSOCIATION WITH LOBE OF VORTICITY ROTATING THROUGH UPPER
TROUGH BASE. THE STORMS WILL SUBSEQUENTLY SPREAD EWD INTO THE CNTRL
CAROLINAS. BOUNDARY LAYER WARMING AND MID-UPPER 60S DEWPOINTS WILL
CONTRIBUTE TO MODERATE INSTABILITY AND 30-35 KT VERTICAL SHEAR ALONG
SRN PERIPHERY OF UPPER TROUGH COULD RESULT IN ORGANIZED MULTICELLS
OR STORMS WITH MARGINAL SUPERCELL STRUCTURES. ISOLATED DAMAGING WIND
AND HAIL WILL BE THE MAIN THREATS...MAINLY DURING THE AFTERNOON.
...MID ATLANTIC THROUGH OH VALLEY...
SCATTERED CONVECTION WILL CONTINUE DEVELOPING ALONG SURFACE BOUNDARY
AND WITHIN ZONE OF DPVA ASSOCIATED WITH SLOW MOVING UPPER TROUGH.
HOWEVER...THE UPPER LOW CONTINUES TO FILL AND WEAKEN AND VERTICAL
SHEAR WILL LIKELY BE WEAKER THAN ON FRIDAY. MOREOVER...WIDESPREAD
CLOUDS WILL LIMIT INSTABILITY. A MODEST THREAT FOR ISOLATED DAMAGING
WIND AND HAIL MAY EXIST WITH STORMS DEVELOPING DURING THE DAY...BUT
OVERALL THREAT DOES NOT WARRANT A CATEGORICAL RISK AT THIS TIME.
..DIAL/GRAMS.. 05/22/2010
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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