SWODY2
SPC AC 230540
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT WED APR 23 2008
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE CNTRL
PLAINS INTO THE MID-UPPER MS VALLEY...
...SYNOPSIS...
LEAD SHORTWAVE TROUGH THAT WILL MOVE THROUGH THE PLAINS WEDNESDAY
WILL EJECT NEWD THROUGH THE MID-UPPER MS VALLEY EARLY THURSDAY AND
THE GREAT LAKES LATER THURSDAY AFTERNOON. A SRN PIECE OF THIS TROUGH
IS FORECAST SHIFT EAST THROUGH THE LOWER MS VALLEY AND A PORTION OF
THE SERN STATES. ANOTHER UPPER TROUGH WILL MOVE THROUGH THE CNTRL
ROCKY MOUNTAIN REGION...REACHING THE CNTRL HIGH PLAINS THURSDAY
EVENING. WEAK IMPULSES EMBEDDED WITHIN SUBTROPICAL MOISTURE PLUME
MAY MOVE THROUGH S TX.
COLD FRONT WILL LIKELY STRETCH FROM NW MN SWWD THROUGH SD AND NRN
ROCKIES THURSDAY MORNING. SHORTWAVE TROUGH THAT WILL EJECT THROUGH
THE UPPER MS VALLEY EARLY WILL PROVIDE IMPETUS FOR THE FRONT TO MOVE
SWD. DRYLINE WILL PERSIST SOUTH OF THE FRONT THROUGH THE CNTRL AND
SRN PLAINS AND MIX EWD DURING THE DAY. SURFACE LOW WILL LIKELY
DEVELOP ALONG PORTION OF FRONT OVER WRN KS IN RESPONSE TO VERTICAL
MOTION ATTENDING UPPER TROUGH MOVING OUT OF THE CNTRL ROCKIES. THE
FRONT WILL SURGE SWD INTO THE SRN PLAINS AS THE LOW LIFTS NEWD
OVERNIGHT.
...CNTRL PLAINS THROUGH UPPER MS VALLEY...
BOUNDARY LAYER DEWPOINTS IN THE 60S WILL PERSIST IN WARM SECTOR FROM
TX NWD THROUGH OK AND KS WITH UPPER 50S TO LOW 60S MORE LIKELY INTO
ERN NEB AND THE UPPER MS VALLEY. STORMS SHOULD BE ONGOING OVER A
LARGE PART OF THE CNTRL THROUGH NRN PLAINS AND MID-UPPER MS VALLEY
EARLY THURSDAY WITHIN ZONE OF WARM ADVECTION AND LIFT ACCOMPANYING
THE EJECTING SHORTWAVE TROUGH AND ATTENDANT LOW LEVEL JET. ACTIVITY
WILL SHIFT NE WITH TIME...ALLOWING PORTIONS OF UPSTREAM WARM SECTOR
TO DESTABILIZE WHERE LOW CLOUDS CAN MIX OUT. SW FLOW ALOFT WILL
MAINTAIN STEEP MID LEVEL LAPSE RATES OVER THE MOIST AXIS WITH
MODERATE INSTABILITY POSSIBLE BY LATE AFTERNOON.
INITIAL LOW LEVEL JET WILL SHIFT EWD LEAVING WEAK LOW LEVEL FLOW
OVER DESTABILIZING WARM SECTOR. HOWEVER...BOUNDARY LAYER FLOW WILL
INCREASE TOWARD EVENING OVER THE CNTRL PLAINS AS LOW LEVEL JET
STRENGTHENS WITHIN ZONE OF HEIGHT FALLS DOWNSTREAM FROM UPPER TROUGH
AND DEVELOPING SURFACE LOW. THIS PROCESS WILL CONTRIBUTE TO
INCREASING FRONTOGENETIC FORCING AND DEEP ASCENT ALONG THE FRONT AS
THE UPPER TROUGH ADVANCES EWD. STORMS WILL LIKELY REDEVELOP ALONG
THE FRONT BY LATE AFTERNOON OR EARLY EVENING AND SHIFT SEWD
OVERNIGHT. VERTICAL SHEAR PROFILES WILL BECOME SUPPORTIVE OF
SUPERCELLS WITH INITIAL STORMS THAT DEVELOP...BUT ACTIVITY WILL
LIKELY GROW UPSTREAM INTO AN MCS WITH LARGE HAIL AND DAMAGING WIND
THE MAIN THREATS.
THREAT WITH SWD EXTENT ACROSS KS IS MORE CONDITIONAL DUE TO PRESENCE
OF A STRONGER CAP. HOWEVER...POTENTIAL WILL EXIST FOR ISOLATED
STORMS TO DEVELOP AS THE DRYLINE MIXES EWD AND THE LOW LEVEL JET
STRENGTHENS BY EARLY EVENING. VERTICAL SHEAR WILL BECOME SUPPORTIVE
OF SUPERCELLS WITH LARGE HAIL LIKELY...ALONG WITH A WINDOW FOR
ISOLATED TORNADOES.
...MID MS VALLEY...
STRONG LOW-MID LEVEL WIND FIELDS WILL MOVE THROUGH THIS REGION IN
ATTENDANCE WITH EJECTING UPPER TROUGH. LOW LEVEL HODOGRAPHS AND
VERTICAL SHEAR WOULD SUPPORT POTENTIAL FOR SUPERCELLS AND ISOLATED
TORNADOES. HOWEVER...WITH STORMS LIKELY TO BE ONGOING EARLY IN THE
PERIOD...DESTABILIZATION POTENTIAL WILL BE LOW...AND THIS COULD
LIMIT OVERALL THREAT. IF IT BEGINS TO APPEAR MORE INSTABILITY WILL
DEVELOP IN THIS REGION THAN CURRENTLY ANTICIPATED...AN UPGRADE TO
SLIGHT RISK MAY BE NEEDED IN LATER OUTLOOKS.
...SRN PLAINS...
STEEP MID LEVEL LAPSE RATES ABOVE RICH LOW LEVEL MOISTURE WILL
CONTRIBUTE TO MODERATE INSTABILITY OVER CNTRL AND S TX. PRESENCE OF
CAP RESULTING FROM THE EML WILL PROBABLY LIMIT OVERALL THUNDERSTORM
COVERAGE IN THIS REGION. HOWEVER...WEAK IMPULSES EMBEDDED WITHIN
SUBTROPICAL MOISTURE PLUME MIGHT ENHANCE POTENTIAL FOR THUNDERSTORM
INITIATION EAST OF THE DRYLINE AS THE BOUNDARY LAYER WARMS. WEAK
SELY LOW LEVEL FLOW BENEATH MODEST WLY MID-UPPER FLOW WILL
CONTRIBUTE TO VERTICAL SHEAR PROFILES AT LEAST MARGINALLY SUPPORTIVE
OF UPDRAFT ROTATION. PRIMARY THREAT WOULD BE LARGE HAIL IF STORMS
MANAGED TO DEVELOP. UNCERTAINTY REGARDING INITIATION POTENTIAL AND
POSSIBLY LIMITED STORM COVERAGE PRECLUDES INTRODUCING MORE THAN 5%
SEVERE PROBABILITIES AT THIS TIME.
..DIAL.. 04/23/2008
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