SWODY1
SPC AC 260535
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1235 AM CDT SAT JUL 26 2008
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
CNTRL PLAINS INTO THE UPPER MS VALLEY...
...SYNOPSIS...
SYNOPTIC UPPER PATTERN WILL REMAIN DOMINATED BY A TROUGH OVER THE
GREAT LAKES...A RIDGE OVER THE NRN HIGH PLAINS AND A TROUGH OVER THE
PACIFIC NW. A SHORTWAVE TROUGH CURRENTLY APPROACHING THE NRN ROCKIES
WILL CREST UPPER RIDGE OVER THE NRN HIGH PLAINS SATURDAY BEFORE
TURNING ESEWD TOWARD INTO THE DAKOTAS BY LATE AFTERNOON. A COLD
FRONT WILL CONTINUE EWD THROUGH THE GREAT LAKES...APPROACHING NY BY
SATURDAY EVENING. A LEE TROUGH WILL BECOME ESTABLISHED OVER THE NRN
HIGH PLAINS WITH A WARM FRONT EXTENDING ESEWD THROUGH SD AND THE
UPPER MS VALLEY.
...NRN AND CNTRL PLAINS AREA...
RESERVOIR OF RICHER BOUNDARY LAYER MOISTURE WITH DEWPOINTS IN THE
UPPER 60S WILL ADVECT NWD THROUGH NEB AND SD AS SLY FLOW BECOMES
BETTER ESTABLISHED EAST OF DEVELOPING LEE TROUGH. PLUME OF VERY WARM
ELEVATED MIXED LAYER AIR WITH 14-16C AT 700 MB WILL ADVECT EWD INTO
THE HIGH PLAINS ABOVE MOIST AXIS. THESE PROCESSES IN CONJUNCTION
WITH DIABATIC HEATING WILL CONTRIBUTE TO POTENTIAL FOR STRONG
INSTABILITY DURING THE AFTERNOON. HOWEVER...THE WARM BML MAY ALSO
SERVE TO CAP PART OF WARM SECTOR TO SURFACE BASED STORMS MUCH OF THE
DAY.
ELEVATED NON SEVERE CONVECTION MAY STILL BE ONGOING EARLY SATURDAY
IN ASSOCIATION WITH WEAK LEAD IMPULSE MOVING THROUGH THE CNTRL
PLAINS. OTHER STORMS WILL LIKELY DEVELOP DURING THE AFTERNOON OVER
THE HIGHER TERRAIN OF MT AND WY. STORMS WILL SPREAD EWD THROUGH THE
HIGH PLAINS WHERE ELY LOW LEVEL FLOW SHOULD MAINTAIN BOUNDARY LAYER
DEWPOINTS IN THE 50S WITH MODERATE INSTABILITY. PRONOUNCED
DIRECTIONAL SHEAR AND 30-40 KT WLY FLOW AT 6 KM WILL RESULT IN BULK
SHEAR SUFFICIENT FOR ORGANIZED STORMS INCLUDING SUPERCELLS WITH
LARGE HAIL AND DAMAGING WIND THE MAIN THREATS.
STORM DEVELOPMENT FARTHER EAST ACROSS NEB AND SD WILL BE MORE
COMPLICATED BY STRONGER CAP WHICH INCREASES UNCERTAINTY REGARDING
STORM COVERAGE DURING THE DAY. A FEW STORMS MAY DEVELOP BY LATE
AFTERNOON IN VICINITY OF BAROCLINIC ZONE AS SHORTWAVE TROUGH CRESTS
UPPER RIDGE AND INHIBITION WEAKENS. WHERE STORMS FORM...SUPERCELLS
CAPABLE OF PRODUCING VERY LARGE HAIL WILL BE LIKELY GIVEN STRONG 50
KT BULK SHEAR AND STRONG INSTABILITY. SLY LOW LEVEL JET WILL
STRENGTHEN DURING THE EVENING...ENHANCING LIFT IN VICINITY OF WARM
FRONT OVER SD. THIS WILL PROVIDE SUPPORT FOR ADDITIONAL STORMS TO
DEVELOP WITH A THREAT OF LARGE HAIL AND DAMAGING WIND. STORMS WILL
LIKELY EVOLVE INTO AN MCS AND SHIFT ESEWD ALONG THE INSTABILITY
GRADIENT INTO IA OVERNIGHT.
A WINDOW OF OPPORTUNITY MAY ALSO EXIST FOR ISOLATED TORNADOES IF
STORMS MANAGE TO DEVELOP FAR ENOUGH EAST INTO MOIST WARM SECTOR
ACROSS SD AND NRN NEB...MAINLY DURING THE EARLY EVENING AS THE LOW
LEVEL JET STRENGTHENS AND BEFORE THE BOUNDARY LAYER DECOUPLES AND
STORMS EVOLVE INTO AN MCS.
...OH VALLEY THROUGH NY...
MOIST AXIS WILL SHIFT EWD THROUGH THE OH VALLEY AND INTO NY AHEAD OF
FRONT. THIS WILL RESULT IN POTENTIAL FOR DESTABILIZATION WHERE
DIABATIC HEATING OCCURS. HOWEVER...WEAK LAPSE RATES SHOULD LIMIT
MLCAPE TO BELOW 1500 J/KG. STORMS WILL LIKELY DEVELOP AHEAD OF FRONT
WITHIN ZONE OF WEAK CAP AND ASCENT ASSOCIATED WITH SHORTWAVE TROUGH.
UNIDIRECTIONAL WLY FLOW WITH 20-30 KT BULK SHEAR WILL SUPPORT
MULTICELLS. THE STRONGER STORMS MAY BECOME CAPABLE OF PRODUCING
ISOLATED STRONG WIND GUSTS DURING THE AFTERNOON.
..DIAL/HURLBUT.. 07/26/2008
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