SWODY3
SPC AC 230725
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0225 AM CDT FRI MAY 23 2008
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF WI/IL WWD/SWWD
INTO ERN PARTS OF NEB/KS...
...SYNOPSIS...
SHORT WAVE TROUGH OVER THE UPPER GREAT LAKES SUNDAY MORNING WILL
WEAKEN THROUGH THE DAY WHILE MOVING INTO AN INCREASINGLY CONFLUENT
MIDLEVEL FLOW REGIME OVER ONTARIO/QUEBEC. A 40-50 KT BELT OF SWLY
FLOW WILL PERSIST IN IT/S WAKE SWWD THROUGH THE CORN BELT INTO SRN
ROCKIES IN ADVANCE OF NEXT SHORT WAVE TROUGH LIFTING NEWD THROUGH
THE LOWER CO VALLEY.
IN THE LOW LEVELS...LATEST MODEL GUIDANCE INDICATES SLIGHT PHASE
DIFFERENCES IN THE EWD PROGRESSION OF SURFACE LOW AND ATTENDANT
SURFACE BOUNDARIES ACROSS THE NRN PLAINS IN THE UPPER GREAT LAKES.
IN GENERAL...PRIMARY SURFACE LOW IS FORECAST TO DEVELOP FROM ND EWD
THROUGH THE UPPER MS VALLEY BEFORE WEAKENING OVER THE UPPER GREAT
LAKES. AN ASSOCIATED WARM FRONT WILL CONCURRENTLY LIFT NEWD THROUGH
THE CORN BELT INTO THE UPPER GREAT LAKES WHILE A TRAILING
TROUGH/WEAK COLD FRONT PUSHES EWD/SEWD THROUGH THE UPPER MS VALLEY
SWWD INTO THE CNTRL PLAINS.
...UPPER GREAT LAKES SWWD INTO CNTRL PLAINS...
LATEST MODEL GUIDANCE INDICATES THAT PREVAILING SWLY MIDLEVEL FLOW
WILL ALLOW FOR THE NEWD EXPANSION OF STEEP LAPSE RATE /EML/ PLUME
FROM THE CNTRL PLAINS INTO THE UPPER GREAT LAKES. THESE LAPSE RATES
IN CONJUNCTION WITH A MOIST BOUNDARY LAYER BEING ADVECTED NEWD
ACROSS THE CORN BELT WILL RESULT IN THE DEVELOPMENT OF A MODERATE TO
POTENTIALLY STRONGLY UNSTABLE AIR MASS SUNDAY AFTERNOON WITHIN
SYSTEM WARM SECTOR.
CLUSTERS OF ELEVATED TSTMS ARE EXPECTED TO BE ONGOING SUNDAY MORNING
WITHIN LOW-LEVEL WAA PATTERN ATTENDANT TO MIGRATORY SHORT WAVE
TROUGH OVER THE UPPER GREAT LAKES. THIS ACTIVITY WILL LIKELY SPREAD
EWD THROUGH THE DAY...GRADUALLY WEAKENING WHILE BECOMING FURTHER
DISPLACED FROM PRIMARY INSTABILITY AXIS. MORE SIGNIFICANT...DIURNAL
TSTM DEVELOPMENT IS EXPECTED BY AFTERNOON OR EARLY EVENING ALONG
SURFACE TROUGH/WEAK COLD FRONT OVER MN/WRN WI SWD/SWWD INTO IA/ERN
NEB. THE COMBINATION OF THE MODERATE TO STRONG INSTABILITY AND
MODERATELY STRONG DEEP LAYER SHEAR INDICATE THE POTENTIAL FOR
SUPERCELLS AND/OR LARGER-SCALE BOWING STRUCTURES CAPABLE OF LARGE
HAIL...DAMAGING WINDS AND A FEW TORNADOES.
STORMS MAY TEND TO GROW UPSCALE INTO A SEVERE MCS SUNDAY NIGHT WHICH
WOULD EVENTUALLY MOVE INTO PORTIONS OF WI/NRN IL. ADDITIONAL SEVERE
STORMS MAY BACKBUILD WWD INTO ERN NEB ALONG NOSE OF NOCTURNAL LLJ
JET STRENGTHENING ACROSS THE SRN/CNTRL PLAINS.
...OZARK PLATEAU...
A MOIST AND MODERATE TO STRONGLY UNSTABLE AIR MASS WILL PERSIST
ALONG AND W OF SURFACE WARM FRONT SLOWLY PIVOTING EWD. VERTICAL
SHEAR WILL REMAIN RELATIVELY WEAK AS WILL LARGE-SCALE FORCING FOR
ASCENT. HOWEVER...THE DEGREE OF INSTABILITY AND PRESENCE OF THE
LOW-LEVEL CONFLUENT FLOW INVOF THIS BOUNDARY SHOULD BE SUPPORTIVE OF
A FEW ORGANIZED MULTICELL STORMS CAPABLE OF MAINLY DAMAGING WIND
GUSTS.
...CNTRL/SRN HIGH PLAINS...
LOW-LEVEL MASS FIELDS WILL BEGIN TO RESPOND TO UPPER SYSTEM MOVING
THROUGH THE LOWER CO VALLEY WITH A LEE CYCLONE DEVELOPING OVER ERN
CO SUNDAY. INITIALLY...DRYLINE IS EXPECTED TO MIX EWD ACROSS THE
HIGH PLAINS IN RESPONSE TO UPPER SYSTEM LIFTING NEWD INTO THE GREAT
LAKES. HOWEVER...LATER SUNDAY AFTERNOON AND MORE SO SUNDAY
NIGHT...THIS BOUNDARY WILL RETREAT WWD OWING TO THE UPSTREAM
CYCLOGENESIS.
LATEST MODEL GUIDANCE IS RATHER CONSISTENT IN SUGGESTING THAT AT
LEAST ISOLATED...DIURNAL TSTMS WILL BE POSSIBLE ALONG THE DRYLINE
SUNDAY AFTERNOON AND EVENING. RICHER BOUNDARY LAYER MOISTURE MAY BE
DISPLACED E OF SURFACE DRYLINE WITH FORECAST SOUNDINGS INDICATING
RELATIVELY LARGE T/TD SPREADS. NONETHELESS...THE PRESENCE OF STEEP
LAPSE RATES AND MODESTLY STRONG VERTICAL SHEAR SUGGEST SOME
POTENTIAL FOR STORM ORGANIZATION WITH THE PRIMARY THREATS BEING
LARGE HAIL AND DAMAGING WINDS. SOME OF THE DIURNAL STORMS MAY
PERSIST WELL INTO SUNDAY NIGHT AS THEY INTERACT WITH THE RICHER
BOUNDARY LAYER MOISTURE RETURNING WWD/NWWD ALONG STRENGTHENING LLJ.
..MEAD.. 05/23/2008
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