SPC AC 030826
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 AM CST MON NOV 03 2008
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS WED/WED NIGHT ACROSS PARTS OF
THE PLAINS AND LWR/MID MO VALLEY....
...SYNOPSIS...
WHILE A FAIRLY DEEP LOW/MID-LEVEL CYCLONE WITHIN A SOUTHERN BRANCH
OF SPLIT POLAR WESTERLIES ONLY VERY SLOWLY SHIFTS EAST OF THE
SOUTHERN MID ATLANTIC COAST...MODELS INDICATE THAT THE AXIS OF AN
AMPLIFIED UPSTREAM UPPER TROUGH WILL SHIFT EAST OF THE ROCKIES INTO
THE PLAINS DURING THIS FORECAST PERIOD. THIS IS PROGGED TO OCCUR AS
AN EMBEDDED POLAR JET CORE...AND ASSOCIATED PRIMARY MID-LEVEL
IMPULSE...PROGRESS THROUGH THE BASE OF THE UPPER TROUGH...AND
UPSTREAM RIDGING BEGINS TO BUILD INTO THE PACIFIC COAST STATES.
WHILE THE DEEP CYCLONE ACCOMPANYING THE LARGER SCALE TROUGH MAY NOT
DEEPEN SIGNIFICANTLY FURTHER...A STRONG COLD FRONT APPEARS LIKELY TO
SURGE TO THE LEE OF THE ROCKIES...THROUGH MUCH OF THE PLAINS BY 12Z
THURSDAY. THIS IS EXPECTED TO BE PRECEDED BY A MORE SUBSTANTIVE
RETURN FLOW OF MOISTURE OFF THE GULF OF MEXICO...WHICH MAY
CONTRIBUTE TO AN OUTBREAK OF SEVERE STORMS LATE WEDNESDAY AFTERNOON
AND WEDNESDAY NIGHT.
...PLAINS/MISSISSIPPI VALLEY...
THE STRENGTH OF MID-LEVEL INHIBITION ASSOCIATED WITH AN ELEVATED
MIXED LAYER EMANATING FROM THE PLATEAU REGION...THE MAGNITUDE OF THE
LOW-LEVEL MOISTURE RETURN THROUGH THE PLAINS...AND SUBTLE
DIFFERENCES AMONG THE MODELS CONCERNING SMALLER SCALE DETAILS OF THE
LARGE SCALE PATTERN EVOLUTION...ARE ALL UNCERTAINTIES WHICH WILL
AFFECT THE SEVERE POTENTIAL FOR THIS PERIOD. BUT...GUIDANCE
CONTINUES TO SUGGEST A WINDOW OF OPPORTUNITY WILL EXIST FOR THE
DEVELOPMENT OF SCATTERED SUPERCELLS ALONG A PRE-FRONTAL DRY LINE
ACROSS THE CENTRAL PLAINS LATE WEDNESDAY AFTERNOON. SUFFICIENT
MOISTENING AND HEATING MAY OCCUR FOR MIXED LAYER CAPE OF 500-1000
J/KG ACROSS PARTS OF CENTRAL/EASTERN OKLAHOMA AND KANSAS...PERHAPS
FARTHER NORTHWARD INTO THE MID MISSOURI VALLEY. AND...DEEP LAYER
SHEAR BENEATH THE 50-70+ KT SOUTHWESTERLY 500 MB JET STREAK WILL BE
STRONG...WITH LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS NEAR A
30-50+ KT SOUTHERLY 850 JET.
FLOW FIELDS ARE PROGGED TO STRENGTHEN FURTHER INTO WEDNESDAY EVENING
AS THE APPROACHING UPPER JET CORE BEGINS TO NOSE EAST OF THE
DIFLUENT UPPER TROUGH AXIS. COUPLED WITH STRENGTHENING LOW-LEVEL
FORCING AS THE SURFACE COLD FRONT OVERTAKES THE DRY LINE AND SURGES
TOWARD THE MISSISSIPPI VALLEY AND GULF COAST... THE EVOLUTION OF AN
EXTENSIVE SQUALL LINE APPEARS POSSIBLE. THIS IS EXPECTED TO
INCREASE THE SEVERE POTENTIAL FOR A PERIOD WEDNESDAY
EVENING...PARTICULARLY IN THE FORM OF DAMAGING WINDS AND LARGE
HAIL...ACROSS THE SOUTHEASTERN PLAINS INTO THE LOWER MISSOURI
VALLEY/OZARK PLATEAU AND ARKLATEX...WHERE A LINGERING SEVERE THREAT
MAY CONTINUE INTO EARLY THURSDAY.
..KERR.. 11/03/2008
