SWODY2
SPC AC 051656
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1056 AM CST THU MAR 05 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS FRIDAY NIGHT OVER PARTS OF THE
LOWER MO VALLEY...
...SYNOPSIS...
PRIMARY FEATURE OF INTEREST DURING THE DAY TWO PERIOD WILL BE
POSITIVELY-TILTED TROUGH WHICH WILL PROGRESS EWD/SEWD THROUGH THE
CANADIAN PRAIRIES AND INTERMOUNTAIN WEST. THIS SYSTEM WILL TEND TO
FRACTURE WITH TIME WITH SEPARATE HEIGHT FALL CENTERS DEVELOPING OVER
MANITOBA/WRN ONTARIO AND OVER THE SRN ROCKIES. IN THE LOW
LEVELS...MAIN SURFACE FRONT WILL EXTEND INITIALLY FROM LOW PRESSURE
OVER SWRN ONTARIO SWWD THROUGH THE MID MS VALLEY INTO SRN HIGH
PLAINS. THE WRN EXTENSION OF THIS BOUNDARY WILL LIFT NWD INTO THE
CNTRL PLAINS IN RESPONSE TO LEE CYCLOGENESIS OVER ERN CO.
MEANWHILE...A WEAK DRYLINE OR LEE TROUGH WILL BECOME ESTABLISHED
FRIDAY FROM THE LEE LOW INTO WRN TX.
...MID/LOWER MO VALLEY INTO THE OH VALLEY...
INITIALLY VEERED SFC-850 MB FLOW IN PRE-FRONTAL WARM SECTOR OVER THE
SRN PLAINS WILL BACK AND STRENGTHEN THROUGH THE DAY IN RESPONSE TO
THE DEEPENING LOW PRESSURE OVER ERN CO. THIS WILL RESULT IN THE
NWD/NWWD ADVECTION OF AN INCREASINGLY MOIST BOUNDARY LAYER
/DEWPOINTS IN THE 50S/ INTO KS AND THE LOWER MO VALLEY. THIS
MOISTURE INCREASE COUPLED WITH DAYTIME HEATING AND A PRONOUNCED EML
WILL CONTRIBUTE TO A RAPIDLY DESTABILIZING BUT CAPPED AIR MASS ALONG
AND S OF WARM FRONT THROUGH THE DIURNAL HEATING CYCLE.
DYNAMIC RESPONSE TO EVOLVING WRN U.S. TROUGH WILL HASTEN NOCTURNAL
LLJ DEVELOPMENT FRIDAY NIGHT OVER THE CNTRL/SRN PLAINS WITH THIS
FEATURE GRADUALLY VEERING INTO THE OZARK PLATEAU AND MID MS VALLEY
TOWARD THE END OF THE FORECAST PERIOD. ENHANCED CONVERGENCE AND
MOIST/THERMAL ADVECTIONS WITHIN LLJ EXIT REGION ARE EXPECTED TO
FOSTER ELEVATED TSTM DEVELOPMENT ALONG NRN FRINGE OF STRONGER EML
PRIMARILY AFTER 07/03Z OVER THE LOWER MO VALLEY. THIS ACTIVITY WILL
LIKELY EXPAND IN AREAL COVERAGE OVERNIGHT EWD INTO PARTS OF THE OH
VALLEY.
WHILE MOISTURE WILL REMAIN SOMEWHAT MARGINAL...THE PRESENCE OF
RELATIVELY COOL MIDLEVEL TEMPERATURES /AROUND -18 C AT 500 MB/ AND
RESULTANT STEEP LAPSE RATES WILL LARGELY CONTRIBUTE TO MUCAPE
APPROACHING 1500 J/KG. THIS MODERATE INSTABILITY IN CONCERT WITH
40-60 KT OF CLOUD BEARING SHEAR SUGGESTS THE POTENTIAL FOR
ORGANIZED/ROTATING STORMS CAPABLE OF MAINLY SEVERE HAIL. THIS HAIL
THREAT WILL LIKELY BE THE GREATEST WITH THE INITIAL BURST OF
ELEVATED TSTM DEVELOPMENT OVER THE LOWER MO VALLEY.
..MEAD.. 03/05/2009
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