SWODY1
SPC AC 050555
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT WED MAY 05 2010
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE OH VALLEY
AND LOWER GREAT LAKES...
...SYNOPSIS...
PROGRESSIVE QUASI-ZONAL UPPER FLOW PATTERN WILL PERSIST ACROSS THE
CONUS TODAY WITH PRIMARY STORM SYSTEMS TRACKING EWD THROUGH THE NRN
TIER STATES. UPPER TROUGH/CLOSED LOW LOCATED OVER THE UPPER MS
VALLEY AT 12Z TODAY WILL MOVE THROUGH THE GREAT LAKES/ONTARIO
REACHING WRN QUEBEC/LOWER GREAT LAKES BY 12Z THURSDAY. A SURFACE
LOW ATTENDANT TO THIS SYSTEM WILL MOVE ENEWD THROUGH THE UPPER GREAT
LAKES/ONTARIO TO NRN QUEBEC BY 12Z THURSDAY. NRN EXTENT OF A COLD
FRONT TRAILING SWWD FROM LOWER MI TO CENTRAL MO AND THE SRN PLAINS
AT THE START OF THE PERIOD WILL SHIFT EWD TO THE LOWER GREAT LAKES
AND LOWER OH VALLEY BY 06/00Z.
IN THE WEST...A CLOSED LOW/TROUGH IS FORECAST TO AMPLIFY ESEWD
ACROSS THE PACIFIC NW INTO THE NRN ROCKIES. A STRONG COLD FRONT
WITH THIS SYSTEM WILL SPREAD E/SEWD ACROSS THE NRN INTERMOUNTAIN
WEST/ROCKIES TODAY AND SHOULD EXTEND FROM THE NRN HIGH PLAINS TO THE
SRN GREAT BASIN BY EARLY THURSDAY MORNING.
...OH VALLEY AND LOWER GREAT LAKES REGION...
SURFACE OBSERVATIONS INDICATED DEWPOINTS IN THE LOWER-MID 50S
CURRENTLY RESIDE OVER LOWER OH VALLEY. SWLY LOW LEVEL FLOW ACROSS
THE OH VALLEY TODAY IN ADVANCE OF THE APPROACHING COLD FRONT SHOULD
ADVECT THIS MOISTURE NEWD BENEATH A PLUME OF STEEP MIDLEVEL LAPSE
RATES /7 C/KM/ ALSO EXPECTED TO SPREAD NEWD ACROSS THIS REGION.
THIS COMBINED WITH DIABATIC HEATING WILL RESULT IN MLCAPE 500-1000
J/KG IN THE SLIGHT RISK AREA.
ALTHOUGH STRONG FORCING FOR ASCENT SHOULD REMAIN NORTH OF THIS
REGION TODAY...TSTMS ARE EXPECTED TO DEVELOP ACROSS SERN LOWER MI
SWWD INTO CENTRAL IND THIS AFTERNOON AS THE FRONT ADVANCES INTO THE
DESTABILIZING AIR MASS. ACTIVITY SHOULD THEN DEVELOP INTO THE OH
VALLEY AND SRN ONTARIO/LOWER GREAT LAKES. 30 KT SWLY LOW LEVEL
WINDS BENEATH STRENGTHENING WLY WINDS ALOFT WILL SUPPORT INCREASING
EFFECTIVE BULK SHEAR /40-50 KT/ BY AFTERNOON. THIS COMBINED WITH
THE AVAILABLE INSTABILITY AND INVERTED-V THERMODYNAMIC PROFILES
SUGGEST HAIL AND STRONG WIND GUSTS WILL BE THE PRIMARY THREATS.
SEVERE WEATHER THREAT SHOULD DIMINISH THROUGH THE EVENING WITH THE
ONSET OF DIABATIC COOLING STABILIZING THE AIR MASS.
...PACIFIC NW...
VERY COLD MIDLEVEL TEMPERATURES /-30 TO -34 C AT 500 MB/ WITH THE
UPPER TROUGH/CLOSED LOW WILL TRACK ACROSS THIS REGION. SURFACE
HEATING WITHIN THE POST-FRONTAL AIR MASS BENEATH THE COLD MIDLEVEL
TEMPERATURES WILL RESULT IN STEEPENING LAPSE RATES. SHOWERS AND A
FEW TSTMS SHOULD OCCUR WITHIN THIS WEAKLY UNSTABLE ENVIRONMENT.
GIVEN THE STEEP LAPSE RATES/VERY COLD MIDLEVEL TEMPERATURES...SMALL
HAIL WILL BE POSSIBLE. WEAK INSTABILITY AND VERY WEAK SHEAR WILL
PRECLUDE A SEVERE WEATHER THREAT.
..PETERS/JIRAK.. 05/05/2010
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