SPC AC 120545
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT SAT AUG 12 2006
VALID 131200Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY/WRN
GREAT LAKES SWWD ACROSS THE CNTRL PLAINS...
...SYNOPSIS...
BROAD SUB-TROPICAL RIDGE AXIS WILL CONTINUE TO DOMINATE THE SRN HALF
OF THE U.S. THIS PERIOD WITH GENERALLY PROGRESSIVE FLOW EXISTING
ACROSS THE NRN STATES FROM COAST TO COAST. PRIMARY FEATURE AFFECTING
ORGANIZED CONVECTIVE WEATHER WILL BE A PROGRESSIVE TROUGH...EMBEDDED
WITHIN THE FASTER FLOW REGIME...MOVING FROM SCNTRL CANADA/NRN PLAINS
AREA ESEWD TO THE UPPER MS VALLEY/WRN GREAT LAKES. COLD FRONT
ACCOMPANYING THIS SHORT WAVE TROUGH WILL SPREAD SWD ACROSS THE NRN
AND CNTRL HIGH PLAINS...SEWD ACROSS THE MO RIVER VALLEY...AND EWD
ACROSS UPPER MS VALLEY TO THE NRN GREAT LAKES REGIONS FROM SUNDAY
AND INTO EARLY MONDAY.
THE EAST COAST WILL REMAIN UNDER THE INFLUENCE OF STABLE CONTINENTAL
POLAR AIR MASS. THE LEADING EDGE OF THIS AIR MASS WILL CONTINUE TO
BE DEFINED BY A QUASI-STATIONARY FRONTAL BAND...AND SCATTERED DEEP
CONVECTION INCREASING DURING THE AFTERNOON...FROM THE NERN GULF AND
FL WWD TO THE LOWER MS VALLEY.
A SUBTROPICAL DISTURBANCE DRIFTING NWWD AROUND THE SRN PERIPHERY OF
BROAD CNTRL/SRN U.S. UPPER RIDGE...COUPLED WITH MOIST LOW LEVEL
UPSLOPE FLOW AND HIGH PW AIR...WILL RESULT IN NUMEROUS STORMS ACROSS
THE SOUTHWEST AND UPPER RIO GRANDE VALLEY.
...NRN PLAINS ACROSS UPPER MS VALLEY...
MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE MOTION OF THE
FRONT ACROSS THESE AREAS. PRIMARY SHORT WAVE TROUGH TO AFFECT THE
NRN PLAINS AREA ON SUNDAY WAS CURRENTLY ROUNDING THE BASE OF THE
LARGER SCALE TROUGH OVER THE PACIFIC NORTHWEST. THIS FEATURE IS
FORECAST TO MAINTAIN MODEST AMPLITUDE WHILE CROSSING THE ROCKIES
THROUGH SATURDAY. A LEADING IMPULSE...CURRENTLY LIFTING INTO SCNTRL
CANADA...WILL DRIVE A FRONT ACROSS MUCH OF ND AND NWRN SD THROUGH
SATURDAY. THIS BOUNDARY SHOULD STRETCH FROM MN TO WY BY SUNDAY
MORNING. ONGOING MORNING CONVECTION WITHIN WARM CONVEYOR AXIS AHEAD
OF THE COLD FRONT MAY EXIST OVER ERN SD INTO MN. ANOTHER CLUSTER OF
POST-FRONTAL STORMS MAY BE ONGOING AT THE START OF THE PERIOD ACROSS
THE NRN HIGH PLAINS IN AREA OF ENHANCED ASCENT AHEAD OF THE
APPROACHING SHORT WAVE TROUGH OVER MT.
AIR MASS IN THE WAKE OF MN MCS AND AHEAD OF THE FRONT SHOULD BECOME
INCREASINGLY UNSTABLE THROUGH THE AFTERNOON GIVEN RICH LOW LEVEL
MOISTURE AND MODERATE HEATING. SREF GUIDANCE INDICATES MLCAPE VALUES
OF 800-1500 J/KG WILL BE POSSIBLE AHEAD OF THE FRONT...FROM MN INTO
NRN NEB. EXPECT CONVECTIVE INHIBITION IN THIS CORRIDOR TO BE
EFFECTIVELY ERODED AS FRONTAL CIRCULATION DEVELOPS SEWD INTO THE
AREA FROM AFTERNOON THROUGH EVENING. BOTH SHEAR AND FORCING APPEAR
STRONGEST IMMEDIATELY BEHIND THE COLD FRONT AND EXPECT LINE SEGMENTS
AND PERHAPS A FEW SUPERCELLS TO PRODUCE SEVERE HAIL AND WIND OVER
NRN PORTIONS OF THE SLGT RISK AREA AS THE FRONT AND POSSIBLE SQUALL
LINE ADVANCE EWD/SEWD.
...CNTRL PLAINS...
WHILE GREATER WARM SECTOR SHEAR AND FORCING ARE FORECAST TO EXIST
ACROSS THE NRN PLAINS AND UPPER MS VALLEY AREAS THROUGH THE
AFTERNOON AND EVENING...STRONGER DESTABILIZATION IS FORECAST ACROSS
PORTIONS OF THE MO RIVER VALLEY AND ADJACENT PLAINS WHERE AIR MASS
IS LIKELY TO BE CAPPED. HEATING AND WEAK LARGE SCALE FORCING AHEAD
OF THE FRONT SHOULD ACT TO LOCALLY OVERCOME THE CAP IN THESE AREAS
BY AFTERNOON WITH ROBUST CONVECTIVE DEVELOPMENT EXPECTED THROUGH
EVENING. EVEN THOUGH VERTICAL SHEAR DIMINISHES WITH SWD EXTENT
ACROSS THE REGION...THIS MAY BE OFFSET BY MAGNITUDE OF INSTABILITY.
EXPECT WEAKLY ORGANIZED MULTICELLULAR STORMS TO DEVELOP INTO LINEAR
MCS AS THE FRONT SPREADS SEWD. HAIL AND HIGH WINDS MAY ACCOMPANY
THIS ACTIVITY WITH THE CONVECTION DEVELOPING ACROSS SRN NEB/IA...AND
INTO KS/MO AREAS THROUGH SUNDAY NIGHT.
..CARBIN.. 08/12/2006
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
|
