SWODY1
SPC AC 071250
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT THU APR 07 2011
VALID 071300Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM FAR NERN KS ACROSS PORTIONS OF NRN MO...
...SYNOPSIS...
A CONTINUED EQUATORWARD TRANSLATION AND OVERALL INTENSIFICATION OF
PACIFIC NW MIDLEVEL TROUGH IS FORECAST WITH THE MOST SIGNIFICANT
HEIGHT FALLS OVERSPREADING THE CA COAST AND GREAT BASIN INTO LOWER
CO VALLEY. ELSEWHERE...A LOWER-LATITUDE IMPULSE CURRENTLY OVER NWRN
MEXICO INTO THE SRN ROCKIES WILL LOSE AMPLITUDE WHILE LIFTING NEWD
INTO AN INCREASINGLY CONFLUENT MIDLEVEL FLOW REGIME IN PLACE OVER
THE MID-MS VALLEY.
AT THE SURFACE...CYCLONE ANALYZED OVER SWRN OK AS OF 11Z IS FORECAST
TO DEVELOP GENERALLY NWD INTO S-CNTRL KS BY LATE AFTERNOON. THIS
LOW DELINEATES THE INTERSECTION OF DRYLINE AND RETREATING WARM FRONT
WHICH EXTENDS EWD THROUGH THE MID-MS VALLEY. THE WRN EXTENSION OF
THE WARM FRONT WILL REMAIN LINKED TO A DEEPENING LEE CYCLONE OVER
SERN CO.
...ERN KS INTO THE MID MS VALLEY...
LOW-LEVEL MASS RESPONSE TO DEAMPLIFYING SHORTWAVE TROUGH LIFTING
NEWD THROUGH THE CNTRL/SRN PLAINS WILL SERVE TO MAINTAIN A SSWLY LLJ
ACROSS LOWER ELEVATIONS OF THE SRN PLAINS INTO OZARK PLATEAU TODAY.
THE LLJ WILL ENHANCE THE NWD FLUX OF AN INCREASINGLY MOIST AIR MASS
E OF DRYLINE WITH DEWPOINTS RISING THROUGH THE 50S TO PERHAPS LOWER
60S BY AFTERNOON OVER CNTRL/ERN OK...AR...SERN KS AND SRN MO. THIS
MOISTURE INCREASE COUPLED WITH STEEP LAPSE RATES ASSOCIATED WITH A
WELL-DEFINED EML WILL CONTRIBUTE TO A WEAKLY TO MODERATELY UNSTABLE
AIR MASS BY AFTERNOON WHERE MLCAPE WILL APPROACH 500-1500 J/KG.
LATEST MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE SUGGESTS
THAT THE HIGHEST PROBABILITY OF TSTM DEVELOPMENT WILL LIKELY OCCUR
THIS AFTERNOON INTO TONIGHT N OF THE WARM FRONT FROM ERN KS EWD
THROUGH NRN MO INTO PORTIONS OF IL/IND. FORECAST SOUNDINGS INDICATE
MUCAPE VALUES OF 500-1000 J/KG FOR PARCELS BASED IN THE 900-850 MB
LAYER. GIVEN THE STEEP LAPSE RATES AND AROUND 50 KT OF
CLOUD-BEARING SHEAR...STRONGER STORMS WILL BE CAPABLE OF MARGINALLY
SEVERE HAIL.
SOME SREF MEMBERS AND MORE RECENT RUNS OF EXPERIMENTAL HRRR GUIDANCE
SUGGEST A RISK FOR SURFACE-BASED STORM DEVELOPMENT AROUND 08/00Z
NEAR THE SURFACE TRIPLE POINT IN S-CNTRL/SERN KS. WHILE THE AMBIENT
ENVIRONMENT WOULD SUPPORT SUPERCELLS...THE PRESENCE OF THE STRONG
CAP AND EARLY PASSAGE OF SHORTWAVE TROUGH INDICATE THAT THIS IS A
LOW PROBABILITY SCENARIO.
...ERN CO/WRN KS...
A NARROW SPATIAL CORRIDOR OF STRONG TO MARGINALLY SEVERE TSTMS WILL
BE POSSIBLE LATE THIS AFTERNOON INTO EVENING ALONG AND N OF LEE
CYCLONE AND WWD EXTENSION OF WARM FRONT. THIS LOCATION WILL BE W OF
DRYLINE WITH BOUNDARY LAYER DEWPOINTS IN THE 30S TO LOWER 40S
ANTICIPATED N OF WARM FRONT. HOWEVER...LOW TO MIDLEVEL LAPSE RATES
WILL BE STEEP...CONTRIBUTING TO MLCAPE APPROACHING 500 J/KG. WHEN
COUPLED WITH A VERTICALLY VEERING WIND PROFILE AND AROUND 40 KT OF
DEEP WSWLY SHEAR...SETUP MAY YIELD ROTATING UPDRAFTS CAPABLE OF HAIL
AND LOCALLY DAMAGING WIND GUSTS.
...FOUR CORNERS REGION...
LEADING EDGE OF STRONG HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT
ATTENDANT TO EVOLVING WRN U.S. TROUGH WILL BEGIN TO OVERSPREAD THE
REGION THIS AFTERNOON. THIS FORCING IN CONJUNCTION WITH STEEPENING
LAPSE RATES AND STRENGTHENING VERTICAL SHEAR MAY FOSTER A FEW
STRONGER STORMS LATER TODAY WITH A THREAT FOR SOME HAIL AND STRONG
WIND GUSTS.
..MEAD/SMITH.. 04/07/2011
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