SWODY1
SPC AC 120555
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT SAT MAY 12 2007
VALID 121200Z - 131200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WRN AND NRN MT
AND ADJACENT PORTIONS OF NRN ID...
..SYNOPSIS...
LARGE RIDGE ALOFT WILL PREVAIL ACROSS THE CENTRAL CONUS...WHILE A
TROUGH MOVES SLOWLY ONSHORE OVER THE WRN CONUS AND A SECOND TROUGH
AMPLIFIES OVER THE EAST. MEANWHILE...THE REMNANTS OF AN UPPER LOW
WILL CONTINUE MOVING ACROSS THE SERN CONUS THROUGH THE PERIOD.
AT THE SURFACE...PATTERN SHOULD REMAIN RELATIVELY ILL-DEFINED ACROSS
THE ERN CONUS...THOUGH COLD FRONTOGENESIS IS FORECAST E OF THE
APPALACHIANS DURING THE LATTER HALF OF THE PERIOD.
MEANWHILE...BAROCLINIC ZONE EXTENDING FROM MT SEWD ACROSS SD SHOULD
PERSIST THROUGH THE PERIOD.
..PARTS OF NRN ID INTO PORTIONS OF NRN AND WRN MT...
LARGE-SCALE SUBSIDENCE IS FORECAST ACROSS MUCH OF THE ROCKIES AND
INTO THE PLAINS...WHICH SHOULD LIMIT POTENTIAL FOR STORM DEVELOPMENT
FROM THE HIGH PLAINS EWD. FURTHER W HOWEVER...HEIGHT FALLS WILL
SPREAD SLOWLY EWD ACROSS THE PAC NW TOWARD ID/WRN MT THROUGH THE
AFTERNOON/EARLY EVENING...AS UPPER TROUGH MOVES SLOWLY ONSHORE.
WHILE STEEP LAPSE RATES WILL CONTRIBUTE TO LARGE CAPE VALUES FROM
ERN MT INTO THE SD...SUBSIDENCE/CAPPING SHOULD GENERALLY HINDER
STORM DEVELOPMENT. THOUGH STORMS ARE EXPECTED ACROSS NERN SD AND
ADJACENT AREAS IN ZONE OF WARM ADVECTION NE OF SHARPENING WARM
FRONT...IT APPEARS ATTM THAT WEAK/ELEVATED NATURE OF INSTABILITY
SHOULD PRECLUDE APPRECIABLE SEVERE THREAT.
FARTHER W INTO WRN MT/NRN ID AND PERHAPS ERN OREGON...HEIGHT
FALLS/WEAK LARGE-SCALE UVV MAY SUPPORT THE DEVELOPMENT OF SCATTERED
LATE AFTERNOON STORMS. COMBINATION OF 500 TO 750 J/KG MEAN-LAYER
CAPE AND DEEP-LAYER SHEAR 40 TO 50 KT SHOULD ALLOW A FEW
ORGANIZED/ROTATING STORMS TO DEVELOP -- WHICH WOULD BE CAPABLE OF
PRODUCING LOCALLY-DAMAGING WINDS AND/OR HAIL. THEREFORE...WILL
MAINTAIN SLIGHT RISK ACROSS PARTS OF WRN AND NRN MT AND ADJACENT
PARTS OF NRN ID...BUT WILL REMOVE THE SLIGHT RISK FROM ERN MT DUE TO
SUBSTANTIAL CAPPING AND A GENERALLY DRY LOWER TROPOSPHERE FORECAST
ACROSS THIS PART OF THE AREA.
..E TX EWD ACROSS THE SOUTHEAST AND NWD INTO VA/WV AND VICINITY...
SHOWERS AND THUNDERSTORMS ARE FORECAST FROM THE APPALACHIANS SWD
INTO FL AND WWD INTO TX...AS DAYTIME HEATING OF MOIST /60S
DEWPOINTS/ BOUNDARY LAYER RESULTS IN WIDESPREAD 500 TO 1500 J/KG
MEAN-LAYER CAPE.
GREATEST INSTABILITY IS EXPECTED FROM THE CAROLINAS WSWWD ACROSS THE
GULF COAST STATES...THOUGH WEAK FLOW ALOFT ACROSS THIS REGION
SUGGESTS ONLY ISOLATED/PULSE-TYPE SEVERE STORMS.
FURTHER N...STRONGER FLOW WILL ACCOMPANY A SHORT-WAVE TROUGH
FORECAST TO MOVE SEWD ACROSS THE GREAT LAKES -- APPROACHING THE
UPPER OH VALLEY REGION BY LATE AFTERNOON/EARLY EVENING.
HOWEVER...WITH INSTABILITY FORECAST TO REMAIN MORE LIMITED ACROSS
THE UPPER OH VALLEY REGION...AND STRONGER FLOW FORECAST TO REMAIN NW
OF THIS AREA UNTIL AFTER DARK...SEVERE THREAT SHOULD REMAIN LIMITED
HERE AS WELL. THEREFORE...WILL MAINTAIN A LARGE/LOW-PROBABILITY
SEVERE THREAT AREA ACROSS A LARGE PORTION OF THE SRN AND ERN CONUS.
.GOSS/TAYLOR.. 05/12/2007
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