SWODY1
SPC AC 211615
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1115 AM CDT WED APR 21 2010
VALID 211630Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT FROM EXTREME NW TX INTO SE CO...
...THERE IS A SLGT RISK OF SVR TSTMS THROUGH LATE EVENING FOR
UT...WRN CO...SE ID...SW WY...
...SE TX PANHANDLE TO SE CO THIS AFTERNOON THROUGH EARLY TONIGHT...
LOW-LEVEL MOISTURE IS RETURNING NWD ACROSS W/NW TX WITH BOUNDARY
LAYER DEWPOINTS NOW IN THE MID-UPPER 50S INTO THE PVW-ABI-SPS
AREA...AND A SLOW INCREASE IS EXPECTED THIS AFTERNOON WITH CONTINUED
MOISTURE ADVECTION AND LATENT HEAT FLUX FROM THE MOIST GROUND.
MEANWHILE...CLOUD EROSION AND DAYTIME HEATING FROM S TO N WILL
CONTRIBUTE TO DIFFERENTIAL HEATING AND HELP CONSOLIDATE A
SLOW-MOVING WARM FRONT ALONG THE CAO-AMA-CDS-SPS CORRIDOR...ROUGHLY
ALONG THE RED RIVER INTO PALO DURO CANYON. THIS SURFACE BOUNDARY
WILL SERVE TO FOCUS THUNDERSTORM DEVELOPMENT AS CONVECTIVE
INHIBITION WEAKENS THIS AFTERNOON.
MODERATE INSTABILITY /MLCAPE OF 1000-2000 J PER KG/ IS EXPECTED THIS
AFTERNOON ALONG THE FRONT AND E OF A DIFFUSE DRYLINE. THIS
INSTABILITY...IN COMBINATION WITH A GRADUAL INCREASE IN LOW-MIDLEVEL
FLOW...WILL CONTRIBUTE TO AN ENVIRONMENT FAVORABLE FOR SUPERCELLS
THIS AFTERNOON INTO EARLY TONIGHT...ESPECIALLY IN THE AREA BETWEEN
PVW-AMA-CDS. FORECAST HODOGRAPHS SHOW FAVORABLE VERTICAL WIND SHEAR
FOR PERSISTENT STORMS...AND AN INCREASE IN LOW-LEVEL SHEAR LATE THIS
EVENING WITH A DEVELOPING 25-35 KT SLY/SSELY LLJ. A COUPLE OF
TORNADOES...LARGE HAIL...AND ISOLATED DAMAGING WINDS WILL ALL BE
POSSIBLE FROM MID-LATE AFTERNOON THROUGH AT LEAST EARLY TONIGHT.
FARTHER NW INTO SE CO...LOW-LEVEL UPSLOPE FLOW WILL DRAW UPPER 40S
TO LOWER 50S BOUNDARY LAYER DEWPOINTS NWWD...AND A FEW CLOUD BREAKS
WILL ALLOW SURFACE HEATING IMMEDIATELY E OF THE MOUNTAINS.
THUNDERSTORMS WILL LIKELY DEVELOP THIS AFTERNOON OVER THE HIGH
TERRAIN IN CO AND THEN SPREAD SEWD ALONG THE BAROCLINIC ZONE NEAR
THE RATON MESA. THOUGH INSTABILITY WILL BE WEAKER COMPARED TO AREAS
FARTHER SE IN THE TX PANHANDLE...VERTICAL SHEAR WILL BE SUFFICIENT
FOR SUPERCELLS CAPABLE OF PRODUCING AT LEAST ISOLATED LARGE HAIL AND
DAMAGING GUSTS. OVERNIGHT...CLUSTERS OF ELEVATED THUNDERSTORMS WILL
CONTINUE AND SPREAD EWD/NEWD ACROSS WRN/NRN OK INTO KS IN
ASSOCIATION WITH LOW-LEVEL WAA.
...GREAT BASIN THROUGH LATE EVENING...
A STRONG MIDLEVEL LOW AND ASSOCIATED COLD FRONT WILL CONTINUE TO
MOVE SLOWLY EWD ACROSS UT/AZ THROUGH EARLY TONIGHT. A FOCUSED BELT
OF ASCENT ALONG THE FRONT...COMBINED WITH 7-8 C/KM MIDLEVEL LAPSE
RATES AND STEEPENING LOW-LEVEL LAPSE RATES WITH DAYTIME
HEATING...WILL SUPPORT A BAND OF THUNDERSTORMS WHICH WILL SPREAD EWD
ACROSS UT/SE ID INTO SW WY/WRN CO THROUGH THIS EVENING. THOUGH
INSTABILITY WILL NOT BE PARTICULARLY STRONG...SUBSTANTIAL DEEP-LAYER
SLY SHEAR AND INVERTED-V PROFILES IN THE LOW LEVELS WILL SUPPORT
EMBEDDED BOWING SEGMENTS AND/OR ROTATING STORMS WITH THE POTENTIAL
FOR A FEW DAMAGING GUSTS.
..THOMPSON/ROGERS.. 04/21/2010
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