SWODY1
SPC AC 211931
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0231 PM CDT WED APR 21 2010
VALID 212000Z - 221200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT BASIN
AND CNTRL ROCKIES...
..THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CNTRL/SRN
HIGH PLAINS...
..SERN ID TO WRN CO...
LARGE SCALE FORCING AND ASSOCIATED STRONG BAROCLINIC ZONE IS
EXPECTED TO GRADUALLY SHIFT EAST ACROSS THE GREAT BASIN THROUGH UT
INTO SWRN WY/WRN CO. WITHIN THIS ZONE...A CONSIDERABLE AMOUNT OF
CONVECTION AND SCATTERED THUNDERSTORMS HAVE DEVELOPED WITHIN AN
ENVIRONMENT CHARACTERIZED BY STEEP LOW-MID LEVEL LAPSE RATES...BUT
SOMEWHAT MEAGER MOISTURE. GIVEN THE STRONG SHEAR IN PLACE IT
APPEARS GUSTY WINDS MAY ACCOMPANY THE SUSTAINED UPDRAFTS THAT MANAGE
TO BE MORE EFFICIENT PRECIPITATION PRODUCERS...ESPECIALLY GIVEN THE
RELATIVELY DRY SUB-CLOUD LAYER.
..SRN/CNTRL HIGH PLAINS...
NO CHANGE TO EARLIER FORECAST REGARDING THE POTENTIAL FOR ISOLATED
SEVERE THUNDERSTORMS ACROSS THE HIGH PLAINS. BOUNDARY LAYER IS
WARMING SIGNIFICANTLY ACROSS ERN NM INTO THE TX SOUTH PLAINS...PER
RAPID EXPANSION OF CU FIELD WHERE LAPSE RATES ARE NOW IN EXCESS OF 9
C/KM. WITH TIME A FEW STORMS...SOME OF WHICH SHOULD ROTATE...WILL
LIKELY DEVELOP ALONG RETREATING WARM FRONT INTO SERN CO. OTHER
STORMS WILL DEVELOP LATER TONIGHT WITHIN WARM ADVECTION ZONE ATOP
COOLER RETREATING AIRMASS WEDGED OVER ERN CO/KS/NRN OK...ESPECIALLY
AS LLJ INCREASES IN EXCESS OF 40-45KT.
.DARROW.. 04/21/2010
PREV DISCUSSION... /ISSUED 1115 AM CDT WED APR 21 2010/
..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.
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