SPC AC 250617
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1217 AM CST FRI FEB 25 2011
VALID 261200Z - 271200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
QUASI-ZONAL FLOW ALOFT FCST THROUGH MOST OF PERIOD ACROSS
CONUS...PRIMARY EXCEPTION BEING AMPLIFYING SHORTWAVE PERTURBATION
OVER WRN STATES. MID-UPPER CYCLONE -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY OFFSHORE ORE...IS FCST TO DIG SSEWD TO N-CENTRAL CA
BY BEGINNING OF PERIOD...AS STG HEIGHT FALLS/SPEED MAX SHUNT GULF OF
AK ANTICYCLONE SWWD. CA UPPER LOW...AND RELATED SHORTWAVE
TROUGH...IS EXPECTED TO CONTINUE DIGGING SWD TO SSEWD THROUGH ABOUT
27/00Z...BEFORE TURNING EWD ACROSS ERN CA. CONSIDERABLE SPREAD
STILL IS EVIDENT IN INITIAL LOCATION OF THIS EWD TURN...MORESO THAN
IN ITS TIMING...SUCH THAT ASSORTED OPERATIONAL/SREF GUIDANCE HAS
500-MB LOW ANYWHERE FROM IMPERIAL VALLEY TO 4-CORNERS BY END OF
PERIOD. SREF CONSENSUS IS CLOSE TO OPERATIONAL SPECTRAL OVER NRN
AZ...WITH OPERATIONAL WRF FARTHER W NEAR EED IN KEEPING WITH
PRIOR/12Z ECMWF. GIVEN ANTECEDENT STRENGTH OF GULF OF AK
RIDGING...AND DISTANCE TO UPSTREAM HEIGHT FALLS...PRIND SOMEWHAT
SLOWER SOLUTION -- CLOSER TO THOSE WRF/ECMWF FCSTS -- IS MOST
REASONABLE ATTM.
IN EITHER EVENT...BROAD REGIME OF LOW-LEVEL CYCLOGENESIS IS FCST IN
LEE OF CENTRAL ROCKIES THROUGH PERIOD...AS ELEVATED MIXED LAYER
BUILDS OVER WRN PLATEAU/INTERMOUNTAIN REGION AND ADVECTS ENEWD
ACROSS PLAINS. MEANWHILE LOW-LEVEL WAA WILL OCCUR ACROSS
SRN/CENTRAL PLAINS. CONSIDERABLE UNCERTAINTY EXISTS WITH FCST
POSITION OF SFC WARM FRONT EXTENDING EWD TO SEWD FROM CO LEE LOW
ACROSS KS OR OK. AIR MASS S OF THAT FRONT ACROSS SRN
PLAINS/ARKLATEX REGION IS EXPECTED TO REMAIN TOO CAPPED FOR
SIGNIFICANT CONVECTIVE DEVELOPMENT THIS PERIOD...DESPITE SFC DEW
POINTS ATTAINING MID 50S TO MID 60S F OVER MUCH OF AREA S OF WARM
FRONT. FARTHER W...LOW-LEVEL COLD FRONT WILL MOVE EWD ACROSS ERN
GREAT BASIN REGION AND SRN CA/AZ...BUT WITH TIMING UNCERTAINTIES
RELATED TO AFOREMENTIONED MID-UPPER LEVEL SPREAD IN SOLUTIONS.
...CA COAST TO LOWER CO RIVER VALLEY REGION...
COLD AIR ALOFT AND ATTENDANT PLUME OF STEEP LAPSE
RATES...ACCOMPANYING MID-UPPER CYCLONE...IS FCST TO MOVE INLAND
ACROSS IMPERIAL/LOWER CO VALLEY OVERNIGHT. THIS REGIME WILL BE
PRECEDED BY STRONGLY DIFLUENT UPPER FLOW...BUT ALSO RELATIVELY SCANT
LOW-LEVEL MOISTURE. TIME SERIES OF FCST SOUNDINGS SUGGESTS
SUFFICIENT CAPE FOR TSTMS OVER PAC MARINE AIR FOR MOST OF
PERIOD...IN AND NEAR COLD-CORE REGION. THUNDER POTENTIAL INLAND IS
MORE CONDITIONAL...BUT APPEARS POSSIBLE BASED ON JUXTAPOSITION OF
COOLING ALOFT WITH MRGL MOISTURE -- I.E. SFC DEW POINTS INCREASING
INTO 40S F IN LOWER ELEVATIONS.
...LOWER MS VALLEY/TN VALLEY REGION -- LATE NIGHT...
ISOLATED TO WIDELY SCATTERED TSTMS MAY DEVELOP DURING LAST FEW HOURS
OF PERIOD...ALONG LEADING EDGE OF ELEVATED PLUME OF MRGL RETURN-FLOW
MOISTURE. ALTHOUGH MIDLEVEL LAPSE RATES WILL BE JUST SLIGHTLY
CONVECTIVELY UNSTABLE...FCST SOUNDINGS SUGGEST NEAR-SATURATION
BETWEEN 800-900 MB CAN YIELD ESSENTIALLY UNINHIBITED MUCAPE UP TO
ABOUT 500 J/KG. LAPSE RATES AND EFFECTIVE SHEAR MIGHT INCREASE
ENOUGH NEAR END OF PERIOD FOR SOME STORMS TO PRODUCE
HAIL...ESPECIALLY OVER WRN PORTIONS GEN TSTM AREA...BUT THIS FAR IN
ADVANCE...THREAT APPEARS TOO MRGL/CONDITIONAL FOR SPECIFIC AREA OF
AOA 5% SVR PROBABILITIES.
..EDWARDS.. 02/25/2011
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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