DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 050057
SWODY1
SPC AC 050054

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 PM CDT WED SEP 04 2013

VALID 050100Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE INTERIOR
PACIFIC NORTHWEST...

...NORTHWEST...
ISOLATED STRONG TO SEVERE TSTM DEVELOPMENT THROUGH THE AFTERNOON
HOURS APPEARS TO HAVE BEEN DRIVEN PRIMARILY BY DIURNAL HEATING AND
TERRAIN INFLUENCES. MUCH OF THE CONVECTION HAS SHOWN SOME DECREASE
IN INTENSITY DESPITE CONTINUING PRESENCE OF POCKETS OF MODEST
INSTABILITY /MUCAPE TO AROUND 800 J/KG PER BOI/OTX RAOBS/ AND BELT
OF STRONGER 30-40KT DEEP-LAYER VERTICAL SHEAR SITUATED BETWEEN
OFFSHORE TROUGH AND DOMINANT WRN U.S. UPPER RIDGE.

LARGE SCALE ASCENT IS FORECAST TO STRENGTHEN ACROSS ORE/WA/WRN ID
LATER TONIGHT AND ESPECIALLY THROUGH FRI MORNING AS A LOBE OF
VORTICITY AND DPVA...CURRENTLY ROUNDING THE BASE OF THE OFFSHORE
TROUGH PER WATER VAPOR IMAGERY...SPREADS INLAND AND NNEWD. DESPITE A
TENDENCY FOR BOUNDARY LAYER TO STABILIZE WITH LOSS OF DAYTIME
HEATING...SUFFICIENTLY STEEP MID-LEVEL LAPSE RATES AND CONTINUED
MOISTENING/WARNING AROUND 700MB WILL CONTRIBUTE TO MUCAPE OF
500-1000 J/KG AHEAD OF THE UPPER FORCING. CLOUD-BEARING SHEAR WILL
REMAIN SUPPORTIVE OF UPDRAFT ENHANCEMENT AND STORM COVERAGE MAY
INCREASE IN THE 0900-1200 UTC TIME FRAME AS VORTICITY LOBE/DPVA AND
ASSOCIATED SPEED MAX DEVELOP INLAND. WILL MAINTAIN SLGT RISK
PROBABILITIES WITH THE PROSPECT FOR A FEW STORMS BY EARLY MORNING
CAPABLE OF PRODUCING SEVERE HAIL. DESPITE DECOUPLING OCCURRING
OVERNIGHT...GENERALLY DRY/WARM SUB-CLOUD LAYER COULD ALSO CONTRIBUTE
TO LOCALLY GUSTY WINDS.

...CNTRL/NRN HIGH PLAINS...
JUXTAPOSITION OF SFC THERMAL/LEE TROUGH AND MOIST AXIS ALONG
RESIDUAL/DECAYING FRONTAL SEGMENT NEAR SD/NEB BORDER HAS RESULTED IN
A CORRIDOR OF GREATER INSTABILITY SAMPLED WELL BY EVENING RAOB FROM
RAP. LOW LEVEL LIFT ALONG THE TROUGH AND FRONTAL SEGMENT...AS WELL
AS WEAK UPSLOPE FLOW...HAVE SPURRED ISOLATED AND LOCALLY INTENSE
CONVECTIVE DEVELOPMENT FROM THE NEB PNHDL NWWD TO ERN MT. WEAK LOW
LEVEL ELY FLOW TOPPED BY 15-30KT MID-LEVEL FLOW PER RAOBS AND
PROFILER DATA WAS RESULTING IN SUFFICIENT DIRECTIONAL/SPEED SHEAR
FOR STORMS TO PERSIST AND POSE A THREAT FOR LARGE HAIL AND LOCALLY
STRONG DOWNDRAFTS. GIVEN GENERALLY LIMITED/WEAK LARGE SCALE SUPPORT
FOR DEEPER ASCENT NEAR THE CENTER OF LARGE UPPER LEVEL
ANTICYCLONE...EXPECT SEVERE THREAT TO REMAIN TOO ISOLATED FOR HIGHER
PROBABILITIES...ESPECIALLY AT THIS TIME OF DAY.

..CARBIN.. 09/05/2013

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