DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 060541
SWODY1
SPC AC 060538

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1138 PM CST THU FEB 05 2009

VALID 061200Z - 071200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

PROGRESSIVE QUASI-ZONAL UPPER PATTERN WILL EVOLVE OVER THE U.S. THIS
PERIOD DOWNSTREAM FROM AN UPPER TROUGH OVER THE NERN PACIFIC THAT
WILL CONTINUE SWD BEFORE EVENTUALLY CLOSING OFF JUST OFFSHORE OF THE
SRN CA COAST.

...CNTRL AND SRN CA...

VORTICITY MAXIMUM NORTH OF A STRONG CYCLONIC UPPER JET WILL ADVANCE
INLAND THROUGH CNTRL CA EARLY FRIDAY. LARGE SCALE ASCENT ALONG WITH
A SWLY UPSLOPE COMPONENT WILL RESULT IN THE DEVELOPMENT OF SCATTERED
CONVECTION. THE MORE NUMEROUS ACTIVITY WILL GRADUALLY SPREAD THROUGH
CNTRL AND S CNTRL CA DURING THE AFTERNOON AS UPPER TROUGH AMPLIFIES
SWD.

THOUGH THE CORE OF THE UPPER LOW IS FORECAST TO REMAIN OFFSHORE...A
THERMAL TROUGH WITH TEMPERATURES FROM -24 TO -26 C AT 500 MB WILL
SHIFT SWD THROUGH THE STATE AND CONTRIBUTE TO 7 C/KM MID-LEVEL LAPSE
RATES PRIMARILY ACROSS CNTRL CA DURING THE DAY. SURFACE LOW FORECAST
TO DEVELOP IN UPPER JET EXIT REGION WILL HELP MAINTAIN SWLY ONSHORE
FLOW BENEATH STEEPENING MID LEVEL LAPSE RATES. THIS WILL CONTRIBUTE
TO DESTABILIZATION PRIMARILY ALONG THE CNTRL AND S CNTRL CA COASTAL
REGIONS DURING THE AFTERNOON AND SRN COASTAL REGION BY EVENING. THE
EARLY ONSET OF SCATTERED CONVECTION AND WIDESPREAD CLOUDS WILL LIMIT
MAGNITUDE OF INSTABILITY IN MOST AREAS WITH MUCAPE BELOW 500 J/KG
EXPECTED.

CHANNELING OF THE LOW LEVEL FLOW BY THE TERRAIN SHOULD HELP MAINTAIN
A SLY OR SELY COMPONENT OVER SRN CA WEST OF THE COASTAL MOUNTAINS.
THIS SLY COMPONENT WILL EXIST BENEATH A SWD DEVELOPING UPPER JET
RESULTING IN SUFFICIENT BULK SHEAR FOR UPDRAFT ROTATION. STEEPENING
MID LEVEL LAPSE RATES AND SUFFICIENT VERTICAL SHEAR...SUGGEST
ISOLATED STORMS COULD DEVELOP UPDRAFT ROTATION. THE PRIMARY THREAT
WILL BE MARGINALLY SEVERE HAIL...BUT A BRIEF TORNADO CANNOT BE RULED
OUT. MORE THAN 5% SEVERE PROBABILITIES DO NOT APPEAR WARRANTED GIVEN
THE EXPECTED MARGINAL THERMODYNAMIC ENVIRONMENT AND CONDITIONAL
NATURE OF THE THREAT.

..DIAL.. 02/06/2009

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