FXUS66 KEKA 201030
AFDEKA

NORTHWEST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
230 AM PST THU FEB 20 2003

.OBSERVATIONAL OVERVIEW...
UPPER LEVEL LOW SPIRALING OVER SOCAL EARLY THIS MORNING...AS FLAT 
RIDGING ATTEMPTS TO BUILD OVER NORCAL. LIGHT SHOWERS CONTINUE TO 
PESTER THE IMMEDIATE COAST OF ZONE 1 AND EXPECT THEM TO DIMINISH 
SHORTLY AS MID LEVEL TEMPERATURES WARM AND ONSHORE FLOW DIMINISHES. 
RAINFALL TOTALS THRU MIDNIGHT WERE IMPRESSIVE IN A NARROW PART OF 
THE FORECAST AREA...ESPECIALLY AROUND HUMBOLDT BAY WHERE BETWEEN 
1.5" AND 2" FELL. OTHERWISE...MOST LOCALES MEASURED A HALF INCH OR 
LESS. SATELLITE IMAGERY INDICATES WARM ADVECTION CLOUDINESS MOVING 
SOUTHEAST AROUND UPPER RIDGE...AND ADVANCING TOWARD NORCAL IN A 
DRYING STATE. ZONAL UPPER JET IS RACING EASTWARD AROUND 45N WITH A 
CORE AROUND 135W. SURFACE HIGH PRESSURE IS BUILDING OFFSHORE...AND 
PROMOTING A STRENGTHENING NORTH/SOUTH COASTAL GRADIENT WITH ACV-SFO 
NEARING 6MB. 

.SHORT TERM...
FAIRLY PLEASANT DAY EXPECTED THU AS MAINLY DRY NW UPPER FLOW REGIME 
RESIDES OVER NORCAL. SURFACE HIGH PRESSURE OFFSHORE WILL KEEP THE 
NORTHERLY GRADIENT IN PLACE...REPLACING YESTERDAYS ONSHORE FLOW. 
CONTINUED MID AND UPPER LEVEL WARM ADVECTION WILL LESSEN THE STEEP 
LAPSE RATES EXPERIENCED WED...AND WILL ALLOW ISOLATED EARLY MORNING 
SHOWERS TO TAPER OFF. THIN MID AND HIGH LEVEL CLOUDS WILL APPROACH 
FAR NW CA TODAY BUT AREAS TO THE SOUTH SHOULD BE MOSTLY SUNNY...WITH 
TEMPERATURES RETURNING TO NEAR NORMAL. STRONGEST WARM ADVECTION THIS 
EVENING STAYS NORTH OF ORCA BORDER...BUT SURFACE-850MB NORTHWEST 
FLOW AND INCREASING LOW LEVEL MOISTURE MAY ALLOW FOR A FEW SHOWERS 
ALONG LEADING EDGE OF WARM FRONT IN NORTHERN PARTS OF ZONES 1/3 
TONIGHT. RIDGE CONTINUES TO FLATTEN THRU FRI AS WAVES PRESS DOWNWARD 
UPON IT FROM THE NORTHWEST. STRONGER COLD ADVECTION PROGGED TO SWEEP 
THRU FAR NORCAL DURING FRI AS UPPER JET AXIS POKES THROUGH. MOISTURE 
FLOW IS LIMITED...BUT STRONGER DYNAMICS WITH JET MAX ALOFT COULD 
AGAIN SQUEAK OUT SOME LIGHT RAIN SHOWERS NORTHERN ZONES DURING FRI. 
THEREAFTER...SKIES SHOULD CLEAR OUT FRIDAY NIGHT AFTER WAVE PASSAGE 
WITH SOME SUBSIDENCE...AND LOW LEVEL OFFSHORE FLOW USHERING IN DRIER 
AIRMASS TO CONTINUE INTO SATURDAY. 

.LONG TERM...
MODELS DIVERGE BY SUN WITH OPERATIONAL GFS ODD ONE OUT AT THIS TIME. 
FOR THE MOST PART THE ECMWF/CANADIAN/NOGAPS ALONG WITH SEVERAL GFS 
ENSEMBLE MEMBERS ARE IN DECENT AGREEMENT WITH A NEAR REPLAY OF THE 
SYSTEM THAT AFFECTED NW CA THE LAST DAY OR SO. THIS WOULD ENTAIL 
UPPER WAVE ENERGY SLIDING SOUTHEASTWARD TOWARD THE CA COAST DURING 
SUNDAY WITH INITIAL WARM-FRONTAL PRECIPITATION BREAKING OUT SUN AND 
COOL/SHOWERY WEATHER FOR MON INTO TUE. ONLY OPERATIONAL GFS CUTS OFF 
THE UPPER LOW AND LEAVES IT OFFSHORE WITH RIDGING OVERHEAD...AND 
WITH NATIONAL GUIDANCE AND SURROUNDING OFFICES HEDGING TOWARD THE 
OTHER MODEL CONSENSUS...WILL LEAVE CHANCES FOR RAIN IN FORECAST DAYS 
4-7. TEMPERATURES WILL AVERAGE NEAR NORMAL AT THE BEGINNING OF THE 
EXTENDED PERIOD...BUT WILL COOL BY EARLY NEXT WEEK WITH SNOW LEVELS 
AGAIN FALLING TO NEAR THE 3KFT LEVEL AGAIN WITH SEVERAL ROUNDS OF 
COLD SHOWERS EXPECTED. HOWEVER...NO WIDESPREAD HEAVY PRECIPITATION 
APPEARS LIKELY IN THIS NORTHWEST FLOW PATTERN. 

SOROKA

POPS CEC 134 ACV 122 EKA 122 UKI 001

.EKA...SMALL CRAFT ADVISORY PT ST GEORGE TO PT ARENA 0-60NM. 

$$