000 
FXUS66 KEKA 181022
AFDEKA

NORTHWEST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
315 AM PDT SAT MAY 18 2002

COOLER WEATHER HAS BEEN ADVERTISED A WEEK IN ADVANCE NOW AND HAS 
FOLLOWED A PATTERN THAT HAS ALREADY UNFOLDED THREE PREVIOUS TIMES 
THIS SPRING. SO NO SURPRISES EXPECTED FOR A RETURN TO A MUCH COOLER 
AIRMASS ACROSS NW CALIF. THE CHALLENGE WILL BE TO FORECAST HOW 
QUICKLY THE BOUNDARY LAYER CAN RECOVER FROM THIS COLD-CORE SYSTEM.

AS THE APPROACH OF THIS SYSTEM BECOMES MORE AND MORE OF A REALITY... 
THE MAIN AND MOST APPARENT MODEL-DERIVED ADJUSTMENT/CHANGE HAS BEEN 
IN THE BOUNDARY-LAYER WIND FIELDS. SOUTH FLOW IS INCREASING AND 
LOOKS TO REACH LOW-END SMALL CRAFT CRITERIA CLOSE TO AND JUST AHEAD 
OF THE TROUGH AXIS...IE...THE SUNDAY EVENING THROUGH MONDAY MORNING 
TIME FRAME IN NW CALIF COASTAL WATERS. UPPER LOW AND SFC SYSTEM 
GENERALLY POSITIONED INVOF 45.5N 138W AND LATEST 10-HR TREND HAS 
BEEN FOR IT TO TRACK ESEWD. 

BELIEVE FORECASTS ARE ON TRACK THROUGH 72 HOURS. FORECAST LOGIC 
ASSUMES TWO KEY FEATURES OF THIS SYSTEM WILL NOT CHANGE. FIRST AND 
FOREMOST...A TREND FOR THE TROUGH AXIS TO BECOME NEGATIVELY-TILTED 
HAS BEEN AND REMAINS CONSISTENT. FOLLOWED IN IMPORTANCE BY A 
CONSISTENT FORECAST FOR THE TROUGH AXIS TO MAKE LANDFALL SOMETIME 
MONDAY INVOF CAZ001. WHAT HAS BEEN INCONSISTENT THROUGHOUT...IS 
EXACTLY WHERE THE MAIN IMPULSE WILL MAKE LANDFALL. 

EXTENDED...FORECASTS HAVE BEEN ADJUSTED FROM PREVIOUS TRENDS BEYOND 
72 HOURS TO MORE OF A CLOUDY BUT DRY FORECAST. THIS IS ACCEPTED BY 
NEIGHBORING FORECAST OFFICES. POPS CEC/ACV/EKA 01249 UKI 00339

.EKA...NONE.
MJV