FXUS66 KEKA 092250
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
250 PM PST WED DEC 9 2009

.SYNOPSIS...THE COLD AIR MASS WILL CONTINUE TO MODIFY TONIGHT AS A 
STORM SYSTEM IN THE EASTERN PACIFIC MOVES CLOSER TO CALIFORNIA. RAIN 
CHANCES INCREASE DRAMATICALLY BY FRIDAY AS THIS STORM MOVES ACROSS 
THE REGION. PRECIPITATION CHANCES CONTINUE INTO NEXT WEEK AS A 
SERIES OF STORMS MOVE ACROSS THE PACIFIC NORTHWEST.
&&

.DISCUSSION...LITTLE CHANGE IN SYNOPTIC PATTER TODAY AS AN UPPER 
LEVEL RIDGE PREVAILS OVER THE NE PAC. MODELS IN FAIRLY GOOD 
AGREEMENT IN A SPLIT FLOW PATTERN DEVELOPING ACROSS THE PAC BY THIS 
WEEKEND. A BIT OF ENERGY FROM AN UPPER LEVEL LOW NEAR 40N/130W WILL 
CUT UNDER THE RIDGE WITH INCREASING MID AND HI LEVEL CLOUDS ACROSS 
THE REGION EVIDENT OF SAT IMAGERY. THE FIRST CHALLENGE IS THE 
POTENTIAL FOR ANOTHER HARD FREEZE OVERNIGHT INTO THU MORNING. WEAK 
WAA ACROSS THE REGION WILL COMBINE WITH INCREASED CLOUD COVER TO 
PRODUCE LESS THAN IDEAL RADIATIONAL COOLING. EXPECT A SIMILAR NIGHT 
ACROSS THE REDWOOD COAST WITH TEMPS DROPPING RAPIDLY AFTER 
SUNSET...SO HOISTED A HARD FREEZE WARNING FROM LATE TONIGHT THROUGH 
THU MORNING. TRICKIER SCENARIO FOR THE MENDOCINO COAST AS GREATER 
SKY COVER WILL SLOW THE COOLING TREND WITH TEMPS EXPECTED TO DROP 
BELOW FREEZING LATE TONIGHT...SO ISSUED HARD FREEZE WARNING FOR THE 
EARLY MORNING HOURS THU. THE NEXT CHALLENGE IS THE ONSET OF PRECIP 
THU INTO FRI AS THE FIRST IN A SERIES OF STORMS BEGINS TO AFFECT THE 
REGION. PRECIP CHCS WILL INCREASE FROM S TO N THROUGH THE DAY THU. 
MODELS SHOW ANOTHER STORM SLOWLY DRIFTING ACROSS THE REGION BEFORE 
MOVING INTO CENTRAL CA THIS WEEKEND. MODELS FCST QUITE A BIT OF WAA 
ACROSS THE REGION RESULTING IN INCREASING SNOW LEVELS. THE MAIN 
CONCERN IS ACROSS THE INTERIOR VALLEYS WHERE THE COLD AIR WILL BE 
DIFFICULT TO MIX OUT DESPITE WAA. EXPECT SNOW LEVELS TO INCREASE TO 
3500 TO 4000 FT BY FRI...BUT TRAPPED COLD AIR IN THE VALLEYS WILL 
RESULT IN SOME LIGHT ACCUMULATIONS...LESS THAN AN INCH...IN THE 
INTERIOR VALLEYS. A SHORT WAVE RIDGE WILL BRING A BREAK TO THE 
PRECIP MON...BUT AN INSTABILITY SHOWER OR TWO REMAIN POSSIBLE MON. 
MODEL SOLUTIONS DIVERGE SIGNIFICANTLY EARLY NEXT WEEK WITH A GENERAL 
PATTERN OF A LONG WAVE TROUGH OVER THE E PAC AND A RIDGE OVER THE W 
CONUS. GIVEN THE POOR MODEL AGREEMENT THROUGH THE EXTENDED...ELECTED 
TO TREND MORE TOWARDS THE ECMWF AS IT HAS SHOWN BETTER RUN TO RUN 
CONSISTENCY THAN OTHER MEDIUM RANGE MODELS. GIVEN THE PROGRESSIVE 
PATTERN ACROSS THE E PAC WILL MAINTAIN POPS ABOVE CLIMO THROUGH THE 
EXTENDED. BC
&&

.MARINE...BUOYS CONTINUE TO SHOW A LONG PERIOD WESTERLY SWELL 
PROPAGATING THROUGH THE WATERS. HOWEVER, THE SWELL IS RUNNING ABOUT 
3 TO 4 FT LOWER THAN FORECAST, INCLUDING BOTH THE SWAN AND ENP 
MODELS. SO BUMPED THE SWELL DOWN TO BETTER REFLECT THE CURRENT 
OBSERVATIONS. HAVE ALSO DROPPED THE SCA SINCE WE ARE WELL BELOW 
CRITERIA. A WEAK PRESSURE GRADIENT WILL CONTINUE TO BRING LIGHT 
WINDS TO THE WATERS THROUGH THURSDAY. AS A STORM APPROACHES THE 
COAST LATE THIS WEEK, SOUTHERLY WINDS WILL INCREASE FRIDAY INTO 
SATURDAY AND SEAS WILL BECOME MIXED. RIGHT NOW IT LOOKS LIKE IT WILL 
BE A HIGH END SCA FOR WINDS AND HAZARDOUS SEAS. AFTER THIS ANOTHER 
STORM WILL IMPACT THE WATERS EARLY NEXT WEEK, BRINGING WORSE 
CONDITIONS. STROZ
&&

.AVIATION...VISIBLE SATELLITE SHOWS SOME CIRRUS MOVING OVER 
NORTHWEST CALIFORNIA, BUT GENERALLY MOSTLY CLEAR SKIES. THIS STABLE 
AIRMASS IS EXPECTED TO CONTINUE TO BRING VFR CONDITIONS TO THE AREA 
UNDER LIGHT OFFSHORE FLOW. STROZ
&&

.EKA WATCHES/WARNINGS/ADVISORIES...
HARD FREEZE WARNING TONIGHT THROUGH THU MORNING FOR CAZ001-002.
SCA FOR HAZARDOUS SEAS UNTIL 4 PM PST THURSDAY PZZ450-455-470-475.
&&

$$

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