104  
FXUS66 KEKA 281129  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
429 AM PDT FRI AUG 28 2015  
   
SYNOPSIS
 
AN UNSEASONABLY STRONG FRONT WILL RAPIDLY MOVE ACROSS  
NORTHWEST CA TONIGHT...ACCOMPANIED BY RAIN AND HIGH ELEVATION  
GUSTY WINDS THROUGH EARLY SATURDAY MORNING.  
 

 
   
DISCUSSION
 
MAINLY HIGH CLOUDS SPREADING OVER THE REGION THIS  
MORNING IN ADVANCE OF THE VERY SLOW MOVING FRONT STILL WELL OFF  
THE COAST. FORECAST MODELS IN GOOD AGREEMENT IN TERMS OF THE  
FRONT BECOMING SOMEWHAT STATIONARY OFF THE COAST TODAY THEN MOVING  
IT THROUGH AS A COLD FRONT BETWEEN MIDNIGHT TONIGHT AND SUNRISE  
SATURDAY. STILL ANTICIPATING LIGHT TO MODERATE RAIN OVER AREAS  
NORTH OF HWY 299 WITH LIGHTER AMOUNTS SOUTHWARD. ONE CAVEAT IS THE  
RAPID PROGRESSION OF THE FRONT...WHICH WOULD LEND CREDENCE TO  
LESSER AMOUNTS OF RAIN THAN WHAT IS CURRENTLY FORECASTED.  
NONETHELESS IT WOULD BE HARD TO GO AGAINST ALL THE MODEL AGREEMENT  
AT THIS TIME THUS ONLY MADE VERY MINOR ADJUSTMENTS TO THE VALUES  
CURRENTLY IN THE FORECAST (GRIDS). STILL ROUGHLY EXPECTING AT  
LEAST A HALF AN INCH ACROSS RAIN PRONE AREAS OF EXTREME NW CA WITH  
GREATER COLLECTIONS ALONG PREFERRED LOCATIONS. ONCE THE FRONT  
PASSES EARLY SATURDAY SOME SHOWER ACTIVITY WILL LINGER THROUGH THE  
AFTERNOON...ESPECIALLY OVER DEL NORTE COUNTY AND OVER THE HIGHER  
TERRAIN. THE GFS AND ECMWF SHOW ANOTHER IMPULSE MOVING TOWARD THE  
NORTH COAST ON SUNDAY. HOWEVER THE LATEST MODELS DAMPEN-OUT THE  
SURFACE REFLECTION OF THIS WAVE SIGNIFICANTLY. FOR NOW WILL  
MAINTAIN A CHANCE OR SLIGHT OF SHOWERS MAINLY NORTH OF THE  
CAPE...CONSIDERING THE NAM12 DOES SHOW MORE PRECIP SPROUTING UP  
WITH THE ONSHORE FLOW. FROM MONDAY THROUGH THURSDAY...A BROAD  
UPPER LEVEL TROUGH WILL REMAIN OVER THE WEST COAST THROUGH THE  
PERIOD. MAIN AFFECT FOR NW CALIFORNIA WILL BE BELOW NORMAL  
TEMPERATURES IN THE INTERIOR WITH SLIGHTLY ABOVE NORMAL  
TEMPERATURES FOR COASTAL AREAS. SEVERAL WEAK PERTURBATIONS  
EMBEDDED WITHIN THE LARGER SCALE TROUGH WILL MOVE INTO THE PAC NW  
FROM TIME TO TIME. NONE OF THESE SHORTER WAVE LENGTH FEATURES  
APPEAR TO BE STRONG ENOUGH TO GENERATE SIGNIFICANT PRECIP. THE  
TAIL END OF THESE WAVES MAY GENERATE SOME LIGHT SHOWERS NEAR THE  
ORCA BORDER. FOR NOW WILL MAINTAIN NEAR CLIMO PRECIP CHANCES FOR  
MOST OF THE FORECAST AREA AND SLIGHTLY ABOVE NORMAL CHANCES NEAR  
THE ORCA BORDER.  
 

 
   
AVIATION...FOR TONIGHT
 
MID AND HIGH LEVEL CLOUD COVER WILL CONTINUE TO  
INCREASE...AND A BRIEF PERIOD OF IFR TO PERHAPS BRIEFLY LIFR CIGS  
WILL BE POSSIBLE ALONG THE REDWOOD COAST. VFR CIGS WILL LIKELY  
PERSIST THROUGH THE DAY TODAY...BUT THIS WILL CHANGE TOMORROW DURING  
THE OVERNIGHT HOURS AS A FRONTAL SYSTEM REACHES THE COAST...LIKELY  
RESULTING IN A BRIEF PERIOD OF IFR CIGS AND MODERATE RAINFALL PARTICULARLY  
AT CEC. CONDITIONS AT UKI ARE MORE UNCERTAIN...BUT A BRIEF PERIOD  
OF LIGHT RAIN AND LOWERING CIGS WILL BE POSSIBLE TONIGHT HERE AS  
WELL.  
 

 
   
MARINE
 
LIGHT WINDS CONTINUE THROUGHOUT THE WATERS THIS MORNING AS AN EARLY  
SEASON FRONTAL SYSTEM GRADUALLY APPROACHES FROM THE WEST. SEAS  
CONTINUE TO BE MIXED BUT GENERALLY MILD MANNERED...WITH SIGNIFICANT  
WAVE HEIGHTS OF 3 TO 5 FEET AND TWO DISTRICT WAVE GROUPS CENTERED  
AROUND 8 AND 15 SECONDS...RESPECTIVELY. AS THE FRONTAL SYSTEM  
APPROACHES TOMORROW...SOUTH SOUTHWESTERLY WINDS WILL BEGIN TO  
INCREASE...LIKELY INTO THE FRESH RANGE ALTHOUGH THERE IS A BIT OF  
UNCERTAINTY REGARDING JUST HOW STRONG THE WINDS WILL GET. THIS  
FRONT WILL ALSO LIKELY RESULT IN A RELATIVELY BRIEF PERIOD OF  
MODERATE AND PERHAPS PERIODICALLY HEAVY RAINFALL  
TONIGHT...FOLLOWED BY SOME SHOWERY ACTIVITY TOMORROW MORNING. PEAK  
WIND SPEEDS WILL LIKELY BE REACHED DURING THE OVERNIGHT HOURS  
TONIGHT ACROSS THE NORTHERN OUTER WATERS AND BEGIN TO DECREASE BY  
TOMORROW EVENING. THIS SHOULD ALLOW STEEPER SHORT PERIOD SEAS TO  
SETTLE A BIT...BUT MULTIPLE SWELL GROUPS WILL ALSO BE PRESENT IN  
THE WATERS. THE FIRST OF WHICH THAT MAY BE MODERATELY SIGNIFICANT  
WILL BE A WESTERLY LONG PERIOD SWELL SET TO BUILD INTO THE WATERS  
OVERNIGHT TOMORROW AND INTO THE DAY SUNDAY. WHILE NOT OVERLY  
LARGE...THIS WELL WILL LIKELY BUILD TO AROUND 4 FEET AT 17 SECONDS  
SUNDAY AFTERNOON...AT A TIME WHEN WINDS AND SHORT PERIOD SEAS  
SHOULD BE ON THE DECLINE. WHILE NOT A HUGE CONCERN FOR  
BOATERS...THIS COULD PRESENT A MODERATE SNEAKER WAVE THREAT FOR  
AREA BEACHES DEPENDING ON HOW QUICKLY WINDS SUBSIDE ON SUNDAY.  
SUNDAY NIGHT...AN ADDITIONAL NORTHWESTERLY SWELL WILL BUILD INTO  
THE WATERS...ALTHOUGH THIS ITERATION WILL LIKELY COME IN WITH A  
SHORTER PERIOD OF AROUND 12 TO 13 SECONDS. STILL...FORECASTED  
HEIGHTS OF AROUND 6 TO 7 FEET WILL MAKE THIS SWELL SOMETHING TO  
KEEP AN EYE BOTH FOR BOATERS AND BEACHGOERS EARLY IN THE WEEK.  
OTHERWISE...SEVERAL SMALL SOUTHERLY SWELL GROUPS WILL ALSO  
CONTINUE TO PROPAGATE THROUGH THE WATERS OVER THE NEXT WEEK.  
 

 
   
FIRE WEATHER
 
ONLY SUBTLE CHANGES TO CURRENT FORECAST REGARDING  
INCOMING WEATHER SYSTEM. ONE CHANGE WAS TO SLOW DOWN TIMING OF  
PRECIP ARRIVAL TO THE COAST TO RIGHT AROUND OR JUST AFTER  
MIDNIGHT...WITH SOME MINOR ADJUSTMENTS TO CWR. OTHERWISE STILL ON  
TRACK IN TERMS OF EXPECTED QPF AND WINDS. ANTICIPATE A BRIEF  
PERIOD OF WINDS GUSTS TO NEAR 30-35 MPH ALONG ELEVATIONS ABOVE  
4000K FT BETWEEN MIDNIGHT AND SUNRISE WITH FRONTAL PASSAGE. SOME  
ELEVATED VALLEYS AND DRAINAGES IN SOUTH SOUTHWEST ALIGNMENT WILL  
ALSO SEE GUSTY WINDS AS WELL. FORTUNATELY THE WINDS WILL BE  
ACCOMPANIED OR IMMEDIATELY FOLLOWED BY THE PRECIPITATION. SOME  
RESIDUAL SHOWER ACTIVITY IS ANTICIPATED LATER ON SATURDAY WITH  
ANOTHER LESS IMPACTFUL AND WEAKER FRONT EARLY SUNDAY MAINLY OVER  
THE EXTREME NORTHWEST CORNER OF THE CWA. COOL AND MOIST  
CONDITIONS SHOULD CONTINUE THROUGH NEXT WEEK AS A STEADY STREAM OF  
TROUGHINESS CONTINUES. SKIES WILL GENERALLY BE SMOKE FREE AT LEAST  
THE EARLY PORTION OF NEXT WEEK ALLOWING ANY RESIDUAL FIRE ACTIVITY  
TO VENT WELL.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...  
SMALL CRAFT ADVISORY FROM 1 AM TO 9 AM PDT SATURDAY FOR PZZ450.  
 
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 9 AM PDT  
SATURDAY FOR PZZ470.  
 

 
 

 
 
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