996  
FXUS66 KEKA 212313  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
313 PM PST TUE NOV 21 2017  
   
SYNOPSIS
 
UNSETTLED WEATHER CONDITIONS WILL CONTINUE WEDNESDAY  
AND THURSDAY WITH CLOUDY SKIES AND OCCASIONAL LIGHT RAIN. HEAVIER  
RAINS WILL GENERALLY STAY NORTH OF THE AREA. FRIDAY WILL BE MAINLY  
DRY BEFORE ANOTHER STORM SYSTEM BRINGS RAIN FOR THE WEEKEND.  
 

 
   
DISCUSSION
 
THE ATMOSPHERIC RIVER HAS PIVOTED MOSTLY N OF THE  
AREA TODAY, WITH MOST OF THE RAIN ACROSS OR AND WA. IN ADDITION,  
STRONG LOW-LEVEL S-SE WINDS HAVE PROVIDED DOWNSLOPING WINDS ACROSS  
THE COASTAL PLAIN, FURTHER DRYING OUT WHAT PRECIPITATION REMAINS.  
THIS DOWNSLOPING ALSO ALLOWED TEMPERATURES TO REACH OR EXCEEDS  
RECORD HIGHS FOR THIS DATE. THIS INCLUDES A HIGH TEMPERATURE OF 75  
DEGREES AND THE NWS OFFICE ON WOODLEY ISLAND, WHICH SHATTERED THE  
PREVIOUS RECORD OF 70 DEGREES LAST SET IN 1930.  
 
THE WEATHER OVER THE NEXT 2 DAYS WILL REMAIN DOMINATED BY THE  
LOCATION OF THE DEEP PACIFIC MOISTURE PLUME, INDIVIDUAL  
ATMOSPHERIC DISTURBANCES MOVING NE ON THE E SIDE OF THE PACIFIC  
TROUGH, AND DOWNSLOPING WINDS ALONG THE COAST. THE BEST RAIN  
CHANCES AND HEAVIEST RAINS WILL BE GENERALLY FOCUSED OVER THE N  
1/2 OF THE AREA, BUT MUCH OF THE TIME PERIOD WILL CONTINUE WITH  
DOWNSLOPE FLOW. AS A RESULT, HAVE ADJUSTED RAIN CHANCES DOWN  
PERIODICALLY ALONG THE IMMEDIATE COAST ALONG WITH LOWER RAIN  
AMOUNTS. HAVE ALSO TWEAKED COASTAL TEMPERATURES UP A FEW DEGREES  
TONIGHT AND WEDNESDAY.  
 
AFTER MOSTLY DRY WEATHER ON FRIDAY, RAINS WILL RETURN OVER THE  
WEEKEND AND INTO EARLY NEXT WEEK. THERE ARE STILL TIMING ISSUES  
BETWEEN THE GFS AND ECMWF REGARDING THE HEAVIEST BURSTS OF RAIN  
DURING THIS PERIOD, BUT RAINFALL TOTALS OF SEVERAL INCHES APPEAR  
LIKELY. STAY TUNED! /SEC  
 

 
   
AVIATION...COASTAL AIR TERMINALS BECAME VFR OVERNIGHT
 
AND  
REMAINED SO TODAY AS A SHORTWAVE RIDGE OF HIGH PRESSURE MOVED OVER  
NORTHWEST CALIF. A LULL IN RAIN WAS A RESULT OF WEAK SUBSIDENCE  
ASSOCIATED WITH THE HIGH. BY THIS AFTERNOON, THE RIDGE WAS SLOWING  
DRIFTING EASTWARD ALLOWING MOISTURE...ASSOCIATED WITH AN OFFSHORE  
SHORTWAVE IN SOUTH- SOUTHWEST FLOW...TO ADVECT SOME LIGHT RAIN  
INTO THE FAR NORTH AREAS BY MID-AFTERNOON. THEREFORE, MOSTLY LIGHT  
SPRINKLES WILL PASS OVER THE ACV & CEC TERMINALS EVEN THOUGH  
CLOUD BASES WILL REMAIN FAIRLY HIGH. ACROSS INTERIOR AREAS:  
WIDESPREAD LOW CIGS/VIS (IFR/LIFR) DEVELOPED AND SETTLED OVER  
INTERIOR VALLEYS...ESPECIALLY UKI'S AIRPORT WHERE CONDITIONS  
CONTINUED TO AROUND NOONDAY. LLWS FLIGHT HAZARD CONTINUED ACROSS  
THE REDWOOD COAST AFFECTING ACV & CEC AIR TERMINALS TODAY AS 50  
KNOT SOUTHWEST WINDS WERE REPORTED NEAR THE BOUNDARY LEVEL.  
THROUGH THE REMAINDER OF THE TAF PERIOD (TONIGHT- WEDNESDAY  
AFTERNOON), CONTINUED CLOUDINESS WITH INCREASING RAIN CHANCES AND  
MOSTLY VFR CONDITIONS. THE EXCEPTION WILL BE POCKETS OF OVERNIGHT  
LOW VIS & CIGS OVER SOME INTERIOR VALLEYS...BUT GENERALLY AT A  
LESSER EXTENT TOMORROW. /TA  
 

 
   
MARINE
 
WINDS WILL PEAK THIS AFTERNOON, REACHING NEAR GALE  
STRENGTH ACROSS THE WATERS 10+ NM OFFSHORE AND N OF CAPE  
MENDOCINO. WATERS S OF CAPE MENDOCINO AND CLOSER TO SHORE WILL  
REMAIN MORE SHELTERED FROM THESE STRONGER GALES, BUT WILL BE  
MODERATELY BREEZY NONETHELESS. THESE SOUTHERLIES WILL RESULT IN  
BUILDING STEEP SEAS, PARTICULARLY IN THE NORTHERN OFFSHORE AREAS  
WITH THE STRONGEST WINDS.  
 
TONIGHT, WINDS WILL WEAKEN SLIGHTLY, BUT WILL REMAIN FRESH TO  
STRONG THROUGH LATE WEDNESDAY. MEANWHILE, BOTH A FRESH SW SWELL  
AND A LONGER PERIOD NORTHWEST SWELL WILL MOVE THROUGH THE WATERS  
AT THIS TIME, AND THE END RESULT WILL BE A CHAOTIC SEA STATE THAT  
WILL LAST THROUGH WEDNESDAY NIGHT. WINDS WILL WEAKEN THURSDAY AND  
ALLOW THE STEEPER SOUTHERLY SEAS TO SETTLE, BUT THE PREVIOUSLY  
MENTIONED SWELLS WILL MAINTAIN IMPROVED BUT STILL SOMEWHAT  
UNCOMFORTABLE CONDITIONS THROUGH THE END OF THE WEEK.  
 
ON SATURDAY, ANOTHER COLD FRONT WILL BRING A RETURN OF STRONG  
SOUTHERLIES, AND THIS WILL BE FOLLOWED CLOSELY BY A BUILDING LONG  
PERIOD NORTHWEST SWELL. /BRC&SEC  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...  
GALE WARNING UNTIL 4 PM THIS AFTERNOON FOR PZZ470.  
SMALL CRAFT ADVISORY UNTIL 4 AM WEDNESDAY FOR PZZ475.  
 

 
 
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