206  
FXUS66 KEKA 192222  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
322 PM PDT SUN OCT 19 2014  
   
SYNOPSIS
 
A COLD FRONT WILL BRING WIDESPREAD RAIN TO NW  
CALIFORNIA OVERNIGHT AND INTO MONDAY. THIS FRONT WILL ALSO CAUSE  
GUSTY MOUNTAIN WINDS AS IT CROSSES THE REGION. A POST FRONTAL  
TROUGH WILL FOLLOW THE COLD FRONT...BRINGING A FEW STRONG SHOWERS  
AND A POSSIBLE THUNDERSTORM...WHICH MAY CONTAIN SMALL HAIL.  
TEMPERATURES WILL COOL MONDAY NIGHT AS THE CLOUDS CLEAR AND COLD  
AIR FILLS IN BEHIND THIS SYSTEM. MORE RAIN IS EXPECTED TUESDAY  
NIGHT INTO WEDNESDAY...THEN AGAIN LATE IN THE WEEK.  
 

 
   
SHORT TERM (TONIGHT THROUGH WEDNESDAY)
 
AFTERNOON SATELLITE  
IMAGERY SHOWS THE NEXT COLD FRONT ABOUT 7O MILES OFFSHORE.  
HOWEVER, DRY AIR BEING ENTRAINED FROM THE SOUTH CONTINUES TO ERODE  
THE CLOUDS FROM THE FRONT OVER THE COASTAL WATERS. THIS WILL NOT  
BE LONG LASTING THIS EVENING THOUGH AS THE UPPER SUPPORT TO THE  
SURFACE FRONT HELPS TO FORCE THE FRONT TO THE EAST TONIGHT. MODELS  
HAVE SPED UP THE FRONT SLIGHTLY, WHICH SEEMS TO BE IN GOOD  
AGREEMENT WITH VISUAL DATA AND BUOY DATA. BUOY 2 WHICH 275NM WEST  
OF COOS BAY SHOWED THE FRONT PASSING AROUND 5 TO 6 AM WITH A STEEP  
PRESSURE RISE FOLLOWING THE FRONT. WENT AHEAD AND SPED THE FRONT  
UP SLIGHTLY IN THE FORECAST AS WELL, BRINGING RAIN TO THE  
IMMEDIATE COAST AS EARLY AS THIS EVENING. THE BULK OF THE RAIN  
WILL COME OVERNIGHT THOUGH. THE QPF CONTINUES TO BE A TOUGH NUT TO  
CRACK. FRONTAL RAINS SEEMS TO BE CONSISTENT BETWEEN MODELS, BUT  
POST FRONTAL SHOWERS ASSOCIATED WITH A TRAILING TROUGH SHOW A  
SIGNIFICANT DIFFERENCE. THE EC CONTINUES TO SHOW AMPLE QPF OVER  
DEL NORTE AND NORTHERN HUMBOLDT, WHILE THE GFS AND NAM SEEM TO BE  
SOMEWHAT LESS. THERE IS A HINT OF SOME CYCLOGENISIS ON THE TROUGH  
OFF OF CAPE MENDOCINO WHICH COULD CAUSE SOME ENHANCED PRECIP OVER  
COASTAL MENDOCINO. CONFIDENCE IS LOW HERE, SO DID NOT HIT THIS IN  
THE FORECAST, BUT WILL NEED TO BE WATCHED. THIS POST FRONTAL  
TROUGH WILL ALSO PROVIDE A FOCUS FOR INSTABILITY IN THE POST  
FRONTAL COLD POOL. THIS MEANS THERE WILL BE A SHOT OF A  
THUNDERSTORM ALONG THE REDWOOD COAST THROUGH THE DAY ON MONDAY.  
ANY THUNDERSTORM THAT DOES DEVELOP WILL HAVE THE CHANCE OF  
PRODUCING SMALL HAIL. AT ELEVATION IN THIS COLD POOL OF AIR, THERE  
IS A SHOT OF SEEING SOME SNOW SHOWERS WITH SNOW LEVELS DROPPING  
BRIEFLY TO AROUND 6KFT. ANY SNOW THAT DOES FALL WILL NOT STICK  
AROUND LONG DUE TO WARM GROUND AND A QUICKLY MODIFYING AIR MASS.  
 
WINDS WILL REMAIN AN ISSUE WITH THE FRONT AS WELL. PRE FRONTAL  
WINDS ARE ALREADY GUSTING THIS AFTERNOON ALONG COASTAL MOUNTAIN  
RANGES OF HUMBOLDT AND DEL NORTE WITH GUSTS AS HIGH AS THE LOW 30  
MPH RANGE. THIS WILL LIKELY ENHANCE TONIGHT AS THE FRONT  
APPROACHES. PEAK GUSTS CAN BE EXPECTED JUST AHEAD OF FRONT PASSAGE  
TONIGHT WITH RIDGE TOP GUSTS AS HIGH AS 45 MPH. THESE WILL BE VERY  
ISOLATED, BUT BREEZY CONDITIONS IN THE MOUNTAINS CAN BE EXPECTED.  
WITH SATURATING SOILS AND STRONG GUSTY WINDS, THERE IS THE CHANCE  
OF FALLING TREE LIMBS OR FALLING TREES. IF IN THE MOUNTAINS  
TONIGHT OR ON MONDAY, BE CAREFUL. THE POST FRONTAL TROUGH WILL  
BRING ANOTHER HIT OF WINDS ON MONDAY AS WELL, BUT THE GUSTS WILL  
NOT BE AS GREAT.  
 
OVERALL, LOOK FOR WET AND BREEZY CONDITIONS THROUGH MONDAY DUE A  
COLD FRONT AND A POST FRONTAL TROUGH. PRECIP AMOUNTS WILL RANGE  
FROM A QUARTER INCH TO A FEW INCHES OVER UPSLOPE PRONE MOUNTAINS.  
AREA BEACHES WILL ALSO SEE BUILDING SURF DUE TO LARGE POST FRONTAL  
SWELL.  
 
MONDAY NIGHT INTO TUESDAY NW CAL SHOULD SEE A BRIEF DRYING TREND.  
OVERNIGHT LOWS MAY DROP INTO THE MID TO UPPER 30S IN TRINITY  
COUNTY VALLEYS AND INTO THE 40S IN THE COASTAL COUNTY VALLEYS  
UNDER CLEARING SKIES AND COOL AIR LOFT MIXING DOWN. FROSTY  
CONDITIONS ARE POSSIBLE MONDAY NIGHT IN THE EASTERN TRINITY  
VALLEYS. THERE IS A POSSIBILITY THAT THE EASTERN TRINITY VALLEYS  
STAY COOL ON TUESDAY AS COOL AIR MAY BECOME TRAPPED. THIS ALL  
DEPENDS ON HOW STABLE THE TUESDAY AIR MASS BECOMES. AT THIS POINT  
THERE LOOKS LIKE THERE WILL BE ENOUGH MIXING TO SCOUR OUT THE COOL  
AIR AND CAUSE SOME WARMING. HIGH TEMPS ON TUES COULD BE RATHER  
WARM AS SOUTHERLY FLOW DEVELOPS, BRINGING A STRONG AIR MASS  
MODIFICATION. ANOTHER FRONTAL BOUNDARY WILL SINK INTO NW CAL LATE  
TUES INTO WED, BRINGING MORE RAIN TO DEL NORTE AND HUMBOLDT  
COUNTIES. AT THIS TIME IT LOOKS LIKE THE VAST MAJORITY OF PRECIP  
WILL REMAIN OUT OF MENDOCINO ON TUES INTO WED. BFG  
   
LONG TERM (THUR THROUGH SUN)
 
BOTH THE GFS AND ECMWF WERE WET ON  
THU. HOWEVER THERE WERE SIGNIFICANT DIFFERENCES BETWEEN THE  
TWO...BOTH TEMPORALLY AND SPATIALLY. THE GFS HAS THE FRONT AND  
BULK OF RAIN OVER SOUTHERN MENDO COUNTY BY THU MORNING...WITH THE  
NORTH COAST DRYING OUT. MEANWHILE THE ECMWF HAS THE FRONTAL BAND  
DANGLING OFFSHORE THE NORTH COAST WITH THE BULLS-EYE OF RAIN AIMED  
AT DEL NORTE COUNTY. EVENTUALLY THE EMCWF DOES SPREAD THE RAIN  
FARTHER SOUTHWARD AND EASTWARD BY THU AFTERNOON AND  
EVENING...THOUGH IT KEEPS MOST OF MENDO COUNTY DRY. WE BEEFED UP  
THE PRECIP CHANCES ACROSS THE BOARD...LEANING SLIGHTLY IN FAVOR OF  
THE SLOWER ECMWF. BIGGER DIFFERENCES BETWEEN THE TWO MODELS ARISE  
ON FRIDAY. THE GFS BRINGS AN UPPER TROUGH TOWARD THE COAST MUCH  
FASTER WITH RAIN OR SHOWERS INCREASING SUBSTANTIALLY CWA- WIDE.  
THE ECWMF IS MUCH SLOWER WITH THE PROGRESSION OF THE 500MB TROUGH  
AND HAS THE MAIN BAND OF RAIN STILL OFF THE COAST. AVERAGED THE  
WET GFS WITH THE DRY ECMWF FOR ESSENTIALLY MIDDLE OF THE ROAD  
PRECIP CHANCES ON FRI. THE MODELS DO NOT COME INTO REAL GOOD  
AGREEMENT OVER THE WEEKEND...BUT BOTH INDICATE AN UPPER TROUGH  
IMPACTING THE AREA. THE ECMWF FINALLY BRINGS THE FRONT ONTO COAST  
ON SAT...WHILE THE GFS BRINGS A COLD UPPER TROUGH DOWN FROM THE NW  
FOR PERIODIC SHOWERS. CONFIDENCE IS INCREASING THAT NEXT WEEKEND  
WILL BE WET WITH BOUTS OF PRECIP BOTH SAT AND SUN. PRECIP CHANCES  
HAVE BEEN BEEFED UP.  
 

 
   
AVIATION
 
BETTER CONDITIONS ALONG MUCH OF THE NORTH COAST THIS  
AFTERNOON AFTER MORNING WIDE WIDESPREAD MARINE CLOUDS. HOWEVER  
NORTH OF TRINIDAD...CU/SC CLOUDS PERSISTED INTO THE AFTERNOON.  
WIDESPREAD CLOUDS ALSO PERSISTED SOUTH OF CAPE  
MENDOCINO...ESPECIALLY IN THE UKIAH AREA WHERE CIGS WERE IFR TO  
LOW MVFR CONDITIONS THROUGH LATE MORNING...THEN MOSTLY VFR AFTER  
MIDDAY. TERMINALS WILL GRADUALLY DETERIORATE AS AN APPROACHING  
FRONTAL SYSTEM FROM THE PACIFIC NORTHWEST MOVES INTO THE REGION.  
RAIN AND GUSTY WINDS WILL IMPACT THE CEC AND NORTH COAST LATE  
TONIGHT- OVERNIGHT. ALONG THE HUMBOLDT AND DEL NORTE  
COAST...AIRFIELDS MAY SEE SOME LIMITED CONVECTION DURING FORECAST  
PERIOD. TA  
 

 
   
MARINE
 
SEAS HAVE BEEN TRENDING DOWNWARD TODAY WITH BUOYS  
REPORTING 5 TO 7 FT AT 11 SECONDS THIS AFTERNOON. SOUTHERLY WINDS  
HAVE BEEN INCREASING AND SHOULD REACH 20-25 KT IN THE NORTHERN  
OUTER WATERS LATER THIS AFTERNOON AND EVENING. THE NWPS CONTINUES  
TO INDICATE SHORT PERIOD SOUTHERLY WAVES HITTING 9 FT IN THE OUTER  
WATERS THIS EVENING. SEE NO REASON TO SECOND GUESS THE MODEL AT  
THIS POINT. THUS WILL MAINTAIN THE ADVISORY FOR BOTH WINDS AND  
SEAS THROUGH THIS EVENING IN PZZ470. NEXT ISSUE IS THE LARGE  
WESTERLY SWELL EXPECTED TO ARRIVE LATER TONIGHT INTO MONDAY  
MORNING. JASON-2 ALTIMETRY PASS FROM 18Z YESTERDAY SHOWED 20 FEET  
AROUND THE PERIPHERY OF THE WAVE MAX. THIS IS IN PRETTY GOOD  
AGREEMENT WITH THE WW3 MODEL AND WILL CONTINUE TO FOLLOW THE  
GUIDANCE. WE WILL HAVE A MUCH BETTER IDEA ON HOW GOOD THE MODEL IS  
DOING ONCE 15-17 FT SWELL GOES BY BUOY 2 TONIGHT. CONFIDENCE IS  
HIGH THE MODEL IS NOT TOO FAR OFF THE MARK AND AN ADVISORY FOR  
SEAS HAS BEEN POSTED FOR ALL WATERS STARTING LATE TONIGHT AND  
CONTINUING THROUGH TUE. IF THE SWELL FORECAST PANS OUT...HIGH SURF  
CONDITIONS WITH BREAKERS NEAR 20 FEET CAN BE EXPECTED ON MONDAY.  
BOTH THE GFS AND NAM12 HAVE COME IN STRONGER WITH SOUTHERLY WINDS  
TUE NIGHT INTO WED AS A NEW FRONTAL SYSTEM DEVELOPS ACROSS THE PAC  
NW. BEEFED UP THE WIND FORECAST IN THE NORTHERN WATERS. IT WILL  
NEED TO BE WATCHED FOR LOW END GALES.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...  
SMALL CRAFT ADVISORY FROM 3 AM MONDAY TO 11 PM PDT TUESDAY FOR  
PZZ450-455.  
 
SMALL CRAFT ADVISORY UNTIL 11 PM PDT TUESDAY FOR PZZ470.  
 
SMALL CRAFT ADVISORY FROM 3 AM MONDAY TO 11 PM PDT TUESDAY FOR  
PZZ475.  
 

 
 

 
 
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