233  
FXUS66 KEKA 241130  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
430 AM PDT THU APR 24 2014  
   
SYNOPSIS
 
 
WET WEATHER WILL CONTINUE TODAY AS A WEAK FRONT IMPACTS NORTHERN  
CALIFORNIA. AN UPPER LEVEL TROUGH WILL INTRODUCE A COLDER AND MORE  
UNSTABLE AIRMASS TO THE REGION...RESULTING IN A SLIGHT CHANCE FOR  
THUNDERSTORMS ON FRIDAY. A BRIEF PERIOD OF DRY WEATHER WILL RETURN  
LATE ON FRIDAY...FOLLOWED BY MORE RAIN ON THE WEEKEND.  
 

 
   
DISCUSSION
 
A WEAK COLD FRONT IS CURRENTLY MOVING ACROSS THE  
NORTH COAST THIS MORNING PROVIDING LIGHT RAIN TO AREAS NORTH OF  
THE EEL RIVER. THIS FRONT WILL CONTINUE TO SWING WESTWARD WHILE THE  
RAIN BAND GRADUALLY SAGS SOUTH. BY THIS AFTERNOON THE FRONT WILL HAVE  
EXITED THE AREA BUT SHOWER ACTIVITY WILL CONTINUE INTO THE EVENING.  
THE UPPER LEVEL TROUGH WILL CONTINUE DIG SOUTHWARD OVER NORTHERN  
CALIFORNIA INTRODUCING A COLDER AND MORE UNSTABLE AIRMASS  
CONDUCIVE TO THUNDERSTORM DEVELOPMENT ON FRIDAY. UPPER LEVEL  
DYNAMICS FAVOR A MORE UNSTABLE ENVIRONMENT WITH POSITIONING OF THE  
UPPER LEVEL JET PROMOTING DIVERGENCE ALOFT. THE BEST LOW LEVEL  
FORCING WILL OCCUR EARLY FRIDAY MORNING THROUGH THE LATE MORNING  
AS THE TROUGH AXIS TRAVERSES NORTHERN CALIFORNIA. MUCAPE REMAINS  
IN THE LOWER HUNDREDS WITH MARGINAL LIFTED INDICES BARELY DROPPING  
TO -1 C. THE COLDER AIRMASS WILL ENCOURAGE HAIL DEVELOPMENT WITH  
500 MB TEMPERATURES RANGING FROM -28 TO -31 DEGREES CELSIUS WITH  
THE PASSAGE OF THE TROUGH. CONDITIONS WILL QUICKLY STABILIZE AS  
RIDGING BUILDS BEHIND THE TROUGH AXIS PUTTING A HALT TO  
THUNDERSTORM DEVELOPMENT BY FRIDAY EVENING. MODELS APPEAR TO BE IN  
GOOD AGREEMENT WITH PRECIP WINDING DOWN FRIDAY NIGHT THROUGH  
SATURDAY AS A BROAD FLAT RIDGE DEVELOPS IN THE WAKE OF THE TROUGH.  
HOWEVER...ANOTHER WEAKER FRONT MAY BRING LIGHT AMOUNTS OF PRECIP  
SATURDAY NIGHT INTO EARLY SUNDAY MORNING. WE SHOULD SEE BETTER  
DRYING AND WARMING EARLY NEXT WEEK AS STRONGER RIDGING DEVELOPS  
BOTH AT THE SURFACE AND ALOFT. THE GFS MODEL NOW COMING MORE IN  
LINE WITH THE EURO FOR THE MID WEEK PERIOD WITH THIS RIDGING  
AS WELL AS DEPICTING SOME WEAK OFFSHORE FLOW ON TUE AND WED. THUS  
HAVE BUMPED TEMPERATURES UP AS WELL AS REMOVED CLOUD COVER DURING  
THIS PERIOD. JT/KML/DB  
 

 
   
AVIATION
 
A COLD FRONT WILL BRING A BAND OF RAIN WITH IFR TO MVFR  
CONDITIONS THIS MORNING. CONDITIONS WILL LIKELY IMPROVE ALONG THE  
COAST THIS AFTERNOON AND TONIGHT AS OPEN CELL CUMULUS MOVES TOWARD  
THE COAST. LOW CLOUDS MAY BECOME TRAPPED OVER THE INTERIOR  
MOUNTAINS THROUGHOUT THE DAY. AS AN UPPER LEVEL LOW MOVES OVERHEAD  
TONIGHT INTO FRIDAY...SHOWER ACTIVITY WILL ONCE AGAIN INCREASE WITH  
THE STRONGEST SHOWERS CAPABLE OF PRODUCING SMALL HAIL. AN ISOLATED  
THUNDERSTORM IS ALSO NOT OUT OF THE QUESTION. RPA  
 

 
   
MARINE
 
A COLD FRONT WILL MOVE THROUGH THE WATERS EARLY THIS  
MORNING ALLOWING SOUTHERLY WINDS TO DECREASE AND LIGHT TO MODERATE  
NORTHERLIES TO INCREASE THROUGH FRIDAY NIGHT. A LONG PERIOD WESTERLY  
SWELL WILL BUILD INTO THE WATERS TODAY AND TONIGHT ORIGINATING FROM  
A STORM SYSTEM IN THE NORTH-CENTRAL PACIFIC. SEAS ARE EXPECTED TO  
REMAIN BELOW 10 FEET...SO NO SMALL CRAFT ADVISORIES ARE EXPECTED FOR  
THIS SWELL.  
 
THE NEXT COLD FRONT WILL MOVE THROUGH THE WATERS SATURDAY NIGHT  
BRINGING A BRIEF PERIOD OF MODERATE TO STRONG SOUTHERLIES. THE  
COASTAL JET IS CURRENTLY ANTICIPATED TO REMAIN RATHER WEAK WITH 925  
MB WINDS AROUND 30 KT...SO WINDS SHOULD REMAIN BELOW GALE. A STRONG  
UPPER LEVEL RIDGE WILL BUILD BACK OVER THE WEST COAST BEHIND THIS  
FRONT RESULTING IN INCREASING NORTHERLIES OVER THE WATERS FOR NEXT  
WEEK.  
 
THE FIRST SIGNIFICANT SOUTHERLY SWELL OF THE SEASON WILL BUILD INTO  
THE WATERS THIS WEEKEND. ENP GUIDANCE INDICATES IT WILL PEAK  
SOMEWHERE BETWEEN 3 AND 4 FEET AT 17-19 SECONDS. JASON-2 ALTIMETRY  
INDICATES THE SWELL DOES EXIST BUT MAY BE DELAYED SEVERAL HOURS FROM  
THE MODEL DATA. HAVE CONTINUED TO INDICATE THE SWELL AT 3 FEET IN  
THE GRIDS BUT HAVE DELAYED ITS ONSET 6 HOURS. RPA  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 2 PM PDT  
THIS AFTERNOON PZZ470.  
 

 
 

 
 
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