877  
FXUS66 KEKA 280022  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
522 PM PDT MON MAR 27 2017  
   
SYNOPSIS
 
HIGH PRESSURE WILL BUILD BRIEFLY THIS AFTERNOON  
BRINGING DRIER WEATHER CONDITIONS THROUGH TUESDAY. ANOTHER  
RAIN PRODUCING SYSTEM WILL ARRIVE LATE WEDNESDAY FOLLOWED BY  
A DRY AND WARMER PERIOD TOWARD THE WEEKEND.  
 

 
   
UPDATE
 
DID A QUICK UPDATE TO THE FORECAST TO ADD A FROST  
ADVISORY TO NORTHEAST MENDOCINO COUNTY. CLEAR SKIES AND CALM WINDS  
WILL LIKELY ALLOW FROST TO FORM TONIGHT. MKK  
 

 
   
PREV DISCUSSION
 
/ISSUED 353 PM PDT MON MAR 27 2017/  
 
SYNOPSIS...HIGH PRESSURE WILL BUILD BRIEFLY THIS AFTERNOON  
BRINGING DRIER WEATHER CONDITIONS THROUGH TUESDAY. ANOTHER  
RAIN PRODUCING SYSTEM WILL ARRIVE LATE WEDNESDAY FOLLOWED BY  
A DRY AND WARMER PERIOD TOWARD THE WEEKEND.  
 
DISCUSSION...A DRIER NORTHWESTERLY HAS SET UP PROMOTING SUNSHINE  
AND MUCH DRIER AIR. RESPONSIBLE FOR THIS IS SOME UPPER LEVEL  
RIDGING AND STABLE AIR WHICH WILL BUILD TOWARD THE COAST  
THROUGHOUT THE REMAINDER OF THIS AFTERNOON BRINGING A WELCOME END  
TO THE SHOWER ACTIVITY. COOLER AIR WILL SETTLE OVER THE AREA  
TONIGHT AND A FROST ADVISORY HAS BEEN ISSUED FOR THE INTERIOR  
VALLEYS OF MENDOCINO COUNTY. STRONGER SUBSIDENCE AND LIGHT  
OFFSHORE WINDS SHOULD PROVIDE STEADY DRYING THROUGH EARLY TUESDAY.  
A FROST ADVISORY WILL NEED TO BE CONSIDERED WITH TEMPERATURES  
EXPECTED TO FALL TO NEAR 34F- 36F ACROSS THOSE VALLEYS AND  
POSSIBLY LOWER LOCALLY. EXCEPT FOR MORNING FROST, TUESDAY IS  
SHAPING UP TO BE A FINE DAY AFTER THE MORNING LOW CLOUDS AND FOG  
BURN OFF IN THE INTERIOR VALLEYS. DRY CONDITIONS SHOULD LAST  
THROUGH THE MORNING HOURS ON WEDNESDAY AS SURFACE RIDGING REMAINS  
OVER THE AREA. ANOTHER FRONT WILL APPROACH THE WEST COAST WED  
AFTERNOON. THE MODELS HAVE SLOWED DOWN THE WARM FRONT SLIGHTLY,  
BUT STILL HAVE THE COLD FRONT MOVING THROUGH WEDNESDAY NIGHT WHEN  
MOST OF THE RAIN IS EXPECTED. RIDGING ALOFT AND ROBUST NORTHERLY  
FLOW AT THE SURFACE WILL BUILD AFTER THE PASSAGE OF A MID LEVEL  
SHORTWAVE TROUGH ON THU. WITH BRISK NORTHERLY WINDS OFFSHORE,  
COASTAL AREAS WILL PROBABLY GET FAIRLY WINDY EACH AFTERNOON,  
ESPECIALLY ON FRIDAY. DRY WEATHER WILL LIKELY HOLD INTO THE  
WEEKEND, HOWEVER THE GFS AND ECMWF CONTINUE TO FORECAST THE RIDGE  
TO FLATTEN OUT TOWARD THE END OF THE WEEKEND IN RESPONSE TO  
ANOTHER SHORTWAVE TROUGH. SOME RAIN OR SHOWERS WILL CERTAINLY BE  
POSSIBLE SUN OR MON. FOR NOW WILL KEEP THE FORECAST DRY WITH ONLY  
A SLIGHT CHANCE OF RAIN. WE MAY NEED TO BEEF UP THE RAIN CHANCES  
IF THE MODELS CONTINUE ON THEIR PRESENT COURSE. JT/DB  
 
AVIATION...SHOWERS WERE DIMINISHING THROUGH THE DAY. BY THE  
AFTERNOON, WE ARE LEFT WITH SHALLOW CONVECTIVE CLOUDS OVER THE HILLS  
AND MOUNTAINS, GIVING US VFR CONDITIONS. DO EXPECT THESE CONVECTIVE  
CLOUDS TO DISSIPATE AFTER SUNSET AS WE LOSE DAYTIME HEATING. DO  
EXPECT NORTHERLY LOW LEVEL WINDS TO DEVELOP OVER CRESCENT CITY AND  
HUMBOLDT COUNTIES AND THIS WILL BRING IN DRIER AIR INTO THE AREA.  
THE DRY AIR ADVECTION WILL LIMIT THE FOG AND LOW CLOUD POTENTIAL  
OVERNIGHT AT THOSE AIRPORTS. FOR UKIAH AIRPORT, THERE WON'T BE AS  
MUCH DRY AIR ADVECTION. THUS, PUT IN SOME LOW CLOUDS AND REDUCED  
VISIBILITIES FOR POTENTIAL FOG AND LOW CLOUDS FORMATION. TOMORROW  
SHOULD BE A MOSTLY SUNNY DAY ACROSS NW CALIFORNIA. /RCL  
 
MARINE...WESTERLY SWELLS IMPACTING NW CALIFORNIA THROUGH MIDDLE OF  
THE WEEK. NORTHERLY WINDS WILL PREVAIL ACROSS NW CALIFORNIA WATERS.  
WINDS WILL BE INCREASING TO ADVISORY LEVEL STARTING ON THURSDAY.  
 
THROUGH THIS AFTERNOON, AREA BUOYS HAVE BEEN REPORTING NORTHWEST  
WIND AROUND 10 TO 15 KT. DO EXPECT THE NORTHWEST WIND TO CONTINUE  
THROUGH TOMORROW INTO WEDNESDAY AS A HIGH PRESSURE BUILDS OVER THE  
EASTERN PACIFIC OCEAN AND A THERMAL TROUGH SETS UP SHOP OVER  
CENTRAL VALLEY. ON THURSDAY, THE HIGH PRESSURE WILL PUSH EAST AND  
TIGHTENS THE PRESSURE GRADIENT OFF THE COAST OF NW CALIFORNIA.  
THE NORTHERLY WINDS WILL PICK UP TO SMALL CRAFT LEVEL STARTING ON  
THURSDAY. LOOKS LIKE THE STRONG NORTHERLIES WILL PERSIST THROUGH  
THE START OF THE WEEKEND.  
 
SEAS-WISE, IT IS PRETTY EXCITED FOR THE NEXT FEW DAYS. WE HAVE A  
DECAYING WESTERLY MID-PERIOD WAVE GROUP, WHILE A NOTABLE WESTERLY  
SWELL MOVE INTO THE WATERS. THIS WESTERLY SWELL WILL START OFF AT  
AROUND 20 SECONDS. THE PERIOD OF THIS SWELL WILL SHORTEN WITH TIME,  
DOWN TO 12 TO 14 SECONDS BY TUESDAY AND WEDNESDAY. WITH WAVE HEIGHT  
OF AROUND 10 FEET, THIS WARRANT A SMALL CRAFT ADVISORY DUE TO SEAS.  
DO HAVE THE SMALL CRAFT IN EFFECT THROUGH WEDNESDAY.  
 
MINIMAL CHANGES TO THE PREVIOUS FORECAST PACKAGE WERE MADE, AS THE  
FORECAST IS STILL ON TRACK FROM THE PREVIOUS VERSION.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...FROST ADVISORY FROM 1 AM TO 9 AM PDT TUESDAY FOR CAZ110-111-113.  
 
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 3 PM PDT WEDNESDAY FOR PZZ450-455-470-  
475.  
 

 
 

 
 
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SEE THE FORECAST ZONE MAP ONLINE:  
HTTP://WWW.WEATHER.GOV/EUREKA/ZONEMAP.PNG  
 
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