552  
FXUS66 KEKA 250911  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
211 AM PDT TUE SEP 25 2018  
   
SYNOPSIS
 
HOT AFTERNOON TEMPERATURES WILL OCCUR ACROSS MUCH OF  
THE REGION THROUGH THURSDAY. COOLER WEATHER WITH SCATTERED SHOWERS  
WILL THEN SPREAD ACROSS THE AREA THIS WEEKEND.  
 

 
   
DISCUSSION
 
DEEP-LAYER EAST-NORTHEASTERLY FLOW IS OCCURRING  
ACROSS THE REGION EARLY TUESDAY MORNING. THIS FLOW REGIME IS  
FAVORING VERY WARM AND DRY CONDITIONS THAT WILL SUPPORT HOT  
AFTERNOON TEMPERATURES AS WELL AS FIRE WEATHER CONCERNS (REFERENCE  
THE FIRE WEATHER DISCUSSION BELOW). THE INHERITED TEMPERATURE  
GRIDS APPEAR TO BE ON TRACK THROUGH THURSDAY, WITH HIGHS IN THE  
90S EXPECTED ACROSS MOST OF THE INTERIOR, RANGING TO 70S ALONG  
THE COAST. COASTAL LOCATIONS SUCH AS EUREKA WILL LIKELY EXPERIENCE  
HIGHS RELATIVELY EARLY IN THE DIURNAL HEATING CYCLE, FOLLOWED BY  
COOLING LATE IN THE AFTERNOON AS THE SEA BREEZE INITIATES IN  
RESPONSE TO STRONG INLAND HEATING.  
 
AN UPPER LOW POSITIONED WELL OFFSHORE THIS MORNING IS FORECAST TO  
DRIFT EASTWARD THROUGH FRIDAY AS AN UPPER HIGH SHIFTS NORTHWARD.  
BY SATURDAY, MODEL GUIDANCE SHOWS THE UPPER LOW MOVING ONSHORE,  
THOUGH LARGE POSITIONAL DIFFERENCES EXIST BETWEEN VARIOUS  
DETERMINISTIC SOLUTIONS. NEVERTHELESS, SHOWERS AND COOLER  
TEMPERATURES APPEAR PROBABLE DURING SATURDAY, AND THUNDERSTORMS  
CAN'T BE RULED OUT IF THE GFS VERIFIES. THEREAFTER, THE ECMWF  
MAINTAINS A SHOWERY REGIME GOING INTO NEXT WEEK, WHILE THE GFS  
FAVORS A DRY ENVIRONMENT.  
 

 
   
AVIATION
 
ONLY COASTAL STRATUS TO SPEAK OF THIS MORNING IS  
BEING HELD TO THE MENDOCINO COASTLINE, HOWEVER OFFSHORE FLOW HAS  
BEEN PREVENTING INLAND PENETRATION THIS MORNING. PERSISTENT  
SUBSIDENCE AND OFF SHORE FLOW NORTH OF CAPE MENDOCINO HAS ALSO  
BEEN PREVENTING WIDESPREAD STRATUS FROM FORMING. TODAY WILL BE  
ANOTHER LOVELY VFR DAY ACROSS THE NORTH COAST, WITH EVEN LIGHTER  
NORTHERLY WINDS AS COMPARED TO YESTERDAY. LACK OF BOUNDARY LAYER  
MOISTURE AND SUBSIDENCE WILL ONCE AGAIN KEEP COASTAL TERMINALS  
CLEAR THIS EVENING THROUGH TOMORROW MORNING. /WCI  
 

 
   
MARINE
 
NORTHERLY WINDS WILL CONTINUE TO DIMINISH AS WE GO  
THROUGH THE DAY. THE ONE EXCEPTION WILL BE ACROSS THE NORTHWEST  
POTION OF THE NORTHERN OUTER WATERS WHERE NEAR GALE FORCE GUSTS  
WILL REMAIN POSSIBLE THROUGH THIS EVENING. STEEP WAVES OF 7-11  
FEET AT AROUND 9 SECONDS WILL REMAIN POSSIBLE THROUGH EARLY  
WEDNESDAY MORNING THEREFORE SMALL CRAFT ADVISORIES WILL REMAIN IN  
EFFECT. THE WINDS WILL REMAIN FAIRLY LIGHT THROUGH THE REMAINDER  
OF THE FORECAST PERIOD WITH WINDS BECOMING SOUTHERLY LATE THIS  
WEEK. A PERIODIC SW SWELL AT AROUND 16 SECONDS WILL MOVE THROUGH  
THE WATERS BEGINNING LATER TODAY AND PERSISTING THROUGH THIS  
WEEKEND. /WCI  
 

 
   
FIRE WEATHER
 
A RED FLAG WARNING HAS BEEN ISSUED FOR ELEVATIONS  
ABOVE 2000 FEET OVER DEL NORTE AND NORTHERN HUMBOLDT COUNTIES  
THROUGH TUESDAY NIGHT. TEMPERATURES ARE WARM WITHIN THE THERMAL  
BELT EARLY TUESDAY MORNING, WHICH IS RESULTING IN POOR OVERNIGHT  
RH RECOVERY. IN ADDITION, AN OFFSHORE WIND REGIME IS YIELDING  
GUSTS TO 25 MPH ACROSS EXPOSED RIDGES. THESE CONDITIONS ARE AIDING  
IN STRONG HEAT SIGNATURES FROM THE NATCHEZ FIRE LOCATED NEAR THE  
DEL NORTE/SISKIYOU COUNTY BORDER...WHICH IS EVIDENCE OF POTENTIAL  
EXTREME FIRE BEHAVIOR. WINDS WILL WEAKEN SOMEWHAT BY TUESDAY  
AFTERNOON, AND MAY BRIEFLY BECOME WESTERLY BEFORE ACCELERATING OUT  
OF THE EAST ONCE AGAIN THIS EVENING. IN ADDITION, VERY WARM  
AFTERNOON TEMPERATURES COMBINED WITH A DRY ANTECEDENT AIRMASS WILL  
RESULT IN SINGLE DIGIT MIN RH VALUES. THE HOT/DRY AIRMASS COMBINED  
WITH GUSTY RIDGETOP CONDITIONS WILL SUPPORT A CRITICAL FIRE  
WEATHER THREAT DURING THE NEXT 18-24 HOURS.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...RED FLAG WARNING UNTIL 5 AM PDT WEDNESDAY FOR CAZ201-203-204-211.  
 
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL  
3 PM PDT THIS AFTERNOON FOR PZZ450.  
 
HAZARDOUS SEAS WARNING UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ470.  
 
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ475.  
 
HAZARDOUS SEAS WARNING UNTIL 3 AM PDT EARLY THIS MORNING FOR  
PZZ475.  
 

 
 

 
 
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HTTP://WWW.TWITTER.COM/NWSEUREKA  
 
FOR FORECAST ZONE INFORMATION  
SEE THE FORECAST ZONE MAP ONLINE:  
HTTP://WWW.WEATHER.GOV/EUREKA/ZONEMAP.PNG  
 
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