777
FXUS66 KEKA 130706
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1206 AM PDT SUN SEP 13 2026
KEY MESSAGES
* HIGH CONFIDENCE (90 PERCENT CHANCE) THAT POST-FRONTAL RAIN SHOWERS
ACROSS DEL NORTE AND NORTHERN HUMBOLDT COMPLETELY DIMINISH BY
SUNDAY AFTERNOON.
* HIGH PRESSURE OFFSHORE BUILDS SUNDAY NIGHT INTO MONDAY, INCREASING
NORTHERLY WINDS AND BRINGING HAZARDOUS MARINE CONDITIONS TO THE
OUTER WATERS.
SYNOPSIS
AN UPPER-LEVEL TROUGH OVER THE PACIFIC NORTHWEST
CONTINUES TO EXIT EASTWARD, ALLOWING LIGHT SHOWER ACTIVITY OVER
NORTHERN AREAS TO TAPER OFF COMPLETELY BY SUNDAY AFTERNOON. SURFACE
HIGH PRESSURE BUILDING OFFSHORE WILL STRENGTHEN THE ONSHORE PRESSURE
GRADIENT AGAINST THE INTERIOR THERMAL LOW INTO EARLY NEXT WEEK. THIS
PATTERN WILL KEEP A SHALLOW MARINE LAYER PINNED ALONG THE COAST
WHILE BRINGING DRY, SEASONABLE WARMTH BACK TO INTERIOR VALLEYS.
DISCUSSION
WATER VAPOR IMAGERY SHOWS THE 500 MB SHORTWAVE TROUGH
AXIS SHIFTING EAST OF THE REGION EARLY THIS MORNING. HIGH-RESOLUTION
ENSEMBLE GUIDANCE INDICATES THAT LIGHT SHOWER ACTIVITY OVER DEL
NORTE AND NORTHERN HUMBOLDT WILL GRADUALLY WANE THROUGH THE MORNING
HOURS, WITH THE 90TH PERCENTILE FOR SHOWER CESSATION POINTING TO A
COMPLETE END BY SUNDAY AFTERNOON. IN THE WAKE OF THIS DEPARTING
TROUGH, MID-LEVEL RIDGING WILL BUILD OFF THE WEST COAST,
ESTABLISHING A HIGH-PRESSURE PATTERN THAT WILL LINGER THROUGH MID-
WEEK.
AT THE SURFACE, THE ONSHORE PRESSURE GRADIENT BETWEEN THE OFFSHORE
EASTERN PACIFIC HIGH-PRESSURE SYSTEM AND THE INTERIOR THERMAL LOW
WILL TIGHTEN NOTABLY BY SUNDAY AFTERNOON. INLAND MAXIMUM
TEMPERATURES WILL REACH THE 70S TO LOWER 80S ACROSS INTERIOR VALLEYS
ON SUNDAY, WITH MODERATE WARMING CONTINUING MONDAY. MEANWHILE, A
SHALLOW MARINE LAYER WILL REMAIN ANCHORED ALONG THE IMMEDIATE COAST,
MAINTAINING COOL CONDITIONS WITH HIGH TEMPERATURES HELD IN THE 60S.
PROBABILISTIC ENSEMBLE OUTPUT INDICATES THAT MAXIMUM TEMPERATURES
REACHING 90 DEGREES HAVE A 60 TO 80 PERCENT PROBABILITY ON WEDNESDAY
FOR THE WARMEST INTERIOR VALLEYS.
AVIATION
KCEC: VFR CONDITIONS WILL GIVE WAY TO MVFR CEILINGS STARTING AROUND
10Z UNDER LOW STRATUS, PERSISTING THROUGH LATE MORNING BEFORE
CLEARING TO VFR AS LOW-LEVEL MOISTURE DEPARTS AND WINDS TURN
WESTERLY.
KACV: MVFR CEILINGS WILL PERSIST OVERNIGHT UNDER LOW
STRATUS BEFORE LIFTING TO VFR AROUND MID-MORNING. A BRIEF PERIOD OF
IFR VISIBILITY IS EXPECTED MID-TO-LATE MORNING BEFORE CLEARING TO
VFR AS WINDS SHIFT SOUTHWESTERLY TO WESTERLY.
KUKI: VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD AT THIS
REGIONAL TERMINAL. WEST-NORTHWEST WIND GUSTS UP TO 18-19 KTS ARE
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS.
MARINE
GENTLE TO MODERATE BREEZES PERSIST EARLY SUNDAY BEFORE
NORTH WINDS RAMP UP SHARPLY SUNDAY EVENING INTO MONDAY AS THE
ONSHORE PRESSURE GRADIENT TIGHTENS BETWEEN THE EASTERN PACIFIC HIGH
AND THE INTERIOR THERMAL LOW.
* NORTHERN INNER WATERS: SOUTHERLY WINDS SHIFT SOUTHWESTERLY SUNDAY
AFTERNOON BEFORE TURNING NORTHERLY SUNDAY NIGHT. COMBINED SEAS
REMAIN LOW, AND LOW WAVE STEEPNESS WILL KEEP CONDITIONS BELOW
ADVISORY CRITERIA.
* NORTHERN OUTER WATERS: WINDS TURN NORTHERLY SUNDAY EVENING AND
STRENGTHEN INTO MONDAY. SHORT-PERIOD WAVE STEEPNESS INCREASES AS
WINDS BUILD, CREATING HAZARDOUS CONDITIONS FOR SMALL CRAFT LATE
SUNDAY NIGHT THROUGH MONDAY EVENING. A SMALL CRAFT ADVISORY IS IN
EFFECT STARTING LATE SUNDAY NIGHT (3 AM MONDAY).
* SOUTHERN INNER WATERS: ONSHORE BREEZES BUILD INTO MODERATE
NORTHERLIES SUNDAY NIGHT AND MONDAY, WITH LOCALIZED STRONG GUSTS
AROUND CAPE MENDOCINO. WAVE STEEPNESS INCREASES MONDAY AS SHORT-
PERIOD NORTHERLY WIND WAVES BUILD.
* SOUTHERN OUTER WATERS: FRESH TO STRONG NORTHERLY WINDS DEVELOP
SUNDAY EVENING, ACCOMPANIED BY NEAR-GALE GUSTS. STEEP, HAZARDOUS
SEAS DEVELOP AS SHORT DOMINANT WAVE PERIODS COMBINE WITH BUILDING
WAVE HEIGHTS. A SMALL CRAFT ADVISORY IS IN EFFECT STARTING 6 PM
SUNDAY.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
RED FLAG WARNING UNTIL 2 AM PDT EARLY THIS MORNING FOR
CAZ418>421.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 3 AM TO 9 PM PDT MONDAY FOR
PZZ470.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 9 PM PDT
MONDAY FOR PZZ475.
NOTE: THE FULL FORECAST DISCUSSION IS NOW REGULARLY ISSUED BETWEEN
10 AM/PM AND 1 PM/AM. ADDITIONAL UPDATES WILL BE ISSUED AS NEEDED.
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