441
FXUS66 KEKA 132047
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
147 PM PDT SUN SEP 13 2026
KEY MESSAGES
* HIGH PRESSURE OFFSHORE BUILDS TONIGHT INTO MONDAY, INCREASING
NORTHERLY WINDS.
* HIGH PRESSURE IS EXPECTED TO BRING WARMER TEMPERATURES AND DRY
WEATHER MONDAY AND TUESDAY.
* COOLER TEMPERATURES AND A 5 TO 10 PERCENT CHANCE OF
THUNDERSTORMS IN TRINITY COUNTY ARE EXPECTED WEDNESDAY
AFTERNOON AND OVERNIGHT.
SYNOPSIS
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. AN UPPER LOW WILL
BRING COOLER TEMPERATURES AND SLIGHT CHANCE FOR INTERIOR
THUNDERSTORMS WEDNESDAY AFTERNOON AND OVERNIGHT.
DISCUSSION
AN UPPER LEVEL TROUGH IS MOVING THROUGH THE PACIFIC
NORTHWEST. THIS BROUGHT A FEW SHOWERS TO HUMBOLDT AND DEL NORTE
COUNTIES THIS MORNING. AS OF 1:30 PM JUST A FEW CLOUDS REMAIN. LATER
THIS AFTERNOON AND TONIGHT THESE CLOUDS ARE EXPECTED TO DIMINISH
WITH THE LOSS OF DAYTIME HEATING AND HIGH PRESSURE STARTING TO
BUILD INTO THE AREA. THIS WILL BRING SOME OFFSHORE FLOW TO THE
COASTAL AREAS. THE TEMPERATURES ALOFT REMAIN COOL MAKING THE
MARINE INVERSION WEAKER. STILL IT LOOKS LIKE THERE WILL BE SOME
COASTAL STRATUS THAT FORMS AROUND HUMBOLDT BAY AND THE EEL RIVER
DELTA, BUT CONFIDENCE IS LOW ON THE EXTENT OF THE COVERAGE OF
THIS. FARTHER INLAND WILL SEE COOLER OVERNIGHT TEMPERATURES AND
THERE IS A SLIGHT CHANCE FOR FROST IN THE VALLEYS OF EASTERN
TRINITY COUNTY, ESPECIALLY HAYFORK. CURRENTLY THE FORECAST IS
AROUND 37 AND FROST IS NOT EXPECTED, BUT IT WILL BE CLOSE.
MONDAY AND TUESDAY AS WEAK HIGH PRESSURE BUILDS IN AND AFTERNOON
TEMPERATURES WARM UP AGAIN IN THE INLAND AREAS. AFTER TODAY'S
HIGHS IN THE 70S INLAND TEMPERATURES ARE EXPECTED TO WARM BY 10
DEGREES IN MANY AREAS WITH HIGHS IN THE MID 80S TO LOW 90S MONDAY
AND SLIGHTLY WARMER ON TUESDAY.
WEDNESDAY EVENING AN UPPER LEVEL LOW DROPS SOUTH OVER THE AREA.
THIS IS EXPECTED TO KEEP TEMPERATURES A FEW DEGREES COOLER ON
WEDNESDAY AND COULD BRING SOME CLOUDS TO THE AREA. AT THIS POINT
IT LOOKS TO REMAIN TOO DRY TO SEE MUCH RAIN, ALTHOUGH A FEW
CONVECTIVE SHOWERS ARE POSSIBLE IN THE EVENING. THERE IS SOME
INSTABILITY WHICH COULD BRING THE POTENTIAL FOR A THUNDERSTORM OR
TWO LATE WEDNESDAY AFTERNOON OR OVERNIGHT. THE HIGHEST CHANCE
LOOKS TO BE IN TRINITY COUNTY, BUT THIS WILL NEED TO BE WATCHED AS
IT GETS CLOSER. CURRENTLY THERE IS ONLY A 10 PERCENT CHANCE OF A
THUNDERSTORM EVEN IN TRINITY COUNTY. THE MODELS ARE STILL
STRUGGLING ON THE EXACT LOCATION OF THIS LOW AND EVEN A SMALL
SHIFT COULD CHANGE THE POTENTIAL FOR PRECIP OR THUNDERSTORMS. SO
THIS WILL NEED TO BE WATCHED AS IT GETS CLOSER. THURSDAY THE LOW
WILL KEEP TEMPERATURES SLIGHTLY BELOW NORMAL, BUT IT GENERALLY
LOOKS DRY AS THE LOW STARTS TO MOVE OUT OF THE AREA. IF IT STARTS
TO SLOW DOWN THIS COULD POSSIBLY ALLOW SOME PRECIP TO LINGER INTO
THURSDAY MORNING.
SEASONABLE WARM INLAND TEMPERATURES AND DRY WEATHER AREA EXPECTED
TO RETURN FRIDAY AND INTO THE WEEKEND. MKK
AVIATION
THERE ARE A FEW LINGERING CLOUDS IN HUMBOLDT AND DEL
NORTE COUNTIES THIS AFTERNOON. THESE COULD IMPACT ACV AND KCEC
BRIEFLY THIS AFTERNOON, BUT MORE LIKELY THEY WILL REMAIN FARTHER
INLAND. THESE CLOUDS ARE EXPECTED TO DIMINISH QUICKLY WHEN THE
SUN GOES DOWN. TONIGHT SOME OFFSHORE FLOW AND A WEAK INVERSION IS
EXPECTED TO KEEP THE MARINE CLOUDS FAIRLY LIMITED. THEY MAY FORM
BRIEFLY AROUND SUNRISE AT KACV AND WITH A LOW CHANCE AT KCEC.
MONDAY AFTERNOON BREEZY AFTERNOON WINDS ARE EXPECTED AS HIGH
PRESSURE BUILDS INTO THE AREA. MKK
MARINE
HIGH PRESSURE IS BUILDING INTO THE AREA AND THIS IS
EXPECTED TO SWITCH WINDS TO THE NORTHWEST AND THEN MORE NORTHERLY
TONIGHT. THESE ARE EXPECTED TO INCREASE TO AROUND 25 TO 30 ON
MONDAY WITH THE STRONGER WINDS IN THE SOUTHERN WATERS. A FEW GALE
FORCE GUSTS ARE POSSIBLE IN THE LEE OF THE CAPES, BUT AT THIS
POINT THEY ARE NOT EXPECTED TO BE WIDESPREAD ENOUGH TO WARRANT A
GALE WARNING. THE WINDS DO MAKE THEIR WAY INTO THE SOUTHERN INNER
WATERS MONDAY AFTERNOON, BUT WILL LIKELY PUSH FARTHER OFFSHORE
MONDAY NIGHT. THE NORTHERN INNER WATERS ARE NOT EXPECTED TO SEE
WIDESPREAD WINDS OVER 20 KT TO WARRANT A SMALL CRAFT ADVISORY, BUT
THE STEEP SEAS COULD EXCEED 6 FEET AND THIS MAY REQUIRE A SMALL
CRAFT ADVISORY.
WEDNESDAY WINDS AND SEAS ARE EXPECTED TO RAPIDLY DIMINISH. FOR NOW
IT LOOKS LIKE THIS WILL HAPPEN WEDNESDAY EVENING AND OVERNIGHT,
BUT THIS MAY STILL CHANGE SLIGHTLY. A SMALL UPPER LEVEL LOW IS
DROPPING SOUTH OVER THE ARE AND A SMALL SHIFT IN THE TRACK COULD
CHANGE THE WINDS QUITE A BIT. THURSDAY AND FRIDAY FAIRLY LIGHT
SOUTHERLY WINDS ARE EXPECTED BEFORE NORTHERLY WINDS RETURN AND
START TO INCREASE FOR THE WEEKEND. MKK
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM NOON MONDAY TO 3 AM PDT TUESDAY
FOR PZZ455.
SMALL CRAFT ADVISORY FROM 3 AM MONDAY TO 3 AM PDT WEDNESDAY
FOR PZZ470.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 3 AM PDT
WEDNESDAY 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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