907
FXUS66 KEKA 111959
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1259 PM PDT THU SEP 11 2025
SYNOPSIS
INTERIOR SHOWERS AND ISOLATED THUNDERSTORMS POSSIBLE THIS
AFTERNOON AND EARLY EVENING OVER THE HIGHER TERRAIN OF EASTERN
TRINITY, EASTERN MENDOCINO, AND LAKE COUNTIES. DRIER AND WARMER
CONDITIONS FRIDAY AND SATURDAY, FOLLOWED BY A PERIOD OF MORE LIGHT
RAIN FOR THE NORTH COAST ON SUNDAY. THE SYNOPTIC WEATHER PATTERN
TRENDING WARMER AND DRIER EARLY NEXT WEEK.
DISCUSSION
THE SLOW-MOVING, CLOSED, CYCLONIC CIRCULATION
CONTINUES TO MOVE FURTHER EAST OF THE GREAT BASIN TODAY. OVERALL
CALMER WEATHER IS EXPECTED TODAY WITH THE POSSIBILITY FOR ISOLATED
SHOWERS AND A FEW POP-UP THUNDERSTORMS THIS AFTERNOON INTO THE
EVENING OVER THE HIGHER TERRAIN SUCH AS THE TRINITY ALPS/STNF, YOLLA
BOLLYS, AND THE MENDOCINO NAT'L FOREST. MORNING VALLEY FOG HAS
EVAPORATED AWAY LEADING TO DAYTIME HEATING IN THE VALLEYS, WITH COOL
TEMPERATURES EXPECTED INLAND TODAY BETWEEN 75-80F. FOGGY STRATUS
EXPECTED AGAIN TONIGHT INTO FRIDAY MORNING WITH A LESSER EXTENT
INLAND THAN LAST NIGHT. OVERNIGHT TEMPERATURES ARE FORECASTED TO BE
GENERALLY IN THE 50'S.
A SHORTWAVE RIDGE WILL BEGIN TO MOVE OVER THE AREA IN THE WAKE OF
THIS PREVIOUS TROUGH TOMORROW, ADVECTING A DRIER AIR MASS AND
CLEARING SKIES. INLAND HIGHS ARE EXPECTED TO START TO WARM SLIGHTLY
ON FRIDAY, WITH HIGHS FORECASTED TO BE IN THE UPPER 70'S TO UPPER
80'S. ONSHORE FLOW WILL REMAIN FOR THE COASTAL AREAS KEEPING TEMPS
IN THE LOW TO MID 60'S. AREAS OF VALLEY FOG TO DEVELOP AGAIN FRIDAY
NIGHT INTO SATURDAY ALONG THE COAST AND IN THE COASTAL RIVER VALLEYS.
DRY WEATHER IS EXPECTED FOR MUCH OF THE DAY ON SATURDAY WITH
TEMPERATURES 3-5F WARMER COMPARED WITH TOMORROW'S HIGH TEMPERATURE
FORECAST. THE RIDGE ALOFT WILL SHIFT EASTWARD ON SATURDAY, MAKING
WAY FOR AN UPSTREAM H5 TROUGH APPROACHING THE PACIFIC NORTHWEST AND
NORTHERN CALIFORNIA. CLUSTER ANALYSIS AND LONG RANGE GLOBAL MODELS
ARE NOT IN A GOOD AGREEMENT WITH THE POSITIONING OF THIS TROUGH. THE
RANGES SHOW THE LOWER AXIS SOMEWHERE BETWEEN CAPE MENDOCINO AND
WASHINGTON ADDING TO INCREASED VARIABILITY AND LOWER FORECAST
CONFIDENCE. THAT SAID HOWEVER, THERE IS FAIR AGREEMENT IN THE MODELS
FOR LIGHT PRECIPITATION SOMETIME LATE SATURDAY NIGHT INTO SUNDAY,
PRIMARILY IN DEL NORTE, HUMBOLDT AND PORTIONS OF TRINITY COUNTIES.
THERE IS THE POTENTIAL FOR SOME THUNDERSTORMS NEAR THE NORTH COAST.
MONDAY, HIGH PRESSURE BEGINS TO BUILD ACROSS THE WEST COAST. THIS
WILL BRING A WARMING TREND EARLY NEXT WEEK. 850MB TEMPERATURE
ANALYSIS SHOWS INTERIOR VALLEYS REACHING OR EXCEEDING 90'S DEGREES
ON MONDAY WITH WARMING INTO THE UPPER 90'S THROUGH MID NEXT WEEK
ACROSS THE WARMER LOCATIONS OF TRINITY, LAKE, INTERIOR MENDOCINO,
AND INTERIOR HUMBOLDT COUNTIES. /ZVS + DES
AVIATION...18Z TAFS
CEILINGS HAVE LIFTED TO MVFR LEVELS THURSDAY
AFTERNOON. THE MARINE LAYER IS DEEP FROM AN UPPER LOW IN THE
VICINITY, AND THE COASTAL STRATUS HAS BECOME WELL EMBEDDED WITH FAR
INLAND EXTENT. A WEAK WIND EDDY WAS OBSERVED MOVING SOUTHWARD ON
VISIBLE SATELLITE, WITH WEAKNESS/CLEARING NORTH IN THE EDDIE'S WAKE.
THE PROFILER CONFIRMS A WEAK INVERSION, AND DESPITE THE MARINE LAYER
DEPTH, A PERIOD OF SCATTERING TO CLEARING IS LIKELY THIS AFTERNOON.
SOUNDINGS POINT TOWARD SOME MARINE LAYER COMPRESSION AND A RETURN OF
LIFR CONDITIONS TONIGHT.
INTERIOR SHOWERS AND THUNDERSTORMS WILL ONCE AGAIN DEVELOP THIS
AFTERNOON/EVENING. COVERAGE IS EXPECTED TO BE MORE ISOLATED THAN
RECENT DAYS FROM TRINITY TO LAKE COUNTY. THERE IS A LIGHT CHANCE
(15%) FOR A VICINITY THUNDERSTORM CLOSER TO UKI THIS AFTERNOON. SOME
LIGHT AFTERNOON SEAS BREEZES WILL DEVELOP WITH A FEW GUSTS IN THE
16KT AREA, ESPECIALLY IF THERE IS BETTER CLEARING AND SOME SURFACE
WARMING LATER THIS AFTERNOON.
TERMINAL FORECAST/CONFIDENCE...WITH CONTINUED INFLUENCE OF THE UPPER
TROUGH, CONFIDENCE IS MODERATE TO LOW ON THE DURATION OF LIFR
CEILINGS THROUGH FRIDAY MORNING, WITH CEC HAVING THE HIGHEST
CONFIDENCE FOR BETTER LIFR DURATION. THERE IS HIGHER CONFIDENCE FOR
IFR CEILINGS. THOUGH THE STRATUS MADE IT INTO UKI THURSDAY MORNING,
CONFIDENCE IS LOWER FOR ANOTHER OCCURRENCE FRIDAY MORNING.
CEC: 40-55% CHANCE FOR LIFR (7Z-17Z FRIDAY)
60-80% CHANCE FOR IFR (3Z-18Z FRIDAY)
ACV: 30-40% CHANCE FOR LIFR (13Z-17Z FRIDAY)
60-70% CHANCE FOR IFR (6Z-20Z FRIDAY)
UKI: 30-40% MVFR CEILINGS (9Z-17Z FRIDAY)
JJW
MARINE
NORTHERLY WINDS WILL BE TRENDING HIGHER TODAY, WITH
FURTHER STRENGTHENING THROUGH FRIDAY. WINDS WILL PEAK IN THE
AFTERNOONS, WITH GUSTS OF 20-25 KTS POSSIBLE IN THE OTHER WATERS.
LOCALLY STRONGER GUSTS AT OR AROUND 30 KTS ARE POSSIBLE AROUND CAPE
MENDOCINO. NEARSHORE WINDS GENERALLY REMAIN LIGHT. WINDS AND SEAS
EASE SATURDAY INTO SUNDAY. THE NORTHERLIES WILL INCREASE AGAIN LATER
SUNDAY THROUGH MONDAY AS HIGH PRESSURE BUILDS BACK IN. THE LOCAL
PRESSURE GRADIENT WILL BE FURTHER STRENGTHENED BY AN AREA OF LOW
PRESSURE FARTHER NORTH OVER THE PACIFIC NORTHWEST. NBM CURRENTLY
HOLDS A GREATER THAN 50% CHANCE FOR GALE STRENGTH GUSTS OVER MAINLY
THE SOUTHERN WATERS LATE SUNDAY THROUGH MONDAY.
SEAS ARE MOSTLY CHARACTERIZED BY BUILDING SHORT PERIOD WIND WAVES,
WHICH WILL BE STEEP AND HAZARDOUS TO SMALL CRAFTS. DESPITE LIGHTER
WINDS, STEEP SEAS ARE FORECAST TO PROPAGATE TO THE NEARSHORE WATERS
OF MENDOCINO, ESPECIALLY THURSDAY NIGHT THROUGH FRIDAY MORNING. A
LONG PERIOD NW SWELL FILLS IN LATE THURSDAY THROUGH FRIDAY, WHICH
COMBINED WITH THE WIND WAVES OF 6-7 FT, RESULTS IN COMBINED SEAS OF
7-10 FT BY FRIDAY NIGHT. SEAS ARE FORECAST TO EASE SATURDAY INTO
EARLY SUNDAY AS WINDS EASE, BUT ANOTHER MID-PERIOD NW SWELL OF
AROUND 6-8 FT IS FORECAST TO FILL IN SUNDAY, KEEPING SEAS ELEVATED.
ALONG WITH BUILDING SHORT PERIOD WIND WAVES, COMBINED SEAS MAY
EXCEED 10 FT. JB/JJW
BEACH HAZARD
A LONG PERIOD WEST-NORTHWEST SWELL WILL BUILD
LATE THIS AFTERNOON/EARLY EVENING WITH SIGNIFICANT SWELL HEIGHTS
AROUND 3 TO 4 FEET AT 16 TO 17 SECONDS TONIGHT. THIS SWELL HAS
THE POTENTIAL TO BRING A MODERATE RISK OF SNEAKER WAVES,
ESPECIALLY BETWEEN 3 AM TO 8 AM PDT ON FRIDAY. SNEAKER WAVES ARE A
UNIQUE HAZARD, WITH MANY MINUTES BETWEEN WAVES. PAY ATTENTION AND
STAY ABOVE THE HIGH WATER LINE AND ANY WET SAND TO STAY SAFE. IF
THE GROUND IS WET, WAVES HAVE SURGED THERE RECENTLY. STAY SAFE AND
NEVER TURN YOUR BACK ON THE OCEAN! ZVS/JJW
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 11 AM PDT
FRIDAY FOR PZZ455.
SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 11 PM PDT
FRIDAY FOR PZZ470.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT FRIDAY 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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