946
FXUS66 KEKA 131014 CCA
AFDEKA
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE EUREKA CA
314 AM PDT SAT SEP 13 2025
SYNOPSIS
DRY WEATHER WITH SEASONABLY AVERAGE TEMPERATURES
TODAY, BEFORE A PROGRESSIVE TROUGH BRING A CHANCE OF SHOWERS AND A
SLIGHT CHANCE OF THUNDERSTORMS LATE SATURDAY NIGHT THROUGH SUNDAY
MORNING. DRYING AND WARMING TREND RETURNS ON MONDAY AND CONTINUE
THROUGH MID NEXT WEEK.
DISCUSSION
STRATUS AND PATCHES OF FOG ARE BLANKETING THE NORTHERN
COASTAL WATERS AND EXTENDED WELL UP THE ADJACENT RIVER VALLEYS
OVERNIGHT, AND SOUTH OF FORT BRAGG AS WELL. ALTHOUGH, PROFILERS
DATA INDICATE THE MARINE LAYER IS QUITE SHALLOWER THAN PREVIOUS
NIGHT. LOW CLOUDS ARE EXPECTED TO LIFT AND ERODE BACK TO THE COAST
WITH THE DAYTIME HEATING, ALTHOUGH STRATUS NEAR- COASTAL LOCATIONS
ARE EXPECTED TO PERSIST WITH THE GENTLE SEA BREEZE.
THE SHORTWAVE HIGH PRESSURE CONTINUE SHIFTING EASTWARD TODAY,
WHILE A WEAK H5 TROUGH AND ASSOCIATED COLD FRONT APPROACHES THE
PACIFIC NORTHWEST AND NORTHERN CALIFORNIA. EXPECT ANOTHER DAY
WITH DRY AND NEAR-SEASONAL AVERAGE TEMPERATURES. INLAND HIGH
TEMPERATURES ARE FORECAST TO BE SIMILAR TO FRIDAY WITH HIGHS IN
UPPER 70'S TO UPPER 80'S IN THE INTERIOR VALLEYS AND MID 60'S TO
MID 70'S OVER THE FOOTHILLS. COASTAL AREAS WILL REMAIN UNDER THE
MARINE INFLUENCE WITH HIGHS IN THE LOW TO MID 60'S. WINDS WILL
LIKELY TO INCREASE FROM THE NORTHWEST THIS AFTERNOON AND EVENING
ALONG THE COAST AND EXPOSED RIDGES, BECOMING GUSTY AT TIMES,
ESPECIALLY FOR MENDOCINO AND LAKE COUNTIES. SOUTHWEST WINDS ALOFT
WILL BRING AN INCREASING MID TO HIGH LEVEL MOISTURE LATE THIS
AFTERNOON AND EVENING AHEAD OF AN APPROACHING FRONTAL SYSTEM.
THE PROGRESSIVE AFOREMENTIONED TROUGH AND ASSOCIATED COLD FRONT
WILL BRING A CHANCE OF SHOWERS ACROSS THE COAST AND COASTAL
RANGES LATE TONIGHT THROUGH SUNDAY MORNING, MAINLY IN DEL NORTE
AND NORTHERN HUMBOLDT COUNTIES. ALSO, INCREASING INSTABILITY WITH
COLD AIR ALOFT WILL PROMOTE A THREAT OF ISOLATED THUNDERSTORMS
AND BRIEF HEAVY DOWNPOURS LATE TONIGHT INTO EARLY SUNDAY. CONVECTIVE
ALLOWING MODELS (CAMS) INDICATE LOCALIZED STRONG SIMULATED CORES
GREATER THAN 45DBZ OVER DEL NORTE AND FAR NORTHERN HUMBOLDT LATE
TONIGHT OR EARLY SUNDAY. THE HREF GUIDANCE INDICATES A 50-60%
CHANCE FOR RAIN RATES OVER 0.25 INCHES PER HOUR WITH AN ENSEMBLE
MAX OVER 0.50IN/HR LATE TONIGHT INTO EARLY SUNDAY MORNING. ECMWF
ENSEMBLE 75TH PERCENTILE 24-HOUR TOTALS ARE UNDER 0.50 INCHES FOR
DEL NORTE WITH ONE OR TWO OUTLIERS OVER 1 INCH. RAW ECMWF
PROBABILITIES FOR MORE THAN 0.50 INCHES IN 24 HOURS ARE 30-40%,
PRIMARILY OVER COASTAL DEL NORTE NEAR THE ORCA BORDER. THUS,
INSTABILITY AND DEEP MOIST CONVECTION COULD YIELD MUCH HIGHER RAIN
AMOUNTS. OFFICIAL 24-HOUR WPC QPF RAINFALL TOTALS RANGE FROM 0.15
TO 0.35 INCHES IN DEL NORTE DEL NORTE COUNTY AND GENERALLY LESS
THAN A TENTH FOR NORTHERN HUMBOLDT. OTHER THAN LIGHT COASTAL
DRIZZLE OR SPRINKLES, DRY WEATHER AND SOME COOLING OF INTERIOR
HIGH TEMPS ARE EXPECTED THROUGH THE DAY ON SUNDAY.
HIGH PRESSURE WILL BEGIN TO BUILDS IN QUICKLY OVER THE REGION ON
SUNDAY IN THE WAKE OF THE FRONT. BREEZY NORTHERLY WINDS ARE
FORECAST TO DEVELOPED OVER MOSTLY COASTAL AREAS AS SURFACE
PRESSURE GRADIENTS TIGHTEN SUNDAY EVENING. NBM PROBABILITIES
INDICATES A 50-80% CHANCE FOR WIND GUSTS GREATER THAN 25 MPH OVER
THE EXPOSED RIDGES AND COASTAL HEADLANDS ON SUNDAY. ALSO, GUSTY
WEST-NORTHWEST WINDS WILL MOST LIKELY DEVELOP THROUGH CHANNELED
TERRAIN IN THE INTERIOR BEHIND THE FRONT SUNDAY AFTERNOON/EVENING.
MONDAY, 850MB WILL BEGIN TO INCREASE AS THE UPPER-LEVEL HEIGHTS
RISES ACROSS THE WEST COAST. THIS WILL BRING A WARMING TREND
EARLY THROUGH MID NEXT WEEK, WITH THE DRIEST AND WARMER DAY ON
TUESDAY. MONDAY NIGHT INTO TUESDAY, BREEZY OFFSHORE WINDS OVER
THE RIDGES ACROSS THE EASTERN PORTION OF THE FORECAST AREA. INTERIOR
VALLEYS ARE FORECAST TO BE IN THE MID TO UPPER 90'S ON TUESDAY
ACROSS THE WARMER LOCATIONS OF TRINITY, LAKE, INTERIOR MENDOCINO,
AND INTERIOR HUMBOLDT COUNTIES. /ZVS
AVIATION...(6Z TAFS)
IFR CEILINGS ARE BEING OBSERVED AT THE
COASTAL TERMINALS, AND STRATUS IS LIKELY TO CONTINUE INTO DAYLIGHT
HOURS. CURRENTLY, IFR CEILINGS ARE FORECAST TO CONTINUE, WITH BRIEF
DIPS DOWN TO LIFR POSSIBLE NEAR SUNRISE. SOME LIFTING IS LIKELY
AFTER SUNRISE, LIKELY TO MVFR BY THE AFTERNOON. SOME SCATTERING IS
POSSIBLE, BUT IT WOULD BE BRIEF BEFORE STRATUS RETURNS OVERNIGHT.
INLAND AREAS WILL REMAIN VFR THROUGH THE NIGHT WITH MOSTLY CLEAR
SKIES AND LIGHT WINDS OUTSIDE THE AFTERNOON. UKI MAY SEE GUSTY
NORTHWEST WINDS IN THE AFTERNOON. JB
MARINE
NORTHERLY WINDS HAVE STARTED TO EASE AS AN UPPER LOW
OVER THE GREAT BASIN WEAKENS AND MOVE EAST. STILL, WINDS ARE LIKELY
TO REMAIN BREEZY THROUGH THE MORNING SOUTH OF CAPE MENDOCINO, BUT
EASE BELOW 15 KTS BY THE AFTERNOON. SHORT PERIOD SEAS REMAIN
ELEVATED TODAY, ESPECIALLY SOUTH OF THE CAPE, AND ARE MIXED WITH A
DECAYING MID-PERIOD NORTHWESTERLY SWELL.
A SHORTWAVE TROUGH WILL BRING A SLIGHT CHANCE FOR THUNDERSTORMS OVER
THE NORTHERN WATERS LATE SATURDAY AND INTO SUNDAY MORNING. HIGH
PRESSURE WILL BEGIN BUILDING BACK IN LATER SUNDAY BEHIND THE TROUGH,
AND THESE TWO FEATURES WILL INCREASE THE NORTHERLY WINDS LATE SUNDAY
THROUGH MONDAY BEFORE BACKING DOWN TUESDAY. STRONGER NORTHERLIES ARE
POSSIBLE MID TO LATE WEEK. JJW/JB
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 11 AM PDT SATURDAY FOR PZZ455-
475.
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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