554
FXUS66 KEKA 210819
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
119 AM PDT TUE OCT 21 2025
SYNOPSIS
DRIER AND WARMER WEATHER TODAY, BEFORE A COOL-DOWN ON
WEDNESDAY. A SERIES OF LARGE SWELL WILL BRING DANGEROUS BREAKING
WAVES ALONG THE WEST AND NORTHWEST FACING BEACHES THIS WEEK, AS
WELL AS SNEAKER WAVES RISK. CONFIDENCES REMAIN HIGH FOR A
MODERATE ATMOSPHERIC RIVER (AR) IMPACTING NORTHERN CALIFORNIA
FRIDAY INTO THE WEEKEND, BRINGING PERIODS OF HEAVY RAINFALL, HIGH-
ELEVATION HEAVY SNOW, AND STRONG SOUTH WINDS.
DISCUSSION
OVERNIGHT, ABUNDANT CLEAR SKIES AND OFFSHORE FLOW
ARE OBSERVED ACROSS THE AREA AS HIGH PRESSURE CONTINUES BUILDING
INTO THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA. BREEZY EAST-
NORTHEAST WINDS WILL CONTINUE TO DEVELOPED THROUGH EARLY
MORNING, WITH GUSTS FROM 20 TO 30 MPH OVER THE HIGHER TERRAIN.
SURFACE OBSERVATIONS REPORTED OVERNIGHT TEMPEARTURES RUNNING FEW
DEGREES COOLER THAN MONDAY AFTER MIDNIGHT. LOW TEMPERATURES AS LOW
AS 34F IN THE INTERIOR VALLEYS IN TRINITY COUNTY, WHERE A FROST
ADVIISORY IS IN EFFECT THROUGH 9 AM THIS MORNING.
DRIER AND WARMER WEATHER CONDITIONS IS EXPECTED TODAY. TEMPERATURES
WILL CONTINUE TO SLIGHTLY WARMING TODAY, EVEN ALONG THE
COAST. INTERIOR VALLEY'S TEMPERATURES ARE FORECAST TO BE IN THE
HIGHS IN THE UPPER 70S TO LOW 80S, WHILE COASTAL AREAS ARE
EXPECETD TO WARM INTO LOW 70S WITH LIGHT WINDS. TONIGHT, A WEAK
SURFACE LOW OFFSHORE CENTRAL CALIFORNIA WILL BRING A SOUTHERLY
REVERSAL STRATUS SURGE INTO WEDNESDAY, WITH SHALLOW MARINE LAYER
CHARGING UP AND LAPPING THE COASTAL AREAS.
WEDNESDAY, THE HIGH PRESSURE WEAKENS AND SHIFT EASTWARD, WHILE AN
UPPER-LEVEL TROUGH MOVES TOWARD THE PACIFIC NORTHWEST, AND A
CUTOFF LOW OFF THE SOUTHERN CALIFORNIA MOVES ONSHORE. TEMPERATURES
ARE EXPECTED TO COOL-DOWN WITH A SHALLOW MARINE LATER AND A PUSH
OF MARINE AIR INTO THE INTERIOR. THURSDAY, A WEAK HIGH PRESSURE
BUILDS IN, HOWEVER INCREASING CLOUDINESS WILL KEEP HIGH
TEMPERATURES SIMILAR TO WEDNESDAY.
ENSEMBLE CLUSTER AND DETERMINISTIC GUIDANCE CONTINUES SHOWING A
GOOD AGREEMENT WITH PROLONGED UNSETTLED AND WET WEATHER FRIDAY
THROUGH THE WEEKEND. CW3E TOOLS FOR GEFS AND ECMWF EPS INDICATE
THERE IS A 75-85% CHANCE OF IVT GREATER THAN 500 KG/MS IMPACTING
THE AREA. ALTHOUGH, THE GEFS AR SCALE AND IVT FORECAST SHOWS A
SERIES OF TWO MODERATE ATMOSPHERIC RIVER (AR) IMPACTING NORTHERN
CALIFORNIA, WITH THE FIRST AR ARRIVING FRIDAY AFTERNOON/EVENING
AND THE SECOND AR ON SUNDAY. MEANWHILE, THE ECMWF INDICATE A
MODERATE AR ARRIVING FRIDAY AFTERNOON AND A SECONG AND WEAKER IVT
ON SATURDAY. THIS AR HAS THE POTENTIAL TO BRING PERIODS OF HEAVY
RAINFALL, HIGH- ELEVATION HEAVY SNOW, AND STRONG SOUTH WINDS.
NBM CHANCES FOR 72 HR STORM TOTAL PRECIPITATION, FRIDAY THROUGH
SUNDAY, OF OVER AN INCH ARE NEAR 100% NORTH OF CAPE MENDOCINO AND
45% IN SOUTHERN MENDOCINO AND LAKE. NBM CHANCES FOR OVER 3 INCHES
OF PRECIPITATION ARE 80-90% IN DEL NORTE AND 40-70% NORTH OF CAPE
MENDOCINO WITH MUCH LOWER CHANCES (30% OR LESS) IN MENDOCINO AND
LAKE. THE WEATHER PREDICTION CENTER (WPC)INCLUDED DEL NORTE COUNTY
AND HUMBOLDT COUNTY IN THE MARGINAL RISK (AT LEAST 5%) OF
EXCESSIVE RAINFALL FOR FRIDAY. HIGH ELEVATION AREAS OF DEL NORTE
AND THE KING RANGE COULD SEE 5 TO 6 INCHES TOTAL. RAPID RISES IN
SMALL STREAMS AND RIVERS, MINOR FLOOD IMPACTS TO URBAN AREAS, AND
DEBRIS ON ROADWAYS ARE ALL POSSIBLE. NBM IS ALSO SHOWING HIGH
CHANCES FOR WIND GUSTS OF OVER 40 MPH OVER EXPOSED RIDGES AND
COASTAL HEADLANDS WITH SMALL (~15%), BUT NONZERO, CHANCES FOR
WINDS THIS STRONG ESSENTIALLY EVERYWHERE ACROSS THE AREA. IMPACTS
WILL BECOME CLEARER AS THE STORM TRACK SOLIDIFIES IN THE COMING
DAYS. /ZVS
AVIATION...06Z TAF
GENERALLY CLEAR, VFR CONDITIONS HAVE SPREAD
ACROSS THE AREA, AIDED BY GENTLE OFFSHORE FLOW. THAT SAID, STRONG
SURFACE COOLING AND STABLE AIR AT THE SURFACE HAVE ALLOWED FOR VERY
SHALLOW, MVFR FOG TO FORM IN SOME AREAS ALONG THE COAST AND FOR IN
LAND VALLEYS. IFR CONDITIONS ORE UNLIKELY (30% CHANCE) BUT WILL BE
POSSIBLE FOR A SHORT TIME AROUND SUNRISE. OTHERWISE, VFR CONDITIONS
WILL PERSIST DURING THE DAY TOMORROW. /JHW
MARINE
MODERATE NORTHERLY WIND SHAVE GRADUALLY PUSHED OFFSHORE
THROUGH THE EVENING HOURS, THOUGH STEEP SEAS HAVE PERSISTED AS SHORT
PERIOD SEAS AND A DECAYING NORTHWEST SWELL GRADUALLY FALL. WINDS
WILL GENERALLY BE VERY GENTLE TODAY, GRADUALLY TURNING OUT OF THE
SOUTH LATE IN THE EVENING. DESPITE CALM WEEDS, MODERATELY STEEP SEAS
WILL PERSIST AS A NEW NORTHWEST SWELL BUILDS DURING THE DAY UP TO
AROUND 13 FEET AT 16 SECONDS. CONDITIONS WILL THEN GRADUALLY CALM
AGAIN THROUGH THE DAY ON WEDNESDAY AS WINDS REMAIN CALM AND THE
SWELL DECAYS. SOUTHERLY WINDS WILL BEGIN TO GREATLY INCREASE AGAIN
LATE THURSDAY AS A SERIES OF STORM SYSTEMS WILL GENERATE HAZARDOUS
CONDITIONS THROUGH THE WEEKEND. /JHW
BEACH HAZARDS
YET ANOTHER WESTERLY SWELL WILL BUILD INTO THE
WATERS TODAY UP TO AROUND 13 FEET AT 16 SECONDS. SUCH AS SWELL WILL
HAVE THE ABILITY TO GENERATE SURF RUNUP ON BEACHES IN EXCESS OF 20
FEET. WAVES WILL BE PARTICULARLY SNEAKY AND UNEXPECTED DUE TO MOSTLY
CLAM WINDS AND FEW SHORT PERIOD WAVES. THE FIRST FORERUNNERS OF THE
SWELL WILL BEGIN TO BUILD ALONG THE NORTH COAST EARLY IN THE
AFTERNOON THROUGH THE EVENING HOURS. AS THE FIRST WAVES BUILD IN,
SURF MAY RAPIDLY INCREASE EVEN IF THE SEA SEEMS MOSTLY CALM. TAKE
EXTRA CARE ON AREA BEACHES THIS AFTERNOON AND EVENING. /JHW
EKA WATCHES/WARNINGS/ADVISORIES
CA...
BEACH HAZARDS STATEMENT FROM 9 AM PDT TUESDAY THROUGH
TUESDAY AFTERNOON FOR CAZ101-103-104.
FROST ADVISORY FROM 2 AM TO 9 AM PDT TUESDAY FOR CAZ107-108.
BEACH HAZARDS STATEMENT FROM TUESDAY AFTERNOON THROUGH
TUESDAY EVENING FOR CAZ109.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ450.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
PZZ455.
SMALL CRAFT ADVISORY UNTIL 11 AM PDT WEDNESDAY FOR PZZ470.
SMALL CRAFT ADVISORY UNTIL 2 PM 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.
VISIT US AT HTTPS://WWW.WEATHER.GOV/EUREKA
FOLLOW US ON FACEBOOK AND TWITTER AT:
HTTPS://WWW.FACEBOOK.COM/NWSEUREKA
HTTPS://WWW.TWITTER.COM/NWSEUREKA
FOR FORECAST ZONE INFORMATION
SEE THE FORECAST ZONE MAP ONLINE:
HTTPS://WWW.WEATHER.GOV/IMAGES/EKA/ZONEMAP.PNG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page