628
FXUS66 KEKA 220710
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1210 AM PDT WED OCT 22 2025
SYNOPSIS
SNEAKER WAVE AND LARGE SURF RISK CONTINUES THROUGH THE
WEEK. CONFIDENCE REMAINS HIGH FOR AN ATMOSPHERIC RIVER STORM
IMPACTING NORTHERN CALIFORNIA FRIDAY INTO THE WEEKEND. ADDITIONAL
RAINFALL IS FORECAST TO CONTINUE THROUGH SUNDAY AND POSSIBLY INTO
MONDAY.
KEY MESSAGES:
-RISK OF SNEAKER WAVES AND LARGE SURF CONTINUES THROUGH THE WEEK.
-ATMOSPHERIC RIVER ARRIVES TO THE AREA FRIDAY INTO THE WEEKEND,
BRINGING PERIODS OF MODERATE TO HEAVY RAIN, MOUNTAIN SNOW, AND GUSTY
SOUTHERLY WINDS.
-A COLD TROUGH ARRIVAL WILL BRING ADDITIONAL RAINFALL, COASTAL
THUNDERSTORMS AND GUSTY SOUTHERLY WINDS SATURDAY
-UNSETTLED WEATHER AND ADDITIONAL RAINFALL CONTINUES SUNDAY AND
POSSIBLY INTO MONDAY
DISCUSSION
THE ARRIVAL OF OVERNIGHT CLOUDCOVER SHOULD INSULATE
THE INTERIOR FROM COLD TEMPERATURES THAT WERE OBSERVED TUESDAY
MORNING, BUT SOME ISOLATED AREAS OF FROST WILL BE LIKELY. AN UPPER
LOW TO THE SOUTH MOVING INTO CENTRAL TO SOUTHERN CA IS BRINGING IN
IN THIS CLOUDCOVER. LIGHT SHOWERS ASSOCIATED WITH THE LOW ARE
OBSERVED DRIFTING NORTHWARD AND MAY HOLD TOGETHER AS THEY MOVE
INTO LAKE AND FAR SOUTHERN MENDOCINO COUNTIES EARLY WEDNESDAY
MORNING.
AS HIGH PRESSURE WEAKENS, INCREASED GENERAL CLOUDCOVER FROM WEAK
PASSING FRONTS AND A DEEPENING MARINE LAYER WILL TREND TEMPERATURES
DOWN WEDNESDAY AND THURSDAY. EXPECT DAYTIME HIGHS INTO THE 70S FOR
MUCH OF THE INTERIOR VALLEYS AND HIGH 50S TO LOW 60S FOR THE COASTAL
AREAS.
A DEEP AND EXPANSIVE ALEUTIAN LOW WILL DRIVE IN AN ATMOSPHERIC RIVER
TYPE SYSTEM INTO THE PACIFIC NORTHWEST FRIDAY. MULTIPLE
DISTURBANCES WILL ROTATE OFF THIS LOW, IMPACTING NORTHERN CA WITH
THE ATMOSPHERIC RIVER AND MODERATE TO HEAVY PRECIPITATION LATER
FRIDAY INTO SUNDAY.
NBM CONTINUES TO OUTLINE MODERATE TO HIGH CHANCES FOR PERIODS OF
WIND GUSTS OVER 40 MPH FOR PORTIONS OF DEL NORTE AND OVER THE KING
RANGE. CHANCES FOR WINDS GUSTS OF 30 TO 35 MPH ARE HIGH FOR OVER
MOST OF THE AREA, PARTICULARLY SATURDAY WHEN INSTABILITY ARRIVES
WITH THE PASSING OF THE COLD TROUGH. OCEANIC TO COASTAL
THUNDERSTORMS WILL LIKELY FORM SATURDAY AFTERNOON INTO SUNDAY. THE
HIGHER PRECIPITAL WATERS VALUES WILL HAVE SHIFTED SOUTH AT THIS
TIME; HOWEVER, COLD 500MB TEMPERATURES (-20 TO -28C) WITH STEEP
LAPSE RATES AND MODEST SURFACE CAPE WILL CONTRIBUTE TO SOME LOCALLY
HIGHER PRECIPITATION RATES FROM COASTAL HUMBOLDT AND MAINLY DEL NORTE
COUNTY.
PRECIPITATION RANGES FROM THE NBM (COMPARING THE 25TH AND 75TH
PERCENTILES) REMAIN REMARKABLY STABLE WITH 4-6 INCHES FORECAST FOR
DEL NORTE COUNTY, 1.5-3.5 INCHES FORECAST FOR HUMBOLDT AND TRINITY
COUNTIES. THE LARGEST VARIABILITY IS IN SOUTHERN MENDOCINO AND LAKE
WHERE THE RANGE IS JUST 0.25-1.5 INCHES. WITH THIS MUCH RAIN, RAPID
RISES IN SMALL STREAMS AND RIVERS, MINOR FLOOD IMPACTS TO URBAN
AREAS, AND DEBRIS ON ROADWAYS ARE ALL POSSIBLE. SNOW LEVELS ARE
INITIALLY FORECAST TO REMAIN HIGH, ABOVE 7000 FT, BUT TREND DOWNWARD
SATURDAY INTO SUNDAY MORNING, DROPPING AS LOW AS 5000 FT. SNOW
IMPACTS ARE POSSIBLE ALONG SCOTT MOUNTAIN PASS ON HIGHWAY 3 IN
TRINITY COUNTY SATURDAY AND SUNDAY, BUT THERE IS STILL SOME
UNCERTAINTY ON HOW COLD THIS SYSTEM WILL BE. CURRENTLY 1-3 INCHES
ARE FORECAST ABOVE 5500 FT, WHILE 6-12 INCHES ARE FORECAST ABOVE
7000 FT.
MODELS ARE STARTING TO RESOLVE AN ADDITIONAL DISTURBANCE SUNDAY THAT
WILL MAY CONTAIN LIGHT TO MODERATE RAINFALL. FURTHER PRECIPITATION
AMOUNTS DON'T CURRENTLY LOOK IMPRESSIVE, BUT ANY ADDITIONAL RAIN
COULD BRING OR CONTINUE MINOR IMPACTS. ENSEMBLES AND CLUSTERS ARE
TRENDING TOWARDS TROUGHING AND AWAY FROM A MORE PERSISTENT RIDGE MID
NEXT WEEK. JJW/JB
AVIATION
AN UPPER LEVEL LOW OFF THE SOUTHERN CA COAST IS SENDING
A SOUTHERLY SURGE NORTH WITH A LARGE AMOUNT OF STRATUS AND 10 TO 15
KT OF WIND. THIS HAS MADE IT WELL NORTH OF CAPE MENDOCINO. THIS
STRATUS LOOKS LIKE IT WILL MAKE IT ONSHORE EARLY THIS MORNING,
ALTHOUGH THE TIMING REMAINS UNCERTAIN. SOMETIMES IN THIS PATTERN THE
STRATUS REMAINS OFF THE COAST THROUGH THE MORNING DUE TO THE WEAK
OFFSHORE FLOW. FARTHER SOUTH STRATUS IS MOVING NORTH TOWARDS KUKI
AND THIS MAY ARRIVE TOWARDS MORNING. THERE ARE ALSO A FEW SHOWERS
AROUND DUE TO THE UPPER LOW, BUT ANY IMPACTS ARE EXPECTED TO BE
MINIMAL FROM THESE. ONCE THIS STRATUS FINALLY MAKES ITS WAY ONSHORE,
IT IS EXPECTED TO BE LIFR DUE TO FOG AND LOW CLOUDS. THE MARINE
LAYER IS EXPECTED TO DEEPEN THROUGH THE DAY WEDNESDAY AND THIS WILL
LIKELY ALLOW CIGS TO LIFT. IT IS POSSIBLE THE COASTAL SITES WILL SEE
SOME CLEARING IN THE AFTERNOON, BUT AT THIS POINT MVFR CIGS LOOK
MORE LIKELY. MKK
MARINE
AN UPPER LEVEL LOW SOUTH OF THE AREA HAS DEVELOPED A
SOUTHERLY SURGE OF STRATUS AND SOUTHERLY WINDS RAPIDLY MOVING NORTH
ALONG THE COAST. THIS IS BRINGING 10 TO 15 KT SOUTHERLY WINDS AND
SOME PATCHY DENSE FOG. THESE SOUTHERLY WINDS WILL DIMINISH THROUGH
THE DAY AS THE LOW MOVES OFF TO THE EAST. THIS MORNING THE MAIN WAVE
IMPACTING THE WATERS IS A 10 TO 14 FOOT WAVE AT 17 SECONDS. THIS
WAVE IS EXPECTED TO GRADUALLY DIMINISH THROUGH THE DAY.
THURSDAY GENERALLY LIGHT WINDS AND WAVES ARE EXPECTED. IN THE
AFTERNOON A SMALL LONG PERIOD WAVE IS EXPECTED TO START MOVING INTO
THE WATERS AND THIS IS EXPECTED TO BUILD THURSDAY NIGHT AND FRIDAY
PEAKING AROUND 13 FEET AT 16 SECONDS. THURSDAY NIGHT AND FRIDAY
SOUTHERLY WINDS ARE EXPECTED TO BUILD IN AHEAD OF THE NEXT WEATHER
SYSTEM AS WELL. THESE ARE EXPECTED PEAK AROUND 15 TO 25 KT FRIDAY
AFTERNOON. GENERALLY ELEVATED SOUTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE WEEKEND. AT THIS POINT IT DOESN'T LOOK LIKE
THERE WILL BE ANY EXTENDED PERIODS OF GALES, BUT POSSIBLY SOME SHORT
PERIODS. THIS WILL BE MONITORED AS IT GETS CLOSER. A LARGE WEST TO
NORTHWEST SWELL IS EXPECTED TO START BUILDING IN ON SATURDAY.
CURRENTLY THE GFS WAVE MODEL SHOWS THIS PEAKING AROUND 15 TO 20 FEET
AT 14 SECONDS, ALTHOUGH THE NBM WAVE MODEL IS ONLY SHOWING THEM
AROUND 12 TO 16 FEET. NEXT WEEK CURRENT MODELS ARE SHOWING A RETURN
OF NORTHERLY WINDS. MKK
BEACH HAZARDS
THE LONG PERIOD W-NW SWELL GROUP IS PEAKING AROUND
14 TO 16 FEET THIS MORNING. THIS CONTINUES THROUGH THE DAY AND WILL
GRADUALLY DIMINISH BY THE AFTERNOON. THIS MAY BRING SOME POTENTIAL
FOR SNEAKER WAVES, BUT WITH THE WAVE DIMINISHING SET BEHAVIOR IS
EXPECTED TO HAVE DIMINISHED FROM. A SECOND SWELL TRAIN IS FORECAST
TO ARRIVE ON THU MAY ALSO POSE A RISK FOR SNEAKER WAVES. THE SWELL
DOES NOT APPEAR TO ARRIVE UNTIL LATE IN THE DAY AND DURING THE
OVERNIGHT HOURS THU. ONCE AGAIN EXPECT A MIX OF WAVES IN THE
SPECTRUM WITH SHORTER PERIOD BANDS DIMINISHING THU NIGHT. LARGER
SHORTER PERIOD W-NW SWELL FROM 14 TO 20 FT IS EXPECTED TO ARRIVE
OVER THE WEEKEND. THIS MAY BRING BREAKERS NEAR HIGH SURF ADVISORY OF
22 FEET.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
BEACH HAZARDS STATEMENT UNTIL NOON PDT TODAY FOR CAZ101-103-
104-109.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 5 PM PDT THIS AFTERNOON FOR
PZZ450-455.
SMALL CRAFT ADVISORY UNTIL 2 PM PDT THIS AFTERNOON FOR
PZZ470-475.
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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