462
FXUS66 KEKA 150920
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
120 AM PST MON DEC 15 2025
SYNOPSIS
MODERATE TO LOCALLY HEAVY RAIN WILL ARRIVE FOR DEL
NORTE AND HUMBOLDT COUNTIES TODAY INTO TONIGHT. RAIN IS FORECAST
TO SPREAD SOUTHWARD BY TUESDAY FOR MENDOCINO AND LAKE. MORE RAIN
IS FORECAST FOR THE REMAINDER OF THIS WEEK. STRONG GUSTY WINDS
WILL ALSO BE POSSIBLE WITH EACH STORM, ESPECIALLY LATE WEEK AND
NEXT WEEKEND.
DISCUSSION
A STRONG LOW PRESSURE OVER THE THE NERN PACIFIC,
JUST IN THE GULF OF ALASKA, WILL DRIVE A SERIES OF FRONTAL SYSTEM
TO IMPACT NORTHWEST CALIFORNIA TODAY AND INTO WEDNESDAY, WITH
MODERATE TO HEAVY RAIN AND GUSTY WINDS.
SATELLITE AND DOPPLER RADAR IMAGERY DEPICTS THE FIRST OF A SERIES
OF FRONTAL SYSTEMS APPROACHING NORTHWEST CALIFORNIA. AS OF 12 AM,
LIGHT RAIN SHOWERS ARE OBSERVED MOVING NORTHEAST ACROSS DEL NORTE
COUNTY, WHILE A NARROW BAND LIGHT TO MODERATE RAINFALL APPROACHES
THE NORTHERN COASTAL WATERS. A FRONTAL BOUNDARY, ALONG WITH A
LONG PLUME OF SUBTROPICAL MOISTURE INGESTED IN THE SOUTHWESTERLY
FLOW WILL CONTINUE TO APPROACHES THE AREA TODAY INTO TONIGHT
BRINGING INCREASING CHANCE OF PRECIPITATION AND GUSTY WINDS OVER
THE HIGH ELEVATIONS. THIS ROUND WILL BE ALMOST EXCLUSIVELY
FOCUSED ON DEL NORTE AND HUMBOLDT COUNTIES. COLD AIR ALOFT WILL
SPREAD ACROSS THE NORTHERN PORTION OF THE AREA TODAY BRINGING
INCREASING INSTABILITY LATE THIS MORNING AND AFTERNOON,
ESPECIALLY FOR AREAS NORTH OF TRINIDAD. CAMS SHOW MODERATE TO
STRONG RETURNS OVER DEL NORTE AND FAR NORTHERN HUMBOLDT LATE THIS
AFTERNOON. HOURLY MAX RAINFALL RATES OF 0.10-0.25 INCHES IS
EXPECTED, WITH LOCALLY HEAVIER RATES OVER 0.50IN/HR FOR SW FACING
ASPECTS OF DEL NORTE AND HUMBOLDT COUNTIES. MUCH LIGHTER RAIN
RATES ARE EXPECTED FOR MENDOCINO AND LAKE TIL PERHAPS TUE WHEN
MOIST PLUME SAGS SOUTHWARD AND STALLS OUT.
ANOTHER, STRONGER ROUND OF RAIN RAIN WILL BEGIN TO ARRIVE AND SPREAD
FURTHER SOUTH TUESDAY INTO EARLY WEDNESDAY. THIS ROUND WILL MOST
LIKELY HAVE SOME PERIODS OF MODERATE TO HEAVY RAIN TUESDAY NIGHT,
WHICH MAY GENERATE VERY MINOR URBAN FLOODING. THIS SECOND ROUND WILL
SPREAD FURTHER SOUTH WITH ONLY A SLIGHT FOCUS ON THE NORTH COAST.
LOW ELEVATION AMOUNTS WITH THIS ROUND WILL MOST LIKELY BE BETWEEN
0.5 AND 1.5 INCHES WITH UPPER ELEVATION AMOUNTS OF 2 TO 4 INCHES
OF RAIN. IN THIS RAIN, EVEN THE SOUTHERN MOST PART OF THE AREA IS
NEARLY GUARANTEED TO SEE WETTING RAIN.
SOUTHEAST WINDS WILL ALSO BE GUSTY THROUGH THE WEEK. PEAK WIND
GUSTS AT LOWER ELEVATIONS WILL MOST LIKELY BE 20 TO 35 MPH, WITH
A 30% CHANCE OF IMPACTFUL GUSTS OVER 45 MPH ON HIGH COASTAL
RIDGES. WINDS GUSTS WILL MOST LIKELY BE STRONGEST WITH THE SECOND
ROUND OF RAIN TUESDAY INTO WEDNESDAY. ECMWF ENSEMBLE INDICATES
POTENTIAL FOR STRONGEST WINDS THURSDAY OR THURSDAY NIGHT, THOUGH
THERE CONTINUES TO BE LARGE SPREADS. ABOVE AVERAGE WARMTH AND
FAIRLY HIGH SNOW LEVELS WILL SEVERELY LIMIT ALL PROSPECTS FOR
SIGNIFICANT SNOWFALL EXCEPT OVER THE HIGHEST MOUNTAIN PEAKS.
THERE REMAINS GENERALLY HIGH CONFIDENCE (80% OF ENSEMBLE MEMBERS)
THAT A WETTER PATTERN WILL CONTINUE THROUGH THE END OF DECEMBER.
LONG RANGE FORECASTS HAVE PLACED A HIGHER RISK FOR A MODERATE TO
STRONG ATMOSPHERIC RIVER NEAR THE END OF NEXT WEEK AND NEXT
WEEKEND. THIS COULD TRANSLATE INTO HEAVY RAINFALL AND WIND GUSTS
OVER 50 MPH. ENSEMBLE SPREAD REMAINS HIGH BUT HAS GRADUALLY
INCREASED IN CONFIDENCE FOR A PERIOD OF HEAVY RAIN. WITH PRECEDING
RAIN, SOME MINOR FLOODING WILL BECOME POSSIBLE. LENDING SUPPORT
FOR WET AND STORMY WEATHER THROUGH THE END OF DECEMBER IS CPC'S
8-14 DAY OUTLOOK WHICH HAS NW CA IN A HIGH RISK FOR HEAVY PRECIP,
A MODERATE TO HIGH RISK FOR MOUNTAIN SNOW AND A MODERATE RISK FOR
HIGH WINDS.
AVIATION...06Z TAFS
GENERALLY MVFR CONDITIONS HAVE BUILT ACROSS
THE AREA EVEN ALONG THE COAST AS AN APPROACHING STORM SYSTEM HAS
LIFTED CEILINGS AND INHIBITED ANY FOG FORMATION. SHOWERS WILL MOST
LIKELY BEGIN TO BUILD ALONG THE FAR NORTHERN COAST BEFORE SUNRISE
MONDAY. SHOWERS WILL INCREASE IN STRENGTH AND MOVE SOUTH THROUGH THE
DAY WITH THE STRONGEST SHOWERS DURING THE AFTERNOON. MVFR CEILINGS
WITH BRIEF PERIOD OF IFR ARE MOST LIKELY THROUGH THE DAY NEAR THE
COAST. MORE VFR TO MVFR CONDITIONS ARE MOST LIKELY FOR THE SOUTHERN
HALF OF THE AREA THAT WILL REMAIN MORE DRY. SHOWERS WILL LINGER
OVERNIGHT MONDAY INTO TUESDAY WITH ENSEMBLES SHOWING GREATER
POTENTIAL (50% CHANCE) FOR MORE CONSISTENT IFR CEILING AND SOME
PATCHY FOG OVERNIGHT. /JHW
MARINE
AFTER A LONG PERIOD OF CALM CONDITIONS, SOUTHERLY WINDS
HAVE BEGUN TO INCREASE IN THE NORTHERN WATERS AS A STORM SYSTEM
APPROACHES THE AREA. WINDS WILL PEAK IN THE NORTHERN OUTER WATERS
LATER MONDAY MORNING WITH GUSTS OVER 25 KTS. OTHER ZONES WILL SEE
SOME MODERATE SOUTHERLY WIND GUSTS BUT WILL GENERALLY REMAIN CALMER.
WINDS WILL BE JUST STRONG ENOUGH TO BUILD SHORT PERIOD SEAS OVER 6
FEET INT HE NORTHERN OUTER WATERS THROUGH MONDAY NIGHT.
WINDS WILL GENERALLY WEAKEN FOR MUCH OF TUESDAY, BUT A MID PERIOD
WESTERLY SWELL BUILDING OVER 10 FEET WILL MAINTAIN MODERATELY STEEP
SEAS AT LEAST FOR THE THE NORTHERN WATERS THROUGH MUCH OF TUESDAY.
ANOTHER STORM SYSTEM WILL CROSS THE AREA LATE TUESDAY INTO EARLY
WEDNESDAY. SOUTHERLY WINDS WILL AGAIN ONLY BRIEFLY INCREASE OVER 20
KTS AND BE MOSTLY RESTRICTED TO THE NORTHERN WATERS.
CALMER CONDITIONS WILL ARRIVE AGAIN WEDNESDAY THOUGH, ONCE AGAIN, A
MID PERIOD WESTERLY SWELL UP TO 10 FEET WILL LIKELY MAINTAIN VERY
MODERATELY STEEP SEA IN THE NORTHERN WATERS. A STRONGER STORM SYSTEM
IS EXPECTED LATER IN THE WEEK. THIS WILL SPREAD STRONGER SOUTH WINDS
MORE INTO THE SOUTHERN WATERS WITH NEAR GALE GUSTS IN THE NORTHER
WATERS AROUND FRIDAY, THOUGH THE POTENTIAL FOR PROPER GALES REMAINS
LOW (AROUND 20 PERCENT). /JHW
HYDROLOGY
MINOR RISES ARE EXPECTED ON NORTH COAST RIVERS FROM
MONDAY THROUGH WEDNESDAY. ALL MAIN STEM RIVERS ARE FORECAST TO
REMAIN BELOW MONITOR OR ACTION STAGE. MINOR FLOODING OF SMALLER
RIVERS, CREEKS AND STREAMS WITH POOR DRAINAGE WILL BE POSSIBLE.
SOIL MOISTURE IS EXPECTED TO CONTINUE INCREASE OR SATURATE LATE
IN THE WEEK WITH ADDITIONAL RAIN, INCREASING THE RISK OF
ROCKSLIDES AND MUDSLIDES, AND MINOR FLOODING.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 1 AM TO 11 AM PST TUESDAY FOR
PZZ450.
SMALL CRAFT ADVISORY UNTIL 11 AM PST TUESDAY FOR PZZ470.
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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