605
FXUS66 KEKA 152219
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
212 PM PST MON DEC 15 2025
SYNOPSIS
MODERATE TO LOCALLY HEAVY RAIN IS FORECAST TONIGHT
THROUGH TUESDAY NIGHT FOR MOSTLY DEL NORTE, HUMBOLDT, TRINITY
AND NORTHERN MENDOCINO COUNTIES. A BREAK IN THE RAIN IS FORECAST
ON WEDNESDAY, FOLLOWED ANOTHER HIGH CHANCE FOR HEAVY RAIN EITHER
ON THURSDAY OR FRIDAY. ANOTHER CHANCE FOR HEAVY RAIN AND STRONG
WINDS WILL ARRIVE FOR THE LATTER PORTION OF THE WEEKEND.
DISCUSSION
A STRONG LOW PRESSURE OVER THE NERN PACIFIC, CENTERED
IN THE GULF OF ALASKA, WILL SEND A SERIES OF FRONTAL SYSTEMS INTO
NW CALIFORNIA THROUGH WEDNESDAY. EXPECT MODERATE TO HEAVY RAIN
AND GUSTY SOUTHERLY WINDS. FRONTAL PASSAGE, COOLER AND DRIER AIR
WILL ARRIVE DURING THE DAY ON WEDNESDAY.
SATELLITE AND RADAR DATA SHOWED A BAND OF MOISTURE EXTENDING
SOUTHWESTWARD FROM THE PACIFIC NW COAST TO JUST OFFSHORE THE
NORTHERN CALIFORNIA COAST THIS AFTERNOON. EMBEDDED CONVECTION,
A FEW LIGHTNING STRIKES AND HEAVY RAIN RATES (0.30 IN/HR) WITH
THIS STREAM OF DEEP LAYER MOISTURE (PWATS 250% ABOVE NORMAL) HAS
BEEN MOVING OVER DEL NORTE COUNTY THIS AFTERNOON. HREF CONTINUES
TO DEPICT HIGHEST CHANCE FOR HEAVY RAIN > 0.25IN/HR OVER DEL NORTE
AND NORTHERN HUMBOLDT THIS AFTERNOON AND EVENING. A SECONDARY
PRECIP MAX SPIKES UP LATER TONIGHT INTO EARLY TUE ACROSS SW
HUMBOLDT AS THE AXIS OF MOISTURE SHIFTS SOUTHWARD. COVERAGE OF
HEAVIER RAIN RATES OVER 0.25IN/HR WILL EXPAND DURING THE AFTERNOON
TUE INTO TUE NIGHT. THIS WILL NEED TO WATCHED FOR POSSIBLE URBAN
AND SMALL STREAM FLOODING AND POSSIBLE ROCK/MUD SLIDES. MUCH
LIGHTER RAIN RATES ARE EXPECTED FOR SOUTHERN MENDOCINO AND LAKE
COUNTIES WITH STORM TOTAL RAIN AROUND 0.10 INCHES OR LESS ENDING
4 AM WED.
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% CHANCE) THAT A
WET PATTERN WILL CONTINUE THROUGH THE END OF THE WEEK AND INTO
THE WEEKEND. GFS AND ECMWF CONTINUES TO DEPICT ANOTHER MOIST PLUME
IMPACTING THE NORTHERN MOST PORTION OF THE AREA ON THURSDAY.
EVENTUALLY THIS BOUNDARY MOVES ACROSS THE AREA BY FRIDAY, THOUGH
IT COULD SPEED UP OR SLOW DOWN. HIGH PRESSURE AND GENERALLY DRIER
CONDITIONS ARE EXPECTED FOR SATURDAY, HOWEVER ANOTHER STORM IN THE
LINE UP WILL BEGIN TO SPIN UP OFFSHORE AND MAY BEGIN TO IMPACT
THE AREA AS EARLY AS SAT NIGHT OR SUN. THIS LOW PRESSURE SYSTEM HAS
THE POTENTIAL TO GENERATE STRONG AND DAMAGING WINDS AS WELL AS MORE
HEAVY RAIN. TIMING IS STILL UNCERTAIN. LOOKING AT THE CHANCE OF IVT
> 250 KG/M/S THE FOLLOWING WEEK DEC 22-26, CONFIDENCE IS MODERATE TO
HIGH IN WET WEATHER CONTINUING FOR LATTER PORTION OF DEC. CPC'S 8-14
DAY OUTLOOK ALSO HAS NW CA IN A HIGH RISK FOR HEAVY PRECIP AND A
MODERATE RISK FOR HIGH WINDS. STAY TUNED.
AVIATION...18Z TAFS)
A FRONTAL PASSAGE THIS MORNING HAS CAUSED
MVFR CONDITIONS ALONG THE NORTH COAST TODAY DUE TO PASSING
RAINSHOWERS WITH SPORADIC LIGHTNING STRIKES AND MODERATELY LOW CLOUD
BASES. OVERCAST CEILINGS AROUND 1500-2000FT ARE TO BE EXPECTED ALL
OVER NW CA TODAY. THE STRONGEST WINDS ARE EXPECTED IN DEL NORTE AND
HUMBOLDT CO. AND NEAR COASTAL PLAINS (I.E. KCEC AND KACV). WINDS
ALOFT FORECASTED TO DECREASE SIGNIFICANTLY THROUGH THE EVENING
DECREASING THE THREAT OF LLT AND MOUNTAIN WAVE FORMATION. CEILINGS
LOWER TO POTENTIAL LIFR TONIGHT, YET MOST OF THE MODEL DATA SHOWS
IFR IS MORE PROBABLE. RAIN TOMORROW TO THE NORTH COAST BEGINNING
AROUND 15/16Z, WITH A 30% PROBABILITY OF REACHING AS FAR SOUTH AS
KUKI.
MARINE
SOUTHERLY WINDS PRESENT IN THE NORTHERN WATERS AS A WARM
FRONT MOVES OVER THE AREAS. WINDS WILL PEAK IN THE NORTHERN OUTER
WATERS WHILE OTHER ZONES CAN EXPECT MODERATE SOUTHERLY WIND GUSTS
BUT WILL GENERALLY REMAIN CALMER. WIND WAVES CREATING SHORT PERIOD
SEAS OVER 6 FEET IN THE NORTHERN OUTER WATERS THROUGH TONIGHT.
WINDS WILL GENERALLY WEAKEN FOR MUCH OF TOMORROW, BUT A MID PERIOD
WESTERLY SWELL BUILDING TO OVER 10 FEET WILL MAINTAIN MODERATELY
STEEP SEAS AT LEAST FOR THE THE NORTHERN WATERS. ANOTHER STORM
SYSTEM WILL CROSS THE AREA LATE TOMORROW INTO EARLY WEDNESDAY.
SOUTHERLY WINDS WILL AGAIN, ONLY BRIEFLY, INCREASE OVER 20 KTS AND
BE MOSTLY CONFINED TO THE NORTHERN WATERS.
CALMER CONDITIONS FORM AGAIN WEDNESDAY AS A MID PERIOD WESTERLY
SWELL UP TO 10 FEET WILL LIKELY MAINTAIN VERY MODERATELY STEEP SEAS
IN THE NORTHERN WATERS. A STRONGER STORM SYSTEM IS EXPECTED LATER IN
THE WEEK AROUND FRIDAY. THIS WILL FORCE THE SOUTHERLY WINDS INTO THE
SOUTHERN WATERS WITH STRONGER GUSTS IN THE NORTHER WATERS, THOUGH
THE POTENTIAL FOR PROPER GALES REMAINS MODERATE TO LOW (20-40
PERCENT). /JHW/DES
HYDROLOGY
ALL MAIN STEM RIVERS ARE FORECAST TO REMAIN BELOW
MONITOR OR ACTION STAGE THROUGH MID WEEK. 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 INTO THE WEEKEND WITH ADDITIONAL RAIN, INCREASING
THE RISK OF ROCKSLIDES AND MUDSLIDES, AND MINOR FLOODING. CHANCE
OF MAIN STEM RIVER STAGES EXCEEDING MONITOR STAGE WILL ALSO
INCREASE AS WE HEAD INTO THE FOLLOWING WEEK, DEC 22-28.
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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