717
FXUS66 KEKA 180657
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1057 PM PST WED DEC 17 2025
SYNOPSIS
LIGHT RAIN EXPECTED TONIGHT AND THURSDAY. MODERATE TO
LOCALLY HEAVY RAIN FORECAST TO RETURN LATE THURSDAY NIGHT INTO FRIDAY
FOR MOSTLY DEL NORTE, HUMBOLDT AND TRINITY COUNTIES. MODERATE TO
LOCALLY HEAVY RAIN IS FORECAST TO HAVE GREATER IMPACTS ON LAKE
AND MENDOCINO COUNTIES THIS WEEKEND AND EARLY NEXT WEEK.
KEY MESSAGES
- A 15% CHANCE FOR MINOR FLOODING LATE THURSDAY NIGHT THROUGH
FRIDAY WITH ANOTHER ROUND OF MODERATE TO LOCALLY HEAVY RAIN.
- MORE RAIN WITH A 15% CHANCE FOR MINOR FLOODING OVER THE
WEEKEND.
- STRONG GUSTY SOUTHERLY WINDS FROM 25 TO 40 MPH OVER THE RIDGES
AND COASTAL HEADLANDS TONIGHT DEL NORTE AND NORTHERN HUMBOLDT.
- STRONGER WIND GUSTS FROM 45 TO 60 MPH EXPECTED THURSDAY NIGHT
AND FRIDAY MORNING FOR COASTAL HEADLANDS AND MOUNTAINS OF DEL
NORTE AND NORTHERN HUMBODLT.
- SNOW LEVELS FALLING TO 3500 TO 4500 FEET WEDNESDAY WITH VERY
LITTLE OR NO SNOW ACCUMULATIONS EXPECTED.
- PACIFIC STORM TRACK REMAINS ACTIVE WITH ADDITIONAL HEAVY
RAINFALL AND CHANCES FOR STRONG SOUTHERLY WINDS NEXT WEEK.
DISCUSSION
WARM FRONT WILL BRING LIGHT RAIN TONIGHT AND THU,
GENERALLY LESS THAN 0.10 TO 0.25 INCHES IN 6-12 HOURS FOR DEL
NORTE, HUMBOLDT AND TRINITY. SOUTHERN MENDOCINO AND LAKE MAY NOT
GET ANY RAIN AT ALL TONIGHT AND THU.
MAIN IMPACT HEADING INTO THURSDAY WILL BE STRONG AND GUSTY SOUTHERLY
WINDS FOR DEL NORTE AND HUMBOLDT. CHANCE FOR WIND GUSTS FROM 50-60
MPH FOR THE DEL NORTE COAST INCREASES THU NIGHT INTO FRI MORNING
AS A 925MB SPEED MAX AROUND 55-65KT DEVELOPS IN ADVANCE OF THE
NEXT SURFACE FRONT THU. LACKING INSTABILITY WILL LIMIT STRONGER
WIND GUSTS THROUGH LOWER ELEVATIONS. HIGH TERRAIN AND RIDGES HAVE
A GOOD CHANCE (55 TO 70%) TO SEE GUSTS TO 50-60 MPH. CHANCES ARE
HIGH (65 TO 80%) FOR GUSTS OVER 55 MPH FOR COASTAL DEL NORTE. SNOW
LEVELS WILL RAPIDLY INCREASE TONIGHT AND THU IN ADVANCE OF THE
NEXT IVT PLUME, ABOVE 7000-8000 FT.
MODERATE TO HEAVY RAINFALL WILL BEGIN SPREADING INTO DEL NORTE
COUNTY LATE THURSDAY AS THE NEXT IVT PLUME SAGS SOUTH. MEAN HREF
AND RRFS HOURLY RAINFALL RATES ARE 0.3 TO 0.5 INCH PER HOUR, WITH
LOCALLY UP TO 0.6 INCH PER HOUR OVER THE HIGHER AND WINDWARD
FACING TERRAIN THROUGH A LARGE PORTION OF DEL NORTE COUNTY. 75TH
PERCENTILE HOURLY RATES ARE SIMILAR BUT WITH GREATER COVERAGE
THROUGH THE REGION.
THE FRONT AND FOCUS OF MODERATE TO HEAVY RAINFALL AND CHANCES FOR
MINOR FLOODING WILL THEN PROGRESS SOUTHWARD THROUGH N CA
THROUGHOUT THE DAY ON FRIDAY. SOUTH OF DEL NORTE, THE HEAVIEST
RAINFALL RATES WILL BE MOSTLY ALONG THE WINDWARD SLOPES OF THE
HIGHER TERRAIN. ALL MAIN STEM RIVERS ARE FORECAST TO REMAIN BELOW
ACTION OR MONITOR STAGES, HOWEVER RIVERS IN NARROW BASINS WILL
LIKELY ONCE AGAIN QUICKLY RISE. CREEKS AND STREAMS WILL ALSO
QUICKLY RISE AND COULD RESULT IN NUISANCE FLOODING. PONDING ON
ROADWAYS IS ALSO LIKELY THROUGHOUT THE DURATION OF HEAVY RAINFALL.
RAINFALL AMOUNTS OF 2-4 INCHES ARE FORECAST FOR DEL NORTE COUNTY,
WITH 1 TO 3 SOUTH THROUGH NORTHERN MENDOCINO COUNTY. OUTSIDE OF
DEL NORTE, THERE IS UP TO A 70% CHANCE FOR 24 HOUR RAINFALL OVER 3
INCHES FOR SOUTHWEST FACING SLOPES OF CAPE MENDOCINO AND SOME
HIGHER INTERIOR RIDGES OF HUMBOLDT.
RAINFALL WILL TURN MUCH LIGHTER FRIDAY AFTERNOON WITH A TRANSITION
TO LIGHTER RAIN OR SHOWERS. RAINFALL WILL THEN BEGIN TRENDING
HIGHER SATURDAY SOUTH THROUGH LAKE AND MENDOCINO COUNTIES AS THE
FLOW TURNS ZONAL. THE PERSISTENT RIDGE THAT HAS BEEN SOUTH OF THE
REGION WILL THEN EJECT EAST AS A STRONG NE PACIFIC TROUGH TAKES
SHAPE. MODELS DIVERGE ON DEVELOPMENT OF A NEW FRONTAL WAVE AND
NORTHWARD SURGE OF IVT AHEAD OF THE TROUGH, BUT HEAVY RAINFALL
LOOKS TO BE FOCUSED IN MORE OF A NARROW BAND, AND COULD BECOME
MORE PERSISTENT OVER ONE AREA. IT IS LIKELY THAT LAKE AND
MENDOCINO WILL BE IN THE BULLSEYE FOR THIS FOCUS OF MODERATE TO
LOCALLY HEAVY RAIN. THE PRECIP MAX COULD EASILY SHIFT NORTHWARD
SUNDAY AS WE HAVE SEEN MANY TIMES BEFORE. IVT VALUES OVER 500
KG/M/S MAY PERSIST FOR MULTIPLE DAYS NEXT WEEK AND THE SITUATION
WILL NEED TO BE MONITORED CLOSELY AS THE GROUNDS BEGIN TO SATURATE
MORE.
AVIATION
VFR CONDITIONS PREVAIL AT THE COAST THIS MORNING WHILE
SOME OF THE VALLEYS ARE SEEING LOW CLOUDS. THESE MAY REACH INTO UKI
THIS MORNING, BUT CONFIDENCE IS LOW ON THIS. AROUND SUNRISE A WEAK
WARM FRONT MAY START TO BRING SOME MVFR CONDITIONS TO THE AREA.
THESE COULD EASILY END UP BEING HIGHER AND CONDITIONS WILL BE VFR.
SOUTHERLY WINDS ARE EXPECTED TO INCREASE IN DEL NORTE COUNTY KCEC
THIS MORNING. STRONGER SOUTHERLY WINDS ARE EXPECTED TO GRADUALLY
SHIFT SOUTH THROUGH THE EVENING AND OVERNIGHT. GUSTS TO 40 KT OR
HIGHER ARE POSSIBLE TONIGHT AT KCEC. WINDS ARE EXPECTED TO BE
LIGHTER AT KACV WITH GUSTS TO 20 OR 25 KT POSSIBLE. A STRONG LOW
LEVEL JET AROUND 925 MB WILL BRING SOME LOW LEVEL WIND SHEAR TO KACV
AND KCEC. MKK
MARINE
THE NORTHWEST SWELL HAS BUILT IN TO AROUND 9 TO 11
FEET AT 11 SECONDS. THIS IS EXPECTED TO SLOWLY DIMINISH THROUGH THE
DAY. TODAY WINDS ARE EXPECTED TO BECOME SOUTHERLY AGAIN AND INCREASE
TO 15 TO 30 KT MIDDAY THURSDAY THROUGH EARLY FRIDAY MORNING. THE
GALE WARNING FOR THE NORTHERN WATERS REMAINS ON TRACK. WINDS MAY
DIMINISH A FEW HOURS SOONER, BUT WILL LEAVE THE END TIME THE SAME
FOR NOW.
FRIDAY AFTERNOON WINDS WILL BECOME NORTHERLY AGAIN AROUND 5 TO 15
KT. THIS WILL BE SHORTLIVED AND SATURDAY AFTERNOON WINDS WILL
DIMINISH AND BECOME SOUTHERLY ONCE AGAIN. ANOTHER WEATHER SYSTEM IS
EXPECTED ON SUNDAY BUT THERE IS WIDE VARIABILITY IN THE MODEL
SOLUTIONS ON THAT. THE MODELS ARE STRUGGLING TO RESOLVE A STRONG
AREA OF LOW PRESSURE AND WHERE IT WILL EXACTLY TRACK. THE NAM SHOWS
NEAR GALES WITH THE LOW MOVING NORTH OF THE AREA. THE GFS SHOWS A
WEAKER LOWER MOVING INTO THE CA WATERS. THE NAM SOLUTION SEEMS
REASONABLE AND THERE IS CERTAINLY THE POTENTIAL FOR GALES. SO FOR
NOW THE WIND FORECAST REMAINS SOUTHERLY NEAR 20 KT, BUT THIS WILL
LIKELY INCREASE AS IT GETS CLOSER. MKK
HYDROLOGY
A BREAK IN HEAVY RAIN IS EXPECTED TONIGHT AND THU.
LIGHT PRECIP IS EXPECTED WITH A WARM FRONT TONIGHT AND THU.
RIVERS AND STREAMS WILL CONTINUE TO DRAIN AND RECEDE TONIGHT
THROUGH THU. NEXT ROUND OF HEAVY RAINFALL IS EXPECTED TO EDGE INTO
DEL NORTE COUNTY LATE THU NIGHT. ONCE AGAIN LOCALIZED MINOR URBAN
AND SMALL STREAM FLOODING WILL BE POSSIBLE FOR DEL NORTE,
HUMBOLDT, TRINITY AND NORTHERN MENDOCINO. A PROLONGED PERIOD OF
HEAVY RAINFALL IS FORECAST WITH RATES OF 0.3 TO 0.5 INCHES PER
HOUR INITIALLY LATE THURSDAY INTO FRIDAY MORNING FOR DEL NORTE
COUNTY. SOME RATES OVER 0.6 INCH PER HOUR ARE POSSIBLE OVER THE
WINDWARD SIDE OF SOME HIGHER TERRAIN. WIDESPREAD MODERATE TO
HEAVY RAINFALL WILL THEN SPREAD SOUTH THROUGHOUT THE DAY ON
FRIDAY. RAINFALL AMOUNTS OF 2-4 INCHES ARE FORECAST.
THE DURATION AND MAGNITUDE OF THE MOISTURE FLUX IS LOWER AND
HOURLY OR 6 HOURLY PRECIP RATES INITIALLY SEEM LOWER COMPARED TO
RAINSTORM LAST NIGHT. THERE WILL BE OVER 24-36 HOURS BEFORE HEAVY
RAIN DEVELOPS AGAIN WHICH SHOULD HELP TO REDUCE THE THREAT. RISK
FOR ROCK AND MUDSLIDES WILL INCREASE AND COULD IMPACT TRAVEL ON
HIGHWAYS 299, 36, 101 AND 199, ESPECIALLY ON FRIDAY.
ALL MAIN STEM RIVERS ARE FORECAST TO REMAIN BELOW ACTION OR MONITOR
STAGES THROUGH THURSDAY. AT THIS TIME, NONE OF THE MAIN STEM
RIVERS ARE FORECAST TO EXCEED ACTION/MONITOR STAGES. RIVERS IN
NARROW BASINS MAY ONCE AGAIN QUICKLY RISE WITH HEAVY RAIN ON
FRIDAY. THIS IS NOT TOO UNCOMMON FOR OUR RIVERS. ENSEMBLE PLUMES
CONTINUE INDICATE LOW PROBABILITIES (LESS THAN A 10% CHANCE) FOR
FLOOD STAGE EXCEEDANCE LATE IN THE WEEKEND INTO EARLY NEXT WEEK,
PARTICULARLY FOR THE EEL RIVER AT FERNBRIDGE, NAVARRO RIVER AT
NAVARRO AND RUSSIAN RIVER AT HOPLAND. WPC STILL HAS STILL HAS OUR
FORECAST PEGGED WITH A 15% CHANCE OF FLASH FLOOD GUIDANCE
EXCEEDANCE THROUGH THE WEEKEND, SO THIS WILL NEED TO BE MONITORED.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
WIND ADVISORY FROM 5 PM THURSDAY TO 8 AM PST FRIDAY FOR
CAZ101.
WIND ADVISORY FROM 8 AM THURSDAY TO 8 AM PST FRIDAY FOR
CAZ102.
WIND ADVISORY FROM 10 PM THURSDAY TO 8 AM PST FRIDAY FOR
CAZ103.
WIND ADVISORY FROM 10 PM THURSDAY TO 10 AM PST FRIDAY FOR
CAZ104.
WIND ADVISORY FROM 7 PM THURSDAY TO 8 AM PST FRIDAY FOR
CAZ105-106.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 7 PM PST THURSDAY FOR PZZ450.
GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR
PZZ450.
SMALL CRAFT ADVISORY UNTIL 6 AM PST THURSDAY FOR PZZ470.
GALE WATCH FROM THURSDAY MORNING THROUGH FRIDAY MORNING FOR
PZZ470.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM PST
THURSDAY 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.
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