986
FXUS66 KEKA 182150
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
150 PM PST THU DEC 18 2025
SYNOPSIS
MODERATE TO LOCALLY HEAVY RAIN ALONG WITH GUSTY SOUTH
WIND RETURNS THIS EVENING THROUGH EARLY FRIDAY, ESPECIALLY IN DEL
NORTE AND HUMBOLDT COUNTIES. ADDITIONAL SYSTEMS WILL BRING IMPACTFUL
RAINFALL TO THE AREA STARTING LATE SATURDAY INTO NEXT WEEK.
KEY MESSAGES
- POTENTIAL FOR MINOR FLOODING LATE THURSDAY NIGHT THROUGH FRIDAY
WITH ANOTHER ROUND OF MODERATE TO LOCALLY HEAVY RAIN.
- STRONG WIND GUSTS FROM 45 TO 60 MPH EXPECTED TONIGHT AND FRIDAY
MORNING FOR COASTAL HEADLANDS AND MOUNTAINS OF DEL NORTE AND
NORTHERN HUMBODLT.
- PACIFIC STORM TRACK REMAINS ACTIVE WITH ADDITIONAL HEAVY RAINFALL
AND CHANCES FOR STRONG SOUTHERLY WINDS THIS WEEKEND AND EARLY NEXT
WEEK.
- SNOW LEVELS GRADUALLY DROP BY EARLY NEXT WEEK, AND COULD BE AS LOW
AS 3500 TO 4500 FT BY WEDNESDAY.
DISCUSSION
ANOTHER SYSTEM IS APPROACHING THE AREA FROM THE NORTH
AND HAS STARTED TO BRING GUSTY SOUTH WINDS AHEAD OF THE FRONTAL
PASSAGE. WINDS AT AROUND 2000 FT ARE FORECAST TO BE AROUND 55-65
KTS, BUT LIMITED INSTABILITY WILL PREVENT THESE GUSTS FROM BEING
REALIZED IN THE LOWER ELEVATIONS. FORECASTED PEAK WIND GUSTS RANGE
FROM 30-45 MPH FOR MUCH OF THE LOWER ELEVATIONS IN HUMBOLDT AND DEL
NORTE. EXPOSED RIDGES AND COASTAL HEADLANDS COULD SEE GUSTS IN
EXCESS OF 50 MPH BRIEFLY TONIGHT.
MODERATE TO HEAVY RAINFALL WILL START TONIGHT IN DEL NORTE COUNTY
AND MOVE SOUTHWARD. HOURLY RAINFALL RATES OF 0.3 TO 0.5 INCHES ARE
POSSIBLE, WITH LOCALLY HIGHER AMOUNTS ON WINDWARD FACING RIDGES.
TOTAL RAINFALL AMOUNTS OF 2-4 INCHES ARE FORECAST IN THE HIGHER
TERRAIN, WITH MOST LIKELY FALLING IN A 6-12 HOUR TIME PERIOD. WITH
SATURATED SOILS, CREEKS AND STREAMS MAY QUICKLY RISE, WHICH COULD
RESULT IN MINOR FLOODING IMPACTS. ADDITIONALLY, WITH HEAVY RAIN
RATES, THERE IS A GREATER CHANCE FOR MUDSLIDES AND ROCKSLIDES.
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, MENDOCINO, HUMBOLDT, AND TRINITY,
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.
GOING INTO EARLY NEXT WEEK, ENSEMBLE GUIDANCE CONTINUES TO KEEP THE
STORM DOOR OPEN, BUT THE POSITION OF THE SYSTEMS ARE UNCERTAIN. SOME
ENSEMBLES KEEP THE BULLSEYE TO THE SOUTH OF THE AREA TOWARDS THE BAY
AND SOME KEEP THE BULLSEYE IN MENDOCINO AND LAKE COUNTIES. IF
PRECIPITATION IS NEAR-CONTINUOUS FOR SEVERAL DAYS, MORE SIGNIFICANT
FLOODING IMPACTS (SUCH AS MAIN-STEM RIVERS NEARING FLOOD STAGE) ARE
POSSIBLE.
SNOW LEVELS REMAIN HIGH INTO THE WEEKEND AND EARLY NEXT WEEK. SNOW
LEVELS BEGIN TO FALL GOING INTO EARLY TO MID NEXT WEEK, POTENTIALLY
AS LOW AS 3500-4500 FT, WHICH COULD BRING US OUR FIRST IMPACTFUL
SNOW EVENT TO THE HIGHEST MOUNTAIN PASSES. STAY TUNED!
AVIATION...(18Z TAFS)
COAST: LIGHT SHOWERS ALONG THE NORTH COAST CAUSING MVFR-IFR
CONDITIONS TODAY. OVERCAST CEILINGS FORECASTED TO HOLD THROUGH THE
EVENING. SOUTHERLY WINDS INCREASE THROUGH THE DAY AS A FRONTAL
SYSTEM APPROACHES THE AREA. WINDS PEAK LATE TONIGHT WITH GUSTS UP TO
50KTS POSSIBLE FOR COASTAL HEADLANDS. MORE SHELTERED TERMINALS HAVE
GUSTS UP TO 30KTS. THESE SOUTHERLY WINDS ARE ACCOMPANIED WITH A LOW
LEVEL JET OVER THE NORTH COAST WITH WINDS UP TO 60KTS POSSIBLE AT
2000 FT AGL TONIGHT INTO TOMORROW INCREASING THE POTENTIAL FOR LOW
LEVEL TURBULENCE. PERIODS OF HEAVY RAIN WILL LIKELY CAUSE DEGRADED
VISIBILITIES AND BROKEN LOW CLOUDS LEADING TO IFR, AND POSSIBLY LIFR
CONDITIONS AT TIMES. CONDITIONS IMPROVE AROUND 17-18Z 12/19 WITH
LIGHT TO MODERATE NORTHERLIES AND POST FRONTAL, BROKEN CLOUD
COVERAGE.
INLAND: OVERCAST SKIES PERSIST AS HIGH CLOUDS DECREASE DAYTIME
MIXING. WINDS ARE TO REMAIN LIGHT AND VARIABLE IN VALLEY FLOORS AND
ELEVATED AT AND AROUND HIGHER TERRAIN. MOUNTAIN WAVE AND LOW LEVEL
TURBULENCE ARE EXPECTED FOR THE EARLY MORNING THROUGH MIDDAY WITH
WINDS AS HIGH 65KTS AT TIME AS A FRONTAL SYSTEM MOVES NW TO THE SE.
PERIODS OF HEAVY RAIN CAN CREATE DEGRADED VISIBILITIES AND INCREASED
LOW CLOUD COVERAGE LEADING TO IFR TO LIFR CONDITIONS TOMORROW
MORNING.
DS
MARINE
A FAST MOVING COLD FRONT WILL CREATE HAZARDOUS MARINE
CONDITIONS THROUGH THE DAY INTO FRIDAY MORNING. WIND GUSTS CLOSE TO
THE FRONTAL BOUNDARY IN THE NORTHERN WATERS ARE FORECAST TO BE CLOSE
TO 50KTS NORTH OF CAPE MENDOCINO. WINDS WILL INCREASED STEADILY FROM
MIDDAY TODAY THROUGH TOMORROW MORNING BEFORE TURNING TO LIGHT TO
MODERATE NORTHERLIES AFTER THE FRONTAL PASSAGE. STEEP WIND WAVES
WILL INCREASE QUICKLY TO SIG. HEIGHTS OF 11FT. THE QUICK NATURE OF
THIS FRONT ALSO SUGGEST THAT WIND WAVES WILL DECREASE FAIRLY QUICKLY
AS WELL THROUGH TOMORROW AFTERNOON.
ANOTHER WEATHER SYSTEM IS EXPECTED ON SUNDAY BUT THERE IS WIDE
VARIABILITY IN THE MODEL SOLUTIONS. THE MODELS ARE CURRENTLY
STRUGGLING TO RESOLVE A STRONG AREA OF LOW PRESSURE AND WHERE IT
WILL EXACTLY TRACK. THE LATEST RUN OF THE NAM SHOWS NEAR GALES OF 25-
30KTS WITH THE CENTER OF THE LOW MOVING NORTH OF THE AREA, WHEREAS
THE 2ND LATEST RUN SHOWS STRONG GALE FORCE WINDS. THE GFS SHOWS A
WEAKER LOWER MOVING INTO THE CA WATERS. THE NAM'S MOST RECENT
SOLUTION SEEMS REASONABLE FOR NOW, AS THERE IS CERTAINLY THE
POTENTIAL FOR GALES. MORE UPDATES WILL COME AS MODEL DATA EVOLVES.
DS
HYDROLOGY
A FLOOD WATCH HAS BEEN ISSUED FOR HUMBOLDT AND DEL
NORTE COUNTIES FOR THE POTENTIAL OF MODERATE TO HEAVY RAIN TONIGHT
INTO EARLY FRIDAY. TOTAL RAIN AMOUNTS OF 2-4 INCHES ARE FORECAST FOR
THE HIGHER ELEVATIONS, WITH AREAS OF LOCALLY HIGHER TOTALS. LOWER
ELEVATIONS COULD SEE 1-2 INCHES. RISES IN CREEKS AND STREAMS ARE
LIKELY. MAIN STEM RIVERS WILL ALSO RISE, BUT BECAUSE THIS IS A QUICK
MOVING SYSTEM, IT IS VERY UNLIKELY FOR ANY MAIN STEM RIVER TO REACH
EVEN MONITOR/ACTION STAGE. RISK FOR ROCK AND MUDSLIDES WILL INCREASE
AND COULD IMPACT TRAVEL ON HIGHWAYS 299, 36, 101 AND 199.
ADDITIONAL RAIN STARTING SATURDAY NIGHT AND CONTINUING INTO EARLY
NEXT WEEK HAS THE POTENTIAL TO BE MORE IMPACTFUL. THERE IS STILL
SOME UNCERTAINTY ON THE POSITIONING AND HOW LONG THE HEAVIEST RAIN
WILL LAST, BUT THE HEAVIEST RAIN WILL START AROUND CAPE MENDOCINO
AND SOUTHWARD. THIS WILL AGAIN POSE A THREAT FOR QUICK RISES IN
STREAMS AND CREEKS ALONG WITH ROCK AND MUDSLIDES.
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. ENSEMBLES ARE SHOWING SLIGHTLY HIGHER PROBABILITIES FOR
MAIN STEM RIVERS TO REACH FLOOD STAGE WITHIN THE NEXT 10 DAYS. THE
HIGHEST CHANCES ARE MID TO LATE NEXT WEEK, BUT SOME POTENTIAL IS
THERE SUNDAY-TUESDAY. OVER THE NEXT TEN DAYS THE RFC GIVES THE
RUSSIAN RIVER AT HOPLAND A 33% CHANCE TO REACH MINOR FLOOD STAGE.
THE NAVARRO RIVER AT NAVARRO HAS A 24% CHANCE TO REACH MINOR FLOOD
STAGE. THE EEL RIVER AT FERNBRIDGE HAS A 20% CHANCE TO REACH MINOR
FLOOD STAGE AND A 53% CHANCE TO REACH ACTION/MONITOR STAGE. THE MAD
RIVER AT ARCATA HAS A 40% CHANCE TO REACH ACTION/MONITOR STAGE BUT
NO ENSEMBLE MEMBERS SHOW FLOOD STAGE AS A POSSIBILITY.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
WIND ADVISORY FROM 5 PM THIS AFTERNOON TO 8 AM PST FRIDAY
FOR CAZ101.
FLOOD WATCH FROM MIDNIGHT PST TONIGHT THROUGH FRIDAY
MORNING FOR CAZ101>106.
WIND ADVISORY UNTIL 8 AM PST FRIDAY FOR CAZ102.
WIND ADVISORY FROM 10 PM THIS EVENING TO 8 AM PST FRIDAY
FOR CAZ103.
WIND ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST FRIDAY
FOR CAZ104.
WIND ADVISORY FROM 7 PM THIS EVENING TO 8 AM PST FRIDAY FOR
CAZ105-106.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 7 PM PST THIS EVENING FOR PZZ450.
GALE WARNING FROM 7 PM THIS EVENING TO 9 AM PST FRIDAY FOR
PZZ450.
GALE WARNING UNTIL 9 AM PST FRIDAY FOR PZZ470.
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 9 AM PST
FRIDAY 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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