620
FXUS66 KEKA 162243 CCA
AFDEKA
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE EUREKA CA
243 PM PST TUE DEC 16 2025
SYNOPSIS
MODERATE TO LOCALLY HEAVY RAIN TONIGHT FOR MOSTLY DEL
NORTE, HUMBOLDT, TRINITY AND NORTHERN MENDOCINO COUNTIES. LINGERING
SHOWERS EXPECTED WEDNESDAY AND THURSDAY. HEAVY RAIN ARRIVES AGAIN
LATE THURSDAY NIGHT INTO FRIDAY. MORE RAIN AND STRONG GUSTY WINDS
WILL BE POSSIBLE THIS WEEKEND.
KEY MESSAGES
- MODERATE TO LOCALLY HEAVY RAINFALL TONIGHT WITH A 5% CHANCE FOR
MINOR URBAN AND SMALL STREAM FLOODING FOR DEL NORTE, HUMBOLDT,
TRINITY AND NORTHERN MENDOCINO COUNTIES.
- A 15% CHANCE FOR MINOR FLOODING LATE THURSDAY NIGHT THROUGH
FRIDAY WITH ANOTHER ROUND OF MODERATE TO LOCALLY HEAVY RAIN.
- MORE RAIN WITH A 5% 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.
- ANOTHER POWERFUL STORM POSSIBLE THIS WEEKEND.
DISCUSSION
A LONG STREAM OF SUBTROPICAL MOISTURE (PWATS OVER
250% OF NORMAL HAS BEEN STREAMING INTO NORTHWEST CALIFORNIA
THROUGH THE DAY ALONG A QUASI-STATIONARY FRONT. SURFACE RAIN
REPORTS HAVE BEEN RECORDING WIDESPREAD HOURLY RATES FROM 0.10 TO
0.25 WITH LOCALLY HIGHER RATES AROUND 0.50-0.75IN/HR IN
TOPOGRAPHICALLY FAVORABLE LOCATIONS IN SW HUMBOLDT AND NW
MENDOCINO. CHANCE FOR MINOR URBAN AND SMALL STREAM FLOODING WILL
INCREASE TO AROUND 5% AS RAIN RATES INCREASE THIS EVENING AND
OVERNIGHT AS A WESTERLY IVT PLUME (MAX NEAR 750KG/M/S) INTERSECTS
THE COASTAL TERRAIN. CAMS ENSEMBLE HOURLY PRECIP MAX (>95TH
PERCENTILE) ARE OVER 0.75IN/HR ALONG WINDWARD-FACING TERRAIN,
MOSTLY DEL NORTE, HUMBOLDT AND NORTHWEST MENDOCINO. THIS WILL NEED
TO BE WATCHED FOR POSSIBLE RAPID RUN-OFF AND POSSIBLE ROCK/MUD
SLIDES. LIGHTER RAIN RATES (0.10IN/HR OR LESS) ARE EXPECTED FOR
SOUTHERN MENDOCINO AND LAKE COUNTIES. 48 HOUR STORM TOTAL RAINFALL
MAY NOT EXCEED 0.25 INCHES BY 4 AM WEDNESDAY.
GUSTY SOUTH AND SOUTHWEST WINDS ARE EXPECTED THIS EVENING AND
OVERNIGHT FOR THE COASTAL HEADLANDS AND RIDGES OF DEL NORTE AND
HUMBOLDT COUNTIES. PEAK WIND GUSTS AT LOWER ELEVATIONS WILL MOST
LIKELY RANGE FROM 20 TO 35 MPH, WITH 35 TO 45 MPH GUSTS OVER THE
MORE PROMINENT RIDGES AND WIND-PRONE TERRAIN OF DEL NORTE AND
HUMBOLDT. CAMS AND EC ENSEMBLE MEANS SUGGEST A MARGINAL WIND
ADVISORY TONIGHT FOR THE DEL NORTE COAST WITH PEAK NEAR 40 MPH.
CHANCE FOR GUSTS FROM 45-50 MPH FOR THE DEL NORTE COAST INCREASES
THU NIGHT INTO FRI MORNING AND A WIND ADVISORY MAY BE NECESSARY
AS A 925MB SPEED MAX AROUND 45-55KT DEVELOPS IN ADVANCE OF THE
NEXT FRONT THU. ECMWF ENSEMBLE MEAN PEAK WIND GUSTS ARE NEAR 45
MPH WHICH MAY BE TOO HIGH IF THE ATMOSPHERE BECOME TOO STABLE.
FOR NOW WILL HOLD ON HOISTING A WIND ADVISORY FOR THE COASTAL LOW
LANDS. HIGH TERRAIN FOR SURE WILL GUST TO 50 MPH OR MORE.
ABOVE AVERAGE WARMTH WILL KEEP SNOW SNOW LEVELS QUITE HIGH IN
GENERAL THROUGH FRI. SNOW LEVELS WILL DROP TO 3500-4500 FEET ON
WED BUT PRECIP AMOUNTS WILL FALL OFF AND ANY ACCUMULATIONS WILL BE
VERY LIGHT. SNOW LEVEL RAPIDLY INCREASE AGAIN THU NIGHT IN ADVANCE
OF THE NEXT IVT PLUME.
FRONTAL BOUNDARY ON FRIDAY WILL EVENTUALLY SAG SOUTH INTO SRN MENDO
AND SRN LAKE BY SAT MORNING AND PRECIP WILL WIND DOWN IN THE
NORTH. PRECIP MAY CONTINUE FOR SOUTHERN ZONES. MODELS DIVERGE ON
DEVELOPMENT OF A NEW FRONTAL WAVE AND NORTHWARD SURGE OF IVT THIS
WEEKEND LATER IN THE WEEKEND. WE COULD BE IN STORE FOR MORE HEAVY
RAIN AND STRONG WINDS THIS WEEKEND OR EARLY NEXT WEEK. 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 THE
LATTER PORTION OF DEC. IVT DIAGRAMS DO SHOW A SOUTHWARD SHIFT IN
IVT BUT THIS MAY SHIFT BACK NORTHWARD. STAY TUNED.
AVIATION...(18Z TAFS)
STORMS PASSING OVER NW CA ARE CAUSING
DEGRADED CONDITIONS TODAY AND WILL CONTINUE THROUGH THE NIGHT.
CONDITIONS HAVE FLUCTUATED SUPPOSEDLY TODAY WAS STORMS PASS
OVER/NEARBY THE TERMINAL SITES. PERIODS OF HEAVY RAIN ARE TO BE
EXPECTED THROUGH THE NIGHT AS MORE WAVES OF MOISTURE MAKE
LANDFALL. RAIN WILL INCREASE INTENSITY LATE TONIGHT WITH MORE
LIKELY THAN NOT CHANCES (>50% PROBABILITY) OF LIFR CONDITIONS AT
KCEC AND KACV THIS EVENING AND OVERNIGHT. KUKI WILL MORE LIKELY
EXPERIENCE IFR CONDITIONS LATE TONIGHT INTO TOMORROW MORNING,
ESPECIALLY IF LOW CLOUDS SETTLE INTO THE VALLEY IN THE WAKE OF
THIS STORM.
WINDS FROM THIS STORM HAVE UNDER PREFORMED THE FORECAST SO FAR
TODAY, YET THE BULK OF THE SOUTHERLY WINDS HAVE YET TO MAKE
LANDFALL. LATE TONIGHT AROUND 06Z IS WHEN THE BAND OF STRONGER WINDS
SHOULD BE PRESENT. WINDS ALOFT WILL BE MORE WESTERLY AND CAN REACH
SPEEDS UP TO 45KTS AT 2000-2500FT AGL. LOW LEVEL TURBULENCE AND
MOUNTAIN WAVES ARE TO BE EXPECTED THIS AFTERNOON AND TONIGHT.
MARINE
RAINSHOWERS AND FRESH TO STRONG BREEZES ARE EXPECTED
THROUGH THE WATERS THIS AFTERNOON. THE STRONGEST WINDS ARE
FORECASTED NORTH OF CAPE MENDOCINO WITH SUB GALE FORCE GUSTS UP TO
30KTS. LATE TONIGHT, AFTER THE WIND AND RAIN, THROUGH TOMORROW, SEAS
WILL CALM BEFORE ANOTHER STORMS PASSES OVER THE COASTAL WATERS
WEDNESDAY NIGHT THROUGH THURSDAY. GALE FORCE GUSTS IN THE NORTHERN
OUTER WATERS ARE LIKELY (+75%) ACCORDING TO REFS WIND SPEED DATA.
THE NBM IS SUGGESTING WINDS WILL BE STRONG GALES (40-45KTS), YET
FORECAST CONFIDENCE IN THIS OCCURRING IS NOT ENOUGH YET TO COMMIT TO
THIS RESOLUTION. THAT SAID, CHANGES ARE POSSIBLE AS MODEL DATA
HOPEFULLY STARTS TO ALIGN BETTER TOMORROW.
WINDS FROM THESE STORMS WILL CREATE STEEP SHORT PERIOD WIND WAVES UP
TO SIG. WAVE HEIGHTS OF 6FT TONIGHT. HAZARDOUS CONDITIONS WILL BE
PRESENT FOR SMALL CRAFTS IN THE NORTHERN OUTER WATERS THIS EVENING.
THIS NEXT STORM ON THURSDAY WILL CREATE MORE HAZARDOUS CONDITIONS IN
THE OUTER WATERS AND THE NORTHER INNER WATERS AS STEEP WIND WAVES UP
TO SIG. HEIGHT OF 10FT ARE FORECAST. WHILE THESE SOUTHERLY WIND
WAVES ARE FORMED AND CALM, A STEADY STREAM OF WESTERLY SWELLS WILL
ENTER THE WATERS REMAINING BETWEEN 8-11FT @ 11-12S THROUGH THE END
OF THE WORK WEEK. THIS WEATHER PATTERN DOES NOT SEEM TO CHANGE MUCH
AS WE ENTER THE WEEKEND AND NEXT WEEK. IN FACT, STORMS SEEM TO
INCREASE THERE HAZARD POTENTIAL THROUGH NEXT WEEK LOOKING AT LONG
TERM WEATHER MODEL DATA.
HYDROLOGY
ALL MAIN STEM RIVERS ARE FORECAST TO REMAIN BELOW
MONITOR OR ACTION STAGE THROUGH WEDNESDAY. HEAVY RAIN RATES
TONIGHT MAY RESULT IN MINOR URBAN/RURAL FLOODING, ESPECIALLY IN
AREAS WITH POOR DRAINAGE. ANOTHER PERIOD OF HEAVY RAIN IS FORECAST
TO ARRIVE LATE THU NIGHT AND PUSH SOUTHEASTWARD ACROSS THE AREA
ON FRIDAY. WITH SOIL MOISTURE BECOMING MORE SATURATED WITH THE
RAIN TONIGHT AND A HIGH CHANCE FOR HEAVY RAIN RATES ON FRIDAY,
MINOR FLOODING AND THE RISK FOR ROCK AND/OR MUDSLIDES WILL
INCREASE. CHANCE OF MAIN STEM RIVER STAGES TO EXCEED MINOR FLOOD
STAGE WILL INCREASE ABOVE 5-15% AS HEAD INTO THE LATTER PORTION
OF THE WEEKEND INTO THE FOLLOWING WEEK, DEC 22-26. AT HIGHEST RISK
ARE THE EEL RIVER AT FERNBRIDGE, NAVARRO RIVER AT NAVARRO AND
RUSSIAN RIVER AT HOPLAND. NOW THIS WILL DEPEND ON THE TRACK OF THE
TRACK OF A THIRD OR FORTH AR. IVT PLUME OVER 250 KG/M/S MAY END
UP SHIFTING TOO FAR SOUTH DURING THIS FRAME, LEAVING OUR BASINS IN
A COOLER AND DRIER WEATHER REGIME. STAY TUNED.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 11 AM PST THIS MORNING FOR
PZZ450.
SMALL CRAFT ADVISORY UNTIL 5 AM PST WEDNESDAY 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.
VISIT US AT HTTPS://WWW.WEATHER.GOV/EUREKA
FOLLOW US ON FACEBOOK AND TWITTER AT:
HTTPS://WWW.FACEBOOK.COM/NWSEUREKA
HTTPS://WWW.TWITTER.COM/NWSEUREKA
FOR FORECAST ZONE INFORMATION
SEE THE FORECAST ZONE MAP ONLINE:
HTTPS://WWW.WEATHER.GOV/IMAGES/EKA/ZONEMAP.PNG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page