175
FXUS66 KEKA 302341
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
341 PM PST TUE DEC 30 2025
SYNOPSIS
LIGHT TO MODERATE RAIN RETURNS FROM SOUTH TO NORTH
WEDNESDAY INTO THURSDAY, FOLLOWED BY A FRONTAL SYSTEM WITH MODERATE
TO HEAVY RAIN, HIGH MOUNTAIN SNOW, AND GUSTY WINDS ON FRIDAY.
CHANCES FOR MODERATE TO PERHAPS LOCALLY MAJOR COASTAL FLOODING
INCREASE THURSDAY THROUGH SATURDAY. BOUTS OF RAIN AND GUSTY WINDS
ARE FORECAST TO CONTINUE INTO THE WEEKEND AND LIKELY NEXT WEEK.
KEY MESSAGES
-MINOR COASTAL FLOODING IS EXPECTED WEDNESDAY AROUND HUMBOLDT BAY.
-PERSISTENT SOUTHERLY WINDS, HEAVY RAINFALL, AND HIGH SURF MAY
CONTRIBUTE TO MODERATE TO LOCALLY MAJOR COASTAL FLOODING THURSDAY
THROUGH SATURDAY IF SOUTHERLY WINDS AND HEAVY RAINFALL ALIGN.
-STRONG SOUTHERLY WINDS, WIDESPREAD MODERATE TO LOCALLY HEAVY
RAINFALL FROM AN ATMOSPHERIC RIVER BRINGS AN INCREASED RISK OF
URBAN AND SMALL STREAM FLOODING LATE THURSDAY AND INTO SATURDAY.
-DIFFERENCES IN TIMING OF HEAVIEST RAINFALL ONSET REMAIN, AND
FORECAST RAINFALL TOTALS HAVE TRENDED SLIGHTLY HIGHER.
-PACIFIC STORM TRACK TO REMAIN OPEN AND ACTIVE, BRINGING A RISK
FOR ADDITIONAL STRONG STORM SYSTEMS OVER THE WEEKEND INTO EARLY
NEXT WEEK.
DISCUSSION
HIGH PRESSURE REMAINS OVER THE AREA TODAY, BRINGING
MAINLY CLEAR SKIES EXCEPT FOR FOG AND LOW OVERCAST IN SOME INTERIOR
VALLEYS. TONIGHT INTO WED MULTI-LAYER CLOUDS ARE FORECAST TO SPREAD
OVER THE AREA FROM THE SOUTH IN ADVANCE OF AN UPPER LEVEL LOW
APPROACHING THE AREA FROM THE SOUTH. THIS IS EXPECTED TO KEEP
OVERNIGHT TEMPERATURES WARMER. SHALLOW HUMID LAYER FOR COASTAL AREAS
WILL LIKELY KEEP TEMPS WARMER AND MAY EVEN RESULT IN THICKER FOG
AND/OR LOW CLOUDS.
AN AREA OF LOW PRESSURE WILL PUSH INTO SOUTHERN TO CENTRAL CA
WEDNESDAY THROUGH THURSDAY. LIGHT TO LOCALLY MODERATE RAINFALL
WILL SPREAD IN FROM THE SOUTH WEDNESDAY AFTERNOON THROUGH
THURSDAY. GIVEN THE MULTIPLE DAYS OF DRYING, IMPACTS FROM THIS
FIRST SYSTEM ARE EXPECTED TO BE LITTLE TO NONE. PWATS DO INCREASE
TO OVER 250% OF NORMAL, AND SOME OF THE RIDGES FROM CAPE MENDOCINO
AND SOUTHWARD WILL RECEIVE 1-1.5 INCHES OF RAINFALL, POSSIBLE UP
TO 2 INCHES LOCALLY. SOUTHERLY WINDS WILL BECOME BREEZY ON THE
RIDGETOPS WEDNESDAY AFTERNOON, PARTICULARLY SOUTH THROUGH
SOUTHERN MENDOCINO AND LAKE COUNTY. SNOW LEVELS ARE EXPECTED TO
BE FAIRLY HIGH WITH THIS FIRST SYSTEM, LIKELY OVER 6,000 FEET.
A STRONG, NEGATIVELY TILTED TROUGH WITH A DEEPENING SURFACE LOW WILL
TAKE SHAPE OVER THE NE PACIFIC AND PUSH EAST TO NORTHEAST. THE STORM
SYSTEM WILL DELIVER A STRONG COLD FRONT WITH AN ASSOCIATED IVT
PLUME. ENSEMBLES HAVE BETTER AGREEMENT ON THE MAGNITUDE, WITH
ENSEMBLE MEAN JUST OVER 500 KG/M/S, WITH HIGHER END RANGE OF 625 AND
A MODERATE ATMOSPHERIC RIVER. THIS WILL BRING WIDESPREAD MODERATE
RAINFALL, WITH AREAS OF HEAVY RAINFALL RATES. THE MODELED POTENTIAL
DURATION OF CATEGORY ATMOSPHERIC RIVER REMAINS AT MODERATE CRITERIA
THROUGH LATE SATURDAY. THE MODERATE TO HEAVY RAINFALL WILL BE
SHORTER IN DURATION, BUT THIS REFLECTS BIG DIFFERENCES IN THE ONSET
TIMING, WHICH COULD BE AS EARLY AS FRIDAY MORNING OR LATER FRIDAY
NIGHT.
THE GFS IS HINTING AT A SECONDARY AREA OF LOW PRESSURE DEVELOPING
ALONG THE FRONT AND CLOSER TO THE COAST. THIS MAY BRING SOME HIGHER
WINDS TO THE COASTAL RIDGES, THE GFS SHOWS 60 KT WINDS AT 925MB
JUST OFF CAPE MENDOCINO. THERE IS STILL QUITE A BIT OF UNCERTAINTY
ON HOW MUCH STRONGER WINDS WILL MIX DOWN TO THE LOW ELEVATIONS
AROUND HUMBOLDT BAY AND OTHER AREAS ALONG THE COAST. RIDGES WILL
GUST TO 60 MPH OR MORE FOR SURE WITH 65+ KT AT 925MB. RAINFALL
RATES ARE EXPECTED TO BE HIGHER WITH THIS FRONT AS WELL, AND THE
THREAT FOR URBAN AND SMALL STREAM FLOODING WILL INCREASE. GRANTED
WE HAVE HAD MULTIPLE DAYS OF NO RAIN AND RECEDING WATER LEVELS
WHICH MAY MITIGATE TEE RISK FOR RAPID RUN- OFF. THE CURRENT
FORECAST HAS TRENDED HIGHER TO AROUND 1 TO 1.5 INCH IN THE VALLEY
AND RAIN SHADOW LOCATIONS WITH 2 TO 3.5 INCHES IN THE HIGHER
TERRAIN AND WINDWARD SLOPES OVER 36 HOURS.
HIGH TIDES AND RAINFALL RUN-OFF MAY RESULT IN FLOODING AROUND
HUMBOLDT BAY AND ALONG THE COAST. SNOW LEVELS ARE EXPECTED TO STAY
MAINLY OVER 5,000 FEET THROUGH FRIDAY EVENING AND THEN START TO
FALL LATE FRIDAY OR SATURDAY DEPENDING ON THE TIMING OF THE
SYSTEM. IT LOOKS LIKE THE COLDER AIR WILL MOVE IN AFTER THE
HEAVIER PRECIP, BUT THERE MAY BE SOME LIGHT SNOW DOWN TO 3,000 OR
4,000 FEET. GFS AND ECMWF MODELS ARE SHOWING COLD 500MB TEMPS
AROUND -25C, INSTABILITY AND STEEP LAPSE RATES. ISOLATED LOW
TOPPED THUNDERSTORMS AND SOME SMALL HAIL WILL BE POSSIBLE IN THE
COLDER AIR BEHIND THE FRONT LATE FRIDAY INTO SATURDAY. SNOW
LEVELS PLUNGE ON SATURDAY AND SOME LIGHT ACCUMULATIONS ARE
POSSIBLE DOWN TO 3500 FT. NBM SNOW LEVELS WILL NEED TO EVALUATED.
THE PACIFIC STORM TRACK IS TO REMAIN OPEN AND ACTIVE BRINGING A
RISK FOR ADDITIONAL STRONG STORM SYSTEMS OVER THE WEEKEND INTO
EARLY NEXT WEEK. JJW
AVIATION
LIGHT WINDS AND VFR CONDITIONS PREVAILED TUESDAY. A
FRONTAL SYSTEM TO THE SOUTH WILL BEGINS TO INCREASE SOUTHERLY
FLOW AND SURFACE MOISTURE TONIGHT. THIS WILL BRING A LOW
CONFIDENCE CHANCE FOR FOG AROUND HUMBOLDT BAY AND PERHAPS NORTH
ALONG THE NORTH COAST. CHANCES FOR FOG AND LOW CLOUDS QUICKLY
DECREASE AFTER 12Z. UKI RECEIVED SOME BRIEF FOG TUESDAY MORNING
AND CHANCES WERE LOWER FOR WEDNESDAY MORNING. LIGHT PRECIPITATION
WILL THEN BEGIN SPREADING IN FROM THE SOUTH WEDNESDAY AFTERNOON.
JJW
MARINE
LIGHT WINDS AND RELATIVELY LOW SEAS WILL PERSIST THROUGH
AT LEAST WEDNESDAY BEFORE CONDITIONS DETERIORATE LATER INTO THE
WEEK. FRESH SOUTHERLY WINDS WILL DEVELOP ON THURSDAY AND APPROACH
NEAR GALE BY FRIDAY AS A SURFACE TROUGH FROM THE GULF OF ALASKA DIGS
TOWARDS THE U.S. WEST COAST. NATIONAL BLEND OF MODELS IS
HIGHLIGHTING A 40-70% CHANCE OF WIND GUSTS EXCEEDING 34 KT ACROSS
THE NORTHWEST CALIFORNIA COASTAL WATERS, ESPECIALLY AROUND CAPE
MENDOCINO AND THE MENDOCINO COUNTY COAST. ADDITIONALLY, 925MB LEVEL
WINDS ARE PREDICTED BE 50 TO 70 KT WITH THIS SYSTEM. ANY INSTABILITY
ALONG WITH THE FRONTAL PASSAGE COULD POTENTIALLY MIX DOWN SOME STORM
FORCE GUSTS. THUS, WE WILL BE MONITORING THE POTENTIAL AND TIMING
FOR SMALL CRAFT ADVISORIES LEADING UP TO A POTENTIAL GALE WARNING
LATER IN THE WEEK. LARGE, STEEP SEAS WILL DEVELOP WITH THE APPROACH
OF THIS STORM SYSTEM WITH 10 TO 15 FOOT SEAS POSSIBLE IN THE WATERS
OVER THE WEEKEND. KZ
HYDROLOGY
A SERIES OF ATMOSPHERIC RIVERS WILL BRING AN INCREASED
RISK FOR URBAN AND SMALL STREAM FLOODING LATE THIS WEEK, THROUGH
THE WEEKEND AND LIKELY INTO NEXT WEEK. MAINSTEM RIVERS WILL ALSO
LIKELY RISE SHARPLY AND WILL NEED TO BE MONITORED FOR POSSIBLE
FLOOD STAGE EXCEEDANCE. BE ON THE LOOKOUT FOR WATCHES, ADVISORIES
AND WARNING AS THIS NEXT HEAVY RAIN EVENT UNFOLDS. STAY ALERT AND
REMEMBER TO NEVER ATTEMPT TO DRIVE THROUGH WATER COVERED ROADS.
WATER MAY BE MOVING MUCH FASTER THAN YOU THINK.
COASTAL FLOODING
ANOTHER ROUND OF VERY HIGH TIDES IS COMING UP
THE 31ST THROUGH 4TH. THE STORM SURGE MODELS ARE ALREADY SHOWING
NEARLY A FOOT OF SURGE, BUT HIGHER AMOUNTS ARE POSSIBLE IF STRONG
SOUTHERLY WINDS LINE UP WITH THE HIGHEST TIDES. THE HIGH TIDE PLUS
ANOMALY WILL LIKELY YIELD A HIGH TIDE OVER 8.8 FT AT THE NORTH
SPIT GAUGE WEDNESDAY. HIGH TIDES WILL LIKELY EXCEED 9 FT THURSDAY
THROUGH SATURDAY. THE STORM SURGE MODEL HAS BEEN CONSISTENTLY
MODELING A HIGH TIDE UP TO 10 FT AT NORTH SPIT FRIDAY. THIS
SCENARIO WOULD BRING 1 TO 1.5 FEET OF SALTWATER ONTO NORMALLY DRY
GROUND AROUND HUMBOLDT BAY, AND THIS IS PLAUSIBLE IF THE STRONG
WINDS, HEAVY RAINFALL AND BUILDING HIGH SURF ALIGN.
JJW
EKA WATCHES/WARNINGS/ADVISORIES
CA...
COASTAL FLOOD WATCH FROM THURSDAY MORNING THROUGH SATURDAY
AFTERNOON FOR CAZ101-103-104-109.
COASTAL FLOOD ADVISORY FROM 7 AM TO 9 AM PST WEDNESDAY FOR
CAZ103.
NORTHWEST CALIFORNIA COASTAL WATERS...
COASTAL FLOOD ADVISORY FROM 7 AM TO 9 AM PST WEDNESDAY FOR
PZZ415.
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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