972
FXUS66 KEKA 172318
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
318 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 SPREAD SOUTHWARD AND HAVE GREATER
IMPACTS ON LAKE AND MENDOCINO COUNTIES THIS WEEKEND AND NEXT WEEK.
KEY MESSAGES
- POWER OUTAGES POSSIBLE WITH STRONG GUSTY WINDS THURSDAY NIGHT
AND FRIDAY MORNING FOR DEL NORTE AND NORTHERN HUMBODLT.
- SLIGHT RISK FOR URBAN AND SMALL STREAM FLOODING AND MUDSLIDES
DUE TO HEAVY RAINFALL IN DEL NORTE, HUMBOLDT, TRINITY AND FAR
NW MENDOCINO COUNTIES LATE THURSDAY NIGHT INTO FRIDAY.
- IMPACTFUL RAIN TO SPREAD INTO SOUTHERN MENDOCINO AND SOUTHERN
LAKE COUNTIES THIS WEEKEND AND EARLY NEXT WEEK.
- PARADE OF MOIST PACIFIC STORMS TO CONTINUE ALL 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. ECMWF ENSEMBLE MEAN PEAK WIND GUSTS ARE
NEAR 45 MPH WHICH MAY BE TOO HIGH IF THE ATMOSPHERE REMAINS TOO
STABLE. A WIND ADVISORY HAS BEEN ISSUED WHERE THERE ARE IMPACTS.
HIGH TERRAIN AND RIDGES WILL GUSTS TO 50-60 MPH FOR SURE, HOWEVER
THERE WILL BE NO IMPACTS. SNOW LEVELS WILL RAPIDLY INCREASE TONIGHT
AND THU IN ADVANCE OF THE NEXT IVT PLUME, ABOVE 7000-8000 FT.
HEAVY RAIN AND POTENTIAL FLOODING TO INCREASE ON FRIDAY. SHORT
DURATION OF THE HEAVY RAIN RATES, 6 HOURS OR LESS, WILL LIKELY
LIMIT THE RISK FOR MORE URBAN AND SMALL STREAM FLOODING.
FRONTAL BOUNDARY/IVT PLUM ON FRIDAY WILL SAG SOUTH INTO SRN MENDO
AND SRN LAKE BY SAT MORNING. PRECIP SHOULD WIND DOWN IN THE
NORTHERN ZONES. PRECIP WILL CONTINUE FOR MENDO AND LAKE ZONES ALL
WEEKEND. MODELS DIVERGE ON DEVELOPMENT OF A NEW FRONTAL WAVE AND
NORTHWARD SURGE OF IVT THIS WEEKEND. IT IS LIKELY THAT LAKE AND
MENDOCINO WILL BE IN THE BULLSEYE FOR MODERATE TO LOCALLY HEAVY
RAIN, COMPARED TO ALL THE IVT STORMS THIS WEEK WHICH HAVE BEEN
FOCUSED ON DEL NORTE, HUMBOLDT AND TRINITY. THE PRECIP MAX COULD
EASILY SHIFT NORTHWARD AS WE HAVE SEEN MANY TIMES BEFORE. LOOKING
AT THE CHANCE FOR IVT > 250 KG/M/S THE FOLLOWING WEEK DEC 22-28,
CONFIDENCE IS MODERATE TO HIGH IN WET WEATHER CONTINUING ALL NEXT
WEEK. THIS WILL HAVE IMPACTS ON TRAVEL FOR THE HOLIDAYS, SO STAY
TUNED TO THE LATEST WATCHES, ADVISORIES AND WARNINGS AND PLAN
ACCORDINGLY.
AVIATION...(18Z TAFS)
VFR CONDITIONS PERSIST THROUGH THE NORTH
COAST TODAY WITH SCATTERED LOW CLOUDS INLAND, MOSTLY AROUND ELEVATED
TERRAIN. COASTAL WINDS REMAIN LIGHT THROUGH THE EVENING. WINDS
INLAND REMAIN LIGHT IN DEL NORTE, HUMBOLDT, AND TRINITY COUNTIES
THROUGH THE DAY WHEREAS MENDOCINO AND LAKE COUNTIES CAN EXPECT
GUSTIER WINDS TODAY UP TO 20KTS OR SO. TONIGHT INTO TOMORROW,
ANOTHER FRONTAL SYSTEM WILL IMPACT NW CA. SOUTHERLY WINDS WILL BUILD
ALONG THE COAST TO 20-30KT GUSTS. MODEL DATA SHOWS ONLY A 20-30%
PROBABILITY OF IFR CEILINGS AT KCEC AND KACV TOMORROW, YET A HIGH
PROBABILITY OF MVFR CEILINGS THROUGH THE DAY (>70%). INLAND
TERMINALS SHOW A SLIGHT CHANCE OF VALLEY FOG DUE TO INCREASED
MOISTURE TONIGHT BEFORE MVFR CEILINGS FORM TOMORROW MORNING. THE
FINAL NOTE WITH THIS STORM IS INCREASED WINDS ALOFT FOR COASTAL
TERMINALS. MODEL SOUNDINGS SHOW A LOW LEVEL JET OF SW WINDS AT 40-
45KTS AT 2000-2500FT AGL, INCREASING THE CHANCE FOR LOW LEVEL
TURBULENCE AND MOUNTAIN WAVE ACTIVITY TOMORROW BEGINNING IN
THE EARLY MORNING AND LASTING THROUGH THE MORNING FRIDAY. DS
MARINE
NORTHERLY TO NORTHWESTERLY WINDS WILL DIMINISH TO 5 TO
15 KT BY MIDDAY. THIS AFTERNOON THE NORTHWEST SWELL IS EXPECTED TO
INCREASE ONCE AGAIN TO AROUND 10 TO 13 FEET. FOR THE NORTHERN
WATERS, HAVE EXTENDED THE PREVIOUS SMALL CRAFT ADVISORY RIGHT
THROUGH THE START OF THE GALE WATCH DUE TO LINGERING WIND WAVES.
THE SWELL IS EXPECTED TO BRIEFLY REACH 10 FEET IN THE SOUTHERN
OUTER WATERS AND THE SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR
THAT.
TONIGHT INTO THURSDAY, THE WINDS ARE EXPECTED TO BECOME SOUTHERLY
AGAIN AS ANOTHER FRONTAL SYSTEM PASSES OVER THE AREA. THESE WINDS
ARE EXPECTED TO INCREASE TO 15-30 KT MIDDAY THURSDAY THROUGH EARLY
FRIDAY MORNING WITH THE STRONGER WINDS NORTH OF CAPE MENDOCINO. GALE
FORCE GUSTS ARE LIKELY IN THE NORTHERN WATERS (50-80%), AND THE
FORECAST TREND HAS SUPPORTED SLIGHTLY WIDER COVERAGE OF STRONGER
WINDS AS WELL. THEREFORE, THE GALE WATCH IN THE NORTHERN OUTER
WATERS REMAINS ON TRACK AND A GALE WATCH HAS BEEN HOISTED FOR THE
NORTHERN INNER WATERS FOR THURSDAY NIGHT INTO FRIDAY MORNING.
FRIDAY AND SATURDAY THE WINDS ARE EXPECTED TO DIMINISH AND GENERALLY
BE LESS THAN 20 KT. ANOTHER STORM SYSTEM IS EXPECTED ON SATURDAY,
YET THERE IS WIDE VARIABILITY AND SPREAD IN THE MODEL SOLUTIONS FOR
HOW THIS WEEKEND STORM WILL DEVELOP AND WHERE THE BULK OF THE WINDS
WILL BE FOR THE COASTAL WATERS.
HYDROLOGY
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. WIDESPREAD MODERATE TO
LOCALLY HEAVY RAIN RATES ARE EXPECTED TO SPREAD SOUTHEASTWARD
THROUGH THE DAY ON FRIDAY. ONCE AGAIN LOCALIZED MINOR URBAN AND
SMALL STREAM FLOODING WILL BE POSSIBLE FOR DEL NORTE, HUMBOLDT,
TRINITY AND NW MENDOCINO. THE DURATION AND MAGNITUDE OF THE
MOISTURE FLUX IS LOWER AND 1-HOURLY, 3-HOURLY AND 6-HOURLY PRECIP
RATES INITIALLY SEEM LOWER COMPARED TO THE RAINSTORM LAST NIGHT.
THERE WILL BE OVER 24 HOURS BEFORE HEAVY RAIN DEVELOPS AGAIN
WHICH SHOULD HELP TO REDUCE THE RISK FOR FLOODING. RISK FOR ROCK
AND MUDSLIDES WILL INCREASE AND COULD IMPACT TRAVEL ON HIGHWAYS
299, 36, 101 AND 199, ESPECIALLY DURING THE DAY ON FRIDAY.
ALL MAIN STEM RIVERS ARE FORECAST TO REMAIN BELOW ACTION OR MONITOR
STAGES THROUGH THURSDAY. 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 STILL HAS OUR FORECAST PEGGED WITH A 5-15% 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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