144
FXUS66 KEKA 101533
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
833 AM PDT WED SEP 10 2025
SYNOPSIS
PERIODS OF RAIN AND THUNDERSTORMS ARE EXPECTED THIS
AFTERNOON ACROSS THE INTERIOR LATE THIS MORNING THROUGH THIS
EVENING WITH LOCALLY HEAVY RAINFALL. A SHOWER OR TWO MAY MAKE IT
OUT TO THE COAST IN THE AFTERNOON. THURSDAY A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE OVER THE MOUNTAINS. FRIDAY AND SATURDAY
ARE EXPECTED TO REMAIN DRY WITH MORE RAIN POSSIBLE SUNDAY AND
MONDAY WITH DRY WEATHER RETURNING AFTER THAT.
UPDATE
LOWERED THE PROBABILITY FOR RAIN ALONG THE COAST TODAY.
NOW IT LOOKS LIKE THERE WILL JUST BE A SLIGHT CHANCE FOR A
SHOWER OR TWO IN THE MID TO LATE IN THE AFTERNOON IF ANY OCCUR.
FARTHER INLAND REMAINS ON TRACK TO SEE SCATTERED SHOWERS AND
THUNDERSTORMS.
AVIATION.
IFR TO LIFR CONDITIONS ALONG THE COASTAL TERMINALS
DUE TO STRATUS AND DEGRADED VISIBILITIES. LAMP PROBABILITIES SHOWS
HIGH CONFIDENCE (>75%) IN THE CONTINUATION OF MVFR CEILINGS BELOW
3KFT AGL AND ONLY A 30% PROBABILITY OF CEILINGS STAYING BELOW
1KFT AGL (30%) MIDDAY THROUGH THE EARLY EVENING (21Z-03Z. LIGHT
VARIABLE WINDS ARE EXPECTED THIS MORNING BEFORE TURNING INTO LIGHT
NORTHERLY BREEZES, POTENTIALLY INCREASING DAYTIME MIXING/
PERIODIC SCATTERING AT TERMINAL SITES.
KUKI IS ALSO OBSERVING LOW, MVFR CEILINGS. FOR KUKI AND OTHER INLAND
TERMINALS, HREF MODEL DATA IS CONFIDENT IN THE CONTINUATION OF
CLOUDS AROUND INLAND TERMINALS TODAY AS CONVECTION IS FORECASTED
NEAR THE YOLLA BOLLYS AS WELL AS IN MENDOCINO AND LAKE COUNTIES.
GUSTY OUTFLOWS/INFLOW WINDS ARE POSSIBLE, AS IS LOCALLY MODERATE TO
HEAVY RAIN. TURBULENCE IS POSSIBLE NEAR ALL TERMINALS DUE TO MICRO-
SCALE UPDRAFT WINDS. IN AREAS WITHOUT CONVECTION, AFTERNOON BREEZES
ARE EXPECTED.
PREV DISCUSSION
/ISSUED 126 AM PDT WED SEP 10 2025/
DISCUSSION...DOPPLER RADAR DEPICTS PATCHES OF LIGHT TO LOCALLY
MODERATE RAIN SHOWERS CONTINUE MOVING ACROSS THE AREA OVERNIGHT.
THIS SHOWERS ARE EXPECTED TO DIMINISH INTO THE EARLY MORNING AS
THE SURFACE LOW CONTINUE TO MOVES SLOWLY EAST AND SOUTH.
THE COLD CLOSED UPPER LOW BECOMES VERTICALLY STACKED OVER NORTHERN
CALIFORNIA TODAY. SCATTERED TO ISOLATED THUNDERSTORMS ARE EXPECTED
THIS AFTERNOON AND EVENING OVER THE INTERIOR. THE MAIN THREAT,
OTHER THAN CLOUD-TO-GROUND LIGHTNING STRIKES, WILL ONCE AGAIN BE
HEAVY RAIN RATES AND THE POTENTIAL OF LOCALIZED FLOODING OF LOW
LYING AREAS AND PONDING OF WATER ON ROADS. HOURLY RAIN RATES ARE
EXPECTED TO INCREASE FARTHER SOUTH INTO NE MENDOCINO COUNTY AND
LAKE COUNTY. MAX HOURLY RATES AROUND 0.25 TO 0.40 IN/HR ARE
GENERALLY EXPECTED, THOUGH TOPOGRAPHIC FORCING COULD YIELD IN
LOCALLY HIGHER RATES AROUND 0.50 TO 0.80 IN/HR. THE HREF PROBABILITY
OF 1HR PRECIPITATION OVER 0.50 IN/HR SHOWS THE HIGHER CHANCE
(15-30%) OVER THE HIGHER TERRAIN IN LAKE COUNTY LATE THIS AFTERNOON.
MEANWHILE, SUBSTANTIAL DOWNSLOPING EFFECT WILL RESULT IN LESS
SHOWER CHANCES ALONG THE COAST. TEMPERATURES ARE EXPECTED TO BE
FAIRLY SIMILAR TO TUESDAY.
THURSDAY HIGH PRESSURE STARTS TO BUILD INTO THE AREA AND THIS WILL
LIMIT THE POTENTIAL FOR CONVECTION. A FEW SHOWERS ARE POSSIBLE IN
THE FAR EASTERN MOUNTAINS FROM TRINITY COUNTY DOWN TO LAKE COUNTY.
THERE MAY BE FAIRLY WIDESPREAD FOG THURSDAY NIGHT INTO FRIDAY
MORNING. DRY WEATHER AND CLEARING SKIES ARE EXPECTED FRIDAY.
FOR THE WEEKEND, ENSEMBLE CLUSTER INDICATES THE SHORTWAVE RIDGE
SHIFTING EASTWARD. MEANWHILE, AN UPSTREAM UPPER LEVEL TROUGH AND
EMBEDDED CUTOFF TROUGH APPROACHES THE AREA. THERE IS A LOT OF
UNCERTAINTY ABOUT THE EVOLUTION OF THIS SYSTEM ACROSS THE AREA.
JUST 14% OF THE CLUSTER BRING PRECIPITATION ACROSS THE AREA ON
SUNDAY. CLUSTER ARE TRENDING TO INCREASE THE CHANCE OF
PRECIPITATION SUNDAY NIGHT AND MONDAY. MEANWHILE, THE GFS AND
ECMWF ARE IN A BETTER AGREEMENT BRINGING PRECIPITATION ON SUNDAY,
ALTHOUGH DEFFER IN THE LOCATION. THIS MAY ALSO BRING SOME CHANCES
FOR THUNDER AS WELL. /ZVS
AVIATION...6Z TAFS)...STRATUS HAS BROUGHT IFR TO LIFR CONDITIONS
TO THE COASTAL TERMINALS LATE THIS EVENING. UKI IS ALSO OBSERVING
IFR TO MVFR CEILINGS, AND MODELS ARE IN DECENT AGREEMENT FOR THIS TO
CONTINUE FOR MUCH OF THE NIGHT, EVEN AS SHOWERS WIND DOWN. CEILINGS
ARE LIKELY TO LIFT IN THE LATE MORNING HOURS, WHICH IS EXPECTED TO
BRING VFR CONDITIONS BACK TO UKI. THERE IS GREATER UNCERTAINTY ON
IF CEILINGS WILL SCATTER OR CLEAR IN THE AFTERNOON AT THE COASTAL
TERMINALS. NBM IS SHOWING AROUND A 60% CHANCE FOR AT LEAST MVFR
CEILINGS TO CONTINUE THROUGH THE AFTERNOON. REGARDLESS, STRATUS WILL
LIKELY MAKE A RETURN TO THE COAST IN THE EVENING AND OVERNIGHT. /JB
MARINE...AN AREA OF LOW PRESSURE MOVES ONSHORE EARLY THIS MORNING
AND NORTHERLY WINDS ARE FORECAST TO INCREASE BEHIND IT. WINDS PEAK
AT AROUND 20-25 KTS IN THE OUTER WATERS BY LATE MORNING AND EARLY
AFTERNOON. SEAS REMAIN MILD, WITH BOTH A SMALL NORTHWESTERLY SWELL
AND A SOUTHERLY SWELL BEING OBSERVED EARLY THIS MORNING. NORTHERLY
WIND WAVES ARE EXPECTED TO BUILD AGAIN TO 6-7 FT WITH THESE ELEVATED
WINDS BY THURSDAY. A LONG PERIOD NORTHWESTERLY SWELL OF 5-6 IS
FORECAST TO FILL IN THURSDAY NIGHT INTO FRIDAY. COMBINED SEAS MAY
REACH 7-9 FT BY FRIDAY WITH THE COMBINATION OF THE SWELL AND THE
WIND WAVES. WINDS EASE AGAIN THIS WEEKEND AS ANOTHER SYSTEM
APPROACHES THE AREA. SEAS REMAIN ELEVATED AS A LARGER MID-PERIOD NW
SWELL FILLS IN SUNDAY. /JB
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM PDT
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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