661
FXUS66 KEKA 242213
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
313 PM PDT THU APR 24 2025
SYNOPSIS
SHOWERS AND ISOLATED INTERIOR THUNDERSTORMS THIS
AFTERNOON AND EVENING. SCATTERED TO NUMEROUS SHOWERS ARE EXPECTED
FRIDAY THROUGH SATURDAY AS THE CUTOFF LOW MOVES SOUTHWARD. BELOW
NORMAL HIGH TEMPERATURES ARE EXPECTED ON SATURDAY. FOLLOWED BY DRY
AND WARMING TREND SUNDAY THROUGH MID NEXT WEEK.
DISCUSSION
AN ELONGATED UPPER LEVEL TROUGH CONTINUE TO DIG
SOUTHWARD ALONG THE WEST COAST. COASTAL STRATUS REMAIN BLANKETED
THE WEST COAST THIS AFTERNOON, WHILE CUMULUS CLOUDS HAS BEEN
DEVELOPING OVER THE INTERIOR HIGHER TERRAIN DUE TO AN ELEVATING
INSTABILITY, ESPECIALLY AROUND THE TRINITY ALPS AND YOLLA BOLLY.
LATEST DOPPLER RADAR DEPICTS LIGHT TO MODERATE SHOWERS DEVELOPING
ACROSS TRINITY COUNTY. THERE REMAIN A POTENTIAL (15-25%) FOR
THUNDERSTORMS LATE THIS AFTERNOON AND EVENING. THE BEST CHANCE OF
THUNDERSTORMS WILL BE OVER TRINITY COUNTY.
TONIGHT INTO FRIDAY, THE UPPER LEVEL TROUGH SPLIT AND BECOMES IN
A CUTOFF LOW OFF OR/CA COAST. THIS WILL BRING AN INCREASING MID TO
HIGH LEVEL MOISTURE ACROSS THE REGION. CAMS INDICATED ISOLATED
SHOWERS MOVING TOWARD THE NORTH COAST WITH THE FLOW ALOFT
SHIFTING TO SOUTH-SOUTHEAST FRIDAY MORNING. SCATTERED TO NUMEROUS
SHOWERS ARE EXPECTED FRIDAY AFTERNOON THROUGH SATURDAY AS THE
CUTOFF LOW CONTINUE DRIVING SOUTHWARD ALONG THE COAST TOWARD
CENTRAL CALIFORNIA. SATURDAY'S HIGH TEMPERATURES ARE FORECASTED
TO BE 5 TO 12 DEGREES BELOW NORMAL. ECMWF EXTREME FORECAST INDEX
(EFI) HIGHLIGHT HIGHS IN THE 60TH-80TH PERCENTILE BELOW NORMAL
TEMPERATURES ON SATURDAY, ESPECIALLY FOR THE INTERIOR AREAS IN
SOUTHERN HUMBOLDT, INTERIOR MENDOCINO AND LAKE COUNTY. OVERNIGHT
TEMPERATURES ARE EXPECTED TO REMAIN IN THE 40S ACROSS THE VALLEYS
DUE TO LINGERING LOW LEVEL MOISTURE.
SUNDAY CLEARING SKIES ARE EXPECTED AND TEMPERATURES WILL START TO
WARM BACK UP AGAIN AS A HIGH PRESSURE BEGIN TO BUILDS IN
DOWNSTREAM IN THE WAKE OF THE TROUGH. INLAND AREAS ARE EXPECTED
TO SEE HIGHS IN THE 60S. SUNDAY NIGHT INTO MONDAY MORNING IS
EXPECTED TO BE THE COLDEST NIGHT AND FROST IS POSSIBLE IN THE
COLDER VALLEYS. HIGH PRESSURE CONTINUES TO BUILD IN THROUGH THE
WEEK WITH HIGHS AROUND 80 FOR THE INLAND AREAS BY WEDNESDAY.
AVIATION
A DEEP MARINE LAYER WITH TOPS UP TO 3500 FEET IS
FORECAST TO PERSIST TONIGHT INTO FRIDAY. MVFR CEILINGS ARE FORECAST
TO PREVAIL, HOWEVER SHALLOW MOISTURE AAD NORTHWESTERLY SURFACE FLOW
WILL LIKELY YIELD PERIODS OF IFR CONDITIONS IN LIGHT PRECIP TONIGHT
INTO FRIDAY MORNING FOR COASTAL AERODROMES. CUMULUS CONVECTION AND
POSSIBLE THUNDERSTORMS ARE ALSO EXPECTED OVER THE INTERIOR THIS
AFTERNOON AND EARLY EVENING. WRAP AROUND MOISTURE AND RAIN MAY ALSO
RESULT IN MVFR CONDITIONS (20% CHANCE) LATER TONIGHT/FRIDAY FOR
LOCATION OUTSIDE AERODROME AIRSPACE. DB
MARINE
WAVE SPECTRUM REMAINED HEAVILY SKEWED TOWARD SHORTER
PERIOD BANDS (LESS 8 SECONDS) TODAY. MULTIPLE MID PERIOD WAVE BANDS
WERE ALSO PRESENT, CENTERED NEAR 14 AND 11 SECONDS. LONGER PERIOD W
AND SW SWELL GROUPS (>15 SECONDS) WERE CONTRIBUTING MUCH LESS TO THE
TOTAL SEA STATE WHICH HAS BEEN FLUCTUATING NEAR 5 FT. A LIGHTER NW
WIND REGIME (5 TO 15 KT) IS FORECAST TO CONTINUE FOR TONIGHT AND
FRIDAY WITH STEEP SEAS CONTINUING ON A DOWNWARD TREND.
A WEAK SURFACE LOW AND COLD FRONTAL SYSTEM WILL APPROACH THE OUTER
WATERS TONIGHT AND CONTINUE TO WEAKEN THE PRESSURE GRADIENT ACROSS
NW CALIFORNIA WATERS. LIGHTER WINDS AROUND 5 TO 15 KT WITH SEAS 5 FT
OR LESS ARE FORECAST ON FRIDAY. IN THE WAKE OF THE FRONTAL SYSTEM,
NORTHERLY WINDS WILL BEGIN TO INCREASE FRIDAY NIGHT THROUGH SATURDAY
AS HIGH PRESSURE BUILDS EASTWARD TOWARD THE OUTER WATERS. PRESSURE
GRADIENTS TIGHTEN SOME BY SATURDAY, HOWEVER THERE ARE CONSIDERABLE
DIFFERENCES BETWEEN THE MODELS AND THE RATE AT WHICH NORTHERLY WINDS
INCREASE SATURDAY. NBM PROBABILITY FOR WIND GUSTS > 25 KT INCREASE
TO 60-70% ON SATURDAY, HIGHEST IN THE OUTER WATERS AND DOWNWIND OF
CAPE MENDOCINO. WIND GUSTS UP TO 30 KTS ARE EXPECTED BY SUNDAY OVER
THESE SAME AREAS. OUR SPRING TIME NORTHERLY WIND REGIME WILL RETURN
THIS WEEKEND AND CONTINUE INTO AT LEAST EARLY NEXT WEEK. THERE IS A
CHANCE FOR GALE FORCE GUSTS OVER 34 KTS (40% CHANCE) ON MONDAY,
MAINLY FOR THE AFTERNOON SOUTH OF CAPE MENDOCINO. THE DURATION AND
COVERAGE APPEARS QUITE LIMITED AND NO HIGHLIGHTS ARE NECESSARY. DB
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
NONE.
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