740
FXUS66 KEKA 251152
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
452 AM PDT FRI APR 25 2025
SYNOPSIS
SCATTERED TO NUMEROUS SHOWERS ARE EXPECTED TODAY 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
THE ELONGATED TROUGH FURTHER SEPARATES ITSELF FROM THE
UPPER LEVEL WESTERLY FLOW, BECOMING MORE OF A SPLIT FLOW CYCLONIC
LOW THIS MORNING. HAVING MOST OF THE CONVERGENCE AREA OF THE LOW
POSITIONED FAR SOUTH AND WEST OF OUR CWA, TRENDS US TO LESS OF A
CONVECTIVE THREAT ALTHOUGH INSTABILITY AND MODERATE MOISTURE ARE
PRESENT. MID LEVEL CAPPING WILL KEEP CONVECTION SHALLOW AND THE
MODEL SOUNDINGS REFLECT THIS AS WELL WITH VERTICAL BUOYANCY STIFLED,
KEEPING THUNDERSTORMS LIMITED IN DEVELOPMENT. SOME LIGHTNING IS
POSSIBLE AND WE STILL SEE 15% THUNDERSTORM PROBABILITIES FOR THE
INTERIOR MOUNTAINS OF TRINITY, MENDOCINO, AND LAKE COUNTIES
BORDERING THE EASTERN PERIPHERY. SHALLOW CONVECTION WILL NOT HINDER
RAINFALL AS WE SEE THE 50 MEMBER ECMWF ENSEMBLE SHOWING AN AVERAGE
OF 0.2 INCHES OVER THE NEXT 48 HOURS FOR MOST OF THE CWA, WITH
SOUTHERN MENDOCINO AND SOUTHERN LAKE A BIT LOWER IN ACCUMULATION.
CAMS INDICATED ISOLATED SHOWERS MOVING TOWARD THE NORTH COAST WITH
THE FLOW ALOFT SHIFTING THIS MORNING. SCATTERED TO NUMEROUS SHOWERS
ARE EXPECTED THIS AFTERNOON THROUGH SATURDAY AS THE CUTOFF LOW
CONTINUES 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 6000-7000 FEET WILL
PERSIST THROUGH THE DAY. MVFR CEILINGS ARE FORECAST TO PREVAIL,
HOWEVER SHALLOW MOISTURE AND NORTHWESTERLY SURFACE FLOW WILL LIKELY
YIELD PERIODS OF IFR CONDITIONS IN LIGHT PRECIP THIS MORNING FOR
COASTAL AERODROMES. CUMULUS CONVECTION AND POSSIBLE THUNDERSTORMS
ARE LIKELY TO RETURN OVER THE INTERIOR THIS AFTERNOON AND EARLY
EVENING. WRAP AROUND MOISTURE AND RAIN MAY ALSO RESULT IN MVFR
CONDITIONS (20% CHANCE) LATER TONIGHT/SATURDAY FOR LOCATIONS OUTSIDE
OF THE AERODROME AIRSPACE.
MARINE
LIGHT NW WIND (5 TO 15 KT) IS FORECAST TO CONTINUE FOR
FRIDAY WITH STEEP SEAS REMAINING AROUND 4-6 FEET. THESE LIGHTER
WINDS ARE COSED BY A WEAK SURFACE LOW AND COLD FRONTAL SYSTEM
APPROACHING THE OUTER WATERS CONTINUING TO WEAKEN THE PRESSURE
GRADIENT ACROSS NW CALIFORNIA WATERS.
IN THE WAKE OF THE FRONTAL SYSTEM, NORTHERLY WINDS WILL BEGIN TO
INCREASE TONIGHT THROUGH SATURDAY AS HIGH PRESSURE BUILDS EASTWARD
TOWARD THE OUTER WATERS. OFFSHORE PRESSURE GRADIENTS TIGHTEN BY
SATURDAY. NBM PROBABILITY FOR WIND GUSTS >34 KT INCREASE TO ~50% ON
SATURDAY AFTERNOON IN THE OUTER WATERS DOWNWIND OF POINT ST. GEORGE
AND CAPE MENDOCINO. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR
SATURDAY AFTERNOON DUE TO STEEP WIND WAVES BUILDING QUICKLY IN
RESPONSE TO THESE GUSTY WINDS. WIND GUSTS UP TO 30 KTS ARE EXPECTED
ON SUNDAY OVER THESE SAME AREAS. OUR SPRING TIME NORTHERLY WINDS
WILL RETURN THIS WEEKEND AND CONTINUE INTO AT LEAST EARLY NEXT WEEK.
THERE IS A CHANCE FOR GALE FORCE GUSTS OVER 34 KTS (40 - 50%
PROBABILITY) ON MONDAY AFTERNOON SOUTH OF CAPE MENDOCINO. THE
DURATION AND COVERAGE APPEARS QUITE LIMITED AS OF RIGHT NOW AND NO
HEADLINES ARE NECESSARY. DB/DS
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 3 PM SATURDAY TO 9 AM PDT SUNDAY
FOR PZZ450-455-470-475.
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