853
FXUS66 KEKA 050705
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1205 AM PDT FRI SEP 5 2025
SYNOPSIS
DRIZZLE AND STRATUS CONTINUES TO BLANKET THE COAST.
INTERIOR TEMPERATURES TREND DOWNWARD INTO THE WEEKEND. WET WEATHER
POSSIBLY RETURNS LATE SUNDAY INTO EARLY NEXT WEEK, WITH MULTIPLE
CHANCES OF RAIN.
DISCUSSION
THE RIDGE OVER THE WESTERN PORTION OF THE U.S. HAS
STARTED TO MOVE EASTWARD AS AN UPPER TROUGH MOVES TOWARD THE AREA.
AS IT DOES, IT STARTS TO ELONGATE AND A SHORTWAVE TROUGH FORMS SOUTH
OF IT AND STARTS TO ROTATE TOWARDS THE COAST THIS EVENING AND
OVERNIGHT. ANOTHER TROUGH FOLLOWS AND ROTATES AROUND ON SATURDAY
EVENING. FINALLY, ON MONDAY THE UPPER LEVEL LOW STARTS TO BECOME AN
OPEN WAVE AND MOVE ONSHORE.
TODAY THROUGH SUNDAY THESE SHORTWAVES ROTATING AROUND THE LOW IS
EXPECTED TO ENHANCE THE COASTAL DRIZZLE. THE NBM IS STILL SHOWING A
20 TO 30 PERCENT CHANCE OF OVER A TENTH OF AN INCH OF DRIZZLE FOR
THE IMMEDIATE COASTLINE THIS MORNING. THESE PROBABILITIES DROP TO
AROUND 10 TO 20 PERCENT ALONG THE COAST FOR THE WEEKEND. AS THE AIR
ALOFT GETS COOLER AND THE INVERSION STARTS TO WEAKEN, THE CLOUDS AT
THE COAST MAY BREAK UP IN THE AFTERNOON, BUT OTHERWISE CLEARING MAY
BE LIMITED. FAIRLY SIGNIFICANT COOLING IS EXPECTED TODAY AND INTO
THE WEEKEND FOR INTERIOR AREAS. HIGHS TODAY ARE EXPECTED TO BE IN
THE UPPER 80S TO LOW WITH A FEW ADDITIONAL DEGREES OF COOLING BOTH
SATURDAY AND SUNDAY.
SUNDAY AFTERNOON AND EVENING, THE UPPER LEVEL LOW STARTS TO GET
CLOSE TO THE AREA AND MAY START TO BRING SOME SHOWERS TO THE AREA. A
THUNDERSTORM IS NOT COMPLETELY OUT OF THE QUESTION, BUT THIS IS
GENERALLY NOT A PATTERN CONDUCIVE TO THUNDERSTORMS.
MONDAY, THE UPPER LEVEL TROUGH MOVES ONSHORE AND TUESDAY THIS GETS
REINFORCED BY A LARGE TROUGH THAT SETTLES OVER THE WEST COAST AND
REMAINS IN PLACE ON WEDNESDAY AND THURSDAY. OVERALL THE ENSEMBLES
ARE IN PRETTY GOOD AGREEMENT ON THE TROUGH OVER THE WEST COAST. THE
CHALLENGE LIES IN WHERE EXACTLY THIS LOW GOES AND THIS WILL IMPACT
THE DETAILS OF HOW MUCH RAIN OCCURS AND WHERE IT WILL BE. HERE ARE
SOME PROBABILITIES OF RAINFALL TOTALS FROM 5AM SUNDAY THROUGH 5AM
WEDNESDAY. THERE IS A 70 TO 80 PERCENT CHANCE OF EXCEEDING AN INCH
IN DEL NORTE COUNTY, A 50 TO 60 PERCENT CHANCE ON THE HUMBOLDT
COAST, AND AROUND 50 PERCENT CHANCE IN THE MOUNTAINS OF INTERIOR
HUMBOLDT AND TRINITY COUNTIES. THE PROBABILITIES DROP OFF QUICKLY TO
NEAR ZERO IN MENDOCINO AND LAKE COUNTIES FOR AN INCH. HOWEVER, FOR A
TENTH OF AN INCH THERE IS A 40 TO 70 PERCENT CHANCE IN MENDOCINO AND
LAKE COUNTIES WITH THE HIGHEST IN THE NORTHERN MOUNTAINS. THE NBM IS
HIGHLIGHTING THUNDERSTORMS, ESPECIALLY ALONG THE COAST, WITH THIS
SYSTEM AS THE TROUGH MOVES OVERHEAD. CONFIDENCE IS LOW AS
INSTABILITY IS MEAGER, BUT IS SOMETHING TO WATCH. THIS WILL ALSO
KEEP TEMPERATURES COOLER AND INTERIOR HIGH TEMPERATURES WILL LIKELY
BE IN THE 60S TO LOW 70S. MKK/JB
AVIATION...(06Z TAFS)
A DEEPER MARINE LAYER HAS DEVELOPED AS AN
UPPER LEVEL TROUGH APPROACHES FROM THE WEST. EXPECT VARIABLE
CONDITIONS BETWEEN LIFR/IFR/MVFR AT COASTAL TERMINALS THROUGH FRIDAY
MORNING. PATCHY DRIZZLE IS EXPECTED TO OCCUR ALONG THE COAST WITH
THIS SATURATED LAYER. VERY LIGHT S TO VARIABLE WINDS WILL CONTINUE
INTO VERY EARLY FRIDAY MORNING.
FOR INLAND AREAS: INTO FRIDAY MORNING, HIGH-RES MODEL GUIDANCE
SUGGESTS LOW CLOUDS DEVELOPING IN THE VICINITY OF UKI WITH THE
DEEPER MARINE LAYER. THERE IS A 20% CHANCE FOR CEILING HEIGHT AT
1000 FEET OR LOWER BY EARLY FRIDAY MORNING. VERY LIGHT AND VARIABLE
WINDS WILL EXIST THROUGH FRIDAY MORNING; HOWEVER, ANY GENTLE
SOUTHERLY WINDS THAT MAY DEVELOP IN THE RUSSIAN RIVER VALLEY MAY
BRING LOWER CLOUDS TO UKI. /ZVS
MARINE
GENTLE TO MODERATE BREEZES CONTINUE ACROSS THE OUTER
WATERS, WHILE LIGHT TO GENTLE BREEZES CONTINUE OVER THE INNER
WATERS. LOCALIZED GUSTY WINDS UP TO 20 KTS ARE EXPECTED DOWNWIND OF
CAPE MENDOCINO THROUGH TONIGHT.
CONDITIONS ARE EXPECTED TO CONTINUE IMPROVING INTO FRIDAY AND THE
WEEKEND AS AN UPPER LEVEL TROUGH APPROACHES FROM THE WEST AND THE
SURFACE PRESSURE GRADIENT RELAXES. WINDS SHIFT TO SOUTHERLY AND
SLIGHTLY INCREASE AHEAD OF AN ASSOCIATED FRONTAL SYSTEM THIS
WEEKEND. SMALL, MID- PERIOD NW AND SW SWELLS WILL PERSIST THROUGH
THE WEEKEND. OVERALL, RELATIVELY CALM CONDITIONS ARE FORECASTED FOR
THIS WEEKEND THROUGH EARLY NEXT WEEK. /ZVS
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
NONE.
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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