AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
509 AM PDT WED MAY 30 2018

.SYNOPSIS...A TROUGH WILL BRING COOLER TEMPERATURES, AN INCREASE
IN CLOUD COVER, AND CHANCE FOR PRECIPITATION TO THE REGION TODAY.
SHOWER AND ISOLATED STORM ACTIVITY SHOULD STAY CONFINED TO THE
TRINTY ALPS THIS AFTERNOON WITH SHOWERS AND PATCHY DRIZZLE
EXPECTED FOR TRINITY AND HUMBOLDT COUNTIES TONIGHT. TOMORROW, COOL
TEMPERATURES WILL CONTINUE WITH A WARMING TREND RETURNING TO
INTERIOR NORTHWEST CALIFORNIA BY FRIDAY.


&&

.DISCUSSION...SATELLITE IMAGERY THIS MORNING SHOWS, YOU GUESSED
IT, STRATUS AND FOG IN THE EEL AND KLAMATH RIVER VALLEYS AND DOWN
ALONG THE MENDOCINO COAST AND RIVER VALLEYS TOO. CURRENT THINKING
IS THAT THE STRATUS WILL CONTINUE TO SURGE INLAND THIS BUT THAT
MOST AREAS WILL CLEAR OUT THROUGHOUT THE DAY. A TROUGH WILL BRING
A COOLER AND SLIGHTLY UNSTABLE AIRMASS TO THE REGION WHICH MAY
PRODUCE ISOLATED SHOWERS AND THUNDERSTORMS OVER THE TRINITY ALPS
THIS AFTERNOON AND EVENING. AN OVERALL INCREASE IN CLOUD COVER IS
EXPECTED TO MOVE INTO THE REGION LATE TONIGHT WITH A FEW LIGHT
SHOWERS AND PATCHY DRIZZLE BEING POSSIBLE FOR HUMBOLDT AND TRINITY
COUNTIES, AS ONSHORE FLOW DEEPENS THE MARINE LAYER. THE COOLER
MARINE AIR AND CLOUD COVER WILL LIKELY RESULT IN SUBSTANTIALLY
LOWER HIGHS ON THURSDAY FOR THE INTERIOR, WITH TEMPERATURES
PEAKING IN THE MID 60S TO LOW 70S. THE SHOWER AND THUNDERSTORM
RISK SEEMS SUBSTANTIALLY LOWER FOR EASTERN TRINITY AND MENDOCINO
COUNTIES, THUS I HAVE REMOVED THE TSTORM THREAT FOR THE TRINITY
ALPS AND YOLLA BOLLY MOUNTAINS.

LOOKING TO THE WEEKEND, QUIET WEATHER IS IN STORE FOR NORTHWEST
CALIFORNIA. THERE WILL BE A BRIEF PERIOD OF ZONAL FLOW WHICH
WILL ALLOW FOR WARMING CONDITIONS FOR THE INTERIOR AREAS STARTING
ON FRIDAY AND CONTINUING INTO THE WEEKEND. NEAR THE COAST,
NORTH/NORTHWESTERLY WINDS WILL RETURN AS AN OFFSHORE RIDGE
STRENGTHENS.


&&

.AVIATION...WITH NORTHERLY WINDS STAYING STRONGER OVERNIGHT NEAR THE
IMMEDIATE COAST OR JUST OFFSHORE, STRATUS HAS BEEN SLOWER TO FORM
AND EXPAND ALONG THE COAST BETWEEN EUREKA AND CRESCENT CITY. WE DO
HAVE AN AREA OF MVFR AROUND ACV WITH MVFR TO IFR CEILINGS EXTENDING
SOUTH TO THE KING RANGE AND UP THE EEL RIVER VALLEY TO GARBERVILLE.
EXPECT PORTIONS OF THE EEL RIVER VALLEY TO KEEP CLOUDS TODAY, WHILE
COASTAL AREAS AROUND ACV WILL LIKELY CLEAR BY EARLY AFTERNOON. CEC
AND UKI WILL REMAIN CLEAR, WITH GUSTY NORTHERLY WINDS ALREADY IN
PLACE AT CEC, INCREASING ANOTHER 5 TO 7 KT THIS AFTERNOON. STRATUS
WILL RETURN THIS EVENING, AND WITH AN UPPER TROUGH PASSING BY,
EXPECT A DEEPER MARINE LAYER WITH MORE EXTENSIVE AND PERSISTENT LOW
CLOUDS INTO THURSDAY AS NORTHERLY WINDS EASE. AAD


&&

.MARINE...NORTHERLY WINDS ARE STRONGER NEARSHORE THIS MORNING
COMPARED TO YESTERDAY, WITH GALE CONDITIONS CONTINUING ACROSS THE
OUTER WATERS TODAY. AS A LOW PRESSURE TROUGH PUTS A DENT IN EASTERN
PACIFIC HIGH PRESSURE, THE PRESSURE GRADIENT WILL BEGIN TO WEAKEN
TODAY AND ESPECIALLY HEADING INTO THURSDAY. WINDS LOOK LIKE THEY
WILL BEGIN TO DROP OFF THIS EVENING SO THAT THE GALE WARNING MAY BE
ABLE TO BE CANCELLED EARLY IF CURRENT TRENDS HOLD. FOR NOW, AM
CONTINUING THAT HAZARD INTO THE OVERNIGHT HOURS. EITHER WAY,
CONFIDENCE IS HIGH THAT WINDS WILL SUBSTANTIALLY EASE ON THURSDAY,
THOUGH SMALL CRAFT ADVISORIES MAY STILL BE NECESSARY FOR THE OUTER
WATERS. MEANWHILE INSIDE 10 NM OF SHORE, WINDS WILL LOCALLY GUST
NEAR GALE FORCE AROUND CAPE MENDOCINO AND POINT ST GEORGE, WHILE
LARGE, STEEP SEAS PROMPTED A HAZARDOUS SEAS WARNING. INDICATIONS ARE
THAT MOST AREAS NEARSHORE AWAY FROM THE LARGER CAPES AND HEADLANDS
WILL SEE SLIGHTLY BETTER CONDITIONS LATER TODAY, BUT IT IS POSSIBLE
THE HAZARDOUS SEAS WARNING MAY NEED TO BE EXTENDED BEYOND THE
CURRENT END TIME OF 9 AM. FRIDAY WILL SEE THE BEST CONDITIONS OUT OF
THE NEXT SEVERAL DAYS, AS AN INCREASE IN NORTHERLY WINDS ARE
EXPECTED ONCE AGAIN THIS WEEKEND. A 3-6 FT MID-PERIOD NORTHWESTERLY
SWELL WILL MIX IN WITH LESSER SHORT-PERIOD SEAS ON FRIDAY.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...HAZARDOUS SEAS WARNING UNTIL 9 AM PDT THIS MORNING FOR PZZ450-
     455.

     GALE WARNING UNTIL 3 AM PDT THURSDAY FOR PZZ470-475.

&&