059
FXUS66 KEKA 092217
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
317 PM PDT THU APR 9 2020
SYNOPSIS
DRY WEATHER IS EXPECTED TO PREVAIL THROUGH MOST OF
NEXT WEEK AS AN UPPER RIDGE DOMINATES. TEMPERATURES WILL
GENERALLY REMAIN ABOVE NORMAL IN THE INTERIOR. PERSISTENT MARINE
AIR WILL BRING PERIODS OF LOW CLOUDINESS AND ONSHORE WINDS,
KEEPING COASTAL AREAS COOLER.
DISCUSSION
WITH AN INVERTED SURFACE TROUGH SHIFTING JUST
OFFSHORE LAST NIGHT, DEEPENING MARINE LAYER CLOUDINESS FLOWED
QUICKLY NORTHWARD TO CRESCENT CITY BY MID-MORNING TODAY. WITH
THAT, ANY HOPES OF ANOTHER SUNNY AND MILD AFTERNOON WERE DASHED
FOR MOST OF OUR COASTAL LOCATIONS. THE LONE EXCEPTIONS ARE A FEW
SPOTS TO THE NORTH OF COASTAL HEADLANDS AND MOUNTAINOUS TERRAIN,
SUCH AS FORTUNA AND FERNDALE. MEANWHILE, WITH A VERY DEEP MARINE
LAYER INTRUSION ACROSS MENDOCINO COUNTY, CLOUDINESS HAS BEEN SLOW
TO BREAK OR SCATTER EVEN AROUND UKIAH, WHERE TEMPERATURES HAVE
STRUGGLED TO GET INTO THE 60S. PORTIONS OF THE KLAMATH, TRINITY,
AND UPPER MAD RIVER VALLEYS THAT WERE PROTECTED FROM THE SOUTHERLY
FLOW OF MARINE AIR HAVE MANAGED TO RISE INTO THE 70S ONCE AGAIN
THIS AFTERNOON.
HEADING INTO TONIGHT, WE'LL LOOK FOR MARINE CLOUDINESS TO THICKEN
AND EXPAND ONCE AGAIN IN THOSE AREAS WHERE COOLER MARINE AIR
INTRUDED LAST NIGHT AND TODAY. THE REST OF THE INTERIOR INCLUDING
MOST OF TRINITY COUNTY WILL REMAIN CLEAR. EXPECT THE MARINE LAYER
CLOUDINESS TO BE QUITE DEEP; FROM 2000 TO 3000 FEET FOR HUMBOLDT
AND DEL NORTE, BUT EVEN UP TO 4000 FEET ACROSS MENDOCINO AND LAKE
COUNTIES. COMBINED WITH MID AND UPPER-LEVEL RIDGING ALOFT, CLOUDS
WILL BE SLOW TO ERODE BACK TOWARD THE COAST ON FRIDAY. AS SURFACE
WINDS SHIFT TOWARD THE NORTHWEST AND ONSHORE FOR THE AFTERNOON,
WE ARE THINKING THAT ONLY LIMITED BREAKS OF SUN WILL BE FOUND
ALONG THE COASTAL PLAIN, OUTSIDE OF THE LOST COAST AREA ADJACENT
TO THE KING RANGE AROUND SHELTER COVE. THAT SAID, MOST INTERIOR
VALLEYS INCLUDING THOSE ACROSS MENDOCINO AND LAKE COUNTIES SHOULD
SEE A FAIR AMOUNT OF SUN TOMORROW AND TEMPS INTO THE 60S, WITH
EVEN LOW TO MID 70S ALONG THE TRINITY RIVER.
THIS WEEKEND SHOULD BRING A SHALLOWER MARINE LAYER, WITH STRONGER
NORTHWEST WINDS PUSHING ONSHORE AND INLAND DURING THE AFTERNOONS
AND EVENINGS, WHICH SHOULD PROMOTE MORE WIDESPREAD AFTERNOON
CLEARING OF THE MARINE STRATUS AND FOG. OTHERWISE, STRONG UPPER-
LEVEL HIGH PRESSURE LOCKED IN PLACE ACROSS THE EASTERN PACIFIC
WILL EFFECTIVELY BLOCK PACIFIC MOISTURE AND ANY STORM SYSTEMS FROM
THREATENING OUR AREA THROUGH NEXT WEEK. SOME UPPER- LEVEL TROUGHS
ROUNDING THE TOP OF THE RIDGE AND DIVING ACROSS THE NORTHERN
ROCKIES COULD POSSIBLY CLIP OUR AREA AT TIMES OVER THE NEXT 7
DAYS. IT IS NOT OUTSIDE OF THE REALM OF POSSIBILITY THAT ONE OF
THESE MAY TRIGGER A COUPLE STRAY INTERIOR MOUNTAIN SHOWERS,
PERHAPS SPECIFICALLY ON SUNDAY AFTERNOON, BUT AT THIS POINT THE
CHANCE LOOKS LOW ENOUGH TO LEAVE OUT OF THE FORECAST. WITH THAT,
EXPECT DRY CONDITIONS, WITH SEASONABLE COASTAL TEMPERATURES AND
INLAND TEMPERATURES MAINLY STAYING WELL ABOVE SEASONAL AVERAGES
FOR THE WEEKEND INTO NEXT WEEK. /AAD
AVIATION
A RATHER COMPLEX CLOUD PATTERN EXISTS ACROSS THE AREA
THIS AFTERNOON. SOUTHERLY CLOUD-LEVEL FLOW CONTINUES TO PUSH LOW-
LEVEL MOISTURE AND STRATUS INTO THE COAST FROM CAPE MENDOCINO
NORTHWARD. THERE ARE SOME BREAKS IN THIS CLOUDINESS ALONG PORTIONS
OF THE IMMEDIATE COAST, BUT MOISTURE CONTINUES TO PILE UP ON THE
WINDWARD SIDE OF THE COASTAL TERRAIN. PER COASTAL PROFILER DATA, THE
MARINE LAYER APPEARS TO BE ABOUT 3500 FEET DEEP AT ACV AND 5000 FEET
DEEP S OF THE AREA AT BODEGA BAY. MODELS INDICATE THAT THE MARINE
LAYER WILL CONTINUE TO DEEPEN ALONG THE REDWOOD COAST TO 5000 FEET
LATER TONIGHT AND ON FRIDAY BEFORE DROPPING BACK CLOSER TO 3000 FEET
ON SATURDAY. EXPECT CLOUDS TO LOWER AT BOTH KACV AND KCEC THROUGH
THE EVENING HOURS WITH THE CHANCE OF VISIBILITY REDUCTIONS LATER IN
THE FORECAST PERIOD. CEILINGS MAY ONCE AGAIN HOLD IN FOR THE DAY ON
FRIDAY WITH SLOWLY RISING CEILING HEIGHTS. WINDS WILL BE GENERALLY
LIGHT, WITH SOME GUSTS TO AROUND 15 KT AT KCEC INTO THE EVENING
HOURS.
AT KUKI, CEILINGS HAVE RISEN TO OVER 4000 FT, BUT SKIES REMAIN
BROKEN TO OVERCAST. EXPECT CEILINGS TO DROP BACK TO MVFR LEVELS
LATER TONIGHT. NO SIGNIFICANT VISIBILITY REDUCTIONS ARE
ANTICIPATED AT THIS TIME. SOUTHERLY WINDS WILL GUST TO 15 TO 20 KT
THROUGH THE EARLY EVENING HOURS. /SEC
MARINE
THE INTERIOR THERMAL TROUGH HAS PUSHED W A LITTLE CLOSER
TO THE COAST TODAY AND DISRUPTED THE SURFACE PRESSURE GRADIENT. THIS
HAS INDUCED A BRIEF WEAKENING TREND IN THE PERSISTENT NORTHERLY
WIND REGIME WHICH HAS DOMINATED THE PAST SEVERAL DAYS. A SMALL CRAFT
ADVISORY CONTINUES ACROSS THE OUTER WATERS. THE S ADVISORY WILL END
AT 6 PM, WHILE THE N ADVISORY IS EXPECTED TO EXPIRE FRIDAY MORNING.
THE LULL IN THE NORTHERLIES WILL BE SHORT-LIVED AS THE COASTAL
GRADIENT TIGHTENS AGAIN AND NORTHERLIES RE-INTENSIFY FROM LATE
FRIDAY AFTERNOON INTO THE WEEKEND. /CB&SEC
EKA WATCHES/WARNINGS/ADVISORIES
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL
NOON PDT FRIDAY FOR PZZ470.
SMALL CRAFT ADVISORY UNTIL 6 PM PDT THIS EVENING FOR PZZ475.
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