947
FXUS66 KEKA 272227
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
327 PM PDT SUN APR 27 2025
SYNOPSIS
DRYING AND WARMING TREND THROUGH MID-WEEK. BREEZY
NORTHWEST WINDS ALONG THE COASTAL HEADLAND AND EXPOSED RIDGE EACH
AFTERNOON AND EVENING THROUGH TUESDAY. CHANCES OF PRECIPITATION
RETURN ON FRIDAY.
DISCUSSION
LATEST SATELLITE IMAGERY DEPICTS A H5 RIDGING OVER
THE NEPAC BUILDING DOWNSTREAM IN THE WAKE OF THE UPPER LEVEL
TROUGH. THIS IS PROMOTING DRIER NORTHERLY WINDS ALOFT OVER
NORTHWEST CALIFORNIA TODAY, YIELDING IN IMPROVING SKY CONDITIONS
THIS AFTERNOON. AFTERNOON TEMPERATURES HAVE BEEN RUNNING GENERALLY
5 TO 10 DEGREES WARMER THAN YESTERDAYS READING, WITH HIGHS
RANGING FROM 55 TO 65 DEGREES. BREEZY TO LOCALLY WINDY NORTHWEST
WINDS ARE EXPECTED TO CONTINUE ALONG THE COASTAL HEADLANDS AND
EXPOSED RIDGES THROUGH THIS EVENING, WHERE GUSTS FROM 25 TO
AROUND 40 MPH ARE EXPECTED. WINDS WILL DIMINISH ACROSS MUCH OF THE
AREA, BUT BREEZY CONDITIONS PERSIST OVER THE MORE PROMINENT
TERRAIN.
TONIGHT, HIGH PRESSURE OVER THE NEPAC CONTINUE TO BUILD IN THROUGH
MONDAY. A DRY OFFSHORE WIND FLOW IS EXPECTED TO DEVELOP OVER THE
INTERIOR TONIGHT INTO MONDAY, WITH BREEZY WINDS OVER THE HIGHER
TERRAIN. AREAS OF FOG AND PATCHY DENSE FOG ARE ANTICIPATED ALONG
THE SHELTER VALLEYS WITH CLEAR SKIES AND STRONG RADIATIONAL
COOLING. OVERNIGHT TEMPERATURES ARE EXPECTED TO DROP TO UPPER 30'S
TO MID 40'S. NBM CONTINUE SUGGESTING A 20-45% FOR LOW TEMPERATURES
LESS THAN 36 DEGREES FOR MUST OF THE VALLEYS IN TRINITY COUNTY,
WITH A HIGHER CHANCE (90%) FOR HAYFORK. HOWEVER, CONFIDENCE REMAIN
LOW WITH HIGH DEWPOINTS. OTHERWISE, DEPENDING OF HOW QUICKLY
TEMPERATURES DROPS A FROST ADVISORY MAY BE NEEDED. EXPECT MOSTLY
SUNNY SKIES AND WARMER TEMPERATURES ON MONDAY, WITH BREEZY
NORTHWESTERLY WINDS IN THE AFTERNOON.
A SHORTWAVE TROUGH WILL MOVES OVER THE AREA ON TUESDAY, PARTLY TO
MOSTLY MID TO HIGH LEVEL CLOUDS. HOWEVER, A CAPPING INVERSION
WILL INHIBIT ANY SHOWERS TO DEVELOP. RIDGING BUILD BACK TUESDAY
NIGHT AND WEDNESDAY. DRY WEATHER AND WARM TEMPERATURES ARE
EXPECTED TO PERSIST THROUGH THURSDAY, WITH THE WARMEST DAYS ON
WEDNESDAY AND THURSDAY. INTERIOR HIGH TEMPERATURES ARE EXPECTED TO
WARM UP TO MID 80'S ACROSS THE WARMEST INTERIOR VALLEYS.
LONG TERM...THURSDAY THROUGH SUNDAY
500MB PATTERN ON DAY 4
(THURSDAY) WILL RESEMBLE A REX BLOCK. A POSITIVE HEIGHT ANOMALY
WILL REMAIN CENTERED OVER THE PAC NW (WASHINGTON AND OREGON) AND
EXTEND SOUTHWARD INTO NORTHERN CALIFORNIA. A CUT-BACK TROUGH OR
CLOSED 500MB CYCLONIC CIRCULATION OFFSHORE OR OVER CENTRAL/SOUTHERN
CALIFORNIA WILL COMPLETE THE REX-BLOCK PATTERN. IT IS POSSIBLE
FOR WRAP AROUND MOISTURE FROM THE CLOSED LOW TO SPREAD OVER LAKE
AND EASTERN MENDOCINO FOR DIURNAL CONVECTION. ALL 6-HOURLY
ENSEMBLE MEMBERS FROM THE ENS, GEFS AND CMCE INDICATE NO PRECIP.
ALSO, NBM PROBABILITIES FOR TSTMS > 15% ARE WELL TO THE EAST AND
SOUTHEAST; OVER THE SIERRA NEVADA MTN RANGE. INTERIOR HIGH
TEMPERATURE WILL REMAIN ABOVE AVERAGE ON THU UNDER LARGE SCALE
ADIABATIC WARMING FROM THE RIDGE CENTERED OVER THE PAC NW. HIGH
TEMPS IN THE MID 70'S TO MID 80'S ARE GENERALLY EXPECTED, HOWEVER
A FEW HOT SPOTS SUCH BIG BAR RAWS WILL PROBABLY EXCEED 90F.
GET READY FOR MORE COOL AND WET WEATHER. A 500MB TROUGH WILL DIG
SOUTHWARD FROM THE GULF OF ALASKA AND APPROACH NW CAL ON DAY 5
(FRIDAY). ALL DETERMINISTIC MODELS, GFS, ECMWF, GDPS, ICON AS WELL
AS ENSEMBLE MEANS WERE IS GOOD AGREEMENT WITH DRIVING A FRONTAL
BOUNDARY ACROSS THE NORTHERN PORTION OF THE AREA ON FRIDAY. 24-HOUR
ENSEMBLE CLUSTER MEANS CONTINUE TO DEPICT SUBTLE DIFFERENCES WITH
PLACEMENT, TIMING AND OVERALL EVOLUTION OF THE COLD CORE ALOFT.
ABOUT 30-45% OF CLUSTER MEMBERS WERE WETTER THAN THE GRAND ENSEMBLE
MEAN. NBM CONTINUES TO INDICATE 60-70% CHANCES FOR 0.25IN OF RAIN IN
24 HOURS FRIDAY-SATURDAY IN DEL NORTE, 30-50% CHANCES FOR HUMBOLDT,
20-45% CHANCES OF TRINITY AND 10-25% CHANCES FOR MENDOCINO AND LAKE.
BY 5AM SAT, OVER HALF AN INCH WILL BE POSSIBLE (50% CHANCE) FOR
INTERIOR DEL NORTE. NOT A MAJOR RAIN EVENT BY ANY STRETCH BUT WET
WEATHER WILL IMPACT OUTDOOR ACTIVITIES AND PROJECTS. SPRING SNOWFALL
WILL ALSO BE POSSIBLE ABOVE 4000-4500 FEET WITH 1 TO 2 INCHES OF
STORM TOTAL ACCUMULATION BY 5 AM SUNDAY.
INTERIOR TEMPERATURES WILL BE CONSIDERABLY COOLER AND WELL BELOW
NORMAL AGAIN NEXT WEEKEND (SAT MAY 3 AND SUN MAY 4). THERE MIGHT
EVEN BE POCKETS OF MORNING FROST IN THE INTERIOR VALLEYS WITH MIN
TEMPS BELOW 36F. PRECIP CHANCES GENERALLY DIMINISH AS WE HEAD INTO
DAY 7 (SUNDAY) AS THE TROUGH HEADS SOUTHWARD AND EASTWARD. TO WHAT
EXTENT AND HOW FAST THIS OCCURS ARE STILL NOT 100% CERTAIN. PRECIP
COULD WRAP BACK AROUND A POTENTIAL CUT-OFF LOW OR AN UPSTREAM KICKER
MAY KNOCK DOWN THE OFFSHORE RIDGE RESULTING IN MORE LIGHT PRECIP
FROM THE WEST. A FASTER SEWRD PROGRESSION WITH STRONGER RIDGING
OFFSHORE WOULD RESULT IN A MUCH DRIER AND GUSTY NORTH/NORTHWEST WIND
SCENARIO FOR OUR FORECAST AREA. MOST ENSEMBLE MEMBERS SUPPORT THIS
SCENARIO. STAY TUNED. DB
AVIATION
MVFR CEILINGS AT KACV AND UKI HAVE ERODED TODAY WITH
DAYTIME HEATING AND MIXING. UPPER LOW THAT BROUGHT RAIN AND PERIODIC
IFR THE LAST 3 DAYS HAS BEEN EDGING EASTWARD TODAY. MEANWHILE, HIGH
PRESSURE AND DRIER AIR HAS BEEN SLOWLY BUILDING IN FROM THE NW.
EXPECT MVFR CIGS TO REDEVELOP FOR HUMBOLDT BAY AND EEL DELTA THIS
EVENING AND OVERNIGHT, IMPACTING KACV. FOR KUKI, SOME MVFR CIGS MAY
LINGER, BUT OVERALL CONDITIONS ARE EXPECTED TO REMAIN VFR. SHALLOW
FOG AND PERHAPS LOW CLOUDS WILL BE POSSIBLE TONIGHT IN VALLEYS THAT
RECEIVED RAIN OVER THE LAST 2-3 DAYS, IF WINDS REMAIN LIGHT OR CALM
ONCE SKIES CLEAR OUT. GUSTY NORTH-NORTHWEST THIS AFTERNOON AND EARLY
EVENING FOR COASTAL AERODROMES SHOULD DECOUPLE BY MID TO LATE
EVENING WITH A 50% CHANCE FOR LOW LEVEL SHEAR AND/OR LOW LEVEL
TURBULENCE IN THE VICINITY OR JUST OUTSIDE KACV AERODROME. MUCH
HIGHER CHANCES EXIST OVER THE KING RANGE. GUSTY NORTH-NORTHWEST
WINDS PICK UP AGAIN FOR KACV AND KCEC WITH DIURNAL HEATING AND
MIXING ON MONDAY. DB
MARINE
NORTHERLY WINDS AND STEEP WAVES ARE FORECAST TO REMAIN
ELEVATED THROUGH MID WEEK. EXPANSION FAN REGIONS DOWNWIND OF CAPE
MENDO AND PT ST GEORGE WILL CONTINUE TO RESULT IN LOCALIZED RIBBONS
OF GALE FORCE WINDS TONIGHT INTO MONDAY. AREAL COVERAGE WITH
SOUTHERN EXPANSION FAN SOUTH OF CAPE MENDO, WELL, EXPANDS IN THE
AFTERNOON. THUS UPGRADED THE GALE WATCH TO A GALE WARNING. NORTH
WINDS AND STEEP SEAS IN THE LEE OF CAPE MENDO AND OVER THE OUTER
WATERS WILL REMAIN SUFFICIENT FOR AN ADVISORY INTO AT LEAST WED,
MAYBE INTO THU SOUTH OF CAPE MENDO. INNER WATERS NORTH OF CAPE MENDO
SHOULD CALM DOWN WITH GREATER TROUGHINESS NEARSHORE. CONFIDENCE
REMAINS LOW AND DETAILS LACKING AT THIS POINT. LARGE SCALE SYNOPTIC
PATTERN INDICATES BRISK NORTHERLIES DIMINISHING MORE SUBSTANTIALLY
TOWARD THE END OF THE WEEK AS A COLD FRONT BUSTS DOWN THE RIDGE AND
PRESSURE GRADIENT RELAXES OVER THE AREA. INLAND LOW PRESSURE MAY
STILL SERVE TO LOCALLY ACCELERATE WINDS OVER THE SOUTHERN END OF
MENDOCINO WATERS, HOWEVER. NORTHWEST AND NORTH WINDS WILL INCREASE
AFTER FRONTAL PASSAGE NEXT WEEKEND WITH GUSTS OVER 34KT AND STEEP
WAVES OVER 10 FT A HEAVY WEIGHTED CONTENDER IN POSSIBLE OUTCOMES. DB
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 11 PM PDT MONDAY FOR PZZ450-455.
HAZARDOUS SEAS WARNING UNTIL 9 PM PDT THIS EVENING FOR
PZZ470.
HAZARDOUS SEAS WARNING UNTIL 2 PM PDT MONDAY FOR PZZ475.
GALE WARNING FROM 2 PM TO 11 PM PDT MONDAY FOR PZZ475.
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