701
FXUS66 KEKA 280955
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
255 AM PDT MON APR 28 2025
SYNOPSIS
DRY CONDITIONS ARE ANTICIPATED TODAY AS RIDGING BUILDS
ALOFT. A QUICK PASSING TROUGH WILL BRING INCREASED CLOUD COVER
AND A POSSIBILITY OF MOUNTAIN SHOWERS ON TUESDAY. DRY WEATHER
RETURNS ON WEDNESDAY WITH TEMPERATURES WARMING WELL ABOVE NORMAL
THROUGH THURSDAY.
DISCUSSION
SHORT TERM...THROUGH WEDNESDAY
THE STORM SYSTEM THAT BROUGHT
SHOWERS TO THE REGION OVER THE LAST FEW DAYS HAS NOW MOVED EAST
OF THE REGION LEAVING DRY NORTHERLY FLOW OVER NORTHWEST
CALIFORNIA. LINGERING LOW LEVEL MOISTURE HAS KEPT CLOUD COVER
FAIRLY PERSISTENT OVERNIGHT IN MANY VALLEY LOCATIONS AND ACROSS
MUCH OF HUMBOLDT COUNTY. AS DRIER AIR CONTINUES TO FILTER IN,
SKIES SHOULD CLEAR THROUGH THE DAY LEAVING A RATHER PRESENT DAY
IN STORE FOR THIS AFTERNOON. COASTAL CLOUDS WILL EXPAND AGAIN
TONIGHT INTO TUESDAY MORNING.
A SHORTWAVE TROUGH WILL DIVE THROUGH THE PACIFIC NORTHWEST ON
TUESDAY. MODEL GUIDANCE IS TRENDING TOWARD THE POTENTIAL OF RAIN
SHOWERS OVER THE MOUNTAINOUS TERRAIN TUESDAY AFTERNOON/EVENING.
HOWEVER, THE NBM HAS NOT YET CAUGHT ONTO THIS POSSIBILITY. HAVE
KEPT THE CHANCES FOR RAIN OUT OF THE FORECAST FOR NOW, BUT THE DAY
SHIFT WILL NEED TO INCREASE THE RAINFALL CHANCES WITH THE NEXT
UPDATE IF MODEL TRENDS CONTINUE.
RIDGING WILL ONCE AGAIN BUILD BACK OVER THE WEST COAST ON WEDNESDAY
BRINGING WARM TEMPERATURES TO THE INTERIOR WITH HIGH TEMPS IN VALLEY
LOCATIONS EXCEEDING 80 DEGREES IN SOME LOCATIONS. /RPA
LONG TERM...THURSDAY THROUGH SUNDAY
(ISSUED 327 PM APR 27) 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
COASTAL STRATUS IS CREATING LIFR CONDITIONS ALONG THE
REDWOOD COAST THIS MORNING. HREF DATA SHOWS THESE LOW CLOUDS MIXING
OUT AND AWAY FROM THE TERMINALS BY APPROXIMATELY 16-18Z THIS
MORNING. GUSTY NORTH WINDS ARE TO BE EXPECTED THROUGH THE DAYLIGHT
HOURS BEFORE WEANING IN STRENGTH INTO THE EVENING. AS WINDS DIE
DOWN, IT IS LIKELY THAT FOG WILL RETURN TO THE TERMINAL SPACES. KUKI
CAN EXPECT VFR CONDITIONS.
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 THROUGH MONDAY. AREA COVERAGE OF THE SOUTHERN
EXPANSION FAN SOUTH OF CAPE MENDOCINO EXPANDS IN THE AFTERNOON.
THUS GALE WARNING HAS BEEN ISSUED. NORTH WINDS AND STEEP SEAS IN
THE LEE OF CAPE MENDO AND OVER THE OUTER WATERS WILL REMAIN
SUFFICIENT FOR A SMALL CRAFT ADVISORY UNTIL WEDNESDAY AT THE
EARLIEST, MAYBE INTO THURSDAY SOUTH OF CAPE MENDO. INNER WATERS
NORTH OF CAPE MENDO SHOULD CALM DOWN MUCH MORE NEARSHORE. CONFIDENCE
REMAINS LOW AND DETAILS LACKING AT THIS POINT.
THE LARGE SCALE SYNOPTIC PATTERN INDICATES BRISK NORINGTHERLIES
DIMINISHING MORE SUBSTANTIALLY TOWARD THE END OF THE WEEK AS A COLD
FRONT BUSTS DOWN THE UPPER LEVEL 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 THE FRONTAL PASSAGE
THIS COMING WEEKEND WITH GUSTS OVER 34KT AND STEEP WAVES OVER 10 FT
ARE POSSIBLE OUTCOMES AND FORECAST CONFIDENCE WILL INCREASE AS WE
GET CLOSER TO THIS EVENT.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 9 PM PDT TUESDAY FOR PZZ450-455-
470.
HAZARDOUS SEAS WARNING UNTIL 2 PM PDT THIS AFTERNOON FOR
PZZ475.
GALE WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT THIS
EVENING FOR PZZ475.
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