848
FXUS66 KEKA 292150
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
250 PM PDT FRI AUG 29 2025
SYNOPSIS
NEAR SEASONAL AVERAGE TEMPERATURE WILL CONTINUE
THROUGH THE WEEKEND. INCREASING HEAT ACROSS THE INTERIOR EARLY
THROUGH MID NEXT WEEK, WITH INTERIOR WIDESPREAD MODERATE TO
LOCALLY MAJOR HEATRISK.
DISCUSSION
STRATUS ERODED BACK TO THE COAST WITH THE DAYTIME
HEATING EARLY THIS AFTERNOON, WHILE HIGH LEVEL CLOUDS STREAM
EASTWARD ACROSS THE FORECAST AREA. WARM AND DRY WEATHER WILL
CONTINUE THROUGH THE LABOR DAY WEEKEND AS A CLOSED LOW WELL
OFFSHORE THE OREGON COAST CONTINUE TO TRACK NORTHWARD. INTERIOR
HIGH TEMPERATURES GENERALLY IN THE MID 80'S TO MID 90'S, WHILE MID
60'S TO LOW 70'S ALONG THE COAST. EXPECT COASTAL STRATUS EVERY
MORNING WITH A DEEP MARINE LAYER, BEFORE ERODE BACK AND MIX OUT
BY LATE MORNING/EARLY AFTERNOON.
SMOKE FROM THE ACTIVE WILDFIRES IN SISKIYOU COUNTY WILL CONTINUE
TO BE PUSHED TOWARD NORTHEAST WITH THE SOUTHWESTERLY BREEZES ALOFT
THROUGH THIS EVENING, BRINGING SOME IMPROVEMENT IN THE AIR
QUALITY FOR AREAS IN THE NORTHEASTERN PORTION OF HUMBOLDT
COUNTIES, INCLUDING ORLEANS. AIR QUALITY IS EXPECTED TO
DETERIORATE ACROSS THE NORTHEASTERN PORTION OF TRINITY COUNTY AS
THE SURFACE WINDS INCREASE FROM SOUTH TO SOUTHWEST LATER THIS
AFTERNOON AND PUSH THE SMOKE FROM THE PEAK FIRE IN TRINITY AND 5-4
FIRE IN SHASTA COUNTY TOWARD THE AREA. HRRR MODEL INDICATES SMOKE
WILL SPREAD INTO THE NORTHEAST THIS WEEKEND EACH AFTERNOON AGAIN
WITH THE SOUTHWEST WINDS ALOFT.
HIGH PRESSURE BEGIN TO BUILD BACK TO THE WEST COAST WITH 850 MB
TEMPERATURES WARMING FOR THE LABOR DAY (MONDAY). THIS WILL BRING
A WARMING TREND EARLY THIS WEEK, WITH MODERATE HEATRISK RETURNING
ACROSS THE INTERIOR VALLEYS ON MONDAY AND CONTINUE THROUGH MID
WEEK. ECMWF EXTREME FORECAST INDEX (EFI) HIGHLIGHT HIGHS IN THE
60TH-90TH PERCENTILE ABOVE NORMAL TEMPERATURES ON TUESDAY AND
WEDNESDAY ACROSS THE INTERIOR. INTERIOR HIGH TEMPERATURES IN THE
MID 90'S INTO 100'S ARE EXPECTED TO RETURN ACROSS ACROSS THE
WARMER LOCATIONS OF TRINITY, LAKE, INTERIOR MENDOCINO, AND
NORTHEASTERN HUMBOLDT. THE HEAT IS FORECAST TO PEAK ON WEDNESDAY
WITH LOCALLY MAJOR HEAT RISK IN TRINITY, LAKE AND NORTHEASTERN
MENDOCINO COUNTIES. THERE IS A 40 TO 70% CHANCE OF HIGH
TEMPERATURES GREATER THAN 105F ACROSS THE HOTTER VALLEYS, WITH THE
HIGHER CHANCES FOR HOOPA AND BIG BAR IN TRINITY COUNTY.
IN ADDITION, A SOUTHERLY REVERSAL LOW WILL FORM OFF THE CENTRAL
CALIFORNIA COAST ON MONDAY, BEFORE BECOMING ON A NEGATIVE TILT AS
IT MOVES NORTHWARD THROUGH THE AREA TUESDAY THROUGH THURSDAY, AND
BRING SOME THREAT OF INTERIOR THUNDERSTORMS. THERE IS A HIGH
UNCERTAINTY WITH THE EXACT TIMING/LOCATION AT THIS POINT, WITH A
NON- ZERO PROBABILITY OF CONVECTION EXPECTED TUESDAY AND WEDNESDAY.
SEE THE FIRE WEATHER SECTION BELOW. /ZVS
AVIATION...(18Z TAFS)
MVFR CONDITIONS WITH LIGHT VARIABLE
WINDS ALONG THE REDWOOD COAST THIS MORNING. OVERCAST CEILINGS
FORECAST SCATTER OUT LATE THIS MORNING (18Z-20Z) AS THE INFLUENCE
OF A SHORTWAVE TROF DEEPENS THE MARINE LAYER, INCREASING DAYTIME
MIXING. MARINE LAYER EXPECTED AGAIN TONIGHT (ONSET: 02Z-04Z) WITH
A 60-70% PROBABILITY OF CEILINGS BELOW 1KFT AGL AT THE COAST AND
IN ADJACENT RIVER VALLEYS. VISIBILITIES MORE LIKELY THAN NOT TO
REMAIN FAVORABLE. VFR EXPECTED INLAND WITH TERRAIN DRIVEN WINDS.
MARINE
BY THIS AFTERNOON, NORTHERLY WINDS ARE EXPECTED TO
INCREASE TO 5-15KT WITH THE STRONGEST WINDS SOUTH OF CAPE MENDOCINO.
THESE WINDS ARE EXPECTED TO CONTINUE TO INCREASE IN THE SOUTHERN
WATERS SATURDAY AFTERNOON WITH AN AREA OF 15 TO 20 KT WINDS,
ESPECIALLY DOWNWIND OF CAPE MENDOCINO. MODELS ARE IN GOOD AGREEMENT
THAT THE WIND IN THE NORTHERN WATERS WILL REMAIN LIGHT. ON SUNDAY
HOWEVER, THE WINDS MAY INCREASE SLIGHTLY MORE, ESPECIALLY IN THE
SOUTHERN WATERS. SOME MODELS SUGGEST THEY MAY REACH CLOSE TO 20 KT
WHILE OTHERS REMAIN AROUND 10 KT. NORTHERLY WINDS ARE EXPECTED TO
PERSIST, AND POTENTIALLY EVEN INCREASE NEXT WEEK AS WELL.
MARGINAL SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE SUNDAY IN
THE FAR SOUTHERN OUTER WATERS (PZZ475). THAT SAID, THERE IS STILL
FAIRLY GOOD MODEL AGREEMENT ON THEM REMAINING BELOW GALE FORCE.
WAVES REMAIN CALM, AROUND 2 TO 3 FEET. THIS IS MOSTLY FROM A
SOUTHERLY AT ~17 SECONDS. THESE WAVES ARE GENERALLY EXPECTED TO
CONTINUE THROUGH THE WEEKEND WITH THE ADDITION OF SHORT PERIOD WIND
WAVES AS THE WINDS START TO PICK UP. THERE IS A SMALL THREAT FOR
SOME SNEAKER WAVES ALONG SW FACING BEACHES, BUT WITH THE SOUTHERLY
SWELL EXPECTED TO BE COMPARATIVELY SMALL AND NOT TOO LONG OF A
PERIOD, THE THREAT IS NOT EXPECTED TO BE VERY SIGNIFICANT.
FIRE WEATHER
ELEVATED TO LOCALLY CRITICAL FIRE WEATHER
CONDITIONS DUE TO LOW RH AND BREEZY SOUTHWESTERLY WINDS OVER THE
HIGHER TERRAIN IN ZONES 277, 283 & 264 TODAY AND THIS WEEKEND.
SURFACE OBSERVATIONS REPORTED DAYTIME RH VALUES IN THE SINGLE
DIGITS TO MID TEENS ACROSS TRINITY, LAKE AND INTERIOR MENDOCINO
COUNTIES THIS AFTERNOON. WINDS WILL CONTINUE TO BE LIGHT AND
TERRAIN DRIVEN. OTHERWISE, A BRIEF PERIOD OF INCREASING WIND IS
EXPECTED TODAY AND THIS WEEKEND BY LATE AFTERNOON WITH WESTERLY TO
SOUTHWESTERLY BREEZES. MORE WIND PRONE AREAS COULD SEES GUSTS UP
TO AROUND 25 MPH. THE ONSHORE MARINE MOISTURE WILL BRING A SLIGHT
IMPROVEMENT IN THE OVERNIGHT RH RECOVERIES ACROSS THE INTERIOR,
BUT THESE ARE EXPECTED TO REMAIN POOR OVER THE HIGHER TERRAIN WITH
VALUES IN THE 30'S IN TRINITY, LAKE AND EASTERN MENDOCINO
COUNTIES.
WARMING AND DRYING TREND IS EXPECTED EARLY THROUGH MID NEXT WEEK
AS THE HIGH PRESSURE BUILD IN, WITH HIGH TEMPERATURES ACROSS THE
INTERIOR VALLEYS PEAKING IN THE 90S AND INTO 100S ON TUESDAY AND
WEDNESDAY. THE AFTERNOON RH VALUES WILL LIKELY BE IN THE TEENS AND
EVEN IN THE SINGLE DIGITS ACROSS TRINITY, LAKE AND EASTERN
MENDOCINO COUNTIES. HUMIDITY RECOVERIES WILL GRADUALLY DIMINISH
THROUGH THE WEEKEND AND EARLY NEXT WEEK, WITH LOCALLY VERY POOR
RECOVERIES BY TUESDAY.
A SOUTHERLY REVERSAL LOW WILL BRING SOME THREAT OF THUNDERSTORMS
FOR TUESDAY AND WEDNESDAY. THERE IS A HIGH UNCERTAINTY WITH THE
EXACT TIMING/LOCATION AT THIS POINT, WITH A NON- ZERO PROBABILITY
OF CONVECTION EXPECTED TUESDAY AND WEDNESDAY. AT THIS POINT THERE
IS A 10% CHANCE FOR THUNDERTORMS OVER THE TRINITY HORN FOR
TUESDAY AND WEDNESDAY AFTERNOON. /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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