492
FXUS66 KEKA 052035
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
135 PM PDT FRI SEP 5 2025
SYNOPSIS
INLAND AREAS ARE SEEING COOLER TEMPERATURES TODAY AND
THIS TREND IS EXPECTED TO CONTINUE INTO MONDAY. COASTAL CLOUDS
REMAIN IN PLACE THIS AFTERNOON AND ARE EXPECTED TO EXPAND TONIGHT
WITH MORE DRIZZLE EXPECTED. WET WEATHER AND BELOW NORMAL
TEMPERATURES ARE EXPECTED MONDAY AND TUESDAY WITH A GRADUAL
WARMING AND DRYING TREND LATER IN THE WEEK.
DISCUSSION
THE MAIN UPPER LEVEL LOW THAT IS IMPACTING THE AREA
CONTINUES TO SPIN WELL OFF THE WASHINGTON AND BRITISH COLUMBIA
COAST. A SHORTWAVE MOVED OVER THE AREA LAST NIGHT BRINGING DRIZZLE
THE COAST, DEEPENING THE MARINE AND EVEN SOME THUNDERSTORMS TO
THE OREGON COAST. THIS EVENING AND TONIGHT ANOTHER SHORTWAVE IS
MOVING ONSHORE AND THIS IS EXPECTED TO BRING MORE FOG AND DRIZZLE
AS WELL AS KEEP THE MARINE LAYER DEEP. THE QUESTION IS WHETHER
THERE WILL BE ANY THUNDERSTORMS WITH THIS SYSTEM AND IF SO, WHERE
WILL THEY FORM. FOR NOW IT LOOKS LIKE THEY WILL REMAIN OFF THE
COAST. SATURDAY DURING THE DAY IT LOOKS LIKE THERE MIGHT START TO
BE SOME MORE CLEARING AT THE COAST AS THE INVERSION WEAKENS AND
THE CLOUD LAYER OFFSHORE IS LOOKING MORE FRAGMENTED. INLAND THERE
IS THE POTENTIAL FOR SOME SHOWERS AND THUNDERSTORMS IN NORTHERN
TRINITY COUNTY. THE HRRR IS SHOWING SOME CONVECTION IN THE MODELED
REFLECTIVITY AND THE NAM IS SHOWING SOME INSTABILITY. THIS IS
EXPECTED TO BE FAIRLY LIMITED IN COVERAGE AND MAINLY NORTH OF THE
AREA.
SATURDAY NIGHT INTO SUNDAY MORNING THE MARINE LAYER IS EXPECTED
TO REMAIN DEEP AND THERE WILL LIKELY BE WIDESPREAD CLOUDS. DRIZZLE
IS EXPECTED AGAIN. SUNDAY AFTERNOON THERE IS EXPECTED TO BE SOME
LIGHT SOUTHERLY WINDS AND ALONG THE WITH THE WEAK INVERSION THERE
COULD BE SOME ADDITIONAL AFTERNOON CLEARING.
SUNDAY NIGHT INTO THE MONDAY THE MAIN UPPER LEVEL TROUGH AND AN
ASSOCIATED FRONT ARE EXPECTED TO MOVE ONSHORE BRINGING SOME RAIN
TO THE AREA. THE UPPER LEVEL TROUGH AND COLDER AIR ALOFT MOVES
ONSHORE IN THE AFTERNOON. THIS LOOKS LIKE IT MAY BRING SOME
THUNDERSTORMS TO MUCH OF THE AREA NORTH OF MENDOCINO COUNTY.
CONFIDENCE IS LOW ON THESE AND THE NBM THUNDER PROBABILITIES HAVE
DIMINISHED. STILL THERE IS SOME INSTABILITY. IT WILL LIKELY
DEPEND ON MUCH WARMING THERE WILL BE BEFORE THE STORMS. AS THE
EVENT STARTS TO GET CLOSER WE CAN LOOK MORE AT THE TIMING AND
AMOUNTS OF RAIN FOR JUST MONDAY AND MONDAY NIGHT. CURRENTLY IT
LOOKS LIKE AROUND 0.75 INCHES IN DEL NORTE COUNTY, 0.4 TO 0.7 IN
HUMBOLDT AND TRINITY COUNTY, AND GENERALLY A TENTH TO HALF INCH IN
LAKE AND MENDOCINO COUNTIES. AS USUAL THE HIGHER AMOUNTS WILL BE
FARTHER NORTH, HIGHER IN ELEVATION AND CLOSER TO THE COAST. IN
HUMBOLDT AND DEL NORTE COUNTIES DUE TO THE CONVECTIVE NATURE OF
THESE SHOWERS THERE IS THE POTENTIAL FOR SOME LOCALLY HEAVY RAIN THAT
COULD POSSIBLY CAUSE SOME DEBRIS FLOWS ON THE OLD BURN SCARS.
CONFIDENCE IS LOW ON THIS AND WILL CONTINUE TO MONITOR IT.
TUESDAY AND TUESDAY NIGHT THE POTENTIAL FOR HEAVIER RAIN STARTS
TO DIMINISH FAIRLY QUICKLY. THE PROBABILITY OF OVER A HALF INCH IN
24 HOURS DROPS BELOW 50 PERCENT ON TUESDAY AND TUESDAY NIGHT.
ONLY THE HIGHER MOUNTAINS OF HUMBOLDT AND TRINITY COUNTIES HAVE
OVER A 30 PERCENT CHANCE OF RECEIVING A HALF INCH. SOME OF THE
DETERMINISTIC RUNS ARE EVEN SHOWING THIS PERIOD AS MAINLY DRY NOW.
THERE MAY BE SOME CONVECTIVE SHOWERS OR THUNDERSTORMS IN NORTHERN
TRINITY COUNTY THAT COULD BRING SOME RAIN TOO.
WEDNESDAY AND THURSDAY THE ENSEMBLE MODEL CLUSTERS START TO
DIVERGE ON HOW QUICKLY THE RIDGE BUILDS INTO THE AREA. SOME OF THE
MODELS SHOW DRYING AS EARLY AS WEDNESDAY WHILE OTHERS KEEP RAIN
INTO THURSDAY. THIS WILL ALSO HAVE A BIG IMPACT ON HOW QUICKLY
TEMPERATURES WARM BACK UP AND THINGS DRY OUT IN AREAS THAT GOT
RAIN. MKK
AVIATION...05/18Z TAFS
MOSTLY MVFR WITH BRIEF IFR CEILINGS ALONG
THE COASTAL TERMINALS. SATELLITE IMAGERY DEPICTS LOW CLOUDS ERODING
BACK TO THE COAST THIS AFTERNOON, WHILE A SHORTWAVE MOVES NORTHWARD
ALONG THE COAST. THIS SHOULD HELP TO DISRUPT THE COASTAL STRATUS AS
THE LOW-LEVEL INVERSION SLIGHTLY WEAKEN THIS AFTERNOON, RESULTING IN
CEILINGS SCATTERING/DISSIPATING BRINGING A BRIEF PERIOD OF VFR
CONDITIONS LATE THIS AFTERNOON/EARLY EVENING. OTHERWISE, ONSHORE
FLOW WILL PUSH BACK THE STRATUS INLAND DURING THE EVENING. A DEEP
MARINE LAYER WITH A DEPTH UP TO AROUND 3500 FEET ALONG THE NORTH
COAST IS EXPECTED TO REDEVELOPED ONCE AGAIN TONIGHT INTO SATURDAY.
PATCHY DRIZZLE IS EXPECTED TO OCCUR ALONG THE COAST WITH THIS
SATURATED LAYER. EXPECT MAINLY MVFR CEILINGS THROUGH SATURDAY
MONRING. SURFACE WINDS FROM SSW AROUND 5 KTS, BECOMING VERY LIGHT S
WINDS AND VARIABLE AFTER 05/03Z.
FOR INLAND AREAS: PREVAILING VFR CONDITIONS WITH HIGH LEVEL CLOUDS
STREAMING ACROSS THE AREA, INCLUDING IN KUKI. ANOTHER PERIOD OF MVFR
CEILINGS IS EXPECTED ONCE AGAIN AT UKI AROUND 06/13Z WITH A SLIGHTLY
DEEPER MARINE LAYER. ANY LOW CLOUDS IS EXPECTED TO CLEAR OUT AT
UKI WITH THE DIURNAL HEATING SATURDAY MORNING AROUND 16Z. /ZVS
MARINE
GENERALLY LIGHT TO GENTLE NORTHERLY BREEZES, WITH LOCALIZE
GUSTY WINDS UP TO 25 KNOTS IN THE LEEWARD OF CAPE MENDOCINO THIS
AFTERNOON. WINDS SHIFT TO SOUTHERLY AND SLIGHTLY INCREASE AHEAD OF A
FRONTAL SYSTEM THIS WEEKEND. SMALL, MID- PERIOD NW AND SW SWELLS
WILL PERSIST THROUGH THE WEEKEND. OTHERWISE, RELATIVELY CALM
CONDITIONS WITH LIGHT WINDS AND SEAS BELOW 5 FEET ARE EXPECTED
ACROSS THE COASTAL WATERS THIS WEEKEND AND EARLY NEXT WEEK AS AN
AREA OF LOW PRESSURE APPROACHES FROM THE WEST.
MONDAY, THERE IS A CHANCE (15-25%) OF THUNDERSTORMS IN THE WAKE OF
THE FRONT ON MONDAY, ESPECIALLY NORTH OF CAPE MENDOCINO. LIGHTNING
STRIKES AND ERRATIC GUSTY WINDS ARE POSSIBLE WITH THE STRONGEST
STORMS. /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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