617
FXUS66 KEKA 162133
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
233 PM PDT WED SEP 16 2026
KEY MESSAGES
* SLIGHT CHANCE (10%) OF THUNDERSTORMS OVER THE INTERIOR AND MOVING
TOWARDS THE COAST THROUGH WEDNESDAY NIGHT.
* SLIGHT CHANCE (10%) OF THUNDERSTORMS AROUND THE TRINITY ALPS
THURSDAY AFTERNOON.
* WARMER AND DRIER INTERIOR TEMPERATURES FOR THE INTERIOR INTO THE
WEEKEND WITH STRONGER MARINE LAYER ALONG SHORE.
SYNOPSIS
COOL AND MOIST MARINE AIR WILL PEAK OVER THE AREA
THURSDAY ALONGSIDE A SLIGHT CHANCE OF THUNDERSTORMS IN TRINITY
COUNTY. WARMER AND DRIER CONDITIONS WILL REBUILD THIS WEEKEND WITH
SHALLOW MARINE AIR ALONG SHORE.
DISCUSSION
A DEEP CUTOFF TROUGH HAS SLOWLY PUSHED ON LAND
TODAY. THIS HAS GREATLY WEAKENED WINDS ALONG SHORE BUT HAS OTHERWISE
HELPED SLIGHTLY COOLED CONDITIONS ACROSS THE AREA. EVEN THE WARMEST
INTERIOR VALLEYS HAVE STRUGGLED TO REACH 80. THE TROUGH IS ALSO
GENERATING ENHANCED INSTABILITY WITH BROAD CUMULUS FORMATION ACROSS
THE INTERIOR THIS AFTERNOON. CONVECTIVE MODELS SHOW MUCAPE VALUES OF
500 TO 1000 J/KG LATE THIS AFTERNOON AND THROUGH THE EVENING.
MOISTURE IS GENERALLY LACKING, BUT WATER VAPOR SHOWS SOME MOISTURE
ACCUMULATION CENTERED AROUND EASTERN HUMBOLDT. SOME HIGH RESOLUTION
MODELS, PARTICULARLY THE RRFS, SHOW SCATTERED THUNDERSTORMS LATE
THIS AFTERNOON THROUGH THE EVENING. CHANCES ARE GENERALLY ONLY
AROUND 10% WITH THE GREATEST PROBABILITY OVER THE YOLLA BOLLYS,
ALONG SOUTH FORK RIDGE, NEAR ORLEANS, AND AROUND THE SMITH RIVER
VALLEY. ANY STORMS THAT FORM WOULD BE WEAK WITH ONLY ISOLATED
LIGHTNING, WEAK OUTFLOW, AND LIGHT RAIN. STORMS WOULD MOVE TOWARDS
THE COAST WITH SOME SLIGHT POTENTIAL OF IT STORMS EVEN REACHING THE
COAST, ESPECIALLY AROUND KLAMATH.
A COUPLE MODELS, MOSTLY HRRR, SHOW SOME ISOLATED STORM POTENTIAL (5%
CHANCE) OVERNIGHT, MOSTLY AROUND THE SMITH RIVER VALLEY. LOW
PRESSURE WILL CONTINUE TO MEANDER EASTWARD ON THURSDAY. THIS WILL
PULL SOME MORE MARINE INFLUENCE NEAR SHORE WITH WEAK SOUTHERLY WIND.
SOUTHERLY WIND MAY ALSO HELP PULL IN SOME MARINE FOG AND CLOUDS
CLOSER TO THE LOST COAST AND INTO THE UPPER RUSSIAN RIVER. THE
CHANCE (10%) OF THUNDERSTORMS WILL CONTINUE, BUT THE CORE OF
INSTABILITY AND THUNDERSTORM CHANCES WILL SHIFT FURTHER EAST, MORE
FOCUSED AROUND THE TRINITY ALPS. THE POTENTIAL NEAR THE COAST WILL
REDUCE.
A HIGH PRESSURE RIDGE WILL GRADUALLY REBUILD FRIDAY AND INTO THE
WEEKEND. THIS PATTERN WILL ALLOW FOR INTERIOR TEMPERATURES TO DRY
BACK OUT AND WARM BACK INTO THE 90S. MODERATE NORTH WINDS WILL
RETURN NEAR SHORE, HELPING FORM A SHALLOW BUT PERSISTENT MARINE
LAYER ESPECIALLY NORTH OF CAPE MENDOCINO. HIGH PRESSURE WILL MOST
LIKELY PERSIST THROUGH NEXT WEEK. MOST MODELS SHOW WEAK TO MODERATE
HIGH PRESSURE, BUT ABOUT 20% OF ENSEMBLE MEMBERS SHOW UNUSUALLY
STRONG HIGH PRESSURE AROUND NEXT TUESDAY THAT COULD PUSH INTERIOR
HIGHS CLOSER TO 100. ASIDE FROM ISOLATED SHOWERS TODAY AND TOMORROW
THERE IS NEAR 0% CHANCE OF WETTING RAIN FOR THE NEXT 10 DAYS. /JHW
AVIATION
GROWING INSTABILITY FROM PASSING LOW PRESSURE HAS
ALLOWED FOR CLEAR, MOSTLY VFR CONDITIONS TODAY EXCEPT FOR AN
ISOLATED STRIP OF IFR CLOUDS AROUND CRESCENT CITY. VFR CONDITIONS
WILL PERSIST INTO THE EVENING WITH INSTABILITY LIKELY DELAYING
MARINE LAYER FORMATION. MOST MODELS SHOW MARINE CLOUDS REFORMING
BEFORE OR AROUND MIDNIGHT, BUT SOUTHERLY WIND WILL CHANGE THEIR
CHARACTER. THERE IS A 60% CHANCE OF LIFR CEILING AROUND CRESCENT
CITY BUT ONLY 30% CHANCE FOR HUMBOLDT BAY. SOUTHERLY WIND ALSO HAS
SOME POTENTIAL TO PULL IFR CLOUDS UP THE RUSSIAN RIVER VALLEY WITH A
20% CHANCE OF IFR CEILINGS AROUND UKIAH EARLY THURSDAY MORNING.
LINGERING INSTABILITY WILL MOST LIKELY ALLOW QUICK CLEARING TO VFR
THURSDAY, THOUGH CLOUDS MIGHT HANG AROUND A BIT LONGER THAN THEY DID
TODAY. /JHW
&
MARINE
LOW PRESSURE MOVING INLAND HAS WEAKENED NORTHERLY WIND AND
PUSHED STRONG WINDS FURTHER OFFSHORE. SEAS HAVE FALLEN IN THE INNER
WATERS ALONG WITH THE WIND AND WILL CONTINUE TO FALL IN THE OUTER
WATERS OVERNIGHT WITH SEAS GENERALLY BELOW 6 FEET BY MID THURSDAY
MORNING. SOUTHERLY WINDS WILL FORM ALONG SHORE IN THE INNER WATERS
EARLY THURSDAY WITH GENTLE GUSTS STAYING BELOW 15 KTS. MODERATE TO
STRONG NORTHERLY WINDS WILL GRADUALLY RETURN TO THE SOUTHERN WATERS
BY FRIDAY AND GRADUALLY SPREAD NORTH THROUGH THE WEEKEND, THOUGH
WINDS WILL MOST LIKELY REMAIN MUCH CALMER CLOSER TO SHORE. SHORT
PERIOD WIND WAVES WILL DOMINATE THE MARINE ENVIRONMENT WITH ONLY A
VERY MINOR SOUTHWEST MID PERIOD SWELL UP TO 2 FEET TO SPEAK OF. /JHW
FIRE WEATHER
THE THUNDERSTORM RISK DISCUSSED ABOVE IS THE MAIN
FIRE WEATHER CONCERN OVER THE NEXT 36 HOURS. THIS IS A CHANCE (10%)
OF ISOLATED WEAK THUNDERSTORMS OVER INTERIOR HUMBOLDT AND DEL NORTE
THROUGH WEDNESDAY NIGHT WITH STORMS MOVING EAST TOT WEST TOWARDS THE
COAST. THERE IS SLIGHT POTENTIAL FOR STORMS LATE IN THE NIGHT,
MOSTLY OVER THE SMITH RIVER. STORM POTENTIAL WILL REMAIN THURSDAY,
BUT SHIFT FOCUS TOWARDS THE TRINITY ALPS AREA. ANY STORMS WILL BE
WEAK WITH LIGHT RAIN. ASIDE FROM STORMS, WINDS ARE MOSTLY GENTLE AND
TERRAIN DRIVEN WITH GENERALLY HIGH RH OVER 30 PERCENT AND GOOD
OVERNIGHT RECOVERIES. ANY NEW STARTS ARE NOT EXPECTED TO SPREAD
RAPIDLY. CONDITIONS WILL SIGNIFICANTLY DRY AND WARM OVER THE WEEKEND
WITH THERMAL BELTS CONTRIBUTING TO MUCH WORSE RH RECOVERY. THERE IS
LITTLE TO NO CHANCE OF WETTING RAIN FOR THE NEXT 10 DAYS. /JHW
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 8 PM PDT THIS EVENING FOR PZZ455.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PZZ470-475.
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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