071
FXUS66 KEKA 170819
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
119 AM PDT WED JUN 17 2026
SYNOPSIS
THE INTENSE INTERIOR HEAT WILL CONTINUE TO SUBSIDE TODAY
AS HIGH PRESSURE WEAKENS. A PASSING UPPER-LEVEL DISTURBANCE WILL
BRING TEMPERATURES DOWN TO NEAR SEASONAL AVERAGES BY FRIDAY, ALONG
WITH A LOW PROBABILITY OF LIGHTNING STRIKES OVER DRY MOUNTAIN
FUELS.
KEY MESSAGES:
* HIGH TEMPERATURES DECREASE THROUGH FRIDAY, LOWERING HEAT RISK.
* POTENTIAL FOR DRY THUNDERSTORMS OVER INTERIOR MOUNTAINS LATE
THURSDAY AND FRIDAY.
* MARINE STRATUS WILL PERSIST NEAR THE COAST, LIFTING GRADUALLY
LATE IN THE WEEK.
DISCUSSION
THE HEATWAVE HAS PEAKED, WITH VALLEY LOCATIONS COOLING
DOWN INTO THE UPPER 80S TO MID-90S UNDER REDUCED HEATRISK
CATEGORIES. ALONG THE COAST, ENHANCED NORTHERLY WINDS SHOULD DISRUPT
THE MARINE INVERSION ENOUGH TO CLEAR COASTAL SKIES WEDNESDAY
AFTERNOON, THOUGH A SHALLOW STRATUS DECK IS EXPECTED TO REDEVELOP
WEDNESDAY NIGHT INTO THURSDAY MORNING.
A DISTINCT COOLING TREND TAKES PLACE THURSDAY AS AN UPPER-LEVEL
TROUGH MOVES TOWARD THE AREA. THIS FEATURE WILL INTRODUCE INCREASED
CLOUD COVER AND STRENGTHEN ONSHORE FLOW. CONSEQUENTLY, INTERIOR
HIGHS WILL DROP INTO THE 80S BY THURSDAY, WHILE THE COASTAL MARINE
LAYER BECOMES DEEPER.
MID-LEVEL MOISTURE ADVECTING NORTHWARD FROM THE SACRAMENTO VALLEY
WILL INTERFACE WITH THE COOL POOL ALOFT ASSOCIATED WITH THE
APPROACHING TROUGH. THIS SETUP INTRODUCES A 10 TO 20 PERCENT CHANCE
OF DRY THUNDERSTORMS ACROSS HIGHER TERRAIN IN TRINITY AND MENDOCINO
COUNTIES DURING THE LATE AFTERNOON AND EVENING HOURS FOR BOTH
THURSDAY AND FRIDAY. TEMPERATURES WILL REACH THEIR LOWEST POINTS ON
FRIDAY BEFORE A MINOR WARMING TREND INITIATES OVER THE WEEKEND.
AVIATION
EARLY MORNING LIFR CEILINGS AND PERHAPS EVEN LIFR
VISIBILITY FROM TIME TO TIME WILL BECOME VFR BY AFTERNOON WEDNESDAY
DUE TO INCREASED BOUNDARY LAYER MIXING AND INCREASING NORTHWEST
WINDS. CURRENT CONFIDENCE (80% CHANCE) FAVORS RETURN OF LOW STRATUS
AND REDUCED VISIBILITY WEDNESDAY NIGHT. THE MARINE LAYER WILL BECOME
LESS COMPRESSED ON THURSDAY, ALLOWING FOR QUICKER AFTERNOON CLEARING
AND STRONGER COASTAL SEA BREEZES.
MARINE
A TIGHT PRESSURE GRADIENT BETWEEN OFFSHORE HIGH PRESSURE
AND AN INLAND THERMAL TROUGH IS GENERATING A STRONG NORTHERLY WINDS
ACROSS THE OUTER WATERS, WITH GUSTS REACHING GALE FORCE. THIS
PERSISTENT FETCH HAS GENERATED STEEP, SHORT PERIOD WAVES AS WELL.
NEARSHORE WATERS REMAIN SIGNIFICANTLY CALMER REGARDING WIND SPEED,
THROUGH THE SWELL WILL MAINTAIN WAVE HEIGHTS UP TO 10 FEET THROUGH
WEDNESDAY. CONDITIONS WILL GRADUALLY IMPROVE THURSDAY INTO FRIDAY AS
THE CORE OF THE STRONGEST WINDS SHIFTS FARTHER OFFSHORE.
FIRE WEATHER
EXTREMELY HOT AND DRY CONDITIONS OVER THE PAST
SEVERAL DAYS HAVE DRIVEN ENERGY RELEASE COMPONENT (ERC) VALUES
TOWARD THE 90TH PERCENTILE ACROSS INTERIOR ZONES. WHILE AMBIENT
TEMPERATURES WILL COOL INTO THE 80S AND MINIMUM RELATIVE HUMIDITY
VALUES WILL RECOVER ABOVE 25 PERCENT BY THURSDAY, FINE FUELS WILL
REMAIN HIGHLY RECEPTIVE TO IGNITION.
THE PRIMARY OPERATIONAL CONCERN IS THE RISK OF DRY LIGHTNING
THURSDAY AND FRIDAY EVENINGS. MODEL GUIDANCE CONTAINS UNCERTAINTY
REGARDING THE DEPTH OF MOISTURE, BUT INSTABILITY PROBABILITIES
SUPPORT A 10 TO 20 PERCENT CHANCE OF THUNDERSTORM DEVELOPMENT OVER
THE MOUNTAIN RIDGES OF TRINITY AND MENDOCINO COUNTIES. ANY CLOUD-TO-
GROUND STRIKES WILL CARRY A SIGNIFICANT RISK OF FIRE INITIATION DUE
TO PARCHED STATE OF THE VEGETATION.
COASTAL FLOODING
PERIGEAN SPRING TIDES WILL PEAK WEDNESDAY NIGHT
NEAR 9 FEET SHORTLY AFTER MIDNIGHT ENTERING THURSDAY. MINOR TIDAL
OVERFLOW IS EXPECTED TO IMPACT LOW-LYING AREAS SURROUNDING HUMBOLDT
BAY, INCLUDING LOCAL ROADWAYS NEAR ARCATA BOTTOMS AND SOME
PROPERTIES IN KING SALMON.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
COASTAL FLOOD ADVISORY UNTIL 3 AM PDT WEDNESDAY FOR CAZ103.
NORTHWEST CALIFORNIA COASTAL WATERS...
COASTAL FLOOD ADVISORY UNTIL 3 AM PDT WEDNESDAY FOR PZZ415.
SMALL CRAFT ADVISORY UNTIL 9 PM PDT WEDNESDAY FOR PZZ450.
GALE WARNING UNTIL 9 PM PDT WEDNESDAY FOR PZZ470.
SMALL CRAFT ADVISORY UNTIL 3 PM PDT WEDNESDAY FOR PZZ475.
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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