479
FXUS66 KEKA 080706
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1206 AM PDT WED JUL 8 2026
KEY MESSAGES
* PERSISTENT STRATUS: SEASONABLY COOL CONDITIONS ALONG THE IMMEDIATE
COAST WILL ALTERNATE WITH TYPICAL NIGHT AND MORNING LOW CLOUDS AND
FOG.
* BUILDING INTERIOR HEAT: A ROBUST RIDGE OF HIGH PRESSURE WILL
MAXIMIZE TEMPERATURE ANOMALIES ACROSS ALL INLAND VALLEYS,
INCLUDING LAKE, TRINITY, AND INTERIOR MENDOCINO COUNTIES, STARTING
LATE THIS WEEK.
SYNOPSIS
A STRONG SURFACE HIGH PRESSURE SYSTEM OVER THE EASTERN
PACIFIC INTERACTING WITH AN INTENSE INLAND THERMAL TROUGH WILL
MAINTAIN A SHALLOW MARINE LAYER ALONG THE COAST, BRINGING OVERNIGHT
LOW CLOUDS AND LOCALIZED DENSE FOG. INLAND AREAS WILL REMAIN DRY AND
HOT UNDER A BUILDING UPPER-LEVEL RIDGE. TRIPLE- DIGIT HEAT WILL
BECOME WIDESPREAD ACROSS THE INTERIOR VALLEYS OF TRINITY, MENDOCINO,
AND LAKE COUNTIES BY THURSDAY.
DISCUSSION
THE 500 MB ANALYSIS SHOWS A BUILDING UPPER-LEVEL RIDGE
OVER THE SOUTHWEST U.S. EXTENDING INTO CALIFORNIA. THE PERSISTENT
COASTAL MARINE LAYER IS A RESULT OF A TIGHT LOW-LEVEL ONSHORE
PRESSURE GRADIENT BETWEEN THE OFFSHORE MARINE HIGH AND THE INTERIOR
THERMAL LOW. WIDESPREAD IFR/LIFR CEILINGS AND SOME VISIBILITY
RESTRICTIONS WILL IMPACT COASTAL AREAS THROUGH THE MORNING HOURS.
EXPECT PARTIAL AFTERNOON CLEARING ALONG THE IMMEDIATE COAST AS
DAYTIME HEATING DEEPENS THE MIXING LAYER SLIGHTLY, THOUGH LOW
STRATUS WILL RETURN RAPIDLY AFTER SUNSET.
INLAND AREAS WILL EXPERIENCE SIGNIFICANT HEATING AS THE UPPER RIDGE
STRENGTHENS AND MOVES WESTWARD. SUBSIDENCE WILL COMPRESS THE MARINE
LAYER, KEEPING IT SHALLOW AND CONFINED TO THE COAST AND IMMEDIATE
VALLEYS. HIGH TEMPERATURES ON WEDNESDAY WILL REACH THE 90S TO NEAR
100 DEGREES ACROSS THE INTERIOR VALLEYS OF TRINITY, MENDOCINO, AND
LAKE COUNTIES. BY THURSDAY, TRIPLE-DIGIT HEAT WILL EXPAND ACROSS ALL
INTERIOR ZONES, WITH THE HIGHEST VALUES EXPECTED IN THE DEEPEST
VALLEY FLOORS.
AVIATION
THE MARINE BOUNDARY LAYER REMAINS FIRMLY ESTABLISHED
ALONG THE COAST. KACV AND KCEC ARE EXPERIENCING IFR TO LIFR
CONDITIONS DUE TO LOW STRATUS AND FOG, WITH VISIBILITIES LOWER THAN
1 MILE AT TIMES. CLEARING TO VFR IS EXPECTED BY EARLY WEDNESDAY
AFTERNOON BEFORE STRATUS RETURNS AFTER 03Z. KUKI WILL REMAIN
CONSISTENTLY VFR WITH CLEAR SKIES AND TYPICAL DIURNAL WIND SHIFTS.
MARINE
THE PRESSURE GRADIENT BETWEEN THE OFFSHORE HIGH AND THE
INLAND THERMAL LOW IS TIGHTENING ACROSS THE WATERS. WINDS SOUTH OF
CAPE MENDOCINO ARE SUSTAINED AT 20 TO 25 KNOTS, PRODUCING STEEP,
WIND-DRIVEN SEAS THAT WARRANT A CONTINUATION OF THE SMALL CRAFT
ADVISORY FOR THE SOUTHERN INNER AND SOUTHERN OUTER WATERS.
IN THE NORTHERN OUTER WATERS, WIND SPEEDS ARE MODELED TO INCREASE TO
20 TO 25 KNOTS WITH WAVE HEIGHTS REACHING 9 FEET AT A SHORT 8-
SECOND DOMINANT PERIOD LATE TONIGHT. THESE WAVES WILL BE STEEP AND
CHOPPY. A SMALL CRAFT ADVISORY MAY BE ISSUED ON THIS SHIFT TO
ADDRESS THESE CONDITIONS, OR THE DECISION MAY BE DEFERRED TO THE
UPCOMING MIDNIGHT SHIFT TO SEE IF TRENDS CONTINUE. NORTHERN INNER
WATERS WILL REMAIN COMFORTABLY BELOW ADVISORY THRESHOLDS.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PZZ455-475.
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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