882
FXUS66 KEKA 121917
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1217 PM PDT FRI SEP 12 2025
SYNOPSIS
DRIER CONDITIONS TODAY AND SATURDAY WITH BELOW NORMAL
TEMPERATURES. A PERIOD OF RAIN SHOWERS AND OFFSHORE LIGHTNING FOR
THE NORTH COAST ON SUNDAY MORNING. THE SYNOPTIC WEATHER PATTERN
TRENDING WARMER AND DRIER EARLY NEXT WEEK.
DISCUSSION
A SKINNY SHORTWAVE RIDGE MOVES OVER THE AREA
TODAY THROUGH SATURDAY, PROMOTING DRIER AIRMASS AND WARMER
TEMPERATURES ACROSS THE INTERIOR. EXPECT SUNNY SKY ACROSS MUCH OF
THE FORECAST AREA, BUT MOSTLY CLOUDY DAY ALONG THE NORTH COAST WITH
PERSISTENT COASTAL STRATUS. INTERIOR HIGH TEMPERATURES ARE
FORECASTED TO BE IN THE UPPER 70'S TO UPPER 80'S TODAY AND SATURDAY.
ONSHORE FLOW WILL REMAIN THE COASTAL AREAS THE AFTERNOON
TEMPERATURES IN THE LOW TO MID 60'S.
THE RIDGE ALOFT SHIFTS EASTWARD ON SATURDAY, FOLLOWED BY A WEAK,
MOIST H5 TROUGH. MODELS ARE BEGINNING TO SHOW SIGNS OF AGREEMENT ON
THE APEX OF THE TROUGH BEING OVER SOUTHERN OREGON/NORTHERN
CALIFORNIA. HOWEVER, AS THE COLD FRONT MOVES OVER THE AREA, MODELS
ARE SHOWING DIFFERENCES IN TEMPERATURES FOR THE ATMOSPHERIC PROFILE
LEADING TO UNCERTAINTY FOR CONVECTIVE THUNDERSTORMS. DETERMINISTIC
MODEL SOUNDING DATA SHOWS TEMPERATURES AT THE EQUILIBRIUM LAYER ARE
SHOWN TO BE BELOW -20C OFFSHORE AND RIGHT AT, OR A LITTLE WARMER
THAN, -20C OVER CRESCENT CITY. WHILE CONFIDENCE IN THUNDERSTORMS IS
LOW, A PUSH OF LOW LEVEL MOISTURE IN THE FORM OF LIGHT RAINSHOWERS
IS EXPECTED MAINLY ALONG THE COASTAL RANGE IN DEL NORTE AND NORTHERN
HUMBOLDT COUNTIES AND IN THE HIGHER TERRAIN LATE SATURDAY NIGHT
THROUGH THE DAY ON SUNDAY. TOTAL RAINFALL AMOUNTS ARE BETWEEN 0.1"-
0.25" WITH THE POSSIBILITY FOR VARIATION TO EITHER SIDE OF THIS
RANGE IF STORMS ARE TRAINING, OR MISS CERTAIN AREAS COMPLETELY. FOR
OTHER AREAS OF THE FORECAST ZONE INLAND AND DOWN SOUTH, DRY WEATHER
AND SOME COOLING OF HIGH TEMPS IS EXPECTED.
IN THE WAKE OF THIS TROUGH, AN UPPER LEVEL RIDGE AND SURFACE HIGH
PRESSURE WILL QUICKLY FILL IN OVER THE REGION ON SUNDAY. BREEZY
NORTHERLY WINDS ARE FORECAST TO DEVELOPED OVER MOSTLY COASTAL AREAS
AS SURFACE PRESSURE GRADIENTS TIGHTEN SUNDAY EVENING. NBM
PROBABILITIES INDICATES A 50-80% CHANCE FOR WIND GUSTS GREATER THAN
25 MPH OVER THE EXPOSED RIDGES AND COASTAL HEADLANDS ON SUNDAY.
ALSO, GUSTY WEST-NORTHWEST WINDS WILL MOST LIKELY DEVELOP THROUGH
CHANNELED TERRAIN IN THE INTERIOR BEHIND THE FRONT SUNDAY
AFTERNOON/EVENING.
THIS RIDGE WILL INITIATE A WARMING TREND EARLY THROUGH MID NEXT
WEEK. 850MB TEMPERATURE ANALYSIS SHOWS INTERIOR VALLEYS REACHING OR
EXCEEDING 90'S DEGREES ON MONDAY WITH WARMING INTO THE UPPER 90'S
THROUGH MID NEXT WEEK ACROSS THE WARMER LOCATIONS OF TRINITY, LAKE,
INTERIOR MENDOCINO, AND INTERIOR HUMBOLDT COUNTIES. DES/ZVS
AVIATION...18Z TAFS
CEILINGS ARE HOVERING IN MVFR TO IFR LEVELS,
WITH ANTICIPATED SIMILAR CONDITIONS THROUGH THE AFTERNOON. THE
MARINE LAYER REMAINS DEEPENED AS AN UPPER LOW EXITS N CA. THE
COASTAL STRATUS HAS BECOME WELL EMBEDDED WITH FAR INLAND EXTENT. A
WEAK WIND EDDY WAS OBSERVED MOVING SOUTHWARD ON VISIBLE SATELLITE,
WITH ONLY SLIGHT WEAKNESS/CLEARING NORTH IN THE EDDIE'S WAKE. THE
PROFILER SHOWS A WEAK BUT STRENGTHENING INVERSION, AND THIS
DESCRIBED SETUP LOOKS TO MOSTLY INHIBIT CLEARING THIS AFTERNOON.
SOUNDINGS POINT TOWARD SOME MARINE LAYER COMPRESSION TONIGHT WHICH
MAY ALLOW FOR A SLIGHTLY LONGER PERIOD OF LIFR CEILINGS, MAINLY
THOUGH THE EARLY MORNING HOURS. WINDS WILL REMAIN LIGHT AT THE
COASTAL TERMINALS AND UKI THROUGH 18Z SATURDAY. THERE WILL BE
STRONGER NORTHERLY WINDS AROUND CAPE MENDOCINO AND SHELTER COVE THIS
AFTERNOON, WITH THE POTENTIAL FOR SOME LOW LEVEL WIND SHEAR.
TERMINAL FORECAST/CONFIDENCE...WITH CONTINUED INFLUENCE OF THE UPPER
TROUGH, CONFIDENCE IS LOW ON THE DURATION OF LIFR CEILINGS THROUGH
SATURDAY MORNING, WITH CEC HAVING THE HIGHEST CONFIDENCE FOR BETTER
LIFR DURATION. THERE IS HIGHER CONFIDENCE FOR SUSTAINED IFR TO MVFR
CEILINGS. A SOUTHERLY SURGE OF WIND EARLY SATURDAY MORNING MAY
DIRECT STRATUS UP THE RUSSIAN RIVER VALLEY AND CLOSER TO UKI, BUT
CONFIDENCE WAS TOO LOW TO INCLUDE INDICATIONS OF THIS FOR THIS TAF
ISSUANCE.
CEC: 40-65% CHANCE FOR LIFR (8Z-17Z SATURDAY)
70-95% CHANCE FOR IFR (3Z-18Z SATURDAY)
25-35% CHANCE FOR LESS THAN 1SM VIS (8Z-15Z SATURDAY)
ACV: 30-40% CHANCE FOR LIFR (9Z-17Z SATURDAY)
60-70% CHANCE FOR IFR (6Z-18Z SATURDAY)
15-25% CHANCE FOR LESS THAN 1SM VIS (10Z-15Z SATURDAY)
UKI: 10-20% MVFR CEILINGS (13Z-16Z SATURDAY)
JJW
MARINE
THE NORTHERLY WINDS HAVE CONTINUED TO TREND HIGHER. WINDS
IN THE SOUTHERN WATER WILL PEAK THIS AFTERNOON AND EVENING WITH
GUSTS OF 20-25 KTS, WITH LOCALLY HIGHER GUSTS OVER 30 KTS AROUND
CAPE MENDOCINO. SEAS ARE A MIX OF SHORT PERIOD WAVES OF 6-8 FT AND A
LONGER PERIOD NORTHWESTERLY SWELL 5-7 FT. THE PRESSURE GRADIENT IS
ALREADY BEGINNING TO EASE AS AN UPPER LOW WEAKENS OVER THE GREAT
BASIN. WINDS IN THE NORTHERN ZONES WILL DROP BELOW 15 KTS THIS
EVENING, AND FURTHER WEAKENING OF THE NORTHERLIES WILL OCCUR IN ALL
ZONES TONIGHT THROUGH SATURDAY. WINDS WILL GENERALLY DROP TO 10-15
KTS BY SATURDAY AFTERNOON, WITH EVEN LIGHTER WINDS IN THE NORTHERN
ZONES.
A SHORTWAVE TROUGH WILL BRING A SLIGHT CHANCE FOR THUNDERSTORMS OVER
THE NORTHERN WATERS LATE SATURDAY AND INTO SUNDAY MORNING. HIGH
PRESSURE WILL BEGIN BUILDING BACK IN LATER SUNDAY BEHIND THE TROUGH,
AND THESE TWO FEATURES WILL INCREASE THE NORTHERLY WINDS LATE SUNDAY
THROUGH MONDAY BEFORE BACKING DOWN TUESDAY.
JJW
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 11 AM PDT SATURDAY FOR PZZ455-
475.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
PZZ470.
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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