Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 031125
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
425 AM PDT THU SEP 3 2015

.SYNOPSIS...NEAR TO BELOW NORMAL TEMPERATURES WILL CONTINUE
ACROSS THE REGION THIS WEEK AS A LOW PRESSURE TROUGH PERSISTS
OVER THE WEST COAST. SCATTERED SHOWERS AND A FEW THUNDERSTORMS
ARE POSSIBLE OVER THE INTERIOR ON FRIDAY. WARMER INTERIOR
TEMPERATURES ARE EXPECTED NEXT WEEK.

&&

.DISCUSSION...AN UPPER TROF CONTINUES PARKED OVER THE PAC NW.
PATCHES OF LOW CLOUDS ARE EVIDENT ON SATELLITE IMAGERY WITH THE
BULK OF THE CLOUDINESS JUST NE OF THE AREA. THE W COAST UPPER TROF
IS FORECAST TO DIG THRU FRI NIGHT...THEN LIFT NE RAPIDLY ON SAT
AND SUN. AS THE TROF DIGS...AN UPPER LOW WILL NEARLY CUT OFF IN
THE BASE OF THE TROF OVER N CA. THIS FEATURE WILL SUPPORT OUR NEXT
CHANCE OF RAIN...ISOLATED TO LOW END CHANCE SHOWERS OVER MAINLY
THE INTERIOR FOR FRI INTO FRI NIGHT. INCREASED INSTABILITY MAY
SUPPORT AN ISOLATED THUNDERSTORM OR TWO OVER TRINITY COUNTY FRI
AFTERNOON AND EVENING. THE NAM IS HINTING AT ISOLATED SHOWER
ACTIVITY THIS AFTERNOON AS WELL OVER THE EXTREME E...AND THAT
MODEL APPEARS TO BE HANDLING MOISTURE PARAMETERS THE BEST.
HOWEVER...LOOKING AT MODEL SOUNDINGS...IT APPEARS THAT THE
ATMOSPHERE WILL BE A BIT TOO DRY IN OUR COUNTY WARNING AREA TODAY.

THE DEPARTING LOW WILL LEAVE A WEAK...BAGGY TROF JUST SE
OF THE AREA VERY EARLY NEXT WEEK WITH MORE RIDGING EXPECTED
THEREAFTER. WITH THE TROF OVER THE W COAST...TEMPERATURES WILL
REMAIN NEAR TO BELOW NORMAL THRU SAT. TEMPERATURES WILL WARM TO
ABOVE CLIMO OVER THE INTERIOR BY NEXT WEEK. /SEC

&&

.AVIATION...THROUGH THE EARLY MORNING...ACV WILL LIKELY REMAIN
VERY NEAR THE EDGE OF AN AREA OF BROKEN MVFR STRATUS...LIKELY
BOUNCING BETWEEN SCATTERED AND BROKEN UNTIL MIXING CLEARS THE
CLOUDS OUT COMPLETELY LATE IN THE MORNING. PATCHY STRATUS MAY
REDEVELOP OVERNIGHT TONIGHT NEAR ACV...BUT MUCH LIKE TONIGHT IS
NOT EXPECTED TO BE WIDESPREAD. AT ALL OTHER SITES...VFR CONDITIONS
ARE EXPECTED FOR THE NEXT 24 HOURS...WITH BREEZY NW WINDS AT
COASTAL SITES.

&&

.MARINE...THE PREVIOUS FORECAST LOOKS TO BE LARGELY ON TRACK AS
OF THIS MORNING...AS WINDS CONTINUE TO GRADUALLY INCREASE
THROUGHOUT THE WATERS IN RESPONSE TO A TIGHTENING PRESSURE
GRADIENT BETWEEN THE PACIFIC HIGH AND INLAND THERMAL TROUGH. WHILE
WIND SPEEDS APPEAR TO BE LAGGING PREDICTED WIND SPEEDS SLIGHTLY
THUS FAR...THE TREND THROUGHOUT THE OVERNIGHT PERIOD HAS BEEN
UPWARDS...AND THIS IS EXPECTED TO CONTINUE THROUGH THE DAY TODAY.
BY MID AFTERNOON...WIDESPREAD FRESH TO STRONG BREEZES WITH
OCCASIONAL NEAR GALE FORCE GUSTS ARE LIKELY...PARTICULARLY IN THE
SOUTHERN WATERS AND NEAR CAPE MENDOCINO. WHILE STILL TECHNICALLY
BELOW SMALL CRAFT CRITERIA AT 8 TO 9 FEET AND A DOMINANT PERIOD
OF 12 SECONDS...SPECTRAL PLOTS FROM AREA BUOYS ARE BEGINNING TO
REFLECT AN INCREASING CONCENTRATION OF WAVE ENERGY IN SHORTER
PERIODS...WHICH INDICATES THAT STEEPER SHORT PERIOD SEAS ARE
DEVELOPING IN RESPONSE TO THE INCREASING WINDS. THROUGH THE
REMAINDER OF THE DAY AND INTO TONIGHT...THE BUILDING NORTHERLY
SHORT PERIOD SEAS WILL LIKELY BECOME THE DOMINANT WAVE GROUP IN
MUCH OF THE WATERS...EVENTUALLY BECOMING NEARLY INDISTINGUISHABLE
FROM THE ALREADY PRESENT MID PERIOD NORTHWESTERLY SWELL. WINDS
WILL BEGIN TO DECREASE SLIGHTLY FRIDAY MORNING AS A PASSING
SHORTWAVE HELPS TO RELAX THE SURFACE PRESSURE GRADIENT...
HOWEVER...THIS WILL BE SHORT LIVED AS THE PACIFIC HIGH WILL ASSERT
ITSELF ONCE AGAIN OVER THE WEEKEND. THIS SHOULD AT LEAST HELP SEAS
TO SETTLE SOMEWHAT...PARTICULARLY IN THE NORTHERN WATERS WHERE
THEY MAY DROP BELOW ADVISORY CRITERIA FOR A DAY OR SO BEFORE
INCREASING AGAIN AND REMAINING THAT WAY THROUGH THE EARLY HALF OF
THE WEEK.

IN ADDITION TO THE INCREASING SHORT PERIOD SEAS...A MODEST
SOUTHWESTERLY SWELL CURRENTLY PRESENT IN THE WATERS WILL CONTINUE TO
DECAY OVER THE NEXT SEVERAL DAYS...AND ITS PRESENCE WILL BECOME
DECREASINGLY SIGNIFICANT.  LATE IN THE WEEKEND...A SERIES OF
SMALL...LONG PERIOD SOUTHWESTERLY SWELL GROUPS WILL MOVE INTO THE
WATERS...BUT ARE NOT LIKELY TO BE LARGE ENOUGH TO CAUSE SIGNIFICANT
ISSUES. STILL...THEIR PRESENCE MAY BE FELT ALONG BEACHES MOSTLY
SOUTH OF CAPE MENDOCINO...ESPECIALLY IF SWELLS COME IN A BIT LARGER
THAN ANTICIPATED.

&&

.FIRE WEATHER...RH RECOVERIES HAVE BEEN GOOD TONIGHT...WITH MOST
HUMIDITY VALUES ABOVE 70 PERCENT. DRIER AIR IS EXPECTED EARLY
NEXT WEEK AS WEAK OFFSHORE FLOW DEVELOPS AND TEMPERATURES WARM.

AS MENTIONED ABOVE...A DIGGING UPPER TROF AND NEARLY CUT OFF LOW
MAY BRING ENOUGH INSTABILITY FOR AN ISOLATED THUNDERSTORM OR TWO
FRI AFTERNOON AND EVENING OVER TRINITY COUNTY...PERHAPS EXTENDING
S INTO THE YOLLA BOLLYS. QPF VALUES ARE EXPECTED TO BE FAIRLY
LIGHT WITH VERY LOCALIZED HIGHER AMOUNTS BENEATH ANY
THUNDERSTORMS. /SEC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 9 AM FRI FOR PZZ450-455-470.
     SMALL CRAFT ADVISORY UNTIL 3 AM MON FOR PZZ475.

&&

$$

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