Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 312258
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
358 PM PDT MON AUG 31 2015

.SYNOPSIS...TEMPERATURES WILL REMAIN NEAR OR BELOW NORMAL FOR THE
NEXT SEVERAL DAYS AS A TROUGH SITS OVER THE WEST COAST. LITTLE TO
NO RAIN IS EXPECTED...ALTHOUGH A FEW LIGHT SHOWERS WILL BE
POSSIBLE NORTH OF CAPE MENDOCINO EARLY WEDNESDAY.


&&

.DISCUSSION...DRY CONDITIONS WILL PERSIST OVERNIGHT AS A TRANSIENT
SHORTWAVE RIDGE MOVES THROUGH THE PACIFIC NORTHWEST. BOUNDARY LAYER
MOISTURE INCREASES SUBSTANTIALLY OVERNIGHT ALONG THE COAST AND INTO
SOME INTERIOR VALLEYS LIKELY RESULTING IN ANOTHER ROUND OF INTERIOR
VALLEY FOG AND COASTAL STRATUS TONIGHT INTO TUESDAY MORNING.

DURING THE DAY TUESDAY...HEIGHTS WILL GRADUALLY BEGIN TO FALL ACROSS
THE NORTHEAST PACIFIC AS A POTENT SHORTWAVE SLIDES DOWN THE BRITISH
COLUMBIA COAST. TEMPERATURES TUESDAY AFTERNOON ARE NOT LIKELY TO BE
AFFECTED MUCH...BUT A COOL DOWN IS EXPECTED WEDNESDAY THROUGH FRIDAY
AS THE AXIS OF THE PRIMARY TROUGH SLIDES EASTWARD ONTO THE WEST
COAST AND SEVERAL SHORTWAVES MOVE THROUGH THE AREA. ASIDE FROM A FEW
LIGHT SHOWERS IN OUR NORTHERN AREAS ASSOCIATED WITH A WASHED OUT
FRONT OVERNIGHT TUESDAY AND EARLY WEDNESDAY...NORTHWEST CA SHOULD
REMAIN DRY THROUGHOUT THIS PERIOD. ANOTHER LONG SHOT FOR RAIN EXISTS
ACROSS THE INTERIOR TOWARDS THE END OF THE WEEK AS A FINAL VORT MAX
DROPS SOUTH INTO THE PACIFIC NORTHWEST...BUT GUIDANCE HAS THUS FAR
ALMOST UNANIMOUSLY KEPT PRECIPITATION NORTH AND EAST OF OUR AREA.

AT SOME POINT OVER THE WEEKEND...THE TROUGH AXIS WILL FINALLY BEGIN
TO SLIDE EASTWARD...RESULTING IN A WARMING AND DRYING TREND. MODEL
GUIDANCE IS A BIT INCONSISTENT REGARDING WHEN EXACTLY THIS WILL
OCCUR...SO FOR NOW WILL KEEP TEMPERATURES ON THE COOL SIDE UNTIL
SUNDAY WHERE CONFIDENCE IS HIGHEST IN WARMER TEMPERATURES. RPA/BRC


&&

.AVIATION...LOW CLOUDS/FOG ALONG THE COAST AND ACROSS INTERIOR RIVER
VALLEYS THIS MORNING HAVE GIVEN WAY TO CLEAR CONDITIONS THIS
AFTERNOON...WITH GUSTY NORTHERLY WINDS ALONG THE COAST. WINDS WILL
GRADUALLY SUBSIDE THIS EVENING. GOING INTO THE OVERNIGHT...MODELS
INDICATE BL RH INCREASING ALONG THE COAST AND INTO INTERIOR RIVER
VALLEYS. MVFR TO IFR CIGS AND VSBYS ARE POSSIBLE. THINK THAT LOW
CLOUDS ACROSS THE INTERIOR WILL BE SIMILAR TO LAST NIGHT. LIGHT
WINDS AND VFR CONDITIONS WILL PREVAIL AT KUKI THROUGH THE TAF
PERIOD. STP


&&

.MARINE...AS OF 21Z...NEAR SHORE BUOY OBSERVATIONS WERE REPORTING
SEAS OF 7 TO 9 FEET WITH A DOMINANT PERIOD AROUND 12 TO 13
SECONDS. AN 18Z ASCAT PASS CAUGHT THE OUTER WATERS SHOWING
MODERATE TO STRONG WINDS SOUTH OF CAPE MENDOCINO AND LIGHT TO
MODERATE WINDS NORTH OF THE CAPE. THIS MATCHES UP WELL WITH THE
WIND FORECAST. NORTHERLY WINDS AND SHORT PERIOD SEAS WILL CONTINUE
TO BUILD THROUGH TONIGHT...BEFORE BEGINNING TO SUBSIDE ON TUESDAY.
THE HIGHEST WINDS AND SEAS WILL BE SOUTH OF CAPE MENDOCINO. HAVE
CONTINUED THE SMALL CRAFT ADVISORIES FOR THE SOUTHERN WATERS INTO
TUESDAY. A LONG PERIOD WESTERLY SWELL WILL CONTINUE TO PROPAGATE
ACROSS THE WATERS THROUGH TONIGHT. LIGHT TO MODERATE WINDS WILL
PREVAIL THROUGH AT LEAST THURSDAY...WITH NORTHERLY WINDS AND SEAS
INCREASING BY THE WEEKEND AS HIGH PRESSURE BUILDING OVER THE
EASTERN PACIFIC INTERACTS WITH A TROUGH OF LOW PRESSURE MOVING
INLAND. STP


&&

.FIRE WEATHER...RH VALUES ON THE HIGHER MOUNTAIN PEAKS LAST NIGHT
BOTTOMED OUT IN THE 30-40 PERCENT RANGE...LIKELY AN INDICATION OF
THE DRY AIR ALOFT THAT IS PREDICTED TO ONCE AGAIN SINK OVERNIGHT
TONIGHT. AS THE ATMOSPHERE COOLS THIS EVENING RH WILL SPIKE IN ALL
AREAS OF NORTHWEST CALIFORNIA...BUT OVERNIGHT AS THE DRY LAYER
SINKS TO NEAR 3000 FT THE RH VALUES ON THE MOUNTAIN PEAKS WILL
DECREASE...PARTICULARLY OVER THE NORTHERN AND WESTERN PORTIONS OF
NORTHWEST CALIFORNIA. WHAT SEEMED UNLIKELY LAST NIGHT...RH FALLING
INTO THE SINGLE DIGITS IN THE EARLY MORNING HOURS ABOVE 3000
FEET...NOW SEEMS PLAUSIBLE CONSIDERING THE DRYING THAT OCCURRED
LAST NIGHT. MODEL GUIDANCE IS UNANIMOUS IN KEEPING WINDS LIGHT
OVERNIGHT...SO EVEN WITH THE DRY CONDITIONS...HIGH FIRE DANGER
CONDITIONS REQUIRING FIRE WEATHER WARNINGS IS NOT ANTICIPATED.
HOWEVER A HEADLINE HAS BEEN INCLUDED IN THE FIRE WEATHER FORECAST.

DRY CONDITIONS WILL PERSIST THROUGH TUESDAY FOLLOWED BY A QUICK
MOISTENING OF THE ATMOSPHERE AS A WEAKENING FRONT APPROACHES AND
DISSIPATES OVER NORTHWEST CALIFORNIA TUESDAY NIGHT THROUGH
WEDNESDAY. A FEW LIGHT SHOWERS ARE EXPECTED IN HUMBOLDT AND DEL
NORTE COUNTIES WITH WETTING RAINS UNLIKELY. MODEL SOUNDINGS
INDICATE THAT THE COLUMN WILL QUICKLY DRY OUT AGAIN ON THURSDAY
AND FRIDAY DESPITE A TROUGH REMAINING OVER THE WEST COAST.

MUCH DRIER AND WARMER CONDITIONS WILL DEVELOP OVER THE WEEKEND INTO
EARLY NEXT WEEK AS THE TROUGH MOVES EAST OF THE AREA. OFFSHORE FLOW
WITH GUSTY EAST WINDS WILL BE POSSIBLE DURING THE OVERNIGHT PERIODS.
RPA


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 9 AM PDT TUESDAY FOR PZZ455.

     SMALL CRAFT ADVISORY UNTIL 3 PM PDT TUESDAY FOR PZZ475.

&&

$$

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