Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 041110
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
410 AM PDT FRI SEP 4 2015

.SYNOPSIS...NEAR TO BELOW NORMAL TEMPERATURES WILL CONTINUE
ACROSS THE REGION THROUGH THIS WEEKEND AS A LOW PRESSURE TROUGH
PERSISTS OVER THE WEST COAST. ISOLATED TO SCATTERED SHOWERS AND
POSSIBLY A THUNDERSTORM WILL OCCUR ACROSS THE INTERIOR TODAY
PRIMARILY NORTH OF HIGHWAY 299. A WARMING TREND IS IN STORE FOR
NEXT WEEK.


&&

.DISCUSSION...AN UPPER LEVEL LOW WILL DIVE DOWN THE WEST COAST
TODAY...BOTTOMING OUT OVER SOUTHERN OREGON AND FAR NORTHERN
CALIFORNIA. MODELS REMAIN CONSISTENT IN THE BEST INSTABILITY AND
MOISTURE REMAINING NORTH AND EAST OF THE COUNTY WARNING AREA...BUT
STILL SLIGHT CHANCES FOR SHOWERS AND POTENTIALLY THUNDERSTORMS EXIST
ACROSS AREAS OF THE INTERIOR PRIMARILY NORTH OF HIGHWAY 299.

AS THE UPPER LOW AND TROUGH AXIS BEGINS TO MOVE EAST OF THE AREA
OVERNIGHT...NORTHERLY WINDS WILL DEVELOP AND COLD AIR WILL FUNNEL
INTO NORTHWEST CALIFORNIA. OVERNIGHT LOW TEMPERATURES HAVE ALREADY
BEEN FALLING INTO THE 30S IN HAYFORK AND RUTH THE LAST COUPLE OF
NIGHTS AND PATCHY AREAS OF FROST HAVE LIKELY FORMED. CONSIDERING
THERE IS POTENTIAL FOR EVEN LOWER TEMPERATURES TONIGHT IF THE
ATMOSPHERE DECOUPLES AND WINDS SUBSIDE AS FORECAST...WENT AHEAD AND
ISSUED A FROST ADVISORY FOR THE SOUTH-CENTRAL TRINITY COUNTY VALLEYS
FOR EARLY SATURDAY MORNING. CONFIDENCE MAY NOT BE QUITE 80 PERCENT
AT THIS TIME...BUT FIGURED IT WOULD BE GOOD TO GET A LITTLE LEAD
TIME ON THIS POTENTIAL CONSIDERING IT IS VERY EARLY IN THE FALL
SEASON.

AS THE UPPER LOW MOVES EAST OVER THE WEEKEND THICKNESS VALUES WILL
INCREASE AND TEMPERATURES WILL WARM OVER THE INTERIOR AS A RIDGE
BUILDS OVER THE WEST COAST AND EASTERN PACIFIC. THIS WILL ALLOW
NORTHERLY WINDS TO INTENSIFY OVER THE COASTAL WATERS AS A THERMAL
TROUGH STRENGTHENS...BRINGING GUSTY CONDITIONS TO COASTAL LAND AREAS
EACH AFTERNOON THROUGH MID NEXT WEEK. HOWEVER THIS WILL ALSO MEAN
THAT MIXING WILL BE VERY EFFICIENT AND OFFSHORE FLOW WILL BE
PRESENT...LIKELY RESULTING IN PLENTY OF SUNSHINE FOR COASTAL
AREAS.

ACROSS THE INTERIOR TEMPERATURES WILL WARM STEADILY THROUGH NEXT
WEEK BACK INTO THE 90S AND POSSIBLY APPROACHING 100 DEGREES IN
SOME VALLEYS BY LATE WEEK. CONSIDERING BOTH THE GFS AND ECMWF
INDICATE THIS WARMING AND DRYING TREND...CONFIDENCE IS HIGHER THAN
USUAL WITH THE CURRENT FORECAST. RPA



&&

.AVIATION...VFR WILL CONTINUE TO PREVAIL AT KACV...KCEC AND KUKI
TODAY UNDER A COOL AND DRY NORTHERLY FLOW REGIME. SOME FLEETING
CLOUDS MAY FORM TONIGHT...HOWEVER ONLY BRIEF MVFR CEILINGS ARE
EXPECTED AT THE COASTAL AIR TERMINALS.


&&

.MARINE...MODERATE NORTHERLY WINDS WILL PERSIST THROUGH THE WEEKEND
AS SURFACE HIGH PRESSURE REMAINS OFFSHORE. WINDS ACROSS THE NORTHERN
WATERS WILL DECREASE BRIEFLY EARLY TODAY AS A PASSING SHORTWAVE
WEAKENS THE PRESSURE GRADIENT. THUS THE ADVISORIES ACROSS THE
NORTHERN WATERS AND SOUTHERN INNER WATERS SHOULD EXPIRE THIS
MORNING. HOWEVER, ONCE THE TROUGH SHIFTS EAST RIDGING WILL
STRENGTHEN THE PRESSURE GRADIENT TONIGHT THROUGH SAT. AN ADVISORY,
AT LEAST FOR THE NORTHERN OUTER WATERS, WILL BE NEEDED FOR NORTH
WINDS OF 15 TO 25 KT THROUGH THE WEEKEND. CONFIDENCE IS LOW THESE
WINDS WILL BE STRONG ENOUGH AT THE COAST TO WARRANT AN ADVISORY SO
WILL WAIT UNTIL THE HIGH RESOLUTION NAM PAINTS A MORE DECISIVE
PICTURE.

BUOY OBSERVATIONS INDICATED SEAS AROUND 8 TO 9 FEET WITH DOMINANT
PERIODS OF 10 TO 11 SECONDS EARLY THIS MORNING. SEAS SHOULD TREND
DOWN SLIGHTLY TODAY AS NORTHERLY WINDS DIMINISH SLIGHTLY. NWPS AND
ENP INDICATE INCREASING OVER THE WEEKEND INTO EARLY NEXT WEEK IN
RESPONSE TO STRONGER NORTHERLY WINDS. ALSO THERE INTERSPERSED WITHIN
THE SHORTER PERIOD SEAS WILL BE LONGER PERIOD SOUTHERLY SNEAKER
WAVES THAT MAY IMPACT BEACHES SOUTH OF THE CAPE. RIGHT NOW THESE
SOUTHERLY WAVES ARE NOT IMPOSING ENOUGH TO WARRANT AN ADVISORY OR
HEADLINE.


&&

.FIRE WEATHER...A DEEP UPPER LEVEL LOW WILL DIVE SOUTH INTO SOUTHERN
OREGON AND FAR NORTHERN CALIFORNIA TODAY BRINGING SLIGHT CHANCES FOR
SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO TO EASTERN DEL
NORTE...FAR NORTHERN HUMBOLDT...AND NORTHERN/EASTERN TRINITY
COUNTIES. THE BEST MODEL INSTABILITY IS OVER THE SISKIYOU MOUNTAINS
AND EASTERN TRINITY COUNTY. INTRODUCED A SLIGHT CHANCE OF
THUNDERSTORMS IN THE SISKIYOUS AND FAR NORTHERN TRINITY COUNTY NEAR
THE RIVER COMPLEX WHERE THUNDER CHANCES ARE NOT ZERO...BUT CHANCES
ARE STILL VERY LOW. THE BEST CHANCE WILL BE OVER EASTERN TRINITY
COUNTY WHERE THUNDER IS MORE CLIMATOLOGICALLY FAVORABLE. ANY
SHOWERS/STORMS WILL DISSIPATE THIS EVENING AS AFTERNOON HEATING
SUBSIDES.

AFTERNOON HIGH TEMPERATURES WILL GRADUALLY WARM THROUGH THE WEEKEND
AND CONDITIONS WILL DRY OUT AS A RIDGE BUILDS OVER THE WEST COAST.
NORTH FLOW BEHIND THE DEPARTING TROUGH/UPPER LOW WILL INTENSIFY
TONIGHT BRINGING GUSTY RIDGE TOP WINDS AND RATHER COLD
TEMPERATURES FOR THIS TIME OF YEAR. BY SATURDAY NIGHT THE TROUGH
WILL BE FULLY EAST OF THE AREA AND OFFSHORE FLOW WILL COMMENCE
WITH THE STRONGEST GRADIENT EXPECTED IN DEL NORTE AND NORTHERN
HUMBOLDT COUNTIES...AS WELL AS OVER SOUTHERN MENDOCINO COUNTY
WHERE GUSTS 20 TO 30 MPH WILL BE POSSIBLE. FOR DEL NORTE COUNTY
THIS COULD BE A SIMILAR SITUATION TO A FEW WEEKS AGO WHEN WINDS
FUNNELED DOWN THE VALLEY THROUGH GASQUET.

AFTER A BRIEF PERIOD OF NORTHWEST WINDS IN THE AFTERNOON WINDS WILL
TURN BACK OFFSHORE AGAIN SUNDAY NIGHT. STRONGER WINDS WILL BE
POSSIBLE IN DEL NORTE COUNTY WHERE THE PRESSURE GRADIENT
TIGHTENS WITH A STRENGTHENING THERMAL TROUGH OVER INTERIOR
CALIFORNIA. ELSEWHERE WINDS WILL LIKELY BE LIGHTER THAN THE NIGHT
BEFORE. ALL OF THIS OFFSHORE FLOW WILL RESULT IN MUCH DRIER RIDGE
TOP CONDITIONS WITH POORER RH RECOVERIES EXPECTED.

THE DRY PATTERN WITH OVERNIGHT OFFSHORE FLOW WILL PERSIST THROUGH
THE WEEK WITH MODELS TRENDING TOWARD AN AMPLIFIED RIDGE OVER THE
EASTERN PACIFIC/WEST COAST AND ABOVE NORMAL TEMPERATURES BY LATE IN
THE WEEK. RPA


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     FROST ADVISORY FROM 3 AM TO 9 AM PDT SATURDAY FOR CAZ004.

NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 9 AM PDT THIS MORNING FOR PZZ450.

     SMALL CRAFT ADVISORY UNTIL 9 AM PDT THIS MORNING FOR PZZ455.

     SMALL CRAFT ADVISORY UNTIL 5 AM PDT WEDNESDAY FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 5 AM PDT WEDNESDAY FOR PZZ475.

&&

$$

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