Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 272234
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
334 PM PDT THU AUG 27 2015

.SYNOPSIS...HIGH PRESSURE WILL CONTINUE TO BRING DRY WEATHER
CONDITIONS TO NORTHWEST CALIFORNIA THROUGH TONIGHT. A FRONT WILL
APPROACH ON FRIDAY AND EVENTUALLY BRING RAIN MOSTLY NORTH OF CAPE
MENDOCINO BY EARLY SATURDAY MORNING.

&&

.DISCUSSION...HIGH AND MID LEVEL CLOUDS WILL SLOWLY SPREAD OVER
THE AREA TONIGHT AND FRIDAY IN ADVANCE OF A NEARLY STATIONARY
FRONT JUST OUTSIDE 130W THIS AFTERNOON. BY LATE FRI NIGHT AND
EARLY SAT MORNING LIGHT TO MODERATE RAIN IS EXPECTED TO SPREAD
INTO THE AREA AS A COLD FRONT DEVELOPS AND APPROACHES THE COAST.
THE MODELS CONTINUE TO TAKE THE BRUNT OF THE MOISTURE AND HIGHEST
RAIN AMOUNTS INTO DEL NORTE COUNTY AND FAR NORTHERN HUMBOLDT
COUNTY...WITH LIGHTER AMOUNTS TO THE SOUTH. FORECAST MODELS WERE
STILL NOT IN COMPLETE AGREEMENT ON THE RAIN AMOUNTS. SELDEM ARE
THEY...EVEN DURING THE HEART OF A FULL BLOWN WINTER STORM. LEANING
TOWARD THE WETTER GFS/ECMWF AS THESE MODELS TYPICALLY OUT PERFORM
THE NAM12. AT A MINIMUM THE NORTHERN ZONES WILL SEE AT LEAST A
HALF AN INCH. WE INCREASED PRECIP CHANCES UP AND DOWN THE COAST
TO REFLECT HIGHER CONFIDENCE DURING FRONTAL PASSAGE. WE DID NOT
CHANGE QPF VALUES MUCH...THOUGH THE LATEST NAM12 AND GFS HAS
HIGHER RAIN AMOUNTS IN THE MENDOCINO ZONES ON SAT. THIS WILL NEED
TO BE LOOKED AT MORE CLOSELY AS THE EVENT GROWS CLOSER. ONCE THE
FRONT PASSES EARLY SATURDAY SOME SHOWER ACTIVITY WILL LINGER
THROUGH THE AFTERNOON...ESPECIALLY OVER DEL NORTE COUNTY AND OVER
THE HIGHER TERRAIN. THE GFS AND ECMWF SHOW ANOTHER IMPULSE MOVING
TOWARD THE NORTH COAST ON SUNDAY. HOWEVER THE LATEST MODELS
DAMPEN-OUT THE SURFACE REFLECTION OF THIS WAVE SIGNIFICANTLY. FOR
NOW WILL MAINTAIN A CHANCE OR SLIGHT OF SHOWERS MAINLY NORTH OF
THE CAPE...CONSIDERING THE NAM12 DOES SHOW MORE PRECIP SPROUTING
UP WITH THE ONSHORE FLOW. FROM MONDAY THROUGH THURSDAY...A BROAD
UPPER LEVEL TROUGH WILL REMAIN OVER THE WEST COAST THROUGH THE
PERIOD. MAIN AFFECT FOR NW CALIFORNIA WILL BE BELOW NORMAL
TEMPERATURES IN THE INTERIOR WITH SLIGHTLY ABOVE NORMAL
TEMPERATURES FOR COASTAL AREAS. SEVERAL WEAK PERTURBATIONS
EMBEDDED WITHIN THE LARGER SCALE TROUGH WILL MOVE INTO THE PAC NW
FROM TIME TO TIME. NONE OF THESE SHORTER WAVE LENGTH FEATURES
APPEAR TO BE STRONG ENOUGH TO GENERATE SIGNIFICANT PRECIP. THE
TAIL END OF THESE WAVES MAY GENERATE SOME LIGHT SHOWERS NEAR THE
ORCA BORDER. FOR NOW WILL MAINTAIN NEAR CLIMO PRECIP CHANCES FOR
MOST OF THE FORECAST AREA AND SLIGHTLY ABOVE NORMAL CHANCES NEAR
THE ORCA BORDER.

&&

.AVIATION...VFR CONDITIONS HAVE PREVIALED THROUGH MOST OF THE DAY
AFTER THE MORNING FOG. CEILINGS AND PERHAPS FOG SHOULD RETURN TO
THE IMMEDIATE COAST TONIGHT BRINGING MVFR TO IFR CONDITIONS OVERNIGHT.
INTERIOR LOCATIONS CAN EXPECT A VFR DAY APART FROM AREAS OF SMOKE.

&&

.MARINE...LIGHT TO MODERATE WINDS WILL PERSIST THROUGH FRIDAY AS AN
APPROACHING LOW PRESSURE SYSTEM WEAKENS THE PRESSURE GRADIENT ACROSS
THE COASTAL WATERS. A COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL
TURN WINDS OUT OF THE SOUTH THIS WEEKEND DEVELOPING SOME FRESH WIND
GUSTS AND A LIGHT SOUTHERLY WAVE CHOP. THE SEA STATE, ON THE OTHER
HAND, SHOULD BE DOMINATED BY MID TO LONGER PERIOD WAVE SYSTEMS
THROUGH THE REST OF THE WEEK. WAVE RIDER BUOYS CURRENTLY SHOW A
SPECTRUM OF WAVE SYSTEMS OUT OF THE NORTHWEST AND SOUTHWEST. EVEN
THOUGH THESE DIFFERENT LONGER PERIOD SWELLS MAY NOT HAVE MUCH OF AN
AFFECT ON MARINERS IN DEEP WATER THEY WILL CERTAINLY BE NOTICED NEAR
THE SURF ZONE. THIS COULD MEAN BREAKING WAVES OVER SHALLOW WATER
SHOALS AND STRONGER CURRENTS NEARSHORE.

&&

.FIRE WEATHER...ATTENTION TURNING TO FRIDAY NIGHT WHEN MID AND
UPPER LEVEL WINDS WILL INCREASE NOTICEABLY ACROSS UPPER SLOPES AND
RIDGES FRIDAY EVENING. THIS IS RESPONSE TO AN UNSEASONABLY STRONG
FRONT CROSSING THE NORTH COAST. HIGH CLOUDS WILL ALSO MIGRATE
OVER THE REGION ON FRIDAY IN ADVANCE OF THE FRONT. FORECAST MODELS
COMING IN ALIGNMENT NOW...DEPICTING WETTING RAIN (.50 - 1.00 INCHES)
ACROSS DEL NORTE AND NORTHERN HUMBOLDT COUNTIES. CENTRAL AND
SOUTHERN HUMBOLDT AND TRINITY COUNTIES SHOULD SEE CLOSER TO 0.15
TO 0.30 INCHES WHILE LESSER AMOUNTS TO THE SOUTH BY EARLY SATURDAY
MORNING. HAVE UPPED THE CWR VALUES TO REFLECT GREATER CONFIDENCE.
AT A MINIMUM ALL AREAS WILL SEE MUCH HIGHER RH VALUES THROUGH
MONDAY AND PERHAPS LONGER AS A MORE TROUGHY NATURE IS EXPECTED TO
CONTINUE PROVIDING MUCH MORE FAVORABLE WEATHER FOR THE ONGOING
FIRES.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...NONE.
&&

$$

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