Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 281432
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
632 AM PST FRI NOV 28 2014

.SYNOPSIS...TWO FRONTAL SYSTEMS WILL BRING RAIN TO NORTHWEST
CALIFORNIA TODAY AND SATURDAY. PERIODS OF RAIN WILL LIKELY
CONTINUE INTO MID NEXT WEEK AS AN UPPER LEVEL LOW APPROACHES THE
AREA BEHIND THE FRONTAL SYSTEMS.

&&

.UPDATE...PATCHY VALLEY FOG IS BEING REPORTED AT SITES IN TRINITY
COUNTY AND CAN BE SEEN ON WEBCAMS IN WILLITS. UPDATED THE FORECAST
TO INCLUDE THE MENTION OF FOG THROUGH THE MORNING HOURS FOR
INTERIOR AREAS. OTHERWISE THE FORECAST REMAINS ON TRACK WITH RAIN
NOW IMPACTING COASTAL HUMBOLDT AND ALL OF DEL NORTE COUNTIES WITH
THE FRONTAL BOUNDARY THAT HAS BEEN STALLED OFF THE COAST FINALLY
STARTING TO MOVE EAST. RPA

&&

.SHORT TERM...(THROUGH SUNDAY NIGHT) MULTIPLE WAVES OF PRECIPITATION
ARE EXPECTED OVER THE NEXT FEW DAYS. THE FIRST WAVE OF RAIN WILL
MOVE THROUGH NORTHWEST CALIFORNIA AS AN INITIAL FRONTAL SYSTEM
FINALLY MOVES ON LAND. THIS FRONT HAS BEEN STALLED JUST OFF THE
COAST FOR THE LAST 24 OR SO HOURS. DECENT RAINFALL HAS BEEN
OCCURRING NORTH OF THE OREGON BORDER WITH 24 HR RAINFALL TOTALS OF 1-
1.5 INCHES JUST NORTH OF BROOKINGS. RAIN AMOUNTS WILL BE LIGHTER FOR
NORTHWEST CALIFORNIA AS THIS FRONT MOVES THROUGH WITH THE FRONT MUCH
MORE PROGRESSIVE...PASSING FROM DEL NORTE EARLY THIS MORNING THROUGH
MENDOCINO COUNTY BY LATE TONIGHT. RAINFALL WILL RANGE FROM 0.25-1
INCH WITH THE HIGHEST AMOUNTS IN THE MOUNTAINS OF HUMBOLDT AND DEL
NORTE COUNTIES.

THE FIRST FRONT WILL BE QUICKLY FOLLOWED BY A SECONDARY FRONT ON
SATURDAY. RAIN WITH THIS SECOND FRONT WILL REACH DEL NORTE COUNTY
EARLY SATURDAY MORNING AND SPREAD SOUTH TO NEAR SOUTHERN HUMBOLDT
AND TRINITY COUNTIES WHERE THE FRONT WILL LIKELY STALL SATURDAY
EVENING. SOME RAIN MAY SPREAD INTO MENDOCINO COUNTY BUT ANY
RAINFALL WILL LIKELY BE LIGHT AS THE FRONT STALLS...WEAKENS...AND
THEN RETREATS BACK NORTH ON SUNDAY AS A WARM FRONT. RAINFALL OVER
HUMBOLDT...DEL NORTE...AND TRINITY COUNTIES WILL LIKELY RANGE FROM
0.50-2 INCHES...AGAIN WITH THE GREATEST ACCUMULATION IN THE
MOUNTAINS OF NORTHERN HUMBOLDT AND DEL NORTE COUNTIES. SOME
ADDITIONAL SHOWERS WILL DEVELOP AS THE FRONT RETREATS NORTH ON
SUNDAY AT THE SAME TIME AS AN UPPER LEVEL SHORTWAVE MOVES TOWARD
THE CALIFORNIA COAST. THERE IS SOME DISCREPANCY IN THE MODELS AS
TO HOW WIDESPREAD AND HEAVY THE SHOWERS BECOME SUNDAY. MOST AREAS
WILL SEE LESS THAN A QUARTER INCH OF ADDITIONAL RAINFALL THROUGH
SUNDAY NIGHT. RPA


.LONG TERM...(MONDAY THROUGH THURSDAY) ALL OF THE MODELS INDICATE A
CUT OFF LOW WILL APPROACH THE NORTHWEST CALIFORNIA COAST EARLY TO
MID NEXT WEEK. HOWEVER A SLIGHT DIFFERENCE IN THE TRAJECTORY AND
TIMING OF THIS LOW IN THE MODELS IS RESULTING IN SIGNIFICANTLY
DIFFERENT SENSIBLE WEATHER FOR OUR AREA. THE GFS IS FASTER MOVING
THE LOW TO TO 37N 131W BY 12Z TUESDAY WHILE THE ECMWF IS
APPROXIMATELY 200 MILES BEHIND NEAR 34N 134W AT THE SAME TIME. THIS
SMALL DIFFERENCE PLACES NORTHWEST CALIFORNIA EITHER WITHIN THE
STRONG SOUTHERLY FLOW AHEAD OF THE LOW AND WITHIN A REGION OF HIGH
INTEGRATED WATER VAPOR (THE GFS SOLUTION) OR EAST OF THIS REGION AND
RELATIVELY DRY (THE ECMWF SOLUTION) MONDAY NIGHT INTO TUESDAY.
NEEDLESS TO SAY...THE CHANCES FOR PRECIPITATION AND TOTAL RAINFALL
FORECASTS ARE HIGHLY DEPENDENT ON WHICH SOLUTION IS CORRECT. CUTOFF
LOWS ARE TYPICALLY SLOWER THAN PREDICTED...THUS IT IS MORE LIKELY
THAT THE CORRECT SOLUTION WILL BE CLOSER TO THE ECMWF. QPF FORECASTS
FOR THAT PERIOD HAVE BEEN TRENDED TOWARD THE ECMWF WITH THIS
FORECAST UPDATE.

THE SLOWER ECMWF BRINGS RAIN TO THE REGION LATE ON TUESDAY INTO
TUESDAY NIGHT...THOUGH LIGHTER THAN THE GFS...WHILE THE GFS LINGERS
SHOWERS THROUGH THE NIGHT INTO WEDNESDAY. CONSIDERING BOTH SOLUTIONS
RESULT IN AT LEAST SHOWERS ACROSS THE REGION TUESDAY NIGHT AND
WEDNESDAY...HAVE OPTED TO INCREASE CHANCES FOR PRECIPITATION INTO
THE LIKELY CATEGORY FOR THESE TWO PERIODS.

BEYOND WEDNESDAY THERE IS CONSIDERABLE UNCERTAINTY WITH BOTH THE
ECMWF AND GFS INDICATING SOME LIGHT SHOWERS OVER THE AREA AS WEST TO
SOUTHWESTERLY MOIST FLOW DEVELOPS. NOT TOTALLY SOLD THAT ENOUGH
UPPER LEVEL ENERGY WILL REMAIN TO TRIGGER NUMEROUS SHOWERS...SO
CHANCES FOR PRECIPITATION HAVE BEEN KEPT NEAR OR JUST ABOVE
CLIMATOLOGY IN THE EXTENDED PORTION UNDER GENERALLY CLOUDY SKIES.

SNOW LEVELS THROUGHOUT THE WEEK WILL REMAIN RELATIVELY HIGH ABOVE
5000 FEET. NO SIGNIFICANT WINTER WEATHER IMPACTS ARE EXPECTED. RPA

&&

.AVIATION...VFR TO MVFR CONDITIONS AND LIGHT TO MODERATE WINDS ARE
OCCURRING AT KCEC AND KACV. SHOWERS ARE MOVING ACROSS SOME AREAS
THIS MORNING. THE SHOWERS WILL CONTINUE TO SPREAD ACROSS THE AREA
THIS MORNING REDUCING CEILINGS AND/OR VISIBILITIES TO MVFR AND
TEMPORARY IFR CONDITIONS. VFR CONDITIONS WILL CONTINUE AT KUKI
THROUGH THE EARLY MORNING. HOWEVER LATER THIS MORNING SHOWERS
ASSOCIATED WITH A SLOW MOVING COLD FRONT WILL REDUCE CEILINGS AND/OR
VISIBILITIES TO MVFR AND TEMPORARY IFR CONDITIONS. RAIN WILL
CONTINUE ACROSS THE AREA TODAY AND SATURDAY RESULTING IN MVFR TO IFR
CONDITIONS.

&&

.MARINE...A SERIES OF LOW PRESSURE SYSTEMS AND ASSOCIATED COLD
FRONTS WILL IMPACT THE COASTAL WATERS THROUGH EARLY NEXT WEEK.
SOUTHERLY WINDS AND THE SEAS HAVE INCREASED. WINDS WILL BRIEFLY
BECOME NORTHERLY SATURDAY THEN BECOME SOUTHERLY EARLY NEXT WEEK.
THESE LOW PRESSURE SYSTEMS AND FRONTAL BOUNDARIES WILL PRODUCE A
WESTERLY SWELL AND SHORT PERIOD WAVES INTO NEXT WEEK. SMALL CRAFT
ADVISORIES WILL REMAIN IN EFFECT THROUGH THIS EVENING DUE TO THE
INCREASE IN THE WINDS AND/OR SEAS.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 9 PM PST THIS EVENING FOR PZZ450-455.

     SMALL CRAFT ADVISORY UNTIL 9 PM PST THIS EVENING FOR PZZ470-475.

&&

$$

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