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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
320 PM PDT MON MAR 30 2015

.SYNOPSIS...A COLD FRONT WILL PASS ACROSS THE REGION LATE TONIGHT
AND BRING A CHANCE OF LIGHT RAIN INTO EARLY TUESDAY. A COOLER AIR
MASS WILL MAINTAIN SOME SHOWER ACTIVITY INTO WED AFTERNOON.

&&

.DISCUSSION...A COLD FRONT ABOUT 250 MILES WEST OF CAPE MENDOCINO
HAS BEEN STEADILY PROGRESSING EAST THROUGH THE DAY. THIS FRONT
SHOULD MOVE ACROSS THE NORTH COAST AROUND MIDNIGHT OR SHORTLY
THERE AFTER. THE MOISTURE IS NOT DEEP AND EXPECT ANOTHER EPISODE
OF LIGHT MISTY RAIN ALONG THE NORTH COAST WITH PERHAPS SOME
SHOWERS SPREADING INTO THE INTERIOR LATE TONIGHT. ALL THE MODELS
WERE ABOUT THE SAME WITH RAIN AMOUNTS...A QUARTER OF AN INCH OR
LESS...MAINLY ALONG THE NORTH COAST AND IN DEL NORTE COUNTY.
VISIBLE SATELLITE IMAGERY SHOWED A FAIR AMOUNT OF OPEN CELL
CUMULUS CONVECTION BEHIND THE FRONT. THE 500MB PVA MAX WILL MOVE
ACROSS THE FAR NORTH COAST TUE MORNING...AND THEN DAMPEN OUT AS IT
SWINGS NE INTO THE PAC NW TUE AFTERNOON. THIS PVA MAX WILL SPARK
UP ADDITIONAL SHOWERS...MAINLY NEAR THE COAST AND IN DEL NORTE
COUNTY BEFORE WE SEE A BREAK IN THE PRECIP TUE AFTERNOON AND
OVERNIGHT TUE. MODELS INDICATE ANOTHER SHORTWAVE MOVING TOWARD THE
NORTH COAST TUE NIGHT. THIS WAVE WILL BRUSH DEL NORTE IN NW FLOW
ALOFT AND MAY BRING ADDITIONAL SHOWER ACTIVITY TO THE NORTHERN
MOST ZONES ON WED. NAM12 AND GFS INDICATE WEAK INSTABILITY NEAR
THE OREGON BORDER AS 500MB TEMPERATURES FALL TO -30C ON WED. THE
SHORT-WAVE MAY TRIGGER A FEW SHALLOW LOW-TOPPED THUNDERSTORMS
NEAR THE OREGON BORDER ON WED. THIS HAS BEEN ADDED TO THE FORECAST.

A COOLER AIR MASS WILL SETTLE OVER THE AREA ON TUESDAY. THERE
WILL BE AN INCREASING RISK FOR FROST IN THE INTERIOR VALLEYS
THROUGH THE WEEK. INITIALLY THE FROST POTENTIAL MAY BE OFFSET BY
THE PRESENCE OF SHALLOW MOISTURE AND CLOUDS TUE NIGHT. HOWEVER
STRONGER SUBSIDENCE...DRYING AND CLEARING WED NIGHT THROUGH FRIDAY
WILL BE IDEAL FOR FROST DEVELOPMENT. THE MODELS DO SHOW STRONGER
NORTHERLY AND NORTHEAST BOUNDARY LAYER WINDS ON THU. THIS MAY
HAMPER THE RATE OF COOLING AND KEEP SOME SITES IN DEL NORTE AND
HUMBOLDT COUNTIES OUT OF THE MID 30S. WE MAY BE IN STORE FOR
SEVERAL CONSECUTIVE NIGHTS OF FROST IN THE INTERIOR ZONES.

GFS...ECMWF AND GEM INDICATE A BROAD TROUGH ALOFT REMAINING OVER
NORTHERN CALIFORNIA THIS WEEKEND INTO EARLY NEXT WEEK. THE GEM AND
GFS WERE IN FAIRLY GOOD SYNC WITH SHOWING A COLD AND UNSETTLED
PATTERN OVER THE WEEKEND. THE ECMWF ON THE OTHER HAND LOOKED TO
BE AN OUTLIER WITH DIGGING THE 500MB TROUGH DOWN THE CALIFORNIA
COAST AND KEEPING NW CA UNDER A DIFFLUENT SOUTH FLOW ALOFT. THERE
IS HIGH CONFIDENCE THAT TEMPERATURES WILL STAY BELOW NORMAL OVER
THE WEEKEND INTO EARLY NEXT WEEK. THERE IS A FAIR CHANCE WE WILL
SEE PRECIP SAT...SUN...MON OR ALL 3 DAYS. WHERE...HOW FREQUENT
AND HOW MUCH ARE UNCERTAIN. THE MODELS HAVE BEEN STRUGGLING ON
SMALLER SCALE S/W FEATURES AND FOR NOW WILL MAINTAIN A SOMEWHAT
BROAD AND VAGUE CHANCE OF SHOWERS IN EACH ZONE SAT THROUGH MON.

&&

.AVIATION...HIGH CLOUD COVER STREAMED OVER NORTHWEST CALIFORNIA 
TODAY AHEAD OF A WEAK FRONT. LOW CLOUDS ALONG THE COAST NORTH OF 
CAPE MENDOCINO SLOWLY ERODED AWAY RESULTING IN BROKEN COVERAGE AT 
COASTAL AIRFIELDS EARLY THIS AFTERNOON. SCATTERING WILL BE POSSIBLE 
BUT BRIEF THIS EVENING AS THE FRONT BRINGS INCREASING CLOUD COVERAGE 
AND LIGHT SHOWERS TONIGHT. SHOWERS MAY CREATE SOME SLIGHT VISIBILITY 
REDUCTIONS OVERNIGHT. OTHERWISE MVFR TO IFR CONDITIONS WILL BE 
POSSIBLE TONIGHT WITH LIFTING CEILINGS AND IMPROVING CONDITIONS BY 
TUESDAY MORNING. KML

&&

.MARINE...AN APPROACHING COLD FRONT HAS WEAKENED THE COASTAL 
PRESSURE GRADIENT THUS ALLOWING WINDS AND SHORT PERIOD WAVES TO 
SLOWLY DIMINISH TODAY. CONSEQUENTLY THE SMALL CRAFT ADVISORY EXPIRED 
THIS AFTERNOON. THE WESTERLY-NORTHWESTERLY WAVE TRAIN CURRENTLY 
AROUND 8 FT AT 14 SECONDS WILL SLOWLY DECAY BEFORE BUILDING AGAIN ON 
TUESDAY. THIS WILL HELP MAINTAIN AN ELEVATED SEA STATE THROUGH THE 
WEEK. NORTHERLY WINDS WILL ALSO DEVELOP ON TUESDAY AS A RIDGE OF 
HIGH PRESSURE BUILDS BEHIND THE PASSING FRONT CAUSING WINDS AND 
STEEP SEAS TO DEVELOP ONCE AGAIN ON TUESDAY AFTERNOON. THOUGH 
CONDITIONS WILL BE MARGINAL, A SMALL CRAFT ADVISORY HAS BEEN ISSUED 
FOR THE SOUTHERN WATER ZONES ON TUESDAY. GUSTS NEAR 30 KT WILL BE 
POSSIBLE FROM CAPE MENDOCINO DOWN TO POINT ARENA WITH STEEP SHORT 
PERIOD SEAS. ADVISORIES WILL FURTHER BE NEEDED FOR THE NORTHERN 
WATERS ON WEDNESDAY AS THE STRENGTHENING RIDGE AND DEVELOPING 
THERMAL TROUGH RAMP UP WINDS TO NEAR GALE FORCE LATE THIS WEEK. KML

&&

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

&&

$$

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