Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 011209
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
409 AM PST SUN FEB 1 2015

.SYNOPSIS...
DRY WEATHER WILL CONTINUE THROUGH TODAY IN MOST AREAS...BUT A
WEAKENING UPPER RIDGE AND SEVERAL APPROACHING SYSTEMS ARE EXPECTED
TO BRING LIGHT TO MODERATE RAINFALL TO AREAS NORTH OF CAPE
MENDOCINO LATE THIS AFTERNOON THROUGH LATE TUESDAY. DRY WEATHER
WILL RETURN BRIEFLY ON WEDNESDAY...FOLLOWED BY ANOTHER WET PATTERN
LATE IN THE WEEK.

&&

SHORT TERM...THROUGH TUESDAY...
BENIGN WEATHER IS EXPECTED TO CONTINUE THROUGH THE DAY...BUT BIG
CHANGES ARE ON THE WAY THROUGH THE REMAINDER OF THE WEEK AS
SEVERAL STORM SYSTEMS WILL MOVE INTO THE PACIFIC NORTHWEST ALONG
THE PERIPHERY OF A SLOWLY WEAKENING UPPER RIDGE. IN THE IMMEDIATE
FUTURE...BUILDING HIGH CLOUDS ASSOCIATED WITH THE APPROACHING
SYSTEM WILL MOVE OVER THE AREA STARTING THIS MORNING. WHILE PARTS
OF DEL NORTE AND PERHAPS EXTREME NORTHERN HUMBOLDT COUNTY HAVE A
CHANCE OF SEEING SOME LIGHT RAIN OUT OF THIS INITIAL SYSTEM
THROUGH THE DAY...THE STRENGTH OF THE AMBIENT UPPER RIDGE IS
EXPECTED TO PRECLUDE ANY SIGNIFICANT ACCUMULATIONS UNTIL THE
ARRIVAL OF A SLIGHTLY STRONGER SHORTWAVE AND A WEAK FRONT SOMETIME
EARLY MONDAY. MONDAY...DEEPER MOISTURE AND A SLIGHTLY WEAKER
UPPER RIDGE WILL LIKELY ALLOW FOR A PERIOD OF MODERATE RAINFALL
ACROSS PRIMARILY DEL NORTE...NORTHWESTERN TRINITY...AND NORTHERN
HUMBOLDT COUNTIES...WITH A BIT MORE UNCERTAINTY FARTHER SOUTH.
MODEL GUIDANCE CONTINUES RELATIVELY UNIFORM IN KEEPING THE BULK OF
SIGNIFICANT ACCUMULATIONS WELL NORTH OF CAPE MENDOCINO...AND GIVEN
THE PERSISTENT RIDGE THIS SEEMS REASONABLE. RAIN RATES WILL NOT BE
HIGH ENOUGH TO RESULT IN ANY FLOODING CONCERNS EVEN IN THE WETTEST
AREAS. BY TUESDAY ANOTHER SHORT WAVE MOVING INTO THE PACIFIC
NORTHWEST WILL BRING ANOTHER INCREASE IN THE RAIN RATES ACROSS THE
NORTHERN SECTIONS OF NORTHWEST CALIFORNIA.

LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...THE LAST SHORTWAVE
WILL BE ACCOMPANIED BY A WARM FRONT WHICH WILL SHIFT NORTH INTO
OREGON LEAVING NORTHWEST CALIFORNIA IN THE WARM SECTOR OF A
STRENGTHENING SYSTEM OFF THE WEST COAST. MODEL ENSEMBLE AND
DETERMINISTIC RUNS ALL CONTINUE TO INDICATE A DEEP MOISTURE PLUME
WILL MOVE INTO NORTHWEST CALIFORNIA LATE THURSDAY AND CONTINUE
INTO THE WEEKEND AS UPPER LEVEL RIDGING BUILDS OVER THE INTER-
MOUNTAIN WEST LEAVING SOUTHWEST FLOW AIMED AT THE NORTHERN HALF OF
CALIFORNIA. THE WEST COAST ATMOSPHERIC RIVER LANDFALL TOOL
INDICATES HIGH PROBABILITIES OF INTEGRATED VAPOR TRANSPORT (IVT)
OVER 250 KG/M/S THURSDAY NIGHT THROUGH MONDAY AS THE MOISTURE
PLUME UNDULATES NORTH AND SOUTH FROM SOUTHERN OREGON TO NORTH-
CENTRAL CALIFORNIA. WITH THE PROLONGED PERIOD OF HIGH IVT
CONTINUING TO BE PROGED BY THE GFS MODEL...THE MODEL IS PRODUCING
WIDESPREAD HEAVY RAIN IN THE 6-12 INCH RANGE OVER THE REGION. THE
CURRENTLY MORE CONSERVATIVE ECMWF CONTINUES TO INDICATE ONLY 3-7
INCHES. THUS THERE IS UNCERTAINTY WITH THE RAINFALL AMOUNTS BUT
NOT WHETHER IT IS GOING TO RAIN. POPS CONTINUE GENERALLY CATEGORICAL
FRIDAY THROUGH SUNDAY. IT SHOULD BE NOTED THAT REGARDLESS OF
DETAILS THE WEATHER PATTERN DEPICTED IN THE MODELS IS A VERY
FAVORABLE PATTERN FOR HEAVY RAINFALL IN NORTHWEST CALIFORNIA.
DETAILS OF TIMING...LOCATION...AND AMOUNT WILL BECOME MORE CLEAR
AS THE WEEK PROGRESSES.

GUSTY SOUTH WINDS ARE EXPECTED JUST AHEAD OF AND WITH THE HEAVY
RAIN THURSDAY INTO FRIDAY. 925 MB WINDS ARE PREDICTED TO PEAK
BETWEEN 40 AND 60 KT ALONG THE IMMEDIATE COAST WITH EVEN STRONGER
WINDS FARTHER ALOFT IN THE GFS. IF THE GFS IS CORRECT WIND
ADVISORIES OR WARNINGS MAY BE REQUIRED. MKN

&&

.AVIATION...VFR CONDITIONS WILL CONTINUE AT KCEC...KACV...AND KUKI
THROUGH THE EARLY MORNING. VFR CONDITIONS WILL CONTINUE AT KUKI
TODAY WITH LIGHT WINDS TO CALM CONDITIONS OCCURRING. CEILINGS
AND/OR VISIBILITIES WILL DIMINISH THIS AFTERNOON REDUCING CEILINGS
AND VISIBILITIES AT KCEC TO MVFR TO IFR CONDITIONS. VFR CONDITIONS
WILL OCCUR AT KACV DURING THE LATE MORNING AND AFTERNOON. WINDS
WILL REMAIN LIGHT AT KCEC AND KACV. MFM

&&

.MARINE....AN OFFSHORE HIGH PRESSURE RIDGE AND THERMAL LOW PRESSURE
TROUGH ACROSS CALIFORNIA HAS WEAKENED ALLOWING WINDS AND SEAS TO
DIMINISH.  SEAS WILL INCREASE MONDAY AND TUESDAY AS A LONG PERIOD
WESTERLY SWELL TRAVERSES THE WATERS. SOUTHERLY WINDS WILL INCREASE
WEDNESDAY AS A COLD FRONT APPROACHES THE NORTHWESTERN UNITED STATES
COAST. SOUTHERLY WINDS AND THE SEAS WILL INCREASE FURTHER THURSDAY
AS THE COLD FRONT NEARS THE COAST. MFM

&&

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

$$

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