Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 211110
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
410 AM PDT SUN SEP 21 2014

.SYNOPSIS...HIGH PRESSURE WILL CONTINUE TO BRING DRY CONDITIONS
AND SEASONABLE TEMPERATURES TO NORTHWEST CALIFORNIA THROUGH AT
LEAST MONDAY. EXPECT LOW CLOUDS AND FOG ALONG THE COAST DURING
THE NIGHT AND MORNING WITH PARTIAL CLEARING IN THE AFTERNOON. A
TROUGH WILL BEGIN TO MOVE OVER THE WEST COAST EARLY THIS WEEK
BRINGING COOLER TEMPERATURES AND WIDESPREAD RAIN BY THE MIDDLE OF
THE WEEK.


&&

.SHORT TERM (THROUGH TUESDAY) AN UPPER LEVEL LOW CONTINUES TO SPIN
OVER CENTRAL CALIFORNIA PUMPING MOISTURE NORTH INTO NEVADA AND
EASTERN CALIFORNIA. SCATTERED THUNDERSTORMS FORMED IN THE CENTRAL
SIERRAS YESTERDAY WHICH HAVE SPREAD HIGH CLOUDS NORTHWEST OVER
NORTHERN CALIFORNIA. A FEW LIGHT SHOWERS DEVELOPED OVERNIGHT IN THE
VALLEY WHICH MAY HAVE BROUGHT A FEW SPRINKLES TO SOUTHERN MENDOCINO
COUNTY EARLY THIS MORNING. OTHERWISE DRY CONDITIONS HAVE PERSISTED
OVER NORTHWEST CALIFORNIA. MODEL GUIDANCE CONTINUES TO INDICATE
DECENT INSTABILITY OVER THE SCOTT MOUNTAINS AND TRINITY ALPS THIS
AFTERNOON WITH INCREASED MOISTURE PRESENT. AS THE UPPER LOW LIFTS
NORTHEAST TODAY AHEAD OF THE NEXT APPROACHING TROUGH...THERE IS A
SLIGHT CHANCE THAT A THUNDERSTORM COULD FORM OVER THE TRINITY HORN
TODAY. HAVE INCREASED POPS TO MATCH THE NEIGHBORING OFFICES TO
INDICATE THIS SLIGHT POSSIBILITY.

HIGH PRESSURE WILL BUILD OVER THE WEST COAST MONDAY INTO TUESDAY
AHEAD OF THE NEXT ADVANCING DEEP TROUGH RESULTING IN MOSTLY DRY
CONDITIONS AND NEAR NORMAL TEMPERATURES. A WEAK LOW AHEAD OF THIS
TROUGH WILL ATTEMPT TO REACH THE COAST MONDAY INTO MONDAY NIGHT WHILE
DISSIPATING. THIS LOW MAY BRING SOME INCREASED HIGH CLOUD COVER AND
POSSIBLY SOME DRIZZLE WITHIN THE CONTINUED LOW CLOUDS IN THE MARINE
LAYER. RPA

.LONG TERM (TUESDAY NIGHT-SUNDAY) MODELS CONTINUE TO BE IN OVERALL
AGREEMENT THROUGH WEDNESDAY AFTERNOON. EC IS A LITTLE FASTER WITH
TIMING OF FRONT BRINGING IT INTO CEC BY TUE EVENING WHILE GFS BRINGS
IT IN A LITTLE BEFORE SUNRISE WED MORNING. I WILL LEAN TOWARD TIMING
OF GFS WITH FRONTAL PASSAGE THROUGH ALL OF TRINITY AND MENDO COUNTY
BY LATE WEDNESDAY NIGHT. PWATS AHEAD OF FRONT ARE BETWEEN 1-1.5
INCHES AND THE INTEGRATED WATER VAPOR TRANSPORT (IVT) WHICH COMBINES
THE MOISTURE AND WIND IS ALSO HIGH WITH A RETURN INTERVAL OF 10
YEARS NEAR CEC AND 5 YEARS DOWN NEAR UKIAH. GOOD MOISTURE AND
DYNAMICS SHOULD ALLOW BRIEF PERIODS OF HEAVY RAIN WITH THE FRONT.
WITH THE INCREASING SOUTHERLY WINDS AHEAD OF THE FRONT, SHOULD SEE
SOME GUSTY WINDS ESPECIALLY OVER THE HIGHER RIDGES DURING THE DAY
WED. BEHIND THE FRONT, MODELS ARE DIFFERING WITH WHAT TO DO WITH THE
ASSOCIATED TROUGH. GFS SWINGS IT THROUGH ON THURSDAY WITH RIDGE
BUILDING OVER THE WEEKEND WITH A RETURN TO DRY WEATHER. EC IS SLOWER
AND DEEPER WITH THE BROAD TROUGH STILL OVER THE AREA THROUGH THE
WEEKEND WHICH COULD KEEP SHOWERS GOING. WENT WITH WPC`S THINKING
WHICH SWINGS THE TROUGH THROUGH LIKE THE GFS THOUGH A LITTLE SLOWER.
WILL HAVE TO WATCH THE LARGE AREA OF HIGH PRESSURE IN THE EASTERN US
TO SEE IF IT SLOWS DOWN THE TROUGH OR CUTS IT OFF AS IT COMES INTO
THE WEST COAST. WPC`S STILL FORECASTING ABOUT 2.5 INCHES OF RAIN
NEAR CEC FOR THE ENTIRE STORM SYSTEM AND AT LEAST 0.50 INCHES
EVERYWHERE ELSE. COLDER AIR WITH THE TROUGH AS 850MB TEMPS DROP DOWN
TO ABOUT 5C AND VERY HIGHEST PEAKS COULD GET A DUSTING OF SNOW.
LAPSE RATES DO NOT LOOK STEEP ENOUGH FOR ANY THUNDERSTORMS BUT WILL
STILL NEED TO KEEP AN EYE ON IT. DEAN/RPA


&&

.AVIATION...AN EXTENSIVE DECK OF STRATUS WAS COVERING NEARLY THE
ENTIRE COAST THIS MORNING. THE LAYER HAS DEEPENED SOME WITH IFR
CONDITIONS EXTENDING LOCALLY INTO THE COASTAL RIVER VALLEYS. THE
STRATUS WILL CLEAR OUT MOST EVERYWHERE TODAY EXCEPT ALONG THE
IMMEDIATE COAST. CIGS SHOULD LIFT UP THIS AFTERNOON AND SOUTHERLY
WINDS MAY PRODUCE BRIEF CLEARING AROUND EUREKA-ARCATA.

&&

.MARINE...SEAS HAVE BEEN RUNNING AROUND 6-7 FT AT 12 SECONDS EARLY
THIS MORNING. WINDS WERE STILL BREEZY AROUND THE CAPE WITH BUOY 22
GUSTING AROUND 20 KT. THE TROUGH TO THE NW OF THE WATERS WILL SLOWLY
LIFT OUT TO THE NE AND FILL TODAY. HIGH PRESSURE SHOULD BUILD UP
FROM THE SW LATER TODAY AND INTO THIS EVENING. EXPECT WINDS TO TREND
DOWNWARD TODAY AND EVENTUALLY GO LIGHT TONIGHT. A FRONT WILL
APPROACH ON MON AND FORCE THE RIDGE AXIS TO THE ESE. THE SSE WINDS
AHEAD OF THE FRONT DO NOT LOOK INCREDIBLY STRONG AS THE BOUNDARY
DISSIPATES. BEEFED UP THE S AND SE WINDS SLIGHTLY IN PZZ470
WHERE GUSTS TO 20 KT SEEM POSSIBLE IN THE AFTERNOON. STRONGER
SOUTHERLY WINDS SHOULD DEVELOP ON TUE INTO WED AS A MORE POTENT
FRONT APPROACHES THE REGION. ONCE AGAIN WINDS DO NOT LOOK STRONG
ENOUGH TO WARRANT A HEADLINE THIS FAR OUT...BUT I DID BOOST UP THE
WINDS AND WIND WAVES OVER WHAT THE MODELS INDICATE. THE STORM
SYSTEM WILL GENERATES A WESTERLY SWELL NEXT WEEK. THE GFS AND
ECMWF HAVE BEEN FAIRLY CONSISTENT ON THE WIND FIELDS WITH THE
STORM AND FOR NOW I JUST RAN WITH THE OUTPUT FROM THE WAVE MODELS
WHICH HAVE THE SWELL PEAKING AROUND 12 FT ON WED.


&&

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

$$

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