weather.gov     
National Weather Service

Area Forecast Discussion
NWS Homepage
This page is being discontinued on March 12, 2014.
The same data is available at this site. Please update your bookmarks.
Thank you, and we apologize for the inconvenience.
Please send an email to SR-SRH.Webmaster@noaa.gov with any concerns.


Current Version
Previous Version:    01  02  03  04  05  06  07  08  09  10  11  12  13  14  15  
[Printable]
467
FXUS66 KEKA 292346
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
346 PM PST THU JAN 29 2015

.SYNOPSIS...DRY WEATHER WILL CONTINUE THROUGH SATURDAY AS HIGH
PRESSURE REMAINS OVER THE REGION. A WEAK WEATHER SYSTEM WILL
BRING A CHANCE OF LIGHT RAIN SUNDAY INTO MONDAY.

&&

.DISCUSSION...NORTH FLOW INCREASING OVER THE WATERS HAS PRODUCED
A PUSH OF MARINE CLOUDS...MOSTLY AROUND EUREKA AND IN THE DELTA.
THE LOW CLOUDS SHOULD SPREAD SLIGHTLY DEEPER INTO THE NORTH COAST
RIVER VALLEYS THIS EVENING. HOWEVER...OFFSHORE FLOW DEVELOPING
LATER TONIGHT WILL PROBABLY ERODE SOME OF THE LOW CLOUDS OUT
TOWARD THE COASTAL PLAIN BY MORNING. MODELS WERE IN GOOD AGREEMENT
SHOWING BETTER OFFSHORE FLOW DEVELOPING FRI NIGHT INTO SAT AS AN
INVERTED TROUGH DEVELOPS NEAR THE COAST. THUS THE CHANCE FOR MORE
LOW CLOUD DEVELOPMENT WILL DECREASE AS THE ONSHORE NORTHERLY FLOW
EASES UP NEARSHORE. INTERIOR VALLEYS WILL PROBABLY CONTINUE TO SEE
NIGHT/MORNING FOG AND LOW CLOUDS THROUGH THE WEEKEND.

THE AIR MASS WILL WARM UP THIS WEEKEND. THE WARMING POTENTIAL
WILL BE MITIGATED BY A STRONG INVERSION WHICH WILL PREVENT
COMPLETE MIXING AND LAPSE RATES FROM GOING DRY ADIABATIC TO
5KFT IN THE AFTERNOON DURING PEAK HEATING. IT MAY SEEM LIKE
SUMMER...BUT THE MIXING IS JUST NOT STRONG ENOUGH YET. HIGHER
ELEVATIONS SITES WILL PROBABLY SEE THE BEST WARMING...WHILE THE
VALLEYS NOT AS MUCH.

THE MODELS CONTINUE TO STRUGGLE WITH A SYSTEM EXPECTED TO BRING
PRECIP TO NW CA LATE THIS WEEKEND. THE LONG WAVE RIDGE HAS THUS
FAR PROVEN TO BE QUITE DIFFICULT TO OVERCOME. THE LATEST 12Z RUNS
OF THE GFS AND ECMWF CONTINUE TO SLOW DOWN THE RAIN AND REDUCE
THE AMOUNTS. THIS SEEMS TO BE A TREND THIS YEAR WITH THE LONG
WAVE RIDGE IN PLACE. GUT INSTINCT HERE...THE MODELS ARE ONCE AGAIN
OVERDONE. WE DO NOT KNOW FOR SURE, SO WILL ERR ON THE SIDE OF
PRUDENCE HERE...AND MAINTAIN A SLIGHT CHANCE OR CHANCE OF RAIN SUN
NIGHT INTO MON. THAT MEANS CONFIDENCE IS LOW AT THIS POINT IN
TIME. EVEN GOING INTO TUE AND WED THE MODELS CONTINUE TO BRING
MOISTURE OVER THE RIDGE WITH SPOTTY PRECIP FROM TIME TO TIME. ONCE
AGAIN THE MODELS ARE PROBABLY OVERDONE AND WILL SCALE DOWN THE
PRECIP CHANCES TO 10% OR LESS. TOWARD THE LATTER PORTION OF THE
WEEK...THU AND FRI...THE GFS AND ECMWF SHOW A WET FRONTAL SYSTEM
PLOWING INTO THE RIDGE AND BRINGING BOUTS OF MODERATE TO HEAVY
RAIN TO NW CA. THE GFS WAS SLOWER. THE ECWMF FASTER. BOTH MODELS
ARE NOTORIOUS FOR OVERDOING RAIN AMOUNTS WITH THESE WARM/MOIST AIR
ADVECTION PLUMES; THE SO CALLED ATMOSPHERIC RIVERS. WE SHALL SEE.

&&

.AVIATION...NORTHERLY WINDS ARE INCREASING OFF THE COAST RESULTING
IN ENHANCED ONSHORE FLOW INTO THE HUMBOLDT BAY AREA. HIGH BOUNDARY
LAYER MOISTURE ALONG THE COAST HAS ALLOWED FOR WIDESPREAD STRATUS TO
FORM AND MOVE ONSHORE WITH THE WINDS. PERIODS OF IFR TO LIFR
CONDITIONS ARE EXPECTED ALONG MUCH OF THE NORTHWEST CALIFORNIA COAST
...THOUGH SOME OFFSHORE COMPONENT TO THE WINDS IS EXPECTED NEAR
CRESCENT CITY AND JUST SOUTH OF CAPE MENDICINO WHICH COULD KEEP THE
AIRPORTS AT SHELTER COVE AND CRESCENT CITY CLEAR THROUGH THE NIGHT.
INTERIOR VALLEY FOG WILL LIKELY REFORM TONIGHT ACROSS MUCH OF
NORTHWEST CALIFORNIA...AND IF THE NAM MODEL IS RIGHT MAY BRING LOW
CLOUDS TO THE UKIAH AREA. ANY INTERIOR VALLEY FOG WILL DISSIPATE BY
THE LATE MORNING OR VERY EARLY AFTERNOON. RPA

&&

.MARINE...NORTHERLY WINDS WILL INCREASE FROM MODERATE TO STRONG
THROUGH THE EVENING AND OVERNIGHT PERIOD AND PERSIST THROUGH LATE
FRIDAY NIGHT. STEEP SHORT PERIOD SEAS ARE EXPECTED TO DEVELOP AS A
RESULT...PARTICULARLY ACROSS THE OUTER WATERS...ALTHOUGH LATEST
MODEL GUIDANCE SUGGESTS THAT STEEP SHORT PERIOD WAVES WILL DEVELOP
ACROSS AT LEAST PORTIONS OF THE SOUTHERN COASTAL WATERS AS WELL.
IN THESE AREAS...THE MOST HAZARDOUS SEAS ARE EXPECTED TO OCCUR IN
THE VICINITY OF POINT ARENA. TO ACCOUNT FOR LATEST TRENDS...A
SMALL CRAFT ADVISORY WAS ADDED FOR THE SOUTHERN COASTAL WATERS
FROM 9 PM THIS EVENING THROUGH 9 PM TOMORROW...IN ADDITION TO THE
CURRENTLY VALID ADVISORIES FOR THE OUTER WATERS THROUGH 9 AM
SATURDAY. DIMINISHING WINDS WILL ALLOW SHORT PERIOD SEAS TO
SUBSIDE BY EARLY IN THE DAY SATURDAY. IN ADDITION...WESTERLY SWELL
WILL CONTINUE TO MOVE THROUGH THE WATERS OVER THE WEEKEND AND WILL
BE REINFORCED BY A SECONDARY SWELL EARLY IN THE WEEK.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 9 AM PST SATURDAY FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 9 AM PST SATURDAY FOR PZZ475.

&&

$$

VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA

FOLLOW US ON FACEBOOK AND TWITTER AT:
HTTP://WWW.FACEBOOK.COM/NWSEUREKA
HTTP://WWW.TWITTER.COM/NWSEUREKA




U.S. Dept. of Commerce
NOAA National Weather Service
1325 East West Highway
Silver Spring, MD 20910
E-mail: w-nws.webmaster@noaa.gov
Page last modified: May 16, 2007
NATIONAL WEATHER SERVICE: for Safety, for Work, for Fun - FOR LIFE