FXUS66 KEKA 221529 AAA
AFDEKA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE EUREKA CA
415 AM PST TUE DEC 22 2009

.SYNOPSIS...SCATTERED SHOWERS CONTINUE TO INVADE THE REDWOOD COAST 
THIS MORNING AND AREA EXPECTED TO TAPER THIS AFTERNOON AS HIGH 
PRESSURE MOVES INTO THE AREA. A RIDGE WILL THEN DOMINATE THROUGH 
THURSDAY. THE NEXT SYSTEM WILL APPROACH FOR THE WEEKEND.

&&

.DISCUSSION...MORNING UPDATE. THE MORNING FORECAST HAS BEEN UPDATE 
TO INDICATE CONTINUED AND MORE VIGOROUS SHOWERS THROUGH THE NRN HALF 
OF THE FORECAST DOMAIN. SHOWERS HAVE BEEN PERSISTENT OVERNIGHT AND 
ARE EXPECTED TO REMAIN AS SUCH THROUGH THE MORNING AND INTO THE 
AFTERNOON BEFORE TAPERING. BFG

PREVIOUS DISCUSSION. THE COLD FRONT THAT LINGERED ALONG THE COAST 
YESTERDAY HAS MOVED EAST OF OUR REGION. SATELLITE IMAGERY DEPICTING 
A DEEP UPPER LOW WITH A VERY COLD CORE MOVING RAPIDLY SOUTHWARD 
ACROSS SOUTHERN WA/NORTHERN OREGON EARLY THIS MORNING. 06Z GFS HAS 
INITIALIZED THIS FEATURE WELL AND HAS IT PROGGED TO CROSS NORTHEAST 
CA/WESTERN NV LATER THIS AFTERNOON. THE APPROACHING LOW WILL BRIEFLY 
ENHANCE SHOWER COVERAGE AND ACTIVITY LATER THIS MORNING BUT BY 0Z OR 
SO NORTHWEST CA SHOULD BE UNDER THE DRIER NORTHEAST CIRCULATION 
PRETTY MUCH ENDING ANY ADDITIONAL THREATS OF PRECIPITATION.  AT 
ABOUT THE SAME TIME STRONG RIDGING BEGINS TO BUILD FROM THE WEST. 
THIS RIDGE PATTERN WILL DOMINATE THE REGION THROUGH FRIDAY BRINGING 
MOSTLY CLEAR SKIES TO MOST OF THE REGION. THE EXCEPTION WILL BE THE 
WESTERN VALLEYS WHERE PERSISTENT FOGS WILL FORM AND PERSIST MOST OF 
THE DAY AND MAY NOT LIFT AT ALL IN SOME VALLEYS. THIS WILL HOLD DOWN 
TEMPS TO NEAR FREEZING IN THOSE VALLEYS THAT DO NOT CLEAR. 

FORECAST MODELS MAINTAIN A BLOCKED FLOW DOWNSTREAM THROUGH THE 
WEEKEND AS A LARGE AND STRONG STORM PUMMELS THE OHIO VALLEY AND 
GREAT LAKES REGION NEXT WEEKEND...WHILE THE WEST REMAINS UNDER THE 
RIDGE. LATER ON SATURDAY THE FLOW DOWNSTREAM BEGINS TO OPEN UP AGAIN 
ALLOWING THE NEXT WEATHER SYSTEM TO REACH THE WEST COAST...WITH RAIN 
LIKELY TO THE CWA EITHER LATE SATURDAY OR EARLY SUNDAY.  BOTH GFS 
AND EUROPEAN RUNS MAINTAIN A TROUGH LIKE PATTERN OVER THE REGION 
THROUGH MONDAY THEN SUGGEST ANOTHER SHORT WAVE RIDGE TO RETURN LATE 
MONDAY /EARLY TUESDAY OF NEXT WEEK. 

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH THE DAY WITH TEMPO 
MVFR CONDITIONS THIS MORNING MAINLY N OF CAPE MENDOCINO AS SHOWER 
COVERAGE GRADUALLY DIMINISHES. PATCHY FG IS EXPECTED TO DEVELOP 
ALONG THE COAST AND OVER THE INTERIOR VALLEYS OVERNIGHT WITH MVFR TO 
IFR VIS THROUGH MID WED MORNING. BC 

&&

.MARINE...HIGH PRESSURE OVER THE NE PACIFIC WILL MAINTAIN MODERATE 
NORTHWEST TO NORTH WINDS OVER THE WATERS INTO THU. A LONGER PERIOD 
NW SWELL COMBINED WITH A SHORTER PERIOD NW SWELL WILL CONTINUE A 
FAIRLY CONFUSED SEA STATE THROUGH WED AFTERNOON. A MODERATE NW SWELL 
TRAIN WILL DOMINATE THE SEA STATE LATE WED THROUGH FRI. MODELS 
CONTINUE TO FORECAST A MUCH LARGER LONG PERIOD SWELL FOR THE 
WEEKEND. BC

&& 

.EKA WATCHES/WARNINGS...
SCA ALL WATERS.

&&

$$

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