AREA FORECAST DISCUSSION

 
 FXUS66 KEKA 212203
 AFDEKA
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE EUREKA CA
 203 PM PST SAT NOV 21 2009
 
 .SYNOPSIS...A STORM SYSTEM WILL BRING MORE RAIN AND HIGHER ELEVATION 
 SNOW TO NORTHWEST CALIFORNIA TONIGHT INTO SUNDAY. WARMER AND DRY 
 WEATHER IS EXPECTED FOR EARLY NEXT WEEK. ANOTHER CHANCE OF RAIN IS 
 EXPECTED FOR LATE NEXT WEEK. 
 
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 .DISCUSSION...SKIES CLEARED RAPIDLY EARLY TODAY ACROSS NORTHWEST 
 CALIFORNIA...AS A STABLE AIR MASS MOVED IN BEHIND THE DEPARTING 
 COLD FRONT. VISIBLE SAT IMAGES SHOW A CLOUD SHIELD MOVING TOWARD THE 
 COAST...CURRENTLY BEGINNING TO FILTER OVER THE REDWOOD COAST. THIS 
 WILL BRING ADDITION RAIN TO MOST OF THE CWA...WITH SNOW AT THE 
 HIGHER ELEVATIONS. CURRENTLY EXPECT SNOW LEVEL TO BE NEAR 5000 
 FT...ALTHOUGH SOME COLD AIR POCKETS IN THE TRINITY VALLEYS MAY ALLOW 
 A LITTLE SNOW TO MIX DOWN IN CERTAIN LOCATIONS. THE LIKELY SPOTS ARE 
 SHELTERED VALLEYS IN EASTERN HUMBOLDT AND WESTERN TRINITY COUNTIES. 
 RAIN WILL BEGIN LATER THIS AFTERNOON/EVENING...PERHAPS AS EARLY AS 
 AROUND 00Z...ACCOMPANIED BY THE AFOREMENTIONED SNOWFALL. THE EVENT 
 WILL CONTINUE THROUGH LATE MORNING SUNDAY. THINGS WILL TAPER OFF 
 FAIRLY QUICKLY SUNDAY AFTERNOON AS UPPER RIDGING BUILDS INTO THE 
 EASTERN PACIFIC. 
 
 THE UPPER RIDGE WILL MOVE EAST RAPIDLY SUNDAY NIGHT PER GFS 
 FORECAST. THE FIVE WAVE PATTERN SHOWS A VERY LOW AMPLITUDE RIDGE 
 OVER THE WEST COAST WITH PROGRESSIVE FLOW OVER THE PACIFIC. UNDER 
 THIS SCENARIO THE RIDGE WILL WEAKEN AS A SHORT WAVE TROUGH SWINGS 
 ACROSS VANCOUVER ISLAND ON MONDAY. THIS MAY BRING SOME INCREASED 
 CLOUDINESS TO THE FAR NORTHERN CWA BUT LITTLE CHANCE OF RAIN. UPPER 
 RIDGING WILL THEN RETURN FOR TUESDAY AND WEDNESDAY. THIS WILL 
 PROVIDE A COUPLE DAYS OF WARMER AND DRYER WEATHER WITH 500 MB 
 HEIGHTS RISING TO NEAR 580. ANOTHER TROUGH AND ASSOCIATED FRONTAL 
 BAND WILL APPROACH THE PAC NW COAST EARLY THURSDAY. THE ECMWF IS 
 SLIGHTLY FASTER THAN GFS AND CANADIAN...AND DEVELOPS A DEEPER TROUGH 
 AS IT MAKES LANDFALL EARLY FRIDAY. THIS TIME PERIOD IS WHEN MODEL 
 DIFFERENCES START TO BECOME SIGNIFICANT. FOR THE SAKE OF CONSISTENCY 
 HAVE MAINTAINED CHANCE POPS ACROSS THE AREA FOR THURSDAY AND 
 FRIDAY...AND INDICATED AN IMPROVING TREND FOR SATURDAY. THE AIR MASS 
 APPEARS WARM ENOUGH TO SUPPORT SNOW LEVELS NEAR 7000 FT...SO THAT 
 WINTER DRIVING CONDITIONS ARE NOT EXPECTED FOR HOLIDAY TRAVEL. CMC
 
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 .MARINE...SOUTHERLY WINDS WILL INCREASE THIS EVENING AHEAD OF AN 
 APPROACHING COLD FRONT. THE FRONT WILL PUSH EAST THROUGH THE WATERS 
 LATE TONIGHT AND SUNDAY MORNING...WITH WINDS SWITCHING TO 
 NORTHWESTERLY. ALONG WITH A PERSISTENT WESTERLY SWELL...HAZARDOUS 
 CONDITIONS FOR SMALL CRAFT WILL CONTINUE THROUGH TOMORROW NIGHT. A 
 LONGER PERIOD NORTHWEST SWELL WILL AFFECT THE WATERS BY MID 
 WEEK...ALTHOUGH WINDS ARE EXPECTED TO BE RELATIVELY LIGHT NEXT WEEK. 
 HENRY
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 .AVIATION...A COLD FRONT WILL PUSH EAST THROUGH THE NORTH COAST 
 REGION LATE TONIGHT AND SUNDAY MORNING. WHILE NOT QUITE AS WET AS 
 THE LAST SYSTEM...MVFR WITH AREAS OF IFR CONDITIONS ARE EXPECTED 
 WITH PREVAILING RAIN SHOWERS...MAINLY STARTING BTW 03 AND 06Z ALONG 
 THE COAST...AND 05 AND 08Z INLAND TOWARD KUKI. BEHIND THE 
 FRONT...MVFR CIGS ARE EXPECTED TO PREVAIL THROUGH THE DAY SUNDAY. 
 HENRY 
 
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 NORTHWEST CALIFORNIA COASTAL WATERS...
 
      SMALL CRAFT ADVISORY UNTIL 9 PM PST SUNDAY FOR PZZ450-455.
 
      SMALL CRAFT ADVISORY UNTIL 4 AM PST MONDAY FOR PZZ470-475.
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