Current
Version
Previous Version: 1 2 3 4 5 AREA FORECAST DISCUSSION
FXUS66 KEKA 232227
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
227 PM PST MON NOV 23 2009
.SYNOPSIS...AN UPPER RIDGE WILL DOMINATE THE WEATHER PATTERN
THROUGH WEDNESDAY...RESULTING IN SEASONABLY WARM TEMPERATURES AND
DRY CONDITIONS. A LOW PRESSURE SYSTEM WILL COME ASHORE FOR THE
LATTER HALF OF THANKSGIVING DAY THROUGH FRIDAY MORNING. THE
MAJORITY OF THE PRECIPITATION WILL FALL AS RAIN...HOWEVER THERE
MAY BE SOME MIXING WITH SNOW FOR ELEVATIONS ABOVE 4000
FT...ESPECIALLY THURSDAY NIGHT.
&&
.DISCUSSION...AFTERNOON SURFACE ANALYSIS DEPICTS HIGH PRESSURE AXIS
STRETCHING ACROSS THE NORTHWEST CA/OREGON BORDER...A REFLECTION OF
UPPER RIDGE BUILDING ALOFT AS SEEN ON CURRENT WATER VAPOR LOOP.
SUNNY/DRY AIRMASS IN PLACE THIS AFTERNOON...WITH CLEAR CONDITIONS
EXPECTED TO CONTINUE TONIGHT. ALTHOUGH RADIATIONAL COOLING WILL BE
STRONG GIVEN LIGHT WINDS...RISING THICKNESSES SHOULD PREVENT
WIDESPREAD FROST ALONG THE COASTAL ZONES...AS OCCURRED LAST NIGHT.
UPPER RIDGE WILL CONTINUE TO BUILD OVER THE REGION AS THE STORM
TRACK REMAINS WELL TO THE NORTH THROUGH WEDNESDAY.
FORECAST ATTENTION THEN TURNS TO SYSTEM AFFECTING THE AREA STARTING
ON THANKSGIVING DAY. SLIGHTLY NEGATIVE TILTED TROUGH LIFTS ENE AS IT
COMES ASHORE THE PACIFIC NORTHWEST. ECMWF/GFS COMING INTO BETTER
AGREEMENT ON TIMING AND BRING PRECIP TO LAND ZONES BY 00Z FRIDAY.
H85 TEMPS SUPPORT MOSTLY RAIN FOR PTYPE WITH THE BULK OF THE
PRECIP...AND SO TRAVEL SHOULD NOT BE GREATLY IMPACTED. COLD AIR
ADVECTION THURSDAY NIGHT DROP H85 TEMPS TO AROUND 2C BELOW
ZERO...LOWERING SNOW HEIGHTS. SNOW SHOULD THEN MIX WITH RAIN FOR
ELEVATIONS GREATER THAN 4000FT...ALTHOUGH THIS LOOKS TO OCCUR AFTER
MAIN PRECIP BAND HAS PASSED BY.
FRIDAY AND SATURDAY...NORTHWEST FLOW ALOFT WILL BRING SOME
LINGERING LIGHT SHOWERS ON THE FRONT SIDE OF BUILDING RIDGE. DRY
AND WARM WEATHER LOOKS TO RETURN FOR THE LATTER HALF OF THE
WEEKEND AND INTO EARLY NEXT WEEK. HENRY
&&
.AVIATION...LIGHT OFFSHORE WINDS WILL CONTINUE TO BRING VFR FLYING
TO ALL TAF SITES THROUGH TONIGHT...ALTHOUGH LOCALIZED AREAS OF HAZE
MAY BRIEFLY RESTRICT VISIBILITIES THROUGH EARLY EVENING. AREAS OF
VALLEY FOG MAY ALSO FORM AFTER MIDNIGHT...BUT SCATTERED HIGH CLOUDS
SHOULD HELP PREVENT WIDESPREAD FORMATION ESPECIALLY AT THE COAST.
OTHERWISE...VFR WILL PERSIST THROUGH AT LEAST 18Z TUESDAY. BETTWY
&&
.MARINE...EARLY AFTERNOON BUOY OBSERVATIONS INDICATE A RATHER
ROBUST NORTHWEST SWELL IS CONTINUING TO PERSIST OVER AT LEAST A GOOD
PORTION OF OUR WATERS...WITH THE SWELL PERIOD LENGTHENING AT A SLOWER
RATE THAN PREVIOUSLY EXPECTED. WE ANTICIPATE ANOTHER PRONOUNCED
NORTHWEST SWELL TO PROPAGATE THROUGH THE ZONES TONIGHT INTO
TUESDAY...ALONG WITH A MODEST INCREASE IN WIND SPEEDS OVER THE
SOUTHERN OUTER WATERS. SMALL CRAFT CONDITIONS WILL RESULT OVER ALL
WATERS FOR AT LEAST 12-18 HOURS LATE TONIGHT INTO TUESDAY. A
WEAKENING PRESSURE GRADIENT AND SUBSIDING SWELL WILL LIKELY PROVIDE
A PERIOD OF RELATIVELY TRANQUIL SEAS ON WEDNESDAY BEFORE LOW
PRESSURE BRINGS ANOTHER INCREASE IN WINDS AND A LARGER NORTHWEST
SWELL THURSDAY INTO FRIDAY. BETTWY
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST
TUESDAY FOR PZZ450-455-470.
SMALL CRAFT ADVISORY UNTIL 4 PM PST TUESDAY FOR PZZ475.
&&
VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA
|
www.weather.gov 
