Winter Weather Advisory 4, NWS Eureka, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
255 PM PST SUN MAR 1 2009

.SYNOPSIS...A PACIFIC STORM WILL BRING RAIN AND HIGH ELEVATION SNOW
TO NORTHWEST CALIFORNIA TONIGHT THROUGH TUESDAY. LOW PRESSURE OVER THE
NE PACIFIC WILL CONTINUE TO BRING SHOWERS THROUGH THE MIDDLE OF THE
WEEK.

&&

.DISCUSSION...MAIN FORECAST CONSIDERATIONS INCLUDE THE HYDROLOGIC
SITUATION...WIND POTENTIAL LATE TOMORROW/TOMORROW NIGHT...AND SNOW
LEVELS TOMORROW NIGHT AND MONDAY.

AFTERNOON SATPIX PLACE THE PRIMARY LOW NEAR 44N/135W WITH THE
ATTENDANT SURFACE BOUNDARY DRAPED JUST OFFSHORE. THIS BOUNDARY WILL
MAKE LITTLE EASTWARD HEADWAY AS THE STEERING FLOW ALOFT PARALLELS
THE FRONT...SO MILD CONDITIONS WILL CONTINUE OVERNIGHT. AN IMPULSE
SPINNING OFF THE UPPER LOW WILL INDUCE MORE SIGNIFICANT
PRECIPITATION DEVELOPMENT OVERNIGHT ACROSS THE AREA...WITH THE
LATEST QPF GUIDANCE SHOWING 1 TO 2 INCHES OF ADDITIONAL
PRECIPITATION OVERNIGHT. ADDITIONAL SHORTWAVES ROTATING AROUND THE
LOW WILL GRADUALLY DEEPEN THE TROUGH AND SUSTAIN SHOWERS THROUGH THE
DAY MONDAY. EARLIER HYDROGRAPHS INDICATED THE MAIN STEM RIVERS
RUNNING BELOW GUIDANCE...BUT THE MOST RECENT RUNS CAPTURE THE DELAY
IN HEAVIER RAINS WELL...WITH THE EEL RIVER AT FERNBRIDGE FORECAST
NOT TO REACH MONITOR STAGE UNTIL LATE MONDAY NIGHT...AND THE NAVARRO
NEAR FLOOD STAGE TUESDAY AFTERNOON. GIVEN THESE TIMEFRAMES...IT IS
STILL TOO EARLY TO ISSUE ANY HYDROLOGIC PRODUCTS AND...OF
COURSE...UNCERTAINTY REMAINS SIGNIFICANT EVEN AT THIS JUNCTURE.
ANOTHER SURFACE LOW WILL DEVELOP OFFSHORE TOMORROW AFTERNOON WHICH
WILL BRING INCREASING SOUTHEAST WINDS THROUGH THE DAY INTO MONDAY
NIGHT...WITH GUSTS TO 35 MPH POSSIBLE ALONG THE COAST NORTH OF
TRINIDAD AND EVEN HIGHER SPEEDS OVER AREA RIDGES. COLDER AIR WILL
SPILL INTO THE REGION TOMORROW NIGHT INTO TUESDAY...WITH SNOW LEVELS
EXPECTED TO DROP TO THE 2500 TO 3000 FOOT RANGE. DEPENDING ON THE
EXTENT OF LINGERING SHOWER ACTIVITY...A WINTER WEATHER ADVISORY MAY
BE REQUIRED FOR THIS PERIOD BUT ENOUGH UNCERTAINTY REMAINS WITH THIS
ASPECT THAT THIS WILL BE SUBSEQUENTLY EVALUATED. FINALLY...MID LEVEL
LAPSE RATES AND UPPER LEVEL FORCING SUGGEST AT LEAST A SLIGHT
POSSIBILITY FOR ISOLATED THUNDERSTORMS FROM NOW THROUGH TUESDAY...SO
WE WILL RETAIN THESE IN THE OUTGOING PACKAGE.

BEYOND THIS POINT...ENSEMBLES AND VARIOUS OPERATIONAL MODELS
CONTINUE TO GENERALLY SHOW AN UNSETTLED PATTERN BUT OFFER SOMEWHAT
LESSER CHANCES FOR PRECIPITATION TOWARDS LATE WEEK AND WE HAVE
ADJUSTED THE FORECAST ACCORDINGLY. BURGER

&&

.AVIATION...A NUDGE FROM A VERY STRONG SOUTHWESTERLY JET WILL MOVE A
COLD FRONT TOWARDS THE AREA...BRINGING IN PERIODS OF MODERATE TO
HEAVY RAIN TO THE COASTAL AIRPORTS THROUGH EVENING. A TROF AND BAND
SOUTHERLY MOISTURE WILL CONTRIBUTE OF THE HEAVIER RAINFALL AND MAY
HELP TO TRIGGER THE POSSIBILITY OF A THUNDERSTORM IN THE VCNTY OF
THE COASTAL AIRPORTS. THE IMPACT AS FAR AS CIGS/VIS ARE CONCERN
SHOULD NOT BE CRITICAL SINCE THEY ARE EXPECTED ONLY TO DROP TO MVFR
CATEGORY. VFR CONDITIONS EXPECTED OVER UKI WITH OCCASIONAL CONDITIONS
BELOW. SOUTHERLY WINDS WILL GENERALLY REMAIN MODERATE. CARL

&&

.MARINE...SOUTHERLY WINDS WILL CONTINUE TO STRENGTHEN THIS EVENING
AS A LOW PRESSURE SYSTEM INTENSIFIES OVER THE NE PACIFIC.
SCATTEROMETER DATA THIS MORNING SHOWED GALES OVER THE OUTER WATERS.
ALTHOUGH BUOY DATA IS REPORTING WINDS BELOW GALES EARLY THIS
AFTERNOON EXPECT GALES OVER THE INNER WATERS BY THE EARLY EVENING.
THE WINDS WILL RAMP UP AGAIN MONDAY NIGHT AS THE LOW PRESSURE SYSTEM
NEARS THE COAST AND HAVE ISSUED ANOTHER GALE WARNING FOR THAT TIME
PERIOD. THINK THE GALES WILL BE TOO SHORT LIVED TO GENERATE
HAZARDOUS WARNING WIND SEAS AND DID NOT ISSUE A HAZARDOUS SEAS
WARNING. HOWEVER...THE SEAS WILL BE DANGEROUS AS A WEST SWELL SHOULD
BEGIN TO BUILD OVER THE WATERS MON NIGHT AND TUE. SWELL FORECAST
CONFIDENCE IS LOW BEYOND TUE AS MARINE MODELS HAVE BEEN FLIP
FLOPPING AS THE GFS STRUGGLES TO FORECAST THE TRACK OF THE LOW. THE
12Z ENP MODEL HAS BACKED WAY OFF ON THE NW SWELL HEIGHTS FOR TUE AND
WED. HAVE REDUCED THE SWELL HEIGHTS SOME ...BUT DID NOT LOWER THEM
QUITE AS MUCH AS THE 12Z ENP SUGGESTED. TH

&&

.EKA WATCHES/WARNINGS/ADVISORIES...

GALE AND HAZARDOUS SEAS WARNINGS FROM PT ST GEORGE TO PT ARENA
0-60NM.

&&

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