Special Marine Warning 4, NWS Eureka, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
200 AM PST WED MAR 1 2006

.SYNOPSIS...LOOK FOR A RETURN TO WINTER WEATHER ACROSS NORTHWEST
CALIFORNIA TODAY...THURSDAY AND FRIDAY. A FAST-MOVING COLD FRONT
WILL SPREAD A VERY COLD...MOIST AND UNSTABLE AIRMASS ACROSS THE
REGION BY THURSDAY AFTERNOON. SNOW LEVELS ARE EXPECTED TO FALL
TONIGHT FROM 3000 FEET DOWN TO 2000 FEET WITH SNOW SHOWERS LIKELY ON
THURSDAY AND FRIDAY. SNOW SHOWERS MAY BE STRONG ENOUGH TO BRING SNOW
LEVELS DOWN TO THE 1000 TO 1500 FOOT MARK.

&&

.DISCUSSION...WHAT A DIFFERENCE A WEEK MAKES. LOOKING AT WIDESPREAD
WINTER WEATHER...WITH SNOW AND HEAVY SNOW SHOWERS HIGHLIGHTING THE
LOCAL AREA FORECASTS DURING THE NEXT 24 TO 60 HOURS ABOVE 2000FT ON
AVERAGE. BASED ON NUMEROUS PARAMETERS...1000-850MB THICKNESS VALUES
REMAIN IN THE 1304-1312M RANGE WHICH EQUATES TO A GENERIC SNOW LEVEL
OF 1500-2500FT IN THE ABSENCE OF DEEP CONVECTION. H7 TEMPERATURES
REMAIN AT OR BELOW (COLDER) THAN M10C...H85 STAY NEAR M3C TIL SUNDAY
MORNING...AND H5 TEMPERATURES NEAR/COLDER THAN M30C FROM THURSDAY
MORNING TO FRIDAY NIGHT...HAVE UPGRADED CURRENT WINTER STORM WATCH
TO WARNINGS ABOVE 2000FT FOR TONIGHT INTO THURSDAY EVENING TIME
FRAME.

ACCUMULATING SNOWS WILL PROBABLY START OUT AROUND 3000FT THIS
EVENING...AND QUICKLY FALL TO 2000 FT AROUND MIDNIGHT. A GENERIC
SNOW LEVEL AROUND 2000FT FOR THE HEAVY SNOW WARNING (FOR 5 IN
THU/02-14Z WINDOW OR 7 IN THU/02Z-FRI02Z TIME FRAME)...BUT
CERTAINLY MIGHT SEE LOWER LEVEL SNOWFALLS BENEATH INTENSE CONVECTION
WHICH COULD MAKE LO-END ADVISORY NUMBERS. EXPECTING PASSES TO HAVE
SNOW ISSUES OVERNIGHT.

NOT MUCH IN THE WAY OF WARM AIR ADVECTION AT H85 AND H7 WITH THE
APPROACHING MID/UPPER LEVEL FRONT/WIND MAXIMA THAT MAKES LANDFALL
AROUND THU/00Z...THIS AFTERNOON LOCAL TIME. STRONG SOUTHERLY H5-H3
FLOW HAS TRAVERSED FORECAST AREA BY THU/12Z AND COLDER/DEEPER
AIRMASS USHERS IN QUICKLY BEHIND...SPREADING THROUGHOUT FORECAST
AREA BY MID-AFTERNOON THURSDAY. CAN EXPECT INTENSE SHOWER ACTIVITY
AND SNOW LEVELS DOWN TO VALLEY FLOORS OVER THE INTERIOR OF NW CALIF
AT TIMES THURSDAY AND FRIDAY. QUESTION IS...AGAIN WHAT SORT OF AREAL
COVERAGE WILL EVENTUALLY SHAKE OUT AS THE UPPER-LEVEL COLD CORE
PASSES OVER PARTS OF NW CALIF THIS FORECAST PACKAGE.

THIS PATTERN PERSISTS THROUGH FRIDAY AFTERNOON/NIGHT...WITH VERY
COLD AIR...DECENT VERTICAL SHEAR AND STEEP LAPSE RATES. CONSIDERING
THAT THE H5-H3 FLOW WEAKENS TO ONLY 20-30KT ON THURSDAY AND
FRIDAY...THE CONVECTION MOVING ONSHORE WILL BE SLOW-MOVING WITH
PLENTY OF VERTICAL MOTION AND SOME THUNDER/LIGHTNING. HEAVY SNOW
SHOWERS...POSSIBLE IN CAZ076 AND CAZ004 MOUNTAINS. FOR NOW...SEE A
BRIEF BREAK ON SATURDAY INTO SUNDAY MORNING...THEN LOOKING FOR
ANOTHER SYSTEM MOVING INTO NW CALIF BY SUNDAY NIGHT. DIFFICULT TO
SAY HOW MUCH WARMER INLAND AT THIS POINT...GIVEN THE REASONABLE
CONCENSUS FOR 1000-500MB THICKNESS NEAR 5520M...WILL START SNOW
LEVEL OUT AROUND 4000FT.

&&

.AVIATION...PLEASE SEE TAFS/TWEBS FOR DETAILS.

&&

.EKA...WATCHES/WARNINGS/ADVISORIES...
.HEAVY SNOW WARNING...CAZ003-004-076 ABOVE 2000FT
.WIND ADVISORY...CAZ001
.STORM/HAZARDOUS SEAS WARNINGS...PZZ450-470
.GALE WARNING...PZZ455-475

&&
MJV/DJB

VISIT US AT WWW.WEATHER.GOV/EUREKA

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