HAMweather.com Area Forecast Discussion for County Warning Area EKA

Thu, 16 Feb 2012 05:27:25 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
324 PM PST WED FEB 15 2012

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BRING DRY WEATHER TO
NORTHWEST CALIFORNIA THROUGH THURSDAY. PRECIPITATION CHANCES WILL
INCREASE FRIDAY INTO THE WEEKEND AS A STORM SYSTEM IMPACTS THE
REGION.

.DISCUSSION...AN UPPER LEVEL RIDGE WILL BRING DRY WEATHER TO
NORTHWEST CALIFORNIA THROUGH THURSDAY. CONDITIONS WILL BEGIN TO
DETERIORATE FRIDAY AS ANOTHER TROUGH APPROACHES THE REGION. THE
MODELS HAVE COME INTO MUCH BETTER AGREEMENT SHOWING THIS TROUGH
PASSING OVER THE AREA ON SATURDAY. THE TWO MAIN PROBLEMS ARE QPF
AMOUNTS AND SNOW LEVELS. THE MODELS ARE IN GOOD AGREEMENT SHOWING
SNOW LEVELS INITIALLY ABOVE PASS LEVELS FRIDAY AND THEN DROPPING
TO AROUND 3000 FEET SATURDAY MORNING AND CONTINUING THROUGH
SATURDAY NIGHT. THIS IS SLIGHTLY HIGHER THAN WHAT THE MODELS WERE
SAYING, SO HAVE RAISED SNOW LEVELS BY ABOUT 500 FEET DURING THIS
TIME PERIOD. THE NEXT CONCERN IS QPF. THE INITIAL PUSH OF
PRECIPITATION FRIDAY AND FRIDAY NIGHT SHOULD BE ALL RAIN. HOWEVER,
SATURDAY IS WHEN THE MODELS DIVERGE, RIGHT WHEN THE SNOW LEVELS
DROP. THE NAM AND SREF APPEAR TO BE DRIER AND FASTER. THE GFS IS
THE SLOWEST AND WETTEST. THE ECMWF SEEMS TO BE RIGHT IN THE
MIDDLE. DECIDED TO FOLLOW HPC'S GUIDANCE OF GOING MORE WITH A
BLEND (OR ECMWF). HOWEVER, MODEL UNCERTAINTY IS HIGH AND
CONFIDENCE IS LOW. ANY SWING TOWARD WETTER OR DRIER CAN HAVE A
LARGE IMPACT WITH THE LOW SNOW LEVELS. THIS WILL BE WATCHED AND
ADJUSTED WITH THE UPCOMING PACKAGES. PRECIPITATION TAPERS TO
SHOWERS ON SUNDAY. MODELS ARE IN GOOD AGREEMENT SHOWING A LONG
WAVE TROUGH OVER THE U.S. NEXT WEEK. HAVE KEPT POPS AROUND CLIMO
IN THE LONG TERM.

.AVIATION...NORTHERLY FLOW CONTINUES ACROSS THE AREA WITH VFR
CONDITIONS EXPECTED THROUGH THURSDAY. WINDS WILL DECREASE THIS
EVENING AS THE ATMOSPHERE DECOUPLES AND SURFACE HIGH PRESSURE
BUILDS INTO THE REGION. WINDS NEAR THE COAST AND IN INTERIOR
MENDOCINO COUNTY WILL BE MUCH LIGHTER THURSDAY AS THE PRESSURE
GRADIENT WEAKENS. A FEW PATCHY AREAS OF INTERIOR VALLEY FOG ARE
POSSIBLE TONIGHT...HOWEVER VERY DRY AIR HAS SETTLED INTO
NORTHWESTERN CALIFORNIA SO MOST LOCATIONS WILL REMAIN CLEAR. HIGH
CLOUDS WILL SPREAD INTO THE REGION ON THURSDAY AHEAD OF THE NEXT
SYSTEM. RPA

.MARINE...NORTHERLY WINDS CONTINUE TO GUST TO 25 KT OVER THE
WATERS TODAY. THESE WINDS SHOULD DECREASE THROUGH THE EVENING
HOURS INTO THURSDAY AS THE PRESSURE GRADIENT WEAKENS AND SURFACE
HIGH PRESSURE BUILDS INTO NORTHERN CALIFORNIA. SEAS WILL BEGIN TO
DIMINISH THIS EVENING AS THE WINDS DECREASE. THUS SMALL CRAFT
ADVISORIES SHOULD BE ABLE TO EXPIRE OVERNIGHT. LIGHT WINDS AND
LOWER SEAS WILL CONTINUE THROUGH THURSDAY INTO THURSDAY NIGHT. BY
THURSDAY NIGHT A NEW NORTHWESTERLY LONG PERIOD SWELL WILL ARRIVE
RESULTING IN BUILDING SEAS OVER 10 FT ONCE AGAIN FRIDAY REQUIRING
SMALL CRAFT ADVISORIES AT LEAST FOR THE OUTER WATERS...AND LIKELY
FOR THE INNER WATERS.

THE NEXT BIG WEATHER MAKER ARRIVES FOR THE WEEKEND. A SHORTWAVE
DEVELOPING IN THE CENTRAL PACIFIC AROUND 34N 175W WILL MOVE EAST-
NORTHEASTWARD TOWARD THE PACIFIC NORTHWEST THROUGH THE END OF THE
WEEK. MODELS INDICATE THIS SHORTWAVE WILL CUT OFF FROM THE FLOW
FRIDAY OFF THE BRITISH COLUMBIA COAST RESULTING IN THE DEVELOPMENT
OF A SURFACE AREA OF LOW PRESSURE. THE EXACT POSITIONING OF THIS
SYSTEM IS UNCERTAIN AT THIS TIME WITH THE 12Z ECMWF CUTTING OFF
THE SYSTEM A LITTLE FURTHER NORTH THAN THE 12Z GFS. THIS
DIFFERENCE RESULTS IN SIGNIFICANT DIFFERENCES TO THE MARINE
CONDITIONS ON SATURDAY OFF THE NORTHERN CALIFORNIA COAST. THE ENP
GUIDANCE IS BASED OFF OF THE GFS MODEL...AND IT CURRENTLY CREATES
A DYNAMIC FETCH AS THE SURFACE LOW PRESSURE MOVES EAST-SOUTHEAST
TOWARD THE OREGON COAST. WAVES 20-25 FT OR HIGHER WOULD PROPAGATE
TOWARD THE WATERS IN THIS SITUATION. HOWEVER IF THE ECMWF SOLUTION
IS CORRECT...WITH THE SURFACE LOW FURTHER NORTH MOVING INTO THE
OLYMPIC PENINSULA...WAVES WILL ONLY PEAK NEAR 20 FEET. THE SREF
GUIDANCE SUPPORTS THE ECMWF SOLUTION. THUS THE SEAS HAVE BEEN HELD
AT 18 FEET ON SATURDAY FOR THIS UPDATE...A FEW FEET HIGHER THEN
THE PREVIOUS FORECAST. IF MODELS CONTINUE TO INDICATE THE LARGER
SWELL THE WAVE HEIGHTS WILL NEED TO BE RAISED. ANY TREND FURTHER
SOUTH IN THE ECMWF GUIDANCE WOULD ALSO INDICATE HIGHER SEAS FOR
SATURDAY.

WINDS FRIDAY INTO SATURDAY WILL INCREASE OUT OF THE NORTHWEST ON
THE SOUTH SIDE OF THE SURFACE LOW WITH SMALL CRAFT WINDS POSSIBLE
ACROSS THE OUTER WATERS. MODELS DIVERGE A LITTLE MORE
SIGNIFICANTLY ON SUNDAY WITH WIND DIRECTIONS BECOMING MORE
UNCERTAIN. THUS THE SUNDAY FORECAST HAS BEEN LEFT NEARLY UNCHANGED
WITH THIS UPDATE. HOWEVER EARLY NEXT WEEK MODELS GENERALLY
INDICATE UPPER LEVEL RIDGING WILL BUILD JUST OFF THE COAST
RESULTING IN PREVAILING NORTHERLIES. RPA

.EKA WATCHES/WARNINGS/ADVISORIES...

CA...NONE.

NORTHWEST CALIFORNIA COASTAL WATERS...

SMALL CRAFT ADVISORY FOR PZZ450-455-470-475.