033 FXUS66 KEKA 192230 AFDEKA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE EUREKA CA 330 PM PDT TUE MAR 19 2013 .SYNOPSIS...A STORM SYSTEM WILL BRING RAIN AND GUSTY WINDS TONIGHT THROUGH WEDNESDAY. DRY AND COOLER WEATHER WILL RETURN ON THU AND FRI AS HIGH PRESSURE REBUILDS INTO THE REGION. && .DISCUSSION...SURFACE ANALYSIS AND SATELLITE IMAGERY SHOWED A MOIST PLUME TAKING AIM ON THE REGION THIS AFTERNOON. PRECIP HAS BEEN SLOWLY INCREASING IN COVERAGE AND INTENSITY THROUGH THE DAY AS A POSITIVE TILTED UPPER TROUGH WEST OF 130W SLOWLY DIGS SOUTH AND EAST TOWARD THE AREA. SO FAR AMOUNTS HAVE BEEN LIGHT AND SPOTTY ALONG THE COAST BUT WITH GREATER COVERAGE AND HIGHER RAIN RATES INLAND. RATES SHOULD SLOWLY INCREASE LATER TONIGHT AS A COLD FRONT APPROACHES THE COASTLINE. CONCERNED THAT THE GREATER EUREKA AREA MIGHT BE DRY SLOTTED TONIGHT AS STRONG SOUTHERLY WINDS RAMP UP AHEAD THE COLD FRONT. THIS WILL REDUCE THE RAINFALL AMOUNTS UNTIL THE SURFACE BOUNDARY MOVES ONSHORE AND WINDS SHIFT AROUND TO THE WEST BY 12PM WED. IF A REFLECTIVITY HOLE OPENS UP WE MAY SEE ONLY A FEW SPOTTY HUNDREDTHS IN AND AROUND EUREKA. WE ARE STILL LOOKING AT A FAIRLY GOOD SOAKING CWA-WIDE THE NEXT 24 HOURS...WITH GENERALLY 0.75-1.5 INCHES WITH LOCALIZED AMOUNTS UP TO 2.5 INCHES IN THE MOUNTAINS. MOST OF THE RAIN WILL OCCUR AHEAD OF AND ALONG THE COLD FRONTAL BOUNDARY WHICH LOOKS TO PASS THROUGH BY MIDDAY WED...WITH AN HOUR OR TWO OF MODERATE TO HEAVY RAIN. SNOW LEVELS WITH THIS SYSTEM WILL REMAIN ABOVE 6KFT UNTIL THE UPPER TROUGH PASSES OVER LATE WED AFTERNOON INTO EARLY EVENING. 2-4 INCHES OF NEW SNOW IS EXPECTED ABOVE 5500 FEET WED AFTERNOON...WHICH MAY AFFECT SCOTT MOUNTAIN PASS LATE IN THE DAY. THE PRECIP WILL TRANSITION TO SCATTERED SHOWERS BEHIND THE FRONT LATE WED AFTERNOON AND DIMINISH WED NIGHT INTO THU. SNOW LEVELS SHOULD PLUMMET TO 2500-3500 FT WED NIGHT...HOWEVER THE INSTABILITY...MOISTURE AND DYNAMICS IN THE COLD AIR BEHIND THE FRONT DOES NOT LOOK VERY FAVORABLE FOR HEAVY SNOW SHOWERS. A WINTER WEATHER ADVISORY IS NOT ANTICIPATED AT THIS TIME DUE TO INSUFFICIENT AMOUNTS AND SPARSE COVERAGE. DEPENDING ON THE RATE OF CLEARING AND DRYING...WIDESPREAD FROST IS POSSIBLE EARLY THU MORNING. DRYING NORTH FLOW AND CLEARING SKIES SHOULD CONTINUE INTO FRI AND WIDESPREAD FROST LOOKS MORE LIKELY EARLY FRI MORNING. MODELS HAVE BEEN INDICATING A MINOR SHORT WAVE CLIPPING THE EXTREME NORTHERN PORTION OF THE FORECAST AREA ON THU. THEREFORE...KEPT A SLIGHT CHANCE OF PRECIP IN DEL NORTE COUNTY ON THU. THE MODELS WERE IN BETTER AGREEMENT FRI WITH A RIDGE INTENSIFYING AFTER S/W PASSAGE. IT SHOULD BE BREEZY AND COOL ON FRIDAY...ESPECIALLY AT THE COAST. MODELS INDICATE ANOTHER WEAK S/W CLIPPING THE AREA SAT OR SAT NIGHT FOR ANOTHER SLIGHT CHANCE OF LIGHT PRECIP MAINLY NORTH OF THE CAPE. A RIDGE SHOULD THEN BUILD AGAIN ON SUN...KEEPING THE AREA DRY THROUGH MON. 12Z GFS AND ECMWF BRING A STRONGER/DEEPER TROUGH TOWARD THE COAST ON TUE FOR ANOTHER LOW CHANCE OF RAIN. && .AVIATION...CLOUDS WERE PREDOMINANTLY MID LEVEL TODAY ACROSS THE REGION AS A WEATHER SYSTEM APPROACHED NORTHERN CALIFORNIA. LIGHT SPRINKLES OCCURRED OVER SOUTHERN MENDOCINO EARLY A.M. A LARGE SWATHE OF LIGHT RAIN INVADED THE REGION SHORTLY BEFORE NOON... BRINGING LIGHT RAIN FROM FROM CEC-UKI. HOWEVER SOME MODERATE RAIN DID FALL IN REDWAY/GARBERVILLE VICINITY. 2PM RADAR AND SAT PICTURES SHOW WIDESPREAD LIGHT PRECIPITATION ADVANCING TOWARD COAST AGAIN. CIGS/VIS CONTINUED TO SHOW VFR CONDITIONS UNTIL AROUND 3PM WHEN ACV/CEC REPORTED MVFR CIGS/VIS. WINDS REMAINED SOUTHERLY AS EXPECTED...AND SHOULD INCREASE IN INTENSITY TONIGHT AS THE PACIFIC FRONT MOVES TOWARDS THE AREA. EXPECT MVFR AND EVEN OCNL IFR THROUGH THE EVENING MAINLY AT COASTAL LOCATIONS. && .MARINE...A STRONG SYSTEM CONTINUES TO MOVE INTO THE AREA INCREASING SOUTHERLY WINDS AHEAD OF A PRE-FRONTAL TROUGH. A COASTAL JET WITH 45-50 KT WINDS APPROXIMATELY 2KM ABOVE THE SURFACE WILL CONTINUE TO DEVELOP OVERNIGHT INTO EARLY WEDNESDAY MORNING. THIS WILL ALLOW GALE FORCE GUSTS TO MIX TO THE SURFACE WITH GUSTS APPROACHING 45 KT ACROSS THE NORTHERN OUTER WATERS. THE COASTAL JET STAYS PRIMARILY NORTH OF THE CAPE AS THE PRIMARY ENERGY OF THE SYSTEM MOVES INTO THE PACIFIC NORTHWEST. THUS GALE WARNINGS ARE ISSUED FOR BOTH NORTHERN WATER ZONES WHILE ONLY SMALL CRAFT ADVISORIES ARE UP FOR THE SOUTHERN WATER ZONES. SEAS WILL BUILD RAPIDLY IN RESPONSE TO THE WINDS...PEAKING BETWEEN 12 AND 14 FT OVER THE NORTHERN OUTER WATERS. ALL ADVISORIES AND WARNINGS HAVE BEEN EXTENDED A FEW HOURS LATER INTO THE MORNING ON WEDNESDAY AS MODELS HAVE SLOWED DOWN EVEN MORE THAN THEY WERE ANTICIPATED TO SLOW DOWN YESTERDAY. THE PRIMARILY COLD FRONT WILL MOVE TOWARD THE COAST WEDNESDAY MORNING DISSIPATING THE COASTAL JET. THE FRONT WILL MOVE THROUGH THE WATERS DURING THE DAY WEDNESDAY TURNING THE WINDS OUT OF THE NORTHWEST AND ALSO BRING A BUILDING NORTHWEST SWELL. SEAS WILL SUBSIDE ENOUGH ACROSS THE SOUTHERN WATERS FOR A PERIOD OF BELOW SCA CRITERIA SEAS AND WINDS AS THE SOUTHERLY WINDS DIMINISH JUST AHEAD OF THE FRONT. HOWEVER THESE LOWER CONDITIONS WILL BE SHORT LIVED AS THE NORTHWEST SWELL BUILDS IN AND THEN HIGH PRESSURE STRENGTHENS OVER THE EASTERN PACIFIC BEHIND THE COLD FRONT. THIS WILL CAUSE NORTHERLY WINDS TO STRENGTHEN WEDNESDAY NIGHT INTO THURSDAY. SCA TO NEAR GALE CONDITIONS ARE ANTICIPATED ACROSS THE SOUTHERN WATERS THURSDAY INTO THE WEEKEND...WITH SCA CONDITIONS EXTENDING NORTH OF THE CAPE. MODELS ARE NOW IN BETTER AGREEMENT ON THE EXTENDED FORECAST... ANTICIPATING A RIDGE OF HIGH PRESSURE TO PERSIST JUST OFF OR OVER THE WEST COAST THROUGH THE WEEKEND. ANOTHER TROUGH WILL LIKELY ADVANCE TOWARD THE COAST NEXT WEEK. RPA && .EKA WATCHES/WARNINGS/ADVISORIES...CA...NONE. NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING PZZ450. GALE WARNING FROM 11 PM THIS EVENING TO 7 AM PDT WEDNESDAY PZZ450. GALE WARNING UNTIL 7 AM PDT WEDNESDAY PZZ470. SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 7 AM PDT WEDNESDAY PZZ455. SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 7 AM PDT WEDNESDAY PZZ475. && $$ VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA FOLLOW US ON FACEBOOK AND TWITTER AT: HTTP://WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.EUREKA.GOV HTTP://WWW.TWITTER.COM/NWSEUREKA