444  
FXUS66 KEKA 250354  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
854 PM PDT FRI OCT 24 2014  
   
SYNOPSIS
 
A STRONG COLD FRONT WILL BRING RAIN AND VERY GUSTY  
WINDS TONIGHT MAINLY AFTER MIDNIGHT THROUGH SATURDAY MORNING. THIS  
WILL BE FOLLOWED BY POST FRONTAL SHOWERS AND A THREAT OF  
THUNDERSTORMS IN THE AFTERNOON AND OVERNIGHT. SHOWERS WILL  
DIMINISH AND WINDS WILL BE FAIRLY LIGHT ON SUNDAY.  
 

 
   
UPDATE
 
THE LATEST GUIDANCE INDICATES THAT NUMEROUS GUSTS IN  
EXCESS OF 50 KT CAN BE EXPECTED IN THE OUTER COASTAL ZONES JUST  
AHEAD OF AND WITH THE FRONTAL PASSAGE. THUS THE GALE WARNING HAS  
BEEN UPGRADED TO A STORM WARNING IN BOTH OUTER WATER ZONES. WIND  
GUSTS ARE ALREADY APPROACHING ADVISORY CRITERIA IN THE MOUNTAINS  
WITH GUSTS TO 43 MPH AT KNEELAND AS OF 8 PM. THUS THE WIND  
ADVISORY TIMING LOOKS DECENT...THOUGH MAY NEED TO BE STARTED A  
COUPLE OF HOURS EARLY. THE OVERNIGHT SHIFT WILL HAVE TO EXAMINE  
WHETHER AN UPGRADE TO A HIGH WIND WARNING IS REQUIRED FOR LAND  
AREAS AS GREAT MIXING BEHIND THE FRONT MAY ALLOW GUSTS TO APPROACH  
60 MPH ON THE COAST IF CONDITIONS ARE JUST RIGHT.  
 
ADDITIONALLY...THE CONVECTIVE PARAMETERS AHEAD OF THE POST FRONTAL  
TROUGH BEHIND THE FRONT ARE QUITE IMPRESSIVE FOR OUR AREA. LOW  
LEVEL SHEAR IS DECENT WITH CURVED HODOGRAPHS. IN FACT...THE  
ENVIRONMENT IS SUPPORTIVE OF LOW TOPPED SUPERCELLS. THUS THERE IS  
A DISTINCT POSSIBILITY OF WATERSPOUTS WITH STRONG STORMS AHEAD OF  
THE POST FRONTAL TROUGH. THE MOST LIKELY AREA WILL BE NEAR CAPE  
MENDOCINO WHERE THE NATURAL CURVE OF THE COAST INCREASES WIND  
SHEAR/SPIN. CONSIDERING STORMS WILL BE MOVING TOWARD THE COAST AND  
THE ENVIRONMENT WILL BE JUST AS CONDUCIVE FOR STRONG STORMS OVER  
LAND...A LANDFALLING WATERSPOUT IS POSSIBLE...BUT AS USUAL NOT  
VERY LIKELY. ADDITIONALLY...STRONG WIND GUSTS WILL BE POSSIBLE  
WITH THE STRONGER STORMS. RADAR TRENDS WILL HAVE TO BE MONITORED  
CLOSELY ON SATURDAY. RPA  
 

 
   
PREV DISCUSSION......ISSUED AT 312 PM PDT
 
 
SHORT TERM(TONIGHT THROUGH MONDAY)...CURRENT WATER VAPOR IMAGERY  
SHOWS AN AREA OF LOW PRESSURE AROUND 500 MILES WEST OF EUREKA. THE  
ASSOCIATED WARM FRONT HAS MOVED NORTH OF THE AREA INTO OREGON THIS  
AFTERNOON. SKIES HAVE MAINLY CLEARED ACROSS NORTHWEST CA AND  
TEMPERATURES HAVE WARMED TO NEAR 70 ACROSS THE AREA. THE COLD  
FRONT IS APPROACHING THE COAST...BUT REMAINS AROUND 300 MILES  
OFFSHORE. WINDS AHEAD OF THE COLD FRONT HAVE ALREADY STARTED TO  
INCREASE THIS AFTERNOON WITH GUSTS TO 20 MPH AT THE OFFICE IN  
EUREKA.  
 
TONIGHT AS THE FRONT APPROACHES THE WINDS AND RAIN INCREASE. RAIN  
IS EXPECTED TO START AT THE COAST AROUND MIDNIGHT AND SPREAD  
INLAND QUICKLY. AREAS OF HIGHER TERRAIN WILL SEE HEAVIER RAIN AND  
IT WILL START FIRST...ESPECIALLY THE SOUTH SLOPES. WINDS WILL  
INCREASE THROUGH THE NIGHT AS WELL. WINDS WILL PEAK AT THE COAST  
EARLY IN THE MORNING WITH THE FRONTAL PASSAGE. WITH THE FRONTAL  
PASSAGE THE GFS/NAM/ECMWF MODELS ARE SHOWING WINDS AT 850 MB  
PEAKING AT 50 TO 60 KT AT THE COAST AND A BIT LESS INLAND. THIS  
MIX TO THE SURFACE WELL WITH GUSTS AT THE COAST EXPECTED TO BE  
AROUND 40 TO 50 MPH. GUSTS TO 50 TO 70 MPH ARE POSSIBLE OVER THE  
HIGHER ELEVATIONS NEAR THE COAST. FARTHER INLAND GUSTS TO 50 MPH  
ARE POSSIBLE OVER THE HIGHER TERRAIN AND ONLY 30 TO 35 MPH GUSTS  
IN THE VALLEYS. WIND ADVISORY LOOKS TO BE ON TRACK.  
 
BEHIND THE FRONT THERE MAY BE A BRIEF BREAK IN THE RAIN BEFORE  
THE UPPER LEVEL TROUGH MOVES OVER THE AREA. THIS TROUGH IS FAIRLY  
COLD ALOFT AND WILL CREATE SOME INSTABILITY IN THE LATE MORNING  
AND AFTERNOON. THERE LOOKS TO BE ENOUGH INSTABILITY FOR  
THUNDERSTORMS. THE BULK SHEAR LOOKS FAIRLY HIGH WITH 30 TO 40 KT  
IN THE 0-6KM LAYER AND 10 TO 20 KT IN THE 0-1KM LAYER. THIS SHOULD  
BE ENOUGH TO CREATE SOME LONGER LASTING STORMS. THERE IS SOME  
CURVATURE IN THE 0-1KM SHEAR DURING THE LATE MORNING OR EARLY  
AFTERNOON. THIS COULD LEAD TO AN ISOLATED VERY WEAK TORNADO OR  
WATERSPOUT...BUT THIS THREAT REMAINS FAIRLY SMALL THE CAPE IS LESS  
THAN 500 J/KG. WINDS WILL BE DIMINISHING IN THE AFTERNOON...BUT  
THERE IS STILL THE POTENTIAL FOR SOME STRONGER WINDS ALOFT TO MIX  
DOWN TO THE SURFACE. SPC DOES HAVE US IN A MARGINAL RISK (A  
RECENTLY UPDATED WAY OF SAYING "SEE TEXT") FOR SEVERE STORMS.  
THERE WILL LIKELY BE SOME HAIL WITH THESE STORMS...ALTHOUGH 500MB  
TEMPERATURES LOOK TO ONLY BE AROUND -21C WHICH DOESNT MAKE IT COLD  
ENOUGH FOR US TO RECEIVE COPIOUS AMOUNTS OF SMALL HAIL. SATURDAY  
NIGHT SHOWERS WILL CONTINUE ALTHOUGH AS WE LOOSE DAYTIME HEATING  
THEY WILL LIKELY WEAKEN. THERE MAY BE SECONDARY STRENGTHENING  
AGAIN AROUND SUNRISE AS AN UPPER LEVEL JET STREAK MOVES OVERHEAD.  
 
SUNDAY SHOWERS WILL DIMINISH THROUGH THE DAY AND WINDS WILL BE  
FAIRLY LIGHT. TEMPERATURES WILL BE REMAIN FAIRLY COOL. SKIES WILL  
CLEAR THROUGH THE DAY. SOME FOG IS POSSIBLE IN THE MENDOCINO  
COUNTY VALLEYS...BUT ELSEWHERE WILL LIKELY SEE ENOUGH MIXING TO  
KEEP FOG OUT. SUNDAY NIGHT MKK  
 
LONG TERM (TUESDAY THROUGH SATURDAY)...AFTER A BREAK FROM THE  
PRECIPITATION ON MONDAY...THE WET PATTERN RETURNS FOR THE LAST  
WEEK OF OCTOBER. THE NEXT FRONTAL SYSTEM WILL ARRIVE ON TUESDAY  
AND WILL GENERATE RAIN FROM CAPE MENDOCINO NORTHWARD WITH LESSER  
AMOUNTS SOUTH OF CAPE MENDOCINO. THE GFS AND ECMWF SYNOPTIC MODELS  
DIVERGE ON WEDNESDAY AND THURSDAY AS THE FLOW AMPLIFIES AND  
ANOTHER UPPER LEVEL TROUGH DEEPENS AND SLOWLY APPROACHES THE  
COAST. WITH THIS DEEPENING TROUGH...A WEAK FRONTAL BOUNDARY  
BECOMES STATIONARY OVER NORTHERN CALIFORNIA AND OREGON. THIS  
BOUNDARY WILL GENERATE SHOWERS ON THESE TWO DAYS. THE UPPER LEVEL  
TROUGH WILL APPROACH THE COAST FRIDAY NIGHT INTO SATURDAY BRINGING  
ANOTHER ROUND OF SIGNIFICANT PRECIPITATION TO NORTHERN CALIFORNIA.  
 
AVIATION...WIDESPREAD CLEARING TODAY AND BRIEF DRYING AS A WARM  
FRONT...ASSOCIATED WITH A STRONG LOW WELL WEST OF CAPE  
MENDOCINO...LIFTED NORTH AND OUT OF NORTHWEST CALIFORNIA. AREAS OF  
FOG CONTINUED ACROSS SEVERAL INLAND VALLEYS OF MENDOCINO COUNTY.  
LIRF TO IFR CONDITIONS PERSISTED OVER UKIAH UNTIL MIDDAY. A POTENT  
COLD FRONT...ASSOCIATED WITH THE LOW WEST OF CALIFORNIA...WILL  
APPROACH THE COAST LATE TONIGHT. THIS SYSTEM WILL BE ACCOMPANIED  
BY STRONG SOUTHERLY WINDS AND SOME HEAVY RAINS. CIGS AND VIS MAY  
LOWER AS THE COLD FRONT SPREADS ACROSS THE REGION OVERNIGHT. THE  
ENERGY WITH THIS SYSTEM COULD CREATE SIGNIFICANT AVIATION HAZARDS  
AT CEC AND ACV ON SATURDAY. PERIODS OF HEAVY RAIN...LOW  
VIS/CIG...WIND SHEAR AND EVEN THE POSSIBILITY OF THUNDERSTORMS  
WILL BE AIRPORT AND FLIGHT HAZARD THREATS. TA  
 
MARINE...GALE FORCE WINDS ASSOCIATED WITH A POTENT LOW PRESSURE  
SYSTEM WILL ARRIVE TONIGHT. THE STRONGEST WINDS ARE EXPECTED LATE  
TONIGHT INTO SATURDAY MORNING WITH THE COLD FRONT. WIND GUSTS UP TO  
50 KT ARE POSSIBLE LATE TONIGHT OR EARLY SATURDAY IN THE VICINITY OF  
THE FRONT AND NEAR CAPE MENDOCINO. A POST FRONTAL TROUGH MAY ALSO  
KICK UP THE WINDS SATURDAY AFTERNOON AS INSTABILITY INCREASES IN THE  
COOLER AIR BEHIND THE FRONT. NWPS HAS SHORT PERIOD SEAS HITTING 17  
TO 22 FT LATE TONIGHT INTO SATURDAY MORNING. GALE WARNINGS CONTINUE  
FOR ALL THE MARINE ZONES. GALE FORCE WINDS SHOULD START LATE THIS  
AFTERNOON IN THE OUTER WATERS AND THEN EXPAND INTO THE INNER WATERS  
LATER TONIGHT.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA... WIND ADVISORY FROM 2 AM TO 5 PM PDT SATURDAY FOR CAZ001.  
 
WIND ADVISORY FROM 2 AM TO 2 PM PDT SATURDAY FOR CAZ002-076.  
 
WIND ADVISORY UNTIL 5 PM PDT SATURDAY FOR CAZ003.  
 
WIND ADVISORY FROM 2 AM TO 11 AM PDT SATURDAY FOR CAZ004.  
 
NORTHWEST CALIFORNIA COASTAL WATERS...  
STORM WARNING FROM 2 AM TO 2 PM PDT SATURDAY FOR PZZ470.  
 
GALE WARNING UNTIL 2 AM PDT SATURDAY FOR PZZ470-475.  
 
STORM WARNING FROM 2 AM TO 11 AM PDT SATURDAY FOR PZZ475.  
 
SMALL CRAFT ADVISORY UNTIL 2 AM PDT SATURDAY FOR PZZ450-455.  
 
GALE WARNING FROM 2 AM TO 9 PM PDT SATURDAY FOR PZZ450-455.  
 

 
 

 
 
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