255  
FXUS66 KEKA 212221  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
321 PM PDT MON JUL 21 2014  
   
SYNOPSIS
 
AN UPPER LEVEL TROUGH ALONG WITH WEAK INSTABILITY  
WILL BRING A SLIGHT CHANCE OF THUNDERSTORMS TO TRINITY COUNTY  
THIS EVENING AND AGAIN IN THE AFTERNOON ON TUESDAY.  
 

 
   
DISCUSSION
 
A WEAKENING UPPER LEVEL TROUGH APPROACHING THE  
WEST COAST HAS BEEN SPREADING HIGH AND MID LEVEL CLOUDS OVER  
MOST OF THE FORECAST AREA TODAY. THIS TROUGH HAS BEEN CREATING  
TWO BANDS OF POTENTIAL PRECIP. ONE HAS BEEN EDGING IN FROM THE  
WEST AND SLOWLY DISSIPATING. THE OTHER HAS BEEN CREEPING UP FROM  
THE SOUTH. THIS SECOND BAND HAS BEEN GENERATING 25-30DBZ RETURNS  
ALOFT ACROSS MENDOCINO COUNTY. GRANTED MOST OF THIS WAS PROBABLY  
NOT REACHING THE GROUND. HIGHER RESOLUTION MODEL SETS SHOW SOME  
PRECIP AMOUNTS WITH THIS SOUTHERN BAND. THESE HIGH RESOLUTION  
GRIDDED MODELS ARE PROBABLY OVERDONE. I HAVE ADDED THE POSSIBILITY  
OF ISOLATED LIGHT RAIN SHOWERS OR SPRINKLES THROUGH THIS  
EVENING...MAINLY IN MENDOCINO COUNTY AND SECTIONS OF HUMBOLDT  
COUNTY SOUTH OF ABOUT HIGHWAY 36. THE CHANCE FOR MEASURABLE  
PRECIP LOOKS VERY LOW...ABOUT 5-10%. A VERY BRIEF SHOWER OR TWO  
COULD WET THE GROUND AND OTHER SURFACES.  
 
THUNDERSTORM AND LIGHTNING ACTIVITY HAS BEEN OCCURRING WELL TO THE  
EAST OF THE FORECAST AREA...AROUND MT LASSEN AND NE CALIFORNIA THIS  
AFTERNOON. CONVECTIVE PARAMETERS ONCE AGAIN LOOK SUFFICIENT TO  
SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT IN FIRE WEATHER ZONE  
283...WITH LAL'S OF 2. MID LEVEL CAPPING AND CLOUD COVER HAS THUS  
FAR SUPPRESSED STORM DEVELOPMENT. WITH PWATS AROUND 1 INCH...EXPECT  
STORMS TO PRODUCE PRECIP...RAIN OR HAIL. CWA'S ARE STILL NOT EXTENSIVELY  
HIGH DUE TO THE SPOTTY NATURE OF THE PRECIP. ISOLATED SMALL FIRE  
STARTS ARE NOT COMPLETELY OUT OF THE QUESTION EVEN WITH THE HIGHER  
HUMIDITIES AND SPOTTY PRECIP. RAPID FIRE GROWTH APPEARS UNLIKELY.  
THUS I WILL CONTINUE TO HEADLINE THE OFFICIAL FIRE WEATHER TEXT  
PRODUCT TO CALL ATTENTION TO THE TSTM THREAT.  
 
WEAK INSTABILITY WILL LINGER ON TUE AND THERE IS STILL A SLIGHT  
CHANCE FOR STORMS ARISING FROM DAYTIME HEATING IN EASTERN TRINITY  
COUNTY. CONDITIONS LOOK LESS FAVORABLE ON WED AS A SHORT-WAVE  
TROUGH SWINGS INTO THE PAC NW AND WESTERLY FLOW ALOFT IMPORTS  
DRIER AIR INTO THE AREA. A WEAK SURFACE BOUNDARY WILL PUSH ONTO  
THE NORTH COAST ON WED AND MAY GENERATE A LITTLE BIT OF  
RAIN...MAINLY ALONG THE COAST AND NORTH OF ROUTE 299 IN ZONE 3.  
THE GFS AND ECWMF WERE VERY SIMILAR ON THE PROGRESSION OF THE  
500MB TROUGH...THOUGH THE GFS WAS SLIGHTLY SLOWER. EXPECT THE  
COOLING TREND TO CONTINUE ON WED AS MARINE AIR FILTERS INTO THE  
VALLEYS.  
 
MODELS WERE IN DECENT AGREEMENT SHOWING RISING 500MB HEIGHTS  
AND INCREASING 850MB TEMPERATURES ON THU AND FRI AS HIGH PRESSURE  
ALOFT ONCE AGAIN BUILDS UP FROM THE SOUTHWEST. THE MODELS HAVE  
BEEN HINTING AT A WEAK LOW OR TROUGH APPROACHING THE REGION THIS  
WEEKEND. THIS TROUGH MAY DIG FAR ENOUGH SOUTH AND INTERACT WITH  
SUBTROPICAL MOISTURE FOR ANOTHER SLIGHT CHANCE OF STORMS. THIS  
WILL NEED TO BE WATCHED. FOR NOW CONDITIONS LOOK TOO DRY AND  
STABLE AND WILL SKEW THE FORECAST TOWARD CLIMATOLOGY AND  
PERSISTENCE ON SAT...SUN AND MON.  
 

 
   
AVIATION
 
IFR TO MVFR CONDITIONS AND LIGHT TO MODERATE WINDS WILL  
CONTINUE AT KCEC THIS AFTERNOON DUE TO REDUCED CEILINGS. MVFR TO VFR  
CONDITIONS AND LIGHT TO MODERATE WINDS WILL PREVAIL AT KACV THIS  
AFTERNOON. CEILINGS AND/OR VISIBILITIES WILL DECREASE AT KCEC AND  
KACV OVERNIGHT TO IFR CONDITIONS WITH LIGHT WINDS TO CALM CONDITIONS  
OCCURRING. VFR CONDITIONS AND LIGHT TO MODERATE WINDS WILL CONTINUE  
AT KUKI THE NEXT FEW DAYS.  
 

 
   
MARINE
 
REDUCED WINDS AND SEAS WILL PERSIST ACROSS THE WATERS INTO  
WEDNESDAY AS A WEAK LOW PRESSURE TROUGH MOVES OVER THE WATERS. A  
HIGH PRESSURE SYSTEM WILL STRENGTHEN ACROSS THE NORTHEASTERN PACIFIC  
WEDNESDAY NIGHT AND THURSDAY INCREASING THE WINDS AND SEAS ACROSS  
THE WATERS. SMALL CRAFT ADVISORIES WILL BE NECESSARY ACROSS THE  
OUTER WATERS THURSDAY INTO SATURDAY DUE TO THE INCREASE IN THE WINDS  
AND SEAS AND ARE LIKELY ACROSS THE NEAR SHORE WATERS THURSDAY AND  
FRIDAY DUE TO AN INCREASE IN THE SEAS. WIND GUSTS NEAR GALE FORCE  
ARE POSSIBLE ACROSS PORTIONS OF THE NORTHERN OUTER WATERS THURSDAY.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...NONE.  

 
 

 
 
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