Area Forecast Discussion
Issued by NWS Eureka, CA

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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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