Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 042226
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
326 PM PDT WED MAY 4 2016

.SYNOPSIS...AN UPPER LEVEL LOW OFFSHORE WILL BRING A CHANCE
OF SHOWERS AND THUNDERSTORMS THROUGH FRIDAY. THE LOW WILL MOVE TO
OUR EAST OVER THE WEEKEND AND THE THREAT FOR SHOWERS AND
THUNDERSTORMS WILL DECREASE.


&&

.DISCUSSION...AN UPPER LEVEL LOW NEAR 36N/127W WILL CONTINUE TO
PUMP MID LEVEL MOIST AIR OVER NORTHWESTERN CALIFORNIA TONIGHT
THROUGH THURSDAY. LOBES OF VORTICITY WILL PIN-WHEEL AROUND THE
LOW WHICH MAY SPARK UP ISOLATED THUNDERSTORMS DURING THE LATE
NIGHT AND EARLY MORNING HOURS THROUGH FRIDAY. THE MAIN THREAT OF
THUNDERSTORMS WILL BE DURING PEAK HEATING WITH BOTH THE NAM12 AND
GFS INDICATING LIFTED INDICES AROUND -2C TO -3C AND MUCAPES IN
EXCESS OF 1000J/KG. MAIN THREAT LOOKS TO BE CLOUD-TO-GROUND
LIGHTENING STRIKES...SMALL HAIL AND LOCALLY HEAVY RAINFALL.
700-500MB FLOW WILL BECOME EASTERLY ON THU WHICH IS FAVORABLE FOR
RUMBLES OF THUNDER OUT TOWARD THE COAST. HOWEVER THE ENVIRONMENT
WILL NOT BE VERY SUPPORTIVE FOR STORM SURVIVAL AT COAST AND THE
CELLS MAY JUST DECAY INTO LIGHT SHOWERS. EVEN ON FRIDAY AS THE LOW
HEADS INLAND SOUTH OF THE AREA...WRAP AROUND MOIST AIR IN THE
NORTHEAST FLOW WILL BE SUFFICIENT FOR THUNDERSTORMS TO SPARK UP
WITH THE HEATING OF THE DAY. THE AIR ALOFT WILL BE COLDEST ON
THU...AROUND -20C AND STORMS MAY BE STRONGER WITH LARGER HAIL
POSSIBLE. TEMPERATURES WARM UP SLIGHTLY ON FRI...HOWEVER LAPSE
RATES WILL REMAIN STEEP AND STORMS ARE EXPECTED AGAIN.

UPPER LEVEL RIDGING WILL BUILD TOWARD THE AREA ON SAT WITH
TEMPERATURES ALOFT WARMING UP MORE SUBSTAINTIALLY. THE GFS
AND NAM12 WERE STILL INDICATING SOME INSTABILITY AND MOISTURE
IN THE WRAP AROUND NE FLOW AND A FEW MORE STORMS MAY SPRING
UP WITH THE DAYTIME HEATING OVER TRINITY COUNTY. GFS AND ECMWF
CONTINUE TO TREND TOWARD DRIER CONDITIONS DEVELOPING ON SUNDAY
AS THE RIDGE BUILDS OVER THE REGION. HOWEVER THERE ARE
INDICATIONS OF A WEAK SHORT-WAVE IN THE NORTWEST FLOW THAT WILL
MOVE OVER THE RIDGE ON SUNDAY. THIS WAVE LOOKS REALLY DRY AND AT
MOST EXPECT ISOLATED SHOWERS OVER THE MOUNTAINS IN TRINITY COUNTY
AND PERHAPS SOME COASTAL DRIZZLE.

UPPER LEVEL RIDGING WILL LIKELY DOMINATE THROUGH EARLY TO MID
NEXT WEEK PROVIDING DRIER AND SUNNIER WEATHER CONDTIONS AS WELL AS
WARMER TEMPERATURES IN THE INTERIOR. THE SURFACE FLOW PATTERN
WILL BE FAVORABLE FOR NIGHT AND MORNING STRATUS WITH NEAR NORMAL
TEMPERATURES AT THE COAST.

&&

.AVIATION...A LOW PRESSURE SYSTEM CONTINUED TO DIVERSELY IMPACT
LOCAL AIRPORTS ACROSS NORTHWEST CALIFORNIA TODAY. THE REGION HAS
ALSO EXPERIENCED SOME RESIDUAL POST FRONTAL EFFECTS AS WELL AS
CONTINUED WEATHER INFLUENCES FROM AN UPPER LEVEL LOW LOCATED OFF
THE CALIFORNIA COAST. THIS CURRENT WEATHER SYSTEM HAS RESULTED IN
A MIX OF HIGH AND LOW CLOUDS CONTINUING TO BLANKET MOST OF THE
REGION.

COASTAL AIRPORT TERMINALS: MVFR-IFR CIGS/VIS PERSISTED INTO
EARLY AFTERNOON WITH SOME CLEARING BY MID AFTERNOON AS BIG BREAK
IN LOW CLOUDS BRIEFLY DEVELOPED OVER NORTHERN HUMBOLDT AND DEL NORTE
COUNTIES. THROUGH THE REMAINDER OF THE TAF CYCLE...CIGS AND VIS
SHOULD BE VARIABLE VFR/MVFR WITH THE THREAT OF -SHRA AND VCTS
AT CEC & ACV.

INTERIOR AREAS: THE MAIN HAZARD TO INLAND AIRPORTS/AIRFIELDS WILL BE
CONVECTIVE ACTIVITY (SHOWERS & THUNDERSTORMS) THROUGH THE PERIOD AS
THE POSITION AND THE EFFECTS THEREOF FROM THE UPPER LOW CONTINUES
TO BRING IN PLENTY OF MOISTURE AND FURTHER DESTABILIZE CONDITIONS
ACROSS THE INTERIOR MOUNTAINS.


&&

.MARINE...A STRENGTHENING OFFSHORE HIGH PRESSURE RIDGE COMBINED
WITH AN INLAND LOW PRESSURE SYSTEM AND ASSOCIATED FRONTAL BOUNDARY
WILL INCREASE THE PRESSURE GRADIENT ACROSS THE WATERS THE NEXT FEW
DAYS. THEREFORE THE WINDS AND SEAS WILL INCREASE TODAY AND
THURSDAY. ELEVATED WINDS AND/OR SEAS WILL PERSIST ACROSS THE
WATERS THIS AFTERNOON THROUGH FRIDAY. SMALL CRAFT ADVISORIES ARE
CURRENTLY IN EFFECT ACROSS THE OUTER WATERS. THE SMALL CRAFT
ADVISORY WILL EXPIRE ACROSS THE NORTHERN OUTER WATER AT NOON TODAY
FOLLOWED BY A GALE WARNING A GALE WARNING WILL BE IN EFFECT ACROSS
THE NORTHERN OUTER WATERS FROM NOON TODAY THROUGH EARLY SATURDAY
MORNING DUE TO INCREASING WIND GUSTS TO GALE FORCE. A SMALL CRAFT
ADVISORY WILL CONTINUE ACROSS THE SOUTHERN OUTER WATERS THROUGH
EARLY SATURDAY MORNING. A HAZARDOUS SEAS WARNING WILL BE IN EFFECT
ACROSS THE SOUTHERN OUTER WATERS FROM 6 PM THIS EVENING THROUGH
EARLY SATURDAY MORNING DUE TO INCREASING SHORT PERIOD SEAS. A
SMALL CRAFT ADVISORY WILL BE IN EFFECT ACROSS THE NORTHERN NEAR
SHORE WATERS FROM NOON TODAY THROUGH SATURDAY MORNING DUE TO
ELEVATED SEAS. THE SEAS WILL WILL DIMINISH THIS WEEKEND DUE TO THE
COMBINATION OF THE HIGH PRESSURE RIDGE WEAKENING, THE INLAND LOW
PRESSURE SYSTEM PROPAGATING EASTWARD ACROSS THE CENTRAL UNITED
STATES AND A WEAK COLD FRONT APPROACHING THE REGION WHICH WILL
RELAX THE PRESSURE GRADIENT ACROSS THE WATERS.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 11 AM PDT SATURDAY FOR PZZ450.

     GALE WARNING UNTIL 3 AM PDT SATURDAY FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 3 AM PDT SATURDAY FOR PZZ475.

     HAZARDOUS SEAS WARNING FROM 6 PM THIS EVENING TO 3 AM PDT
     SATURDAY FOR PZZ475.

&&

$$

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