Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 292151
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
251 PM PDT FRI APR 29 2016

.SYNOPSIS...DRY AND WARMER WEATHER CONDITIONS ARE EXPECTED
THROUGH THE WEEKEND AS HIGH PRESSURE REBUILDS OVER THE REGION
BEHIND A WEAK FRONT. COOLER AND UNSETTLED WEATHER CONDITIONS
WITH A CHANCE OF SHOWERS WILL RETURN EARLY TO MID NEXT WEEK.

&&

.DISCUSSION...A MID LEVEL SHORT-WAVE TROUGH IN STRONG NORTHWESTERLY
FLOW ALOFT MAY GENERATE ISOLATED SHOWERS THROUGH MID EVENING
TONIGHT....MAINLY OUT TOWARD THE COAST AND ACROSS THE UPPER
ELEVATIONS NORTH OF THE CAPE. SURFACE RIDGING BEHIND THIS WAVE
LATER TONIGHT WILL ALLOW WINDS TO GAIN AN EASTERLY COMPONENT AND
CLOUD COVER SHOULD GRADUALLY DIMINISH OVERNIGHT. THE NORTHERLY
FLOW ON SATURDAY WILL BE QUITE ROBUST ACROSS THE REGION AND
TEMPERATURES IN THE AFTERNOON MAY NOT WARM UP MUCH ESPECIALLY
ALONG THE NORTH COAST. IT WILL BE QUITE CHILLY NEAR THE OCEAN AND
PROBABLY NOT THE BEST DAY TO HEAD TO THE BEACH UNLESS GUSTY WIND
IS DESIRED. A THERMAL TROUGH WILL BEGIN TO TAKE SHAPE SATURDAY
NIGHT AND THE BLUSTERY NORTH WINDS WILL DIMINISH NEAR SHORE.
TEMPERATURES WILL WARM UP BOTH IN THE INTERIOR AND ALONG THE
COAST ON SUNDAY AS THE THERMAL TROUGH PUSHES OFFSHORE. GUSTY
EASTERLY WINDS OVER THE UPPER ELEVATIONS ARE EXPECTED. THERE IS
STILL SOME UNCERTAINTY ON HOW WARM IT WILL GET ON SUNDAY. IT WILL
DEPEND ON HOW FAST THE SEA BREEZES DEVELOP. CURRENT INDICATIONS
ARE FOR WINDS TO REMAIN LIGHT WESTERLY IN THE AFTERNOON AND EXPECT
HIGH TEMPERATURES TO APPROACH 70F OR EXCEED 70F BY A FEW DEGREES
AT THE COAST. INLAND AREAS SHOULD WARM INTO THE LOWER TO MID 80S.
APART FROM THE STRONG NORTHERLY BREEZES ON SAT...IT IS SHAPING UP
TO BE A PLEASANT WEEKEND WITH PLENTY OF SUNSHINE.

THE RIDGE ALOFT WILL BEGIN TO BREAK DOWN AND SHIFT EASTWARD ON
MONDAY AS A DISTINCT ONSHORE FLOW PATTERN EMERGES. THE GFS AND
NAM12 DO INDICATE SOME INSTABILITY DEVELOPING OVER THE INTERIOR
DURING PEAK HEATING...HOWEVER THE ECMWF HAS BEEN CONSISTENTLY
DRIER. WE DO HAVE A SLIGHT CHANCE OF SHOWERS IN TRINITY COUNTY
FOR MONDAY. THE CONVECTIVE PARAMETERS AND THE AMOUNT OF
INSTABILITY THE GFS INDICATES IS PROBABLY OVERDONE. THE COAST
WILL LIKELY SEE A RETURN OF STRATUS AND PERHAPS FOG ON MON INTO
MON NIGHT AS THE ONSHORE FLOW STRENGTHENS.

BOTH THE GFS AND ECMWF SHOW A SPLITTING UPPER TROUGH APPROACHING
TUE INTO WED. THIS TROUGH WILL BRING A COOLING TREND ACROSS THE
INTERIOR THROUGH THE END OF NEXT WEEK. BOTH MODELS WERE IN
GENERALLY GOOD AGREEMENT BUT DIFFERED ON THE RATE OF EASTWARD
PROGRESSION AND EXACTLY WHERE AND WHEN THE CLOSED LOW WILL FORM.
THE LATEST GFS AND ECMWF HAVE TRENDED SLOWER AND FARTHER SOUTH
WITH THE LOCATION OF THE LOW OR CUT-OFF. CONTINUED TO LEAN TOWARD
THE ECMWF WHICH HAS NOT BEEN AS WET WITH THE CONVECTIVE PRECIP
GENERATION. FOR NOW WILL MAINTAIN A BROAD BRUSH SLIGHT CHANCE OR
CHANCE OF SHOWERS IN THE FORECAST FROM TUE TO FRI. THUNDERSTORMS
WILL BE A DISTINCT POSSIBILITY...HOWEVER THE DETAILS AND TIMING
REMAIN VERY ELUSIVE AT THIS POINT WITH THE CONVECTIVE INDICES
VARYING AROUND JUST ABOUT EVERY MODEL RUN. THE ECMWF HAS BEEN MUCH
MORE CONSISTENT AND WILL CONTINUE TO LEAN TOWARD IT. BOTH MODELS
INDICATE A CLOSED LOW ALOFT WITH EASTERLY OR SOUTHEASTERLY FLOW
DEVELOPING THU INTO FRI. THIS LOOKS TO BE THE BEST OPPORTUNITY FOR
THUNDER EVEN OUT TOWARD THE COAST.

&&

.AVIATION...NORTH WINDS THIS EVENING WILL INCREASE TO GALE FORCE
ACROSS THE OUTER WATERS BY SATURDAY AS BUILDING HIGH PRESSURE
PINCHES THE PRESSURE GRADIENT ACROSS THE COASTAL WATERS. SOME
CHANGES WERE MADE TO THE COASTAL HAZARDS AS WINDS RAMP UP AGAIN.
SMALL CRAFT ADVISORIES WERE ISSUED ACROSS THE ENTIRE WATERS THIS
AFTERNOON AS WINDS BEGIN TO INCREASE THROUGH THE EVENING. THEN THE
GALE WATCHES WERE UPGRADED TO WARNINGS STARTING LATE TONIGHT. THE
STRONGEST WINDS WILL OCCUR SATURDAY AFTERNOON WITH GUSTS OFFSHORE
REACHING 40 KT AND GUSTS NEARSHORE REACHING 30-35 KT. LARGE STEEP
WAVES WILL BUILD IN RESPONSE TO THE STRONG NORTH WINDS WITH A NW
SWELL DIMINISHING THROUGH THE WEEKEND. HIGH PRESSURE OFFSHORE WILL
THEN WEAKEN AND A THERMAL TROUGH WILL SHIFT WEST AND COLLABORATIVELY
ALLOW THE PRESSURE GRADIENT TO RELAX. WINDS WILL BEGIN TO DECREASE
ON SUNDAY. THIS WILL MARK THE BEGINNING OF A PERIOD OF LOWER WINDS
AND SEAS THROUGH THE MIDDLE OF THE UPCOMING WEEK. KML


&&

.MARINE...STRONG NORTH WINDS TONIGHT WILL DECREASE ON FRIDAY AS A
PASSING SHORTWAVE CAUSES THE PRESSURE GRADIENT TO RELAX. THE CURRENT
GALE WARNING AND SMALL CRAFT ADVISORIES LOOK ON TRACK FOR TONIGHT
BUT I HAD TO MAKE SOME ADJUSTMENTS TO REFLECT THE DECREASING WINDS
TOMORROW. ADVISORIES SHOULD CONTINUE SOUTH OF CAPE MENDOCINO AS
STRONGER WINDS ARE EXPECTED TO PERSIST BUT THE ADVISORIES NORTH OF
THE CAPE ARE SET TO EXPIRE BY MID-MORNING ON FRIDAY. THIS WILL
SIGNAL THE BEGINNING OF A BRIEF WINDOW FOR LOWER WINDS(15 TO 20 KT)
AND SEAS FRIDAY BEFORE CONDITIONS INCREASE AGAIN ON SATURDAY.
OTHERWISE STEEP WAVES WILL BUILD IN RESPONSE TO THE INCREASING WINDS
WHILE A MIDDLE PERIOD SWELL WILL GRADUALLY DIMINISH THROUGH THE
WEEKEND. THERE WILL BE A BETTER WINDOW FOR SETTLING CONDITIONS
BEGINNING LATE THIS WEEKEND THROUGH EARLY NEXT WEEK. KML

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
 SMALL CRAFT ADVISORY UNTIL 11PM PDT SAT FOR PZZ450.
 SMALL CRAFT ADVISORY UNTIL 3AM PDT SAT FOR PZZ470.
 GALE WARNING FROM 3AM SAT TO 3AM PDT SUN FOR PZZ470-475.
 SMALL CRAFT ADVISORY UNTIL 11PM PDT SAT FOR PZZ455.
 SMALL CRAFT ADVISORY UNTIL 3AM PDT SAT FOR PZZ475.

&&

$$

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