Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 222359 CCA
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
323 PM PDT FRI MAY 22 2015

.SYNOPSIS...DRIER NORTHERLY FLOW WILL DEVELOP OVER NORTHWEST
CALIFORNIA THIS WEEKEND RESULTING IN DECREASING CLOUD COVER AND
SHOWER ACTIVITY ACROSS THE INTERIOR. THE COAST WILL CONTINUE TO
SEE MOSTLY CLOUDY SKIES.

&&

.SHORT TERM...THE BROAD UPPER LEVEL TROUGH OVER THE AREA BRINGS
THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS OVER THE AREA THIS
AFTERNOON. ONE DIFFERENCE TODAY IS THE CENTER OF THE UPPER LEVEL
LOW IS MOVING FARTHER OFF TO THE SOUTH AND EAST. THIS IS GIVING
THE SHOWERS MORE MOVEMENT TODAY THAN PREVIOUS DAYS AND THEY ARE
MOVING FROM NORTH TO SOUTH. THIS SHOULD KEEP RAINFALL AMOUNTS
LOWER IN THE SHOWERS THAN WE SAW YESTERDAY. THERE HAS BEEN QUITE A
BIT OF CLOUD COVER OVER THE INLAND AREAS AND THIS IS KEEPING
TEMPERATURES IN THE 60S IN TRINITY COUNTY WHICH MAY LIMIT THE
POTENTIAL FOR THUNDER IN THE SHOWERS.

TONIGHT SHOWERS ARE EXPECTED TO TAPER OFF BY LATE EVENING. THE
MARINE LAYER WILL BE DEEP ONCE AGAIN SO COASTAL AND VALLEY CLOUDS
WILL BE WIDESPREAD. SATURDAY THE UPPER LEVEL LOW CONTINUES TO MOVE
AWAY FROM THE AREA. THIS WILL INHIBIT MOST SHOWERS...ALTHOUGH A
SHORTWAVE MOVING DOWN FROM THE NORTH MAY INITIATE A FEW SHOWERS
OVER THE HILLS IN THE YOLLA BOLLYS. NORTHERLY WINDS WILL START TO
INCREASE...HOWEVER IF THE COAST CLEARS IT WILL LIKELY BE ONLY FOR
A SHORT PERIOD.

SUNDAY THE RIDGE IS OVERHEAD AND IT LOOKS LIKE THE INTERIOR AREA
WILL BE SIGNIFICANTLY WARMER AND DRIER THAN IT HAS BEEN OVER THE
PAST FEW DAYS. HIGH TEMPERATURES WILL CLIMB TO AROUND 80 IN MOST
INLAND AREAS. ALONG THE COAST PERSISTENT LOW CLOUDS ARE LIKELY
ALTHOUGH THERE LOOKS TO BE A SLIGHTLY BETTER CHANCE FOR SOME
BREAKS IN THE AFTERNOON. THERE ARE SOME HINTS OF OFFSHORE FLOW
ALOFT.

MONDAY THE MODELS SHOW A WEAK SHORTWAVE COMING FROM THE WEST AND
SQUASHING DOWN THE RIDGE. HAVE ADDED THUNDERSTORMS TO THE FORECAST
FOR MONDAY AFTERNOON. NAM AND GFS MODELS ARE INDICATING
INSTABILITY OVER 1000 J/KG OF CAPE AND A COUPLE TENTHS OF AN INCH
OF CONVECTIVE PRECIP. THIS IS A PATTERN THAT IS TYPICALLY TOO DRY
FOR CONVECTION..HOWEVER THE MODELS ARE SHOWING PLENTY OF MOISTURE
WITH PWATS AROUND 0.9 INCHES. HOWEVER...CONFIDENCE STILL IS LOWER
THAN AVERAGE. THIS INCREASED CONVECTION AND SHORTWAVE WILL LIKELY
COOL INLAND TEMPERATURES A BIT AND REINFORCE THE STRATUS AT THE
COAST. WILL ALSO ADD SOME DRIZZLE AT THE COAST AS THE SHORTWAVE IS
MOVING OVERHEAD AND WILL LIKELY SQUEEZE SOME COASTAL DRIZZLE OUT.
MKK

.LONG TERM...THIS SHORTWAVE REMAINS IN PLACE ON TUESDAY BRINGING
THE POSSIBILITY OF SCATTERED OR ISOLATED SHOWERS TO MAINLY THE
INTERIOR NORTH OF CAPE MENDO. MOISTURE WILL BE SOMEWHAT
LIMITED...SO THE ACTIVITY SHOULD NOT BE AS WIDESPREAD IN THE
INTERIOR AS WE HAVE SEEN THIS WEEK. HIGHEST RAIN CHANCES HAVE BEEN
CONFINED TO TRINITY COUNTY AND HIGHER ELEVATIONS. THERE ARE
INDICATIONS IN THE DATA FOR THUNDERSTORMS AS WELL ON BOTH DAYS.
SINCE IT IS STILL A FEW DAYS OUT, WILL NOT ADD ANY THUNDERSTORMS
TO THE FORECAST UNTIL THERE IS BETTER CONSISTENCY. FORECAST
CONFIDENCE REALLY TAKES A NOSE DIVE ON WED AND THU. THE ECMWF HAS
A BROAD FLAT RIDGING DEVELOPING OVER THE AREA...WHILE THE 00Z GFS
AND CMC GEM MAINTAIN AN UPPER TROUGH. NO CHANGES WERE MADE TO THE
FORECAST FOR THIS TIME PERIOD.

&&

.AVIATION...ONCE AGAIN A PLETHORA OF CLOUDINESS CONTINUED TO NEARLY
COVER MOST OF NORTHWEST CALIFORNIA TODAY...ESPECIALLY AT THE COAST.
THE DEEP MARINE LAYER KEPT COASTAL SITES IN IFR/LIFR CONDITIONS
THROUGH EARLY MORNING...THEN CIGS AND VIS LIFTED TO MVFR. HOWEVER...
BY 1 PM ACV WAS EXPERIENCING SOME SCRAGGLEY IN/OUT IFR CIGS ABOUT
600 FEET. FOR INLAND AVIATION WEATHER...SOME WEAK (SLOW NORTH-SOUTH
MOVING SHOWERS) DEVELOPED OVER THE EASTERNMOST MOUNTAINOUS AREAS OF
THE FORECAST ZONES. THE MARINE LAYER WILL REMAIN DEEP AND PERSISTENT
THROUGH AT LEAST EARLY SATURDAY AFFECTING THE COAST AND SOME COASTAL
INTERIOR VALLEYS. TA

&&

.MARINE...WINDS AND SEAS REMAIN LOW ACROSS THE WATERS THIS
AFTERNOON. SEAS ARE A MIXTURE OF LOCALLY GENERATED WAVES FROM THE
10 TO 15 KT WINDS AND A 10 TO 12 SECOND NORTHWESTERLY WAVE.

A WEAK SURFACE PRESSURE GRADIENT WILL MAINTAIN LIGHT WINDS AND
LOW SEAS THIS EVENING. NORTHERLY WINDS AND STEEP SEAS WILL
INCREASE LATE TONIGHT AND INTO THE WEEKEND AS AN OFFSHORE HIGH
PRESSURE SYSTEM STRENGTHENS INCREASING THE PRESSURE GRADIENT.
ANOTHER UPPER LEVEL SYSTEM WILL DIMINISH THE WINDS BY THE MIDDLE
OF NEXT WEEK.

&&

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

    SMALL CRAFT ADVISORY FROM 2 PM SATURDAY TO 3 AM PDT TUESDAY
    FOR PZZ470.

SMALL CRAFT ADVISORY FROM 3 AM SATURDAY TO 3 AM PDT TUESDAY
    FOR PZZ475.

&&

$$

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