Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 301121
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
421 AM PDT TUE JUN 30 2015

.SYNOPSIS...VERY HOT AFTERNOON HIGH TEMPERATURES ACROSS INTERIOR
NORTHWEST CALIFORNIA WILL PERSIST THROUGH THE WORK WEEK. LATE
NIGHT AND MORNING COASTAL CLOUDINESS WILL GIVE WAY TO AFTERNOON
SUNSHINE.


&&

.DISCUSSION...UPPER LEVEL RIDING REMAINS SITUATED OVER THE WESTERN
UNITED STATES WITH NORTHWEST CALIFORNIA ON THE WESTERN PERIPHERY.
VERY HOT CONDITIONS ARE EXPECTED FOR THE NEXT SEVERAL DAYS WITH
AFTERNOON HIGH TEMPERATURES ACROSS INTERIOR NORTHWEST CALIFORNIA
CLIMBING INTO THE 100S TODAY THROUGH THURSDAY. MODEL GUIDANCE HAS
TRENDED HOTTER IN THE LAST 24 HOURS...AND NOW INDICATES THAT NEAR
RECORD HIGH TEMPERATURES WILL BE POSSIBLE ACROSS THE INTERIOR...
INCLUDING AT WEAVERVILLE AND UKIAH. OVERNIGHT LOWS WILL FALL INTO
THE 60S AND LOWER 70S EACH NIGHT...A LITTLE BELOW THE LEVEL AT
WHICH HEAT ADVISORIES ARE ISSUED. THUS NO HEAT PRODUCTS WILL BE
ISSUED AT THIS TIME DESPITE THE VERY HOT AFTERNOON HIGH
TEMPERATURES.

MOISTURE WILL BEGIN TO SPREAD OVER NORTHWEST CALIFORNIA TODAY WITHIN
SOUTHEASTERLY FLOW ON THE WESTERN EDGE OF THE RIDGE. THIS MOISTURE
WILL RESULT IN AN INCREASE IN HIGH AND MID LEVEL CLOUD COVER AND A
MORE UNSTABLE ATMOSPHERE. PRECIPITABLE WATER VALUES...CURRENTLY
AROUND A HALF INCH...WILL INCREASE TO 1-1.5 INCHES BY THURSDAY
THROUGH SATURDAY. MOISTURE RETURN TODAY AND WEDNESDAY DOES NOT
APPEAR TO BE SUFFICIENT TO OVERCOME A MID LEVEL INVERSION...THOUGH
SOME CONVECTIVE BUILDUPS WILL BE POSSIBLE. OPTED TO HOLD ONTO THE
SLIGHT CHANCES FOR SHOWERS OVER THE YOLLA BOLLY MOUNTAINS
CONSIDERING A STRAY SHOWER COULD DEVELOP BUT THUNDER SEEMS
UNLIKELY.

ONCE THE BETTER MOISTURE MOVES INTO THE REGION...THE ATMOSPHERE WILL
BECOME MUCH MORE UNSTABLE AND THUNDERSTORM CHANCES WILL INCREASE.
THE GFS...AND NOW NAM...ARE VERY BULLISH WITH 500-1500 J/KG OF
SURFACE BASED CAPE EACH AFTERNOON THURSDAY THROUGH SATURDAY OVER THE
INTERIOR MOUNTAINS AND ADDITIONAL HIGH BASED INSTABILITY DURING THE
OVERNIGHT PERIODS INCLUDING OVER THE COAST. ADD IN SOME DECENT 0-6KM
SHEAR ON SATURDAY AS A JET STREAK MOVES OVERHEAD...AND STORMS COULD
BECOME SCATTERED AND POSSIBLY STRONG IF CONDITIONS PAN OUT AS THE
GFS CURRENTLY INDICATES. WITH THIS ALL SAID...THERE IS STILL
CONSIDERABLE UNCERTAINTY WITH THE THUNDERSTORM FORECAST AS MID AND
HIGH CLOUD COVER COULD EASILY RESTRICT STORM DEVELOPMENT EACH DAY.
DECIDED TO TARGET SATURDAY AS THE MOST LIKELY DAY FOR STORM
DEVELOPMENT BY INTRODUCING 25 TO 30 PERCENT POPS OVER THE HIGHER
MOUNTAINS.

WITH THE INCREASING CLOUD COVER ACROSS THE REGION FRIDAY INTO THE
WEEKEND...TEMPERATURES WILL LIKELY STEADILY DECLINE BACK TO CLOSER
TO NORMAL BY SUNDAY.

STRATUS WILL IMPACT COASTAL AREAS DURING THE NIGHT AND MORNING HOURS
THROUGH AT LEAST WEDNESDAY. SOME WEAK OFFSHORE FLOW MAY BRING BETTER
CLEARING TO THE COAST THURSDAY THROUGH SATURDAY BEFORE A SOUTHERLY
SURGE DEVELOPS SENDING MORE WIDESPREAD STRATUS BACK NORTH UP THE
COASTLINE. RPA


&&

.AVIATION...EXTENSIVE STRATUS WAS COVERING THE COAST AND ADJACENT
COASTAL RIVER VALLEYS THIS MORNING. EXPECT THE STRATUS TO CLEAR OUT
IN THE RIVER VALLEYS AROUND LATE MORNING. COASTAL AREAS WILL
PROBABLY SEE SOME IMPROVEMENT...HOWEVER THE LAYER OF LOW CLOUD WILL
PROBABLY REDEVELOP BY THIS EVENING AS NORTH FLOW STRENGTHENS.


&&

.MARINE...SEAS HAVE BEEN SLOW TO INCREASE THROUGH THE NIGHT
ACCORDING TO THE FEW BUOYS ANCHORED IN NW CALIFORNIA WATERS.
BUOY 14 HAS BEEN CREEPING UP TO ADVISORY LEVEL WITH 6 FOOT SEAS AT 7
SECONDS AS OF 2AM. CANCELLED THE SMALL CRAFT ADVISORY FOR THE INNER
WATERS SOUTH OF THE CAPE TODAY GOING WITH THE THINKING THAT THE
WAVES DID NOT REFLECT THE 25-30 KT OF WIND THE HIGH RESOLUTION MODEL
SHOWED SOUTH OF CAPE MENDO. THE COVERAGE OF THE STRONG WIND DEPICTED
BY THE HIGH RESOLUTION MODEL IS ALSO NOT SUFFICIENT TO WARRANT AN
ADVISORY.

THE BASIC PRESSURE PATTERN REMAINS THE SAME. HIGH PRESSURE OFFSHORE
WILL CONTINUE TO BUILD TOWARD THE COAST WHILE THERMAL LOW PRESSURE
INTENSIFIES ACROSS THE INTERIOR TODAY. THIS WILL RESULT IN A TIGHT
PRESSURE GRADIENT ACROSS THE NORTHERN WATERS BY LATE AFTERNOON. THE
MODELS CONTINUE TO INDICATE BOUNDARY LAYER WINDS AROUND 40KT IN THE
OUTER WATERS NORTH OF CAPE MENDO (20-60NM OFFSHORE) LATE THIS
AFTERNOON AND TONIGHT. THIS HIGHER MOMENTUM MAY NOT BE REALIZED DOWN
TO MEAN SEA LEVEL. CONFIDENCE IS NOT HIGH IT WILL BE A FULL
GALE...WITH WIDESPREAD GUSTS TO 40 KT. MOST OF THE AREA (PZZ470)
WILL BE SUB GALE. HOWEVER...SEAS ARE EXPECTED TO RAMP UP TO 10 TO 13
FT WITH PERIODS OF 7 TO 9 SECOND LATE THIS AFTERNOON INTO TONIGHT
THROUGHOUT HALF OR MORE OF THE ZONE. THUS WILL GO FORWARD WITH A
GALE WARNING DUE TO THE RESULTING LARGE STEEP SEAS.

THE MODELS CONTINUE TO SHOW WINDS SLACKENING UP ON WED THEN PERHAPS
STRENGTHENING A TAD TOWARD THE LATER PART OF THE WEEK OVER THE OUTER
WATERS. NORTH WINDS LOOK TO EASE UP ON SAT AS BROAD LOW PRESSURE
DEVELOPS OVER THE AREA AND SOUTHERLY WINDS SURGE NORTHWARD ALONG THE
ENTIRE COAST.


&&

.FIRE WEATHER...VERY HOT AFTERNOON TEMPERATURES AND LOW MIN RH IN
THE TEENS IS EXPECTED THROUGH THURSDAY ACROSS INTERIOR NORTHWEST
CALIFORNIA WITH A RIDGE OF HIGH PRESSURE IN PLACE. WINDS WILL REMAIN
PRIMARILY DIURNALLY AND TERRAIN BASED...SO DESPITE THE HEAT...NO
SIGNIFICANT FIRE WEATHER CONCERNS ARE EXPECTED BASED OFF THE
TEMPERATURES...RH...AND WIND ALONE.

A MORE SIGNIFICANT CONCERN WILL BE ANOTHER CHANCE FOR
THUNDERSTORMS THURSDAY THROUGH SATURDAY...INCLUDING THE POTENTIAL
FOR STORMS TO APPROACH COASTAL AREAS...AFTER THE VERY HOT AND DRY
WEATHER. AT THIS TIME THE BEST CHANCE LOOKS TO BE SATURDAY OVER
THE INTERIOR PORTIONS OF NORTHWEST CALIFORNIA WHERE STORMS HAVE
THE POTENTIAL TO BE SCATTERED. HOWEVER...WITH PRECIPITABLE WATER
VALUES OVER AN INCH...STORMS WILL LIKELY BE OF THE WET VARIETY.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     GALE WARNING FROM 5 PM THIS AFTERNOON TO 8 AM PDT WEDNESDAY FOR
     PZZ470.

     SMALL CRAFT ADVISORY UNTIL 5 PM PDT WEDNESDAY FOR PZZ475.

&&

$$

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