Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 011222
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
522 AM PDT SAT AUG 1 2015

.SYNOPSIS...SUB-TROPICAL MOISTURE STREAMING IN FROM THE SOUTH AND
A VIGOROUS LOW OF THE COAST WILL COMBINE TO GENERATE THUNDERSTORMS
ACROSS NW CALIFORNIA TODAY. CONDITIONS WILL GRADUALLY IMPROVE
THROUGH THE WEEK WHILE TEMPERATURES COOL.

&&

.DISCUSSION...AN UPPER LOW WELL WEST OF THE NW CAL COAST WILL
STALL OVER THE NEXT COUPLE OF DAYS WHILE BEING ABSORBED INTO A
BROAD SCALE UPPER TROUGH APPROACHING FROM THE SOUTHERN GULF OF
ALASKA. IN THE MEANTIME, MORNING SATELLITE SHOWS THIS LOW
CONTINUING TO PULL SUB-TROPICAL MOISTURE NORTHWARD TOWARD NW CAL.
AT THE SAME TIME, AN UPPER RIDGE NOSING INTO SOUTHERN OREGON FROM
THE FOUR CORNERS AREA IS STEERING MONSOONAL MOISTURE NORTHWESTWARD
THROUGH THE CENTRAL VALLEY. AS A RESULT, NW CAL WILL HAVE PLENTY
OF MOISTURE TODAY WITH PWATS OVER AN INCH WHILE SHORT WAVES SWING
ACROSS THE AREA FROM THE OFFSHORE LOW. THIS WILL PROVIDE A FOCUS
FOR CONVECTIVE DEVELOPMENT. MODEL CAPES ARE SEVERAL THOUSAND AND
LI`S ARE IN THE -3 RANGE. PUT TERRAIN INTO THIS EQUATIONS AND WE
WILL NOT BE LACKING FOR LIFT. FOR MORE DISCUSSION ON THUNDERSTORM
CHANCES FOR NW CAL SEE THE FIRE WEATHER DISCUSSION BELOW.

AFTER A DAY OF THUNDERSTORMS THROUGH THIS EVENING, WE COULD SEE
ANOTHER BOUT ON SUNDAY. BY EARLY NEXT WEEK, THE LOW OFFSHORE WILL
HAVE FILLED SIGNIFICANTLY AND BECOME ABSORBED INTO A BROAD EAST
PACIFIC TROUGH. THIS PATTERN WILL HELP TO COOL NW CAL AND BRING
HIGHER HUMIDITY LEVEL WITH DEEPENING MARINE LAYER. OVERALL, THERE
WERE FEW CHANGES TO THE ONGOING FORECAST, JUST NUDGINGS AND
TWEAKINGS.

SMOKE...OFFSHORE FLOW IS NOT EXPECTED TODAY. THEREFORE, SMOKE
SHOULD NOT IMPACT THE NW CAL COAST. HOWEVER, WITH NUMEROUS FIRES
ALREADY BURNING, SOUTH AND WEST WINDS WILL LIKELY KEEP THE
INTERIOR REGIONS PLAGUED WITH SMOKE AND ASHFALL.

COASTAL AREAS...THE LOW OFFSHORE HAS BEEN ACTING TO LIFT THE
MARINE LAYER SLIGHTLY THIS MORNING, ALLOWING FOR LIMITED FOG
DEVELOPMENT. HAVE MAINTAINED FOG AND DRIZZLE IN THE FORECAST DUE
TO A STRENGTHENING RIDGE FROM THE DESERT SW, WHICH COULD BRIEFLY
COMPRESS THE MARINE LAYER THIS MORNING. THIS WILL NEED TO BE
WATCHED TO SEE HOW IT EVOLVES. BFG

&&

.AVIATION...STRATUS HAS BEEN QUITE VARIABLE OVERNIGHT WITH
CONDITIONS RAPIDLY CHANGING AROUND FROM IFR TO VFR. CEILINGS HAVE
BEEN RANGING FROM 500-1200FT AT BOTH KACV AND KCEC. ALSO A SMOKE
LAYER ALOFT NEAR 7500 FEET HAS BEEN REPORTED. THE STATISTICAL MOS
GUIDANCE HAS BEEN BIASED BY CLIMATOLOGY AND FOR THE MOST PART NOT
UTILIZED IN THE TERMINAL FORECASTS. HIGH RESOLUTION MODELS
CONTINUE TO INDICATE HIGH BOUNDARY LAYER HUMIDITIES THIS
MORNING...SO SUSPECT THERE WILL BE AREAS OF IFR CEILINGS AT THE
AIRPORTS INTO AT LEAST MID MORNING. THE SOUTHERLY WIND FLOW NEAR
THE SURFACE AND ALOFT WILL PROBABLY SCOUR OUT MOST OF THE LOW
CLOUDS BY THIS AFTERNOON WITH GENERALLY SMOKEY LAYERS ALOFT
PREVAILING THROUGH THE REMAINDER OF THE DAY. SUSPECT THERE WILL BE
SOME MVFR OR IFR CLOUD LAYERS TONIGHT AS DAYTIME HEATING WANES.
CONFIDENCE IS NOT HIGH WITH THE SPECIFICS.

&&

.MARINE...WINDS AND SEAS WILL REMAIN BELOW OUR CRITERIA FOR
ADVISORIES FOR SMALL CRAFT THE NEXT SEVERAL DAYS. OVER MOST OF THE
AREA WINDS WILL REMAIN LIGHT WITH SPEEDS NOT EXPECTED TO EXCEED 10
KT. WEAK LOW PRESSURE DEVELOPING WEST-SOUTHWEST OF CAPE MENDO WILL
GENERATE SOUTHERLY WINDS OVER MOST OF THE AREA TODAY. HIGH
RESOLUTION MODELS CONTINUE TO INDICATE WINDS UP TO 15 KT AROUND
THE CAPE TODAY. WINDS MAY BRIEFLY GUSTS TO AROUND 20 KT AS THE
LAND MASS HEATS UP. THIS LOW SHOULD SLOWLY MEANDER SOUTHWARD SUN
THROUGH MON AS HIGH PRESSURE BEGINS TO BUILD TOWARD THE WEST
COAST. WIND FIELDS WILL CONTINUE TO BE LIGHT ON BOTH THESE DAYS.
LATEST GUIDANCE SUGGESTS NORTHERLY WINDS REMAINING UNDER ADVISORY
CRITERIA EVEN INTO TUE. SEAS WILL REMAIN LOW FOR THE NEXT SEVERAL
DAYS AS WELL. IF ANYTHING SEAS WILL TREND DOWNWARD SUN AND MON AS
THE NORTHERLY WINDS OFFSHORE ABATE. IN THE MEANTIME...SEAS WILL BE
MADE UP OF A SHORT PERIOD NW GROUP AROUND 3 TO 4 FT AT 8 SECONDS
AND A LONGER PERIOD GROUP AROUND 2-3 FT FROM THE SW CENTERED NEAR
14 SECONDS. MORE DOMINATING SHORT PERIOD WAVES WILL BUILD EARLY TO
MID NEXT WEEK AS NORTHERLY WINDS INCREASE IN THE OUTER WATERS.

&&

.FIRE WEATHER...OPTED TO ISSUE A RFW FOR TRINITY AND EASTERN DEL
NORTE COUNTIES DUE TO EXPECTED ABUNDANT LIGHTNING THIS AFTERNOON
AND EVENING. MODELS ARE INDICATING THE FOUR CORNERS UPPER HIGH
STRENGTHENING THIS MORNING, PUSHING THE MONSOONAL MOISTURE STREAM
COMING UP THROUGH CALIFORNIA OFF TO THE WEST, WHILE LOW PRESSURE
OFF THE NOR CAL COAST IS PULLING SUB-TROPICAL MOISTURE IN FROM
THE SW AND PROVIDING A TRIGGER MECHANISM. LOOKING AT MORNING
SATELLITE, THIS SHOULD LINE UP FOR NW CAL. ONE CONCERN, IN TERMS
OF WHERE LIGHTNING WILL HIT, IS THAT THE CONVECTION COULD SHIFT A
TOUCH WEST BRINGING FWX ZONES 211 AND 212 INTO ABUNDANT LIGHTNING
REALM. WE`LL CROSS THAT BRIDGE IF WE COME TO IT. THE OTHER
CONCERN IS THE POTENTIAL FOR WETTING RAINS. MODEL PWATS ARE IN THE
1.25 INCH RANGE, WHICH TELLS ME THAT THESE STORMS SHOULD HAVE SOME
RAIN FALL WITH THEM. HOWEVER, THE AREAS WHERE THE RFW IS ISSUED,
DAYTIME HIGHS ARE FORECAST TO BE IN THE UPPER 90S TO LOW 100S.
WHATEVER RAIN FALLS FROM THESE STORMS SHOULD BE LIMITED IF NOT
TOTALLY EVAPORATE BEFORE HITTING THE GROUND. BESIDES, WITH
ABUNDANT LIGHTNING EXPECTED, STRIKES AWAY FROM A RAIN SHAFT ARE
HIGHLY LIKELY. IF THE PATTERN REMAINS SIMILAR, WE MAY NEED A WATCH
FOR SUNDAY TOO. AGAIN, WE`LL CROSS THAT BRIDGE WHEN WE COME TO IT.
CONFIDENCE IS MODERATE IN RFW VERIFICATION. BFG

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 9 PM PDT THIS
     EVENING FOR CAZ003-004.

NORTHWEST CALIFORNIA COASTAL WATERS...NONE.
&&

$$

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