Hazardous Seas Warning 22, NWS Eureka, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
316 PM PDT FRI JUL 17 2009

.SYNOPSIS...STRONG HIGH PRESSURE OVER THE WESTERN US WILL CONTINUE
TO BRING HOT AND DRY CONDITIONS TO INLAND AREAS...WITH SEASONAL
CONDITIONS EXPECTED ALONG THE COAST...THROUGH THE WEEKEND. AN
INCREASE IN TROPICAL MOISTURE WILL BRING A SLIGHT CHANCE OF
THUNDERSTORMS TO INTERIOR AREAS STARTING SATURDAY AFTERNOON.

&&

.DISCUSSION...FORECAST IS ON TRACK TODAY WITH ONLY MINOR EDITS MADE.
AT THE COAST...LOW CLOUDS AND FOG CAN BE EXPECTED IN THE MORNING
HOURS THROUGH AT LEAST MID WEEK AS SEASONAL NORTHERLY WINDS OFFSHORE
CONTRIBUTE TO UPWELLING...COMBINED WITH AN APPROACHING S/WV MONDAY
WORKING TO KEEP THE MARINE LAYER SUFFICIENTLY DEEP. CLEARING IN THE
AFTERNOON HOURS...MUCH LIKE TODAY...IS EXPECTED BRINGING VERY
PLEASANT CONDITIONS AS TEMPS REMAIN SEASONAL. INLAND...THERE IS
STILL A THREAT OF AFTERNOON/EVENING CONVECTION STARTING TOMORROW
AFTERNOON AS A PLUME OF SUBTROPICAL MOISTURE MOVES UP THE WEST
COAST...INCREASING PW VALUES IN EXCESS OF 1 IN BY SAT AFTERNOON.
MOSTLY CLEAR SKIES IN THE MORNING SHOULD CONTRIBUTE TO EFFICIENT
DAYTIME HEATING...ALLOWING VERTICAL MOTION TO GET STARTED OVER
MOUNTAIN TOPS. STEEP MID LEVEL LAPSE RATES (7.5-8.0 C/KM) WILL HELP
SUSTAIN UPDRAFTS LEADING TO AT LEAST ISOLD TS DEVELOPMENT ACROSS
TRINITY COUNTY...AND POSSIBLY EVEN INTO EASTERN HUMBOLDT COUNTY. DO
THINK MOST OF THE CONVECTION WILL BE LIMITED TO MOUNTAINOUS
TERRAIN...AND HAVE KEPT POPS HIGHEST OVER THESE AREAS. INITIAL
DEVELOPMENT WILL LIKELY LEAD TO MOSTLY DRY LIGHTNING STRIKES HOWEVER
CONSIDERING THE AMOUNT OF MOISTURE INVOLVED...THINK SHOWERS ARE
LIKELY UNDER TS CORES. SOME DRY STRIKES OUTSIDE OF CORES WILL STILL
BE A THREAT. ACTIVITY SHOULD TAPER OFF IN THE EVENING.

NOT MUCH CHANGE IS EXPECTED INTO SUNDAY...ALTHOUGH A WEAK S/WV
INDICATED BY GFS/NAM MOVING OVER EASTERN TRINITY COUNTY LATE SAT
NIGHT/EARLY SUN MORNING COULD POSE A THREAT OF ISOLD TS OVER THESE
AREAS ATTM. CONFIDENCE IS NOT HIGH...BUT IT IS WORTH A MENTION AT
THIS POINT CONSIDERING HOW UNSTABLE THE ENVIRONMENT WILL BE. SUN
AFTERNOON SHOULD BE A REPEAT OF SAT WITH AFTERNOON CONVECTION
DEVELOPING...PRIMARILY OVER THE MOUNTAINS. MOST LIGHTNING WILL BE
DRY IN NATURE...WITH SHOWERS LIKELY UNDER TS CORES. AGAIN...MOST
ACTIVITY WILL TAPER OFF AFTER SUNSET.

GFS HAS ALTERED ITS THINKING GOING INTO MON AS PW VALUES DO NOT
DECREASE AS FAST AS ORIGINALLY THOUGHT. LATEST GFS/ECMWF GUIDANCE
SHOWS A S/WV TROF OUT OVER 40N/140W FINALLY BEGINNING TO MOVE TOWARD
THE COAST AS THE RIDGE OVER THE WEST SLOWLY WEAKENS. THIS WILL
INCREASE MID/UPPER LEVEL FLOW OVER NW CA...AND COUPLED WITH PW
VALUES NEAR 1 IN AND INTENSE SFC HEATING...MAY JUST LEAD TO MORE
ISOLD TS DEVELOPMENT ON MON AFTERNOON. WILL NOT GO CRAZY AND PUT IN
A SLIGHT CHANCE JUST YET...BUT IT IS SOMETHING TO KEEP AN EYE ON.

LOOKS LIKE THE RIDGE OVER THE WESTERN US WILL BEGIN BUILDING BACK
OVER THE WEST COAST ON TUES. TS CHANCES JUST WONT COMPLETELY GO
AWAY THROUGH THE END OF THE WEEK OVER THE INTERIOR MOUNTAINS AND
HAVE INTRODUCED BELOW CLIMO POPS FOR THESE AREAS THROUGH THE
EXTENDED. DAYTIME TEMPS WILL REMAIN HOT THIS WEEK...WITH ISOLD
INLAND VALLEY LOCATIONS LIKELY REACHING THE CENTURY EACH DAY. BK

&&

.AVIATION...THE STRATUS HAS MIXED OUT THIS AFTERNOON...OCCURRING
ABOUT TWO HOURS EARLIER THAN YESTERDAY. LIKE YESTERDAY...LIGHT NORTH
WINDS WILL CONTINUE TO KEEP THE SHALLOW MARINE LAYER IN PLACE.
EXPECT LIFR CONDS TO RETURN AFTER SUNSET AND PERSIST THROUGH ABOUT
17Z. VFR INLAND. JCA

&&

.MARINE...A TIGHTENING PRESSURE GRADIENT WILL INCREASE WINDS
BEGINNING IN THE OUTER WATERS LATER TONIGHT. GALE FORCE WIND GUSTS
ARE STILL POSSIBLE...ESPECIALLY IN PZZ470, BUT TIMING AND STRENGTH
ISSUES WILL PRECLUDE US FROM UPGRADING TO A WARNING WITH THIS
FORECAST PACKAGE. STEEP, SHORT PERIOD SEAS WILL ACCOMPANY THE
STRENGTHENING WINDS...RESULTING IN A HAZ SEAS WATCH FOR THE OUTER
WATERS BEGINNING LATE SATURDAY. JCA

&&

.FIRE WEATHER...MAIN CONCERN REMAINS THE THREAT OF CONVECTION OVER
INTERIOR MOUNTAINS TOMORROW AND SUNDAY. A PLUME OF MID LEVEL
MOISTURE IS STILL PROGGED TO INCREASE ATMOSPHERIC MOISTURE CONTENT
ON SAT AFTERNOON INTO SUNDAY...COMBINED WITH HOT DAYTIME TEMPS
SHOULD YIELD AT LEAST ISOLATED DEVELOPMENT EACH AFTERNOON. INITIAL
STRIKES WILL LIKELY BE DRY EACH DAY...HOWEVER MARGINAL WETTING RAINS
CAN BE EXPECTED UNDER TS CORES. LOW LEVELS WILL REMAIN WARM AND
DRY...WITH A CONTINUATION OF MODEST OVERNIGHT HUMIDITY RECOVERIES
EXPECTED. WINDS WILL REMAIN LIGHT AND TERRAIN DRIVEN...WITH GUSTY
WINDS EXPECTED IN VICINITY OF THUNDERSTORMS. BK

&&

.EKA WATCHES/WARNINGS/ADVISORIES...

GALE AND HAZ SEAS WATCH PZZ470.
HAZ SEAS WATCH PZZ475.
SCA PZZ470, PZZ475.

&&

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