Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 111737
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1037 AM PDT FRI JUL 11 2014

.SYNOPSIS...A SERIES OF WEAK DISTURBANCES WILL BRING A CHANCE
OF THUNDERSTORMS OVER INTERIOR NORTHWEST CALIFORNIA MOUNTAINS
EACH AFTERNOON THROUGH THE WEEKEND. ISOLATED THUNDERSTORMS ARE
POSSIBLE OVER THE NORTHERN REDWOOD COAST AND ADJACENT COASTAL
WATERS THROUGH EARLY AFTERNOON.

&&

.UPDATE...HAVE SHAVED OFF FIRE WX ZONES 211...212...AND 277 AS
DRIER AND MORE STABLE AIR HAS MOVED INTO THOSE AREAS. UPDATED
RFW...FWF AND HWO PRODUCTS TO REFLECT THE CHANGE. /SEC

&&

.PREV DISCUSSION...ISSUED AT 519 AM...

SYNOPSIS...A SERIES OF WEAK DISTURBANCES WILL BRING A CHANCE
OF THUNDERSTORMS OVER INTERIOR NORTHWEST CALIFORNIA MOUNTAINS
EACH AFTERNOON THROUGH THE WEEKEND. ISOLATED THUNDERSTORMS MAY
REACH THE REDWOOD COAST AND ADJACENT COASTAL WATERS TODAY.

DISCUSSION...RADAR SHOWED ISOLATED LIGHT SHOWERS MOVING INTO THE
AREA FROM THE SOUTHEAST EARLY THIS MORNING. STREAM OF MID LEVEL
MOISTURE WILL COMBINE FORCES WITH A SHORTWAVE TROUGH MOVING UP
FROM THE SW TO PRODUCE SCATTERED SHOWERS AND TSTMS THIS MORNING.
THE ACTIVITY APPEARS TO DWINDLE THIS AFTERNOON AFTER S/W TROUGH
PASSAGE. MODELS INDICATE BOUNDARY LAYER INSTABILITY LINGERING OVER
EASTERN DEL NORTE AND FAR NE HUMBOLDT COUNTIES IN THE
AFTERNOON...SO A SECONDARY SPIKE MAY OCCUR WITH DAYTIME HEATING.

THE MID LEVEL CLOUDS AND CONVECTION MAY DISRUPT THE MARINE LAYER
STRATUS TODAY AND BRING A MINI-WARM UP TO THE REDWOOD COAST. FOR
THE MOST PART...COASTAL AREAS WILL CONTINUE TO SEE NIGHT AND
MORNING LOW CLOUDS AND PATCHES OF FOG THROUGH THE WEEKEND.

MODELS CONTINUE TO SHOW A WEAK TROUGH ALOFT BURROWING TOWARD THE
COAST THIS WEEKEND. GFS INDICATES WEAK INSTABILITY LINGERING
AROUND THE PERIPHERY OF THE FORECAST AREA NEAR SISKIYOU COUNTY
THROUGH THE WEEKEND. THERE WILL BE TOWERING CUMULUS OPPORTUNITIES
EACH AFTERNOON. FOR THE MOST PART THE FORECAST AREA SHOULD DRY OUT
AND STABILIZE. GFS AND ECMWF WERE IN DECENT AGREEMENT WITH
TEMPERATURES WARMING UP LATE THIS WEEKEND INTO EARLY NEXT WEEK.
TEMPS SHOULD COOL DOWN AGAIN MID TO LATE NEXT WEEK AS SE FLOW AND
MID LEVEL MOISTURE INCREASES AGAIN. IF THIS TREND CONTINUES...TSTM
COVERAGE WILL NEED TO BE INCREASED.

AVIATION...12Z SATELLITE IMAGERY SHOWS EXTENSIVE STRATUS ALONG THE
COAST WITH SURFACE OBSERVATIONS SHOWING IFR TO LIFR CONDITIONS.
IMPROVING CONDITIONS ALONG THE COAST WILL BE DIFFICULT TODAY WITH A
DEEPER MARINE LAYER. HOWEVER, CEILINGS ARE EXPECTED TO FLUCTUATE AS
A BOUNDARY PASSES OVER THE REGION THROUGH THE AFTERNOON. THERE IS A
SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS WITH THE BOUNDARY
PASSAGE FOR EASTERN TRINITY, HUMBOLDT, AND DEL NORTE COUNTIES. BRIEF
VFR TO MVFR CONDITIONS ARE POSSIBLE ALONG THE COAST TODAY AND THEN
DETERIORATE ONCE AGAIN IN THE EVENING. OTHERWISE MOSTLY VFR
CONDITIONS ARE EXPECTED ACROSS INTERIOR AREAS OF NW CALIFORNIA WITH
THE EXCEPTION OF SOME TURBULENCE WITH SHOWERS AND THUNDERSTORMS. KML

MARINE...MARINE CONDITIONS CONTINUED TO SUBSIDE OVERNIGHT WITH 11Z
SEAS HOVERING AROUND 6 TO 7 FT AROUND 9 SECONDS. LAST NIGHT`S ASCAT
PASS REVEALED PREDOMINATELY LIGHT WINDS ACROSS THE COASTAL WATERS
WITH SPARSE AREAS OF MODERATE WINDS AROUND 15 KT OUT 60 NAUTICAL
MILES. THE SMALL CRAFT ADVISORY EXPIRED AT THE 3AM UPDATE AS MARINE
CONDITIONS HAVE FALLEN BELOW CRITERIA.

CONDITIONS WILL CONTINUE TO SUBSIDE INTO THE WEEKEND AS LOW PRESSURE
OFFSHORE MAINTAINS A RELAXED PRESSURE GRADIENT ACROSS THE COASTAL
WATERS. SEAS WILL FALL TO AS LOW AS 3 TO 4 FT OVER THE WEEKEND.
CONDITIONS WILL DETERIORATE AGAIN EARLY NEXT WEEK AS THE PACIFIC
RIDGE BUILDS TOWARDS THE PACIFIC NW. THE INTERACTION BETWEEN THE
BUILDING RIDGE AND THE CALIFORNIA THERMAL TROUGH WILL STRENGTHEN THE
PRESSURE GRADIENT AND THUS WINDS WILL INCREASE AND SEAS WILL
STEEPEN. KML

FIRE WEATHER...A RED FLAG WARNING IS NOW IN EFFECT FOR ALL ZONES
EXCEPT 201...202 AND 276. NEW FIRE STARTS ARE POSSIBLE AS FUELS
REMAIN CRITICALLY DRY. SO FAR NO LIGHTNING ACTIVITY HAS BEEN
DETECTED ACROSS NW CA ZONES AS OF 430 AM PDT. A SHORTWAVE TROUGH
WILL SWING THROUGH THE AREA FROM THE SW THIS MORNING AND TRIGGER
TSTM ACTIVITY OVER THE AREA. ACTIVITY LOOKS TO FIRST FIRE UP
ACROSS 283 AND 277 EARLY THIS MORNING AND THEN SHIFT INTO ZONES
211...203 AND 204 BY MID TO LATE MORNING. FOR MOST OF THE
AREA...CONDITIONS LOOK TO STABILIZE IN THE AFTERNOON AFTER
SHORTWAVE TROUGH PASSAGE. INSTABILITY WILL LINGER ACROSS EASTERN
SECTIONS OF 203 AND 204 IN THE AFTERNOON AND ADDITIONAL STORMS
MAY SPARK UP WITH DAYTIME HEATING.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...RED FLAG WARNING UNTIL 5 PM THIS AFTERNOON CAZ003-004-283.
NORTHWEST CALIFORNIA COASTAL WATERS...NONE.

&&

$$

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