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Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 291042
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
342 AM PDT TUE JUL 29 2014

.SYNOPSIS...COASTAL REGIONS WILL AGAIN BE SUBJECT TO FOG AND AREAS
OF DRIZZLE THIS MORNING. INTERIOR LOCATIONS WILL BEGIN THE DAY
GENERALLY CLEAR...THEN CLOUD OVER AS AN UPPER DISTURBANCE TRANSITS
NW CALIFORNIA. THIS DISTURBANCE WILL BRING A THREAT OF THUNDERSTORMS
ACROSS MUCH OF THE NW CALIFORNIA INTERIOR THIS AFTERNOON AND EARLY
EVENING.

.SHORT TERM (TODAY THROUGH FRIDAY)...COASTAL AREAS THIS MORNING WILL
CONTINUE TO REMAIN IN THE LOW CLOUDS AND FOG ALONG WITH AREAS OF
DRIZZLE. AN UPPER TROUGH WILL HELP TO LIFT THE MARINE LAYER A BIT
ALLOWING FOR A LESS FOGGY DAY THAN MONDAY. HOWEVER, THIS UPPER
TROUGH WILL BRING MID LEVEL CLOUDS TO NW CAL CAUSING PARTLY TO
MOSTLY CLOUDY CONDITIONS TO ALL AREAS BY AFTERNOON. AN ISOLATED
LIGHT SHOWER IS POSSIBLE ACROSS MENDOCINO AND TRINITY COUNTIES LATE
THIS MORNING AS THE TROUGH APPROACHES. TEMPS WILL BE VERY SIMILAR
TODAY TO THOSE OF MONDAY. HOT TEMPS WILL CONTINUE INLAND THROUGH THE
END OF THE WEEK WHILE THE COAST REMAIN MODERATE.

SYNOPTICALLY SPEAKING; MONSOONAL MOISTURE CONTINUES TO BE PULLED
INTO CALIFORNIA AROUND THE WESTERN PERIPHERY OF AN UPPER HIGH OVER
THE DESERT SOUTHWEST. THIS IS BEING JOINED TODAY BY A VIGOROUS
SHORTWAVE ROUNDING THE BOTTOM A BROAD UPPER LOW OVER THE GULF OF
ALASKA. MORNING WATER VAPOR SATELLITE IMAGE SHOWS STOUT SHORTWAVES
MOVING FROM THE SSW TO THE NNE, CURRENTLY NEAR 35N135W.

THESE SHORTWAVES SHOULD MOVE ACROSS NORTHERN CAL AND INTO OREGON AT
ABOUT THE TIME WHEN MONSOONAL MOISTURE STREAMS OVER THE REGION AND
DURING PEAK HEATING OF THE DAY. THE SHORTWAVE AND DAYTIME HEATING
SHOULD PROVIDE ENOUGH INSTABILITY TO TRIGGER ISOLATED THUNDERSTORMS
ACROSS TRINITY, NE MENDOCINO, AND EASTERN DEL NORTE COUNTIES. THE
BEST DYNAMICS CONTINUE TO BE OVER SISKIYOU COUNTY AND TO THE NE, BUT
SCATTERED THUNDERSTORMS ARE POSSIBLE OVER THE TRINITY ALPS AND HORN
THIS AFTERNOON. TO BOIL DOWN THE CONVECTIVE PARAMETERS, LAPSE
RATES ARE STEEP AT OVER 7DEG C/KM WITH A WEAK STABLE LAYER AROUND
500MB, PWATS ARE AROUND 0.7IN OR BETTER, FREEZING LEVELS AROUND
14KFT, STRONGLY NEG LI`S, PLENTY OF CAPE, AND LIMITED CIN. THE
ONLY CONVECTIVE PARAMETER THAT IS NOT GREAT IS THE 0-6 KM BULK
SHEAR. SEEING AS A COUPLE STORMS DEVELOPED MONDAY AFTERNOON WITH A
CAP STRONGER THAT WHAT IS EXPECTED TODAY, THERE IS NO REASON WHY
STORMS SHOULD NOT DEVELOP THIS AFTERNOON. AS SUCH, HAVE BROADENED
THE AERIAL COVERAGE OF THUNDERSTORMS INSTEAD OF KEEPING THEM
CONFINED TO JUST THE MOUNTAINS. IF SHEAR INCREASES THROUGH THE
DAY, THERE IS A CHANCE OF STRONG THUNDERSTORMS DEVELOPING.

WEDNESDAY LOOKS LIKE ANOTHER DAY WITH A POTENTIAL FOR CONVECTION,
EVEN WITH A STRONGER BUT THINNER CAP AROUND 650MB. DAYTIME HEATING
SHOULD BE PLENTY TO BLAST THROUGH THIS CAP. THURSDAY CONTINUES TO
LOOK LIKE THE WEAKEST DAY FOR CONVECTION OVER THE AREA, BUT FRIDAY
WILL BRING YET ANOTHER THREAT OF CONVECTION ACROSS THE NORTHEASTERN
AREAS OF NW CAL. I WILL SAY THE 06Z GFS IS TRYING TO POP CONVECTION
AGAIN ON THU, BUT NOT HOPING ON BOARD QUITE YET. WILL WAIT FOR MORE
MODEL CONSISTENCY. BFG

.LONG TERM (SATURDAY THROUGH TUESDAY)...GFS CONTINUES TO INDICATE
HIGH PWATS AS WELL AS FAVORABLE CONVECTIVE PARAMETERS FOR STORMS
OVER THE NORTHERN ZONES THROUGH THE FORECAST PERIOD. BOTH THE ECMWF
AND GFS HAVE AN UPPER TROUGH/LOW APPROACHING THE COAST THIS WEEKEND.
THE APPROACH OF THIS TROUGH SHOULD HELP TO WEAKEN THE STABLE MID
LAYER...THOUGH THERE IS VIRTUALLY NO COOLING ALOFT INDICATED IN THE
MODEL DATA. THERE IS STILL A LOT OF UNCERTAINTY DUE TO THE PRESENCE
OF THIS STABLE MID LAYER WHICH MAY CAP THE CONVECTION. FOR NOW WILL
CONTINUE WITH A BROAD BRUSH FORECAST OF A SLIGHT CHANCE OF
THUNDERSTORMS EACH AFTERNOON AND EVENING. 850MB TEMPERATURES DO NOT
CHANGE MUCH THROUGH THE PERIOD AND ANY CHANGES WILL MOST LIKELY
RESULT FROM MORE CLOUD COVER AND/OR MARINE AIR FILTERING INLAND. THE
FORECAST ALONG THE COAST HAS BEEN BASED LARGELY ON CLIMATOLOGY AND
PERSISTENCE.

.AVIATION...LOWER CEILINGS AND LIGHT WINDS ARE OCCURRING AT KCEC.
CEILINGS AND VISIBILITIES WILL DECREASE TO IFR CONDITIONS EARLY
THIS MORNING AT KCEC. IFR CONDITIONS ARE OCCURRING AT KACV DUE TO
REDUCED CEILINGS AND VISIBILITIES AND WILL PERSIST THROUGH THE
EARLY MORNING. VFR CONDITIONS AND CALM WINDS WILL CONTINUE AT KUKI
THE NEXT FEW DAYS. CEILINGS AND VISIBILITIES WILL IMPROVE LATER
THIS MORNING AND VFR CONDITIONS WILL OCCUR AT KCEC AND KACV THIS
AFTERNOON.

.MARINE...THE PERSISTENT HIGH PRESSURE SYSTEM OFFSHORE INTERACTING
WITH THE PERSISTENT THERMAL LOW PRESSURE TROUGH ACROSS CALIFORNIA
WILL MAINTAIN THE TIGHT PRESSURE GRADIENT OVER THE OUTER WATERS
THROUGH EARLY NEXT WEEK. SUBSEQUENTLY ELEVATED WINDS AND SHORT
PERIOD SEAS WILL PERSIST ACROSS THE OUTER WATERS THROUGH EARLY
NEXT WEEK. THEREFORE SMALL CRAFT ADVISORIES WILL CONTINUE IN
EFFECT ACROSS THE OUTER WATERS THROUGH FRIDAY EVENING AND WILL
LIKELY BE EXTENDED INTO EARLY NEXT WEEK.

.FIRE WEATHER...SEE THE MAIN DISCUSSION FOR CONVECTION INFORMATION.
OPTED NOT TO ISSUE A FIRE WEATHER WARNING OR WATCH FOR ZONES 203,
204, OR 283 TODAY DUE TO THE LACK OF SCATTERED AERIAL COVERAGE IN
EACH ZONE AND NO EXPECTING THESE STORMS WILL NOT BE DRY. THE MAIN
FOCUS OF TSTMS SHOULD BE OVER THE TRINITY ALPS AND HORN THIS
AFTERNOON AND EARLY EVENING, WITH AN ISOLATED STORM OR TWO OVER
THE DEL NORTE SISKIYOUS. AN ISOLATED STORM COULD NOT BE RULED OUT
FOR YOLLA BOLLS, WESTERN TRINITY COUNTY, OR FAR NE HUMBOLDT
COUNTY, SO HAVE INCLUDED THUNDERSTORMS FOR THOSE AREAS IN THE
FORECAST. IF ISOLATED TO SCATTERED THUNDERSTORMS BEGIN TO DEVELOP
FARTHER SOUTH IN THE CWA, MAY NEED TO ISSUE A SHORT LEAD TIME FIRE
WEATHER WARNING. FOR NOW TRUSTING WHERE MODELS ARE SHOWING THE
BEST CHANCES. WEDNESDAY`S THREAT LOOKS TO BE FARTHER TO THE NE
THAN TODAY`S. BFG

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT FRIDAY PZZ470-475.

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