552
FXUS66 KEKA 250911
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
211 AM PDT TUE SEP 25 2018
SYNOPSIS
HOT AFTERNOON TEMPERATURES WILL OCCUR ACROSS MUCH OF
THE REGION THROUGH THURSDAY. COOLER WEATHER WITH SCATTERED SHOWERS
WILL THEN SPREAD ACROSS THE AREA THIS WEEKEND.
DISCUSSION
DEEP-LAYER EAST-NORTHEASTERLY FLOW IS OCCURRING
ACROSS THE REGION EARLY TUESDAY MORNING. THIS FLOW REGIME IS
FAVORING VERY WARM AND DRY CONDITIONS THAT WILL SUPPORT HOT
AFTERNOON TEMPERATURES AS WELL AS FIRE WEATHER CONCERNS (REFERENCE
THE FIRE WEATHER DISCUSSION BELOW). THE INHERITED TEMPERATURE
GRIDS APPEAR TO BE ON TRACK THROUGH THURSDAY, WITH HIGHS IN THE
90S EXPECTED ACROSS MOST OF THE INTERIOR, RANGING TO 70S ALONG
THE COAST. COASTAL LOCATIONS SUCH AS EUREKA WILL LIKELY EXPERIENCE
HIGHS RELATIVELY EARLY IN THE DIURNAL HEATING CYCLE, FOLLOWED BY
COOLING LATE IN THE AFTERNOON AS THE SEA BREEZE INITIATES IN
RESPONSE TO STRONG INLAND HEATING.
AN UPPER LOW POSITIONED WELL OFFSHORE THIS MORNING IS FORECAST TO
DRIFT EASTWARD THROUGH FRIDAY AS AN UPPER HIGH SHIFTS NORTHWARD.
BY SATURDAY, MODEL GUIDANCE SHOWS THE UPPER LOW MOVING ONSHORE,
THOUGH LARGE POSITIONAL DIFFERENCES EXIST BETWEEN VARIOUS
DETERMINISTIC SOLUTIONS. NEVERTHELESS, SHOWERS AND COOLER
TEMPERATURES APPEAR PROBABLE DURING SATURDAY, AND THUNDERSTORMS
CAN'T BE RULED OUT IF THE GFS VERIFIES. THEREAFTER, THE ECMWF
MAINTAINS A SHOWERY REGIME GOING INTO NEXT WEEK, WHILE THE GFS
FAVORS A DRY ENVIRONMENT.
AVIATION
ONLY COASTAL STRATUS TO SPEAK OF THIS MORNING IS
BEING HELD TO THE MENDOCINO COASTLINE, HOWEVER OFFSHORE FLOW HAS
BEEN PREVENTING INLAND PENETRATION THIS MORNING. PERSISTENT
SUBSIDENCE AND OFF SHORE FLOW NORTH OF CAPE MENDOCINO HAS ALSO
BEEN PREVENTING WIDESPREAD STRATUS FROM FORMING. TODAY WILL BE
ANOTHER LOVELY VFR DAY ACROSS THE NORTH COAST, WITH EVEN LIGHTER
NORTHERLY WINDS AS COMPARED TO YESTERDAY. LACK OF BOUNDARY LAYER
MOISTURE AND SUBSIDENCE WILL ONCE AGAIN KEEP COASTAL TERMINALS
CLEAR THIS EVENING THROUGH TOMORROW MORNING. /WCI
MARINE
NORTHERLY WINDS WILL CONTINUE TO DIMINISH AS WE GO
THROUGH THE DAY. THE ONE EXCEPTION WILL BE ACROSS THE NORTHWEST
POTION OF THE NORTHERN OUTER WATERS WHERE NEAR GALE FORCE GUSTS
WILL REMAIN POSSIBLE THROUGH THIS EVENING. STEEP WAVES OF 7-11
FEET AT AROUND 9 SECONDS WILL REMAIN POSSIBLE THROUGH EARLY
WEDNESDAY MORNING THEREFORE SMALL CRAFT ADVISORIES WILL REMAIN IN
EFFECT. THE WINDS WILL REMAIN FAIRLY LIGHT THROUGH THE REMAINDER
OF THE FORECAST PERIOD WITH WINDS BECOMING SOUTHERLY LATE THIS
WEEK. A PERIODIC SW SWELL AT AROUND 16 SECONDS WILL MOVE THROUGH
THE WATERS BEGINNING LATER TODAY AND PERSISTING THROUGH THIS
WEEKEND. /WCI
FIRE WEATHER
A RED FLAG WARNING HAS BEEN ISSUED FOR ELEVATIONS
ABOVE 2000 FEET OVER DEL NORTE AND NORTHERN HUMBOLDT COUNTIES
THROUGH TUESDAY NIGHT. TEMPERATURES ARE WARM WITHIN THE THERMAL
BELT EARLY TUESDAY MORNING, WHICH IS RESULTING IN POOR OVERNIGHT
RH RECOVERY. IN ADDITION, AN OFFSHORE WIND REGIME IS YIELDING
GUSTS TO 25 MPH ACROSS EXPOSED RIDGES. THESE CONDITIONS ARE AIDING
IN STRONG HEAT SIGNATURES FROM THE NATCHEZ FIRE LOCATED NEAR THE
DEL NORTE/SISKIYOU COUNTY BORDER...WHICH IS EVIDENCE OF POTENTIAL
EXTREME FIRE BEHAVIOR. WINDS WILL WEAKEN SOMEWHAT BY TUESDAY
AFTERNOON, AND MAY BRIEFLY BECOME WESTERLY BEFORE ACCELERATING OUT
OF THE EAST ONCE AGAIN THIS EVENING. IN ADDITION, VERY WARM
AFTERNOON TEMPERATURES COMBINED WITH A DRY ANTECEDENT AIRMASS WILL
RESULT IN SINGLE DIGIT MIN RH VALUES. THE HOT/DRY AIRMASS COMBINED
WITH GUSTY RIDGETOP CONDITIONS WILL SUPPORT A CRITICAL FIRE
WEATHER THREAT DURING THE NEXT 18-24 HOURS.
EKA WATCHES/WARNINGS/ADVISORIES
CA...RED FLAG WARNING UNTIL 5 AM PDT WEDNESDAY FOR CAZ201-203-204-211.
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL
3 PM PDT THIS AFTERNOON FOR PZZ450.
HAZARDOUS SEAS WARNING UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ470.
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ475.
HAZARDOUS SEAS WARNING UNTIL 3 AM PDT EARLY THIS MORNING FOR
PZZ475.
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