724
FXUS66 KEKA 221323
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
523 AM PST SAT FEB 22 2025
SYNOPSIS
CHANCE OF RAIN WILL INCREASE TODAY AND PEAK TONIGHT.
HEAVY RAIN IS FORECAST FOR DEL NORTE AND FAR NORTHERN HUMBOLDT
COUNTIES TONIGHT. ELSEWHERE, GENERALLY LIGHT RAIN IS EXPECTED. A
LOW PRESSURE SYSTEM WILL GENERATE LOCALLY STRONG AND GUSTY
SOUTHERLY WINDS OVER THE HEADLANDS AND INTERIOR MOUNTAINS THIS
WEEKEND. STRONG SOUTHERLY WINDS WILL BE POSSIBLE AGAIN ON MONDAY.
DISCUSSION
A LONG FETCH OF DEEP LAYER MOISTURE EMANATING FROM
THE SUBTROPICS (PWATS OVER 1 INCH) WILL INTERSECT THE COASTAL
TERRAIN LATE TODAY INTO TONIGHT. HEAVY RAIN IS FORECAST FOR DEL
NORTE AND FAR NORTHERN HUMBOLDT COUNTIES TONIGHT. HOURLY RAIN
RATES AROUND 0.30IN/HR ARE PROBABLE (70-80% CHANCE) IN THE
INTERIOR OF DEL NORTE FROM 8 PM SAT TO 5 AM SUN. DETERMINISTIC
CONVECTIVE ALLOWING MODELS SUCH AS THE HRRR AND ARW INDICATE
LOCALIZED HOURLY RATES APPROACHING 0.50IN/HR, LIKELY THE RESULT
OF TOPOGRAPHIC FORCING. THE BRUNT OF THIS ATMOSPHERIC RIVER
(AR2/AR3) WILL BE AIMED NORTH OF THE AREA WITH DEL NORTE ON THE
SOUTHERN EDGE OF THE IVT PLUME MAX (500-600KG/M/S). EVEN THOUGH
THE DURATION OF THE AR IS OVER 48 HOURS, HEAVY RAIN RATES DO NOT
APPEAR TO LAST THAT LONG BASED ON THE LATEST HREF GUIDANCE. EVEN
MODERATE RAIN RATES (0.20IN/HR) FALL OFF DURING THE DAY ON SUNDAY.
WE STILL CANNOT RULE OUT RAINFALL RUN-OFF IMPACTS TONIGHT. MINOR
FLOODING WILL BE POSSIBLE TONIGHT INTO SUNDAY MORNING. ALSO,
MUD/LANDSLIDES OR ROCK FALLS WILL ALSO BE POSSIBLE IN THE STEEP
TERRAIN. SLIDES WILL MOST LIKELY IMPACT HIGHWAY 199 IN DEL NORTE
COUNTY AND POSSIBLY HIGHWAY 101 NORTH OF KLAMATH. FOR NOW WILL
HIGHLIGHT THIS THREAT IN A WEATHER STORY GRAPHIC AND SOCIAL MEDIA
POST. OTHERWISE, RAINFALL BE LIGHT TO MODERATE FOR THE REMAINDER
OF THE FORECAST AREA. SOUTHERN LAKE AND SOUTHERN MENDOCINO MAY
NOT GET ANY MEASURABLE RAIN THIS WEEKEND. SNOW LEVELS WILL REMAIN
QUITE HIGH THIS WEEKEND, ABOVE 6000 FEET AND TEMPERATURES WILL
REMAIN ABOVE NORMAL EVEN UNDER THICKER CLOUD COVER.
GUSTY SOUTH WINDS WILL DEVELOP ALONG NORTH COAST THIS AFTERNOON
AND EVENING AS SURFACE LOW PRESSURE APPROACHES THE WEST COAST AND
GRADIENTS TIGHTEN. STRONGEST WINDS WILL BE OVER THE COASTAL
HEADLAND, ESPECIALLY PT ST GEORGE WHERE GUSTS AROUND 40 MPH ARE
PROBABLE. THE GUSTY WINDS SHOULD PERSIST THROUGH SUNDAY.
A SURFACE LOW IS FORECAST TO DEVELOP JUST OUTSIDE 135W NORTH OF
40N SUNDAY AS THE QUASI-STATIONARY FRONTAL BOUNDARY NORTH OF THE
ORCA BORDER BUCKLES AND A SURFACE CYCLONE DEVELOPS AND RAPIDLY
PROGRESSES NE OUTSIDE 135W. SYNOPTIC SCALE MODEL GUIDANCE
CONTINUES TO KEEP THE STRONGEST AND MOST DAMAGING WINDS WITH THIS
CYCLONE WELL OFFSHORE AND JUST NORTH OF THE FORECAST AREA, ALONG
THE OREGON COAST. SURFACE PRESSURE GRADIENTS WILL TIGHTEN UP
AGAIN BY MONDAY MORNING AND STRONGER WIND GUSTS TO 50 MPH ARE
PROBABLE FOR THE COASTAL HEADLANDS AND INTERIOR RIDGES AS A 60KT
925MB SOUTHERLY SPEED MAX DEVELOPS IN ADVANCE OF THE BOUNDARY.
ALL MODELS HAVE SPED UP THE TIMING OF STRONGEST WINDS. ECMWF HAS
BEEN CLUSTERING AROUND MONDAY AFTERNOON/EVENING, BUT LATEST
RUN HAS SHIFTED EARLIER IN THE DAY. ECMWF ENSEMBLE MEAN WIND
GUSTS IS OVER 50 MPH FOR PT ST GEORGE AND KCEC AIRPORT. IN FACT
THERE ARE MANY MEMBERS, 30% OF 100, OVER 55 MPH FROM 4 AM TO 4
PM MON. LOOKING AT THE NBM, 90TH PERCENTILE MAX GUSTS ARE ON THE
ORDER OF 55 TO 65 MPH OVER THE INTERIOR MOUNTAINS OF DEL NORTE
WITH LOWER PROBABILITIES FOR GUSTS TO 55 MPH FOR THE HUMBOLDT
INTERIOR MOUNTAINS; SPECIFICALLY KNEELAND AND BERRY SUMMIT. WIND
THIS STRONG WILL MAKE DRIVING DIFFICULT AND COULD KNOCK DOWN TREE
BRANCHES. WE ARE LEANING TOWARD A WIND ADVISORY FOR THIS EVENT.
FOR NOW WILL HOLD OFF ON HOISTING AN ADVISORY MULTIPLE DAYS OUT
AND WAIT TO SEE HOW DETERMINISTIC MODELS AND ENSEMBLE DATA SETS
TREND. WE WILL MESSAGE THE POTENTIAL FOR HAZARDOUS WINDS IN
WEATHER STORY GRAPHIC AND SOCIAL MEDIA POSTS.
PRECIP WILL END ON TUESDAY AS A BROAD UPPER RIDGING QUICKLY
SPRINGS BACK AND HOLDS INTO MID WEEK (WED). THE RIDGE ALOFT WITH
ABOVE NORMAL 500MB HEIGHTS WILL LIKELY REMAIN THE DOMINANT FEATURE
CONTROLLING NW CALIFORNIA WEATHER INTO LATE NEXT WEEK. TEMPERATURES
WILL REMAIN ABOVE NORMAL. DB
AVIATION
STRATUS HAS MADE PERIODIC PUSHES TOWARD THE COASTAL
TERMINALS EARLY THIS MORNING, BRINGING OCCASIONAL LIFR/IFR CEILINGS.
STRATUS MAY LINGER UNTIL SUNRISE, WHEN ANY REMAINING LOW CLOUDS
SHOULD LIFT AND SCATTER OUT. AN APPROACHING SYSTEM WILL BRING
INCREASING CLOUDS AND RAIN TO THE AREA. VFR CEILINGS WILL DROP TO
MVFR BY LATE AFTERNOON OR EVENING, WHILE MVFR VISIBILITIES ARE
POSSIBLE DURING PERIODS OF MODERATE TO HEAVY RAIN. GUSTY SOUTHERLY
WINDS ARE FORECAST AT CEC, PERHAPS AS HIGH AS 35 KTS, AND ARE
FORECAST CONTINUE INTO THE NIGHT. AT ACV, WINDS COULD OCCASIONALLY
GUST TO 25 KTS THIS EVENING AND OVERNIGHT. LLWS WILL ALSO BE A
THREAT AT THE COASTAL TERMINALS THIS AFTERNOON AND OVERNIGHT.
CONDITIONS REMAIN VFR AT UKI AS THE SYSTEM PRIMARILY IMPACTS DEL
NORTE AND HUMBOLDT COUNTIES, THOUGH A STRAY SHOWER IS POSSIBLE
OVERNIGHT. JB
MARINE...NORTH OF CAPE MENDOCINO
SOUTHERLY WINDS WILL GRADUALLY
INCREASE TODAY AHEAD OF AN APPROACHING SHORTWAVE. WIND GUSTS OF 20-
30 KTS ARE LIKELY THROUGH SUNDAY NEARSHORE, WITH GALE FORCE GUSTS
LIKELY IN THE OUTER WATERS AND AROUND PT ST GEORGE. SEAS WILL REMAIN
ELEVATED THIS WEEKEND, AS STEEP WIND WAVES OF 7-9 FT AT 8 SECONDS
COMBINE WITH A DECAYING MID-PERIOD WESTERLY SWELL OF 8-10 FT. WINDS
MAY DIMINISH SLIGHTLY SUNDAY NIGHT, BUT SHARPLY INCREASE AGAIN
MONDAY MORNING AS A STRONGER FRONT ARRIVES. NEAR-GALE TO GALE FORCE
GUSTS ARE POSSIBLE NEAR SHORE, WITH STRONG GALES OF UP TO 45 KTS
POSSIBLE OFFSHORE.
SOUTH OF CAPE MENDOCINO...LIGHT TO MODERATE SOUTHERLY BREEZES ARE
FORECAST TODAY, WHILE SEAS ARE DOMINATED BY A DECAYING WESTERLY
SWELL. SEAS ARE FORECAST TO FALL BELOW 10 FT BY THE LATE AFTERNOON,
AND REMAIN BELOW 10 FT INTO THE WEEKEND. WINDS INCREASE SLIGHTLY
MONDAY AS A FRONT PASSES TO THE NORTH, WITH STRONGER BREEZES AND
STEEP SEAS POSSIBLE. JB
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 6 AM PST MONDAY FOR PZZ450.
SMALL CRAFT ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR
PZZ455-470-475.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 3 PM PST SUNDAY
FOR PZZ470.
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