519
FXUS66 KEKA 211500
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
700 AM PST SAT DEC 21 2024
SYNOPSIS...SOUTHERLY WINDS AND HEAVY RAINFALL WILL GRADUALLY DIMINISH
THROUGH THE DAY WITH INCREASED CHANCE OF CONVECTIVE SHOWERS THIS
AFTERNOON. A SIMILAR AR STORM SYSTEM WILL ARRIVE LATE SUNDAY
MORNING, FOLLOWED QUICKLY BY A MORE IMPACTFUL SYSTEM MONDAY NIGHT
INTO TUESDAY. INCREASING HYDROLOGIC IMPACTS ARE EXPECTED BY
MIDWEEK.
DISCUSSION...MILD TEMPERATURES, STRONG SOUTHERLY WINDS AND AREAS OF
HEAVY RAINFALL ARE BEING OBSERVED THIS MORNING AS A FAST-MOVING COLD
FRONT APPROACHES THE COAST. HREF INDICATES THE HEAVIEST RAINFALL
RATES (UP TO 0.25 INCHES/HOUR) WILL CONTINUE TO DEVELOP OVER THE
NEXT FEW HOURS. ACCUMULATIONS WILL BROADLY BE 0.50 TO 1.5 INCHES,
WITH HIGHER AMOUNTS APPROACHING 2 INCHES ALONG SW FACING SLOPES
IN THE KING RANGE AND ELEVATED TERRAIN OF DEL NORTE. THE VALLEYS,
COASTAL PLAINS AND SOUTHERN MENDOCINO AND LAKE COUNTIES WILL BE ON
THE LOWER END OF THE SPECTRUM.
ADDITIONALLY, WIND GUSTS EXCEEDING 40 TO 50 MPH ARE BEING REPORTED
THIS MORNING ACROSS HIGHER ELEVATIONS AND EXPOSED COASTAL AREAS OF
DEL NORTE AND HUMBOLDT COUNTIES. A STRONG COASTAL JET IS EXPECTED TO
MAX OUT AT 60 TO 70 KNOTS ALOFT AS THE FRONT MOVES THROUGH. A WIND
ADVISORY WILL REMAIN IN EFFECT THROUGH 10 AM FOR THE INTERIOR WITH
GUSTS 55 TO 60 MPH POSSIBLE ON EXPOSED TERRAIN. THE ADVISORY IS
STILL ON TRACK TO EXPIRE A BIT SOONER FOR GUSTS 35 TO 50 MPH ALONG
THE DEL NORTE COAST INCLUDING CEC.
HEAVIEST RAINFALL IS EXPECTED TO TAPER OFF BEGINNING EARLY THIS
AFTERNOON. SHORT RANGE MODELS ARE INCREASINGLY CONFIDENT IN MODERATE
INSTABILITY PRODUCING SCATTERED CONVECTIVE SHOWERS AND POTENTIAL
THUNDERSTORMS IN THE WAKE OF THE FRONT. GREATEST CHANCE OF STORM
ACTIVITY WILL BE ALONG THE COAST NORTH OF CAPE MENDOCINO.
A BRIEF BREAK IN THE RAINFALL IS EXPECTED LATE TONIGHT THROUGH EARLY
SUNDAY AFTERNOON. MODEL GUIDANCE IS INCREASINGLY CONFIDENT IN THE
NEXT AR STORM SYSTEM ARRIVING JUST AFTER 12 PM IN THE NORTHERN
PORTION OF THE CWA, WHILE THE TRAILING PORTION OF THE COLD FRONT
ARRIVES 4 TO 6 HOURS LATE IN MENDOCINO AND LAKE COUNTIES. WPC IS
FORECASTING SIMILAR QPF TOTALS RANGING 0.50 TO 1.5 INCHES WITH AN
EMPHASIS ON THE KING RANGE AND INTERIOR TERRAIN. WINDS WILL BEGIN
INCREASING IN THE MORNING PRIOR TO THE RAINFALL, BEFORE ANOTHER JET
MAX ARRIVES ALONG THE NORTH COAST BY EARLY TO MID AFTERNOON. NBM
PROBABILITIES ARE MUCH LOWER FOR THIS SYSTEM FOR GUSTS EXCEEDING 40
MPH.
AFTER ANOTHER BRIEF BREAK LATE SUNDAY NIGHT INTO MONDAY MORNING, A
MORE IMPACTFUL AR SYSTEM IS EXPECTED TO ARRIVE MONDAY AFTERNOON INTO
TUESDAY MORNING. BOTH WPC AND GFS ARE FORECASTING WIDESPREAD 2
INCHES TO NEARLY 4 INCHES IN PORTIONS OF INTERIOR DEL NORTE AND THE
KING RANGE, WITH THE HEAVIEST RAINFALL LIKELY OVERNIGHT INTO
TUESDAY. NBM PROBABILITIES ARE TRENDING A BIT LOWER FOR WINDS
EXCEEDING 40 MPH. CNRFC ENSEMBLES ARE SHOWING SEVERAL RIVERS
(INCLUDING THE EEL RIVER AT FERNBRIDGE, THE RUSSIAN RIVER AT HOPLAND
AND THE NAVARRO RIVER) HAVE A 50 TO 75% CHANCE OF REACHING MINOR
FLOOD STAGE BY WEDNESDAY. THERE IS STILL A DECENT AMOUNT OF
UNCERTAINTY SURROUNDING THE FOLLOWING AR STORM SYSTEM EXPECTED TO
ARRIVE LATE WEDNESDAY INTO THURSDAY. LOWER SNOW LEVELS CHRISTMAS DAY
WILL QUICKLY RISE IN TIME FOR THIS ADDITIONAL PRECIPITATION, BUT MAY
STILL HOVER AROUND 4000 TO 5000 FEET BY THURSDAY MORNING.
AVIATION...A QUICK MOVING WARM FRONT BROUGHT GUSTY WINDS, LIGHT
RAIN AND LIGHTNING TO THE TERMINALS THIS MORNING. SOME INSTABILITY
AS WELL INCREASED LIGHTNING AND SPARSE HAIL. EXPECT LIGHT SHOWERS TO
CONTINUE THROUGH THE TAF PERIOD WITH A FEW PERIODS OF REDUCED
VISIBILITY POSSIBLE THIS MORNING, MVFR/VFR WILL PREVAIL BY THE
AFTERNOON. GUSTY WINDS AND LOW LEVEL WIND SHEAR ARE LIKELY TO
RETURN BY THE NEXT PASSING FRONT, SUNDAY. /EYS
MARINE...A PASSING WARM FRONT BROUGHT CONVECTIVE LINES OF
THUNDERSTORMS THROUGH THE AREA WATERS THIS MORNING. POST FRONTAL
SHOWERS ARE EXPECTED THROUGH THE MORNING. GALE FORCE WINDS ARE STILL
BEING REPORTED BY BUOYS AS OF 13Z. A LULL IN BETWEEN THE NEXT
FRONTAL BOUNDARY WITH GALE FORCE GUSTS WILL LIKELY RESULT IN A
HAZARDOUS SEAS ADVISORY OR A SMALL CRAFT ADVISORY FOR THIS
AFTERNOON. A LARGE, LONG PERIOD WESTERLY SWELL WILL CONTINUE TO
BUILD THROUGH THE MORNING. AN ADDITIONAL STORM SYSTEM ON SUNDAY WILL
INCREASE SOUTHERLY WINDS AGAIN. THESE WINDS WILL CREATE STEEP, SHORT-
PERIOD WIND WAVES LEADING TO HAZARDOUS CONDITIONS IN ADDITION TO THE
SOUTHERLY GALES. ANOTHER ROUND OF STRONG TO NEAR-GALE-FORCE WINDS IS
FORECASTED FOR SUNDAY.
HYDROLOGY...FORECAST IS STILL ON TRACK FOR RAINFALL TOTALS 0.5 TO 1.5
INCHES BY THIS EVENING, WITH THE HIGHEST TOTALS IN THE HIGHER
TERRAIN OF INTERIOR DEL NORTE AND HUMBOLDT. A STRONGER SYSTEM IS
EXPECTED MONDAY NIGHT INTO TUESDAY WITH MORE SIGNIFICANT RAIN
IMPACTS AS IVT VALUES EXCEED 500 KG/M/S. WPC IS OUTLINING A
MARGINAL EXCESSIVE RAINFALL OUTLOOK FOR MOST OF THE CWA ON TOP OF
INCREASINGLY SATURATED SOILS, WITH 2 TO 4 INCHES OF RAINFALL
CURRENTLY FORECAST. CNRFC RIVER FORECASTS ARE TRENDING HIGHER,
INCLUDING THE NEAR TERM DETERMINISTIC - THERE IS NOW A 50 TO 75%
CHANCE OF EXCEEDING MINOR FLOOD STAGE BY WEDNESDAY FOR THE MAD
RIVER AT ARCATA, THE EEL RIVER AT FERNBRIDGE, THE RUSSIAN RIVER AT
HOPLAND AND THE NAVARRO RIVER. AS MENTIONED IN THE PREVIOUS
DISCUSSION, FLOODING WILL DEPEND LARGELY ON HOW MUCH THE RIVERS
ARE ABLE TO DIMINISH IN THE BREAKS BETWEEN RAINFALL. THIS WILL BE
ESPECIALLY IMPORTANT FOR THE FOLLOWING SYSTEM ARRIVING THURSDAY.
NBM PROBABILITIES ARE TRENDING >50 TO 75% FOR 1 TO 3 INCHES OF
RAINFALL BY THURSDAY EVENING, THE HIGHER END OF WHICH WILL ONCE
AGAIN LAND IN DEL NORTE AND THE KIND RANGE. RIVER ENSEMBLE
FORECASTS ARE ALREADY SHOWING RESPONSIVE TENDENCIES AFTER A BRIEF
BREAK TO DIMINISH EXPECTED ON WEDNESDAY.
BEACH HAZARDS...A SERIES OF LONG PERIOD, WESTERLY SWELLS WILL
CONTINUE TO IMPACT THE COASTAL WATERS OF NORTHWEST CALIFORNIA EARLY
NEXT WEEK. A HIGH SURF ADVISORY HAS BEEN ISSUED DUE TO THE GFS WAVE
MODEL SUGGESTING ANOTHER LARGE SWELL OF AROUND 18 TO 20 FEET IN AS
MANY SECONDS FOR PERIOD/SWELL. THIS IS EXPECTED TO BRING BREAKERS
BETWEEN 21 TO 23 FEET ALL DAY SATURDAY INTO THE EARLY HOURS OF
SUNDAY. HAZARDOUS SURF CONDITIONS DUE TO THE BREAKING WAVES WILL BE
POSSIBLE ALONG WEST- NORTHWEST FACING BEACHES. MORE HAZARDOUS SURF
IS FORECASTED FOR MONDAY AS THE WAVE BULLETIN SUGGESTS BREAKERS 23
TO 28 FEET, MAXING OUT BY HIGH NOON.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
WIND ADVISORY UNTIL 8 AM PST THIS MORNING FOR CAZ101.
HIGH SURF ADVISORY FROM 1 PM THIS AFTERNOON TO 9 AM PST
SUNDAY FOR CAZ101-103-104-109.
WIND ADVISORY UNTIL 10 AM PST THIS MORNING FOR CAZ102-
104>106.
NORTHWEST CALIFORNIA COASTAL WATERS...
GALE WARNING UNTIL 9 AM PST THIS MORNING FOR PZZ450-455-470-
475.
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