171
FXUS66 KEKA 172229
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
229 PM PST MON FEB 17 2025
SYNOPSIS
SHOWER ACTIVITY DWINDLES THIS AFTERNOON, WITH
BRIEFLY DRIER AND CALM WEATHER EXPECTED TONIGHT AND ON TUESDAY.
ADDITIONAL RAIN MOVES ONSHORE TUESDAY NIGHT AND WEDNESDAY. A PERIOD
OF DRY AND WARM WEATHER IS EXPECTED TO SETTLE IN FOR THE END OF THE
WORK WEEK.
DISCUSSION
A SHORTWAVE RIDGE BRIEFLY BUILDS THIS EVENING AND
TUESDAY BEHIND YESTERDAY'S FRONTAL PASSAGE. FOR AREAS WHERE SKIES
CLEAR OUT QUICKLY, AREAS OF VALLEY FOG ARE EXPECTED TO DEVELOP INTO
TUESDAY. OVERNIGHT TEMPERATURES ARE FORECAST TO RANGE FROM MID 30'S
TO LOW 40'S, WITH LOWS IN THE UPPER 20'S TO LOW 30'S IN TRINITY
COUNTY. WARMER TEMPERATURES ARE EXPECTED ON TUESDAY AS THE RIDGE
MOVES OVERHEAD, WHILE ANOTHER FRONTAL SYSTEM APPROACHES THE AREA
FROM THE WEST. MID TO HIGH LEVEL MOISTURE WILL INCREASE THROUGHOUT
THE DAY ON TUESDAY. PWAT VALUES ARE EXPECTED TO INCREASE TO 0.8 TO
1.0 INCHES ALONG THE NORTH COAST LATE MORNING/EARLY AFTERNOON ON
TUESDAY. RESULTING IN SOME LIGHT RAIN SHOWERS MOVING INLAND ALONG
THE NORTH COAST EARLY TUESDAY EVENING.
A SHORTWAVE TROUGH AND ASSOCIATED FRONTAL SYSTEM WILL MOVE IN
TUESDAY NIGHT AND WEDNESDAY. SOUTHERLY WINDS WILL INCREASE TUESDAY
NIGHT WITH A LOW LEVEL COASTAL JET IN ADVANCE OF THE FRONT WILL
LIKELY PRODUCE GUSTS AROUND 25 TO LOCALLY 40 MPH OVER THE MORE
PROMINENT COASTAL HEADLANDS AND EXPOSED RIDGES. ALONG THE FRONTAL
SYSTEM, A ZONE OF WAA AND WEST- SOUTHWESTERLY MOISTURE FLUX WILL AID
IN A REINFORCING OF THE PRECIPITATION ACROSS THE NORTHERN HALF OF
THE FORECAST AREA, WITH MODERATE TO LOCALLY HEAVY RAINFALL OVER DEL
NORTE AND FAR NORTHERN HUMBOLDT LATE TUESDAY NIGHT INTO EARLY
WEDNESDAY. THESE FRONT WILL BE PROGRESSIVE, LIMITING THE DURATION OF
THE HEAVIEST PRECIPITATION. PRECIPITATION WILL BECOME SHOWERY IN THE
WAKE OF THE FRONT.
A COLDER AIR MASS WILL SUBSEQUENTLY SPREAD ACROSS THE WEST COAST
WEDNESDAY MORNING, WITH 500 MB TEMPERATURES OF -25C TO -28C. GFS AND
NAM ARE SHOWING LESS INSTABILITY WITH THIS SYSTEM THAN IN PREVIOUS
RUNS. HOWEVER, SOME SHALLOW INSTABILITY WITH A COLD LAYER ALOFT OVER
DEL NORTE AND HUMBOLDT COUNTIES WILL BE CAPABLE OF PRODUCE MODERATE
SHOWERS WEDNESDAY MORNING AND AFTERNOON. SNOW LEVELS HOVER AROUND
5000 FEET WEDNESDAY MORNING, LOWERING TO 4000 FEET BY WEDNESDAY
EVENING. LINGERING SHOWERS ARE EXPECTED TO TAPER OFF WEDNESDAY
EVENING AS HIGH PRESSURE BUILDS IN ALOFT.
LONG RANGE ENSEMBLES REMAIN IN GOOD AGREEMENT THAT A LONG PERIOD OF
DRY AND WARM WEATHER IS EXPECTED TO SETTLE IN BY THURSDAY. CLIMATE
PREDICTION CENTER'S 6-10 DAY TEMPERATURES AND PRECIPITATION OUTLOOK
INDICATES 70-80% PROBABILITY OF ABOVE NORMAL TEMPERATURES AND 30-50%
BELOW NORMAL PRECIPITATION FOR THE WEST BEGINNING NEXT WEEKEND. /ZVS
AVIATION
COASTAL SHOWERS ARE KEEPING CLOUD CEILINGS LOW WITH
PERIODIC BURSTS OF RAIN SHOWERS OVER TERMINAL SPACES. THIS IS
EXPECTED TO CONTINUE THROUGH THE DAYLIGHT HOURS BEFORE OFFSHORE WIND
INCREASES, CAUSING HIGHER CLOUD CEILINGS AND CLOUD COVERAGE
DECREASING. INLAND, MOISTURE FROM THE PREVIOUS DAYS RAIN HAS A
CHANCE OF SATURATING WITHIN VALLEYS, CAUSING LIFR CEILINGS AND
VISIBILITIES UNTIL ATMOSPHERIC MIXING TOMORROW AFTER SUNRISE CAN
HELP CREATE CLEARER CONDITIONS.
MARINE
LIGHT WESTERLY WINDS WILL CONTINUE THROUGH TODAY BEFORE
INCREASING IN STRENGTH AGAIN TUESDAY. A SHARP BOOST IN WIND SPEEDS
WILL BE FORCED BY ANOTHER QUICK MOVING FRONTAL SYSTEM RACING
THROUGH OUR AREA. THIS FRONTAL SYSTEM WILL FORCE NEAR GALE TO GALE
FORCE SOUTHERLY WINDS IN THE NORTHER WATERS TUESDAY EVENING THROUGH
WEDNESDAY MORNING. A PREVIOUSLY ISSUED GALE WATCH IS NOW A GALE
WARNING AS FORECAST CONFIDENCE ON THE TIMING AND STRENGTH OF THE
WINDS HAS INCREASED WITHIN THE LAST 12 HOURS.
A WESTERLY SWELL IS DECREASING IN SIZE FROM TODAY THROUGH TUESDAY
NIGHT BEFORE ANOTHER PULSE OF ENERGY INCREASES ON TUESDAY NIGHT
THROUGH WEDNESDAY MORNING. STEEP WIND WAVES WILL ALSO BUILD IN
RESPONSE TO THE STRONG WINDS TUESDAY NIGHT.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
SMALL CRAFT ADVISORY UNTIL 3 AM PST TUESDAY FOR PZZ450-455-
470-475.
GALE WARNING FROM 8 PM TUESDAY TO 6 AM PST WEDNESDAY FOR
PZZ470.
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