361
FXUS66 KSEW 080420
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
817 PM PST FRI MAR 7 2025
SYNOPSIS
AN EXITING RIDGE WILL ALLOW FOR A MORE ACTIVE
PATTERN OVER WESTERN WASHINGTON. AS THE DEPARTING RIDGE SHIFTS EAST,
A SERIES OF SYSTEMS WILL MOVE THROUGH THE AREA OVER THE WEEKEND AND
INTO THE MIDDLE OF NEXT WEEK. THESE SYSTEMS WILL BRING LOWLAND RAIN,
MOUNTAIN SNOW AND GUSTY WINDS INTO THE FORECAST AT TIMES.
SHORT TERM /TONIGHT THROUGH MONDAY/
CURRENT SATELLITE IMAGERY
SHOWS MID TO HIGH LEVEL CLOUDS PUSHING INTO THE AREA IN ADVANCE OF
THE NEXT INCOMING SYSTEM EXPECTED TO BRING RAIN TO THE WESTERN HALF
OF THE CWA OVERNIGHT TONIGHT. CURRENT RADAR SHOWING SOME WEAK ECHOES
AS FAR EAST AS THE SOUND, BUT NOT SEEING ANY GROUND TRUTH TO MATCH
UP. THE MAIN PRECIP STILL WELL OFF OVER THE OUTER COASTAL
WATERS...WHICH LOOKS TO MATCH WELL WITH TIMING OF INHERITED
FORECAST. AS SUCH, NO EVENING UPDATE NEEDED. PLEASE REFER TO THE
PREVIOUS DISCUSSION SECTION BELOW FOR FORECAST DETAILS.
18
FROM PREVIOUS DISCUSSION...LINGERING MID AND UPPER LEVEL CLOUDS ARE
GIVING WAY TO MORE BLUE SKY THIS AFTERNOON. TEMPERATURES IN THE MID
50S WILL PERSIST INTO THE REST OF THE DAY FOR PLEASANT CONDITIONS. A
SYSTEM DROPPING IN FROM THE GULF OF ALASKA TOMORROW WILL INTRODUCE
RAIN AND SOME BREEZY WINDS TO THE NORTH COAST TOMORROW MORNING AND
FILL IN THROUGHOUT THE DAY FOR RAIN IN THE LOWLANDS. THE NORTH
CASCADES, NAMELY THE MOUNT BAKER AREA WILL RECEIVE BETWEEN 3-7
INCHES OF SNOW THROUGH TOMORROW AFTERNOON. SNOW LEVELS WILL BE ABOVE
PASS LEVEL IN THE REST OF THE CASCADES FOR MINIMAL TO NO SNOW
ACCUMULATION. AS THE PRECIPITATION GETS INTO PUGET SOUND, EXPECT
BREEZY WINDS IN AREAS NORTH OF EVERETT AND A GENERALLY MILD AIRMASS
WITH TEMPERATURES IN THE UPPER 50S.
THE QPF FOR SUNDAY INCREASED, PARTICULARLY IN THE NORTH CASCADES
AND OLYMPIC PENINSULA. SNOW LEVELS ALSO COME DOWN TO 3000 FEET OR
LOWER ACROSS THE CENTRAL CASCADES, WHICH COULD MAKE FOR SOME
ADDITIONAL SNOW ACCUMULATIONS ACROSS STEVENS AND SNOQUALMIE PASS
LATE SUNDAY NIGHT INTO MONDAY MORNING. BETWEEN SUNDAY AFTERNOON
AND MONDAY AFTERNOON, A TOTAL OF 4 TO 8 INCHES OF SNOW COULD FALL
IN THESE AREAS, WITH LOCALLY HIGHER AMOUNTS TOWARD MOUNT BAKER
AND THE NORTH CASCADES. MONDAY WILL BE MORE OF A TRANSITION DAY,
WITH SCATTERED SHOWERS AND AN OVERALL DECREASING PRECIPITATION
TREND, BUT THIS WILL BE SHORT LIVED AS THE NEXT SERIES OF SYSTEMS
WILL ARRIVE THEREAFTER.
LONG TERM /TUESDAY THROUGH FRIDAY/...FROM PREVIOUS DISCUSSION
A
WEAK SYSTEM DROPPING IN FROM THE NORTH WILL DECAY OVER THE REGION ON
TUESDAY FOR CLOUDY AND COOLER CONDITIONS WITH A FEW ISOLATED
SHOWERS.
A STRONGER SYSTEM WILL APPROACH THE AREA BY THE MIDDLE OF NEXT
WEEK BUT THE RANGE OF IMPACTS ARE LARGE BECAUSE THE RANGE OF
POSSIBLE TRACKS ARE LARGE AS WELL. WHAT WE CAN SEE AT THIS POINT
IS THE POTENTIAL FOR IT TO BE A STRONGER LOW PRESSURE SYSTEM, BUT
WHERE IT ULTIMATELY TRACKS WILL BE THE DECIDING FACTOR ON THE
STRENGTH OF THE WINDS THAT IT WOULD BRING, AMOUNT OF PRECIPITATION
AND TEMPERATURE FOR MOUNTAIN SNOW POTENTIAL. UPON EARLIER
EXAMINATION OF THE SYSTEM, THE RANGE OF POSSIBLE WIND GUST SPEEDS
BETWEEN THE MEAN AND EVEN 90TH PERCENTILE VALUES WAS CONSIDERABLE.
MORE DETAILS WILL BE ASCERTAINED AS THE SYSTEM AND TIMELINE NEARS.
21
AVIATION
WESTERLY FLOW BECOMING SOMEWHAT NORTHWESTERLY AS THE
RIDGE SHIFTS EASTWARD, ALLOWING FOR UPPER LEVEL TROUGHING TO NUDGE
INTO WESTERN WASHINGTON. VFR CONDITIONS AREA-WIDE THIS EVENING AND
INTO THE REMAINDER OF THE TAF PERIOD, WITH MAINLY MID TO HIGH LEVEL
CLOUDS MOVING IN AHEAD OF INCOMING WEATHER SYSTEM. NOT MUCH
CONFIDENCE IN LOW CLOUD COVER TONIGHT, WITH A 15-20% CHANCE OF
SEEING MVFR IN LOCATIONS PRONE TO LOWER CIGS IN THE INTERIOR.
KSEA...VFR CONDITIONS WITH SOME HIGH TO MID LEVEL CLOUDS STREAMING
ACROSS THE REGION. VFR WILL CONTINUE INTO SATURDAY MORNING, WITH A
15% OF LOW MVFR CLOUDS DEVELOPING AROUND 09Z-14Z. WITH HIGH CLOUDS
AROUND, THIS SEEMS LESS LIKELY. S/SW WINDS 4 TO 8 KNOTS OVERNIGHT
INTO SATURDAY MORNING BEFORE SPEEDING UP TO 8-12 KTS IN THE
AFTERNOON, WITH OCCASIONAL GUSTS POSSIBLE.
MAZURKIEWICZ/18
MARINE
A SURFACE HIGH OFFSHORE WILL SLOWLY BE REPLACED BY A
WEAK FRONT CROSSING THE AREA WATERS TONIGHT INTO SATURDAY.
SOUTHERLIES WILL INCREASE OVER THE COASTAL WATERS LEADING TO SMALL
CRAFT ADVISORIES, ALONG WITH THE EAST ENTRANCE OF THE STRAIT, THE
NORTHERN INLAND WATERS, AND ADMIRALTY INLET. THESE WINDS WILL
GRADUALLY DECREASE INTO SUNDAY.
ACTIVE WATER LOOKS LIKELY EARLY NEXT WEEK INTO MIDWEEK, WHERE A
DEVELOPING LOW PRESSURE SYSTEM COULD BRING STRONGER WINDS AND
ELEVATED SEAS TO THE COASTAL WATERS.
COMBINED SEAS THIS AFTERNOON AROUND 6 TO 8 FEET WILL START TO
INCREASE TO AROUND TO 10 TO 14 FEET TONIGHT AND INTO SATURDAY
MORNING, REMAINING ABOVE 10 FEET THROUGH THE WEEKEND. SEAS WILL
SUBSIDE ON MONDAY BEFORE INCREASING AGAIN MIDWEEK WITH THE
AFOREMENTIONED LOW PRESSURE SYSTEM.
MAZURKIEWICZ
HYDROLOGY
NO RIVER FLOODING IS EXPECTED OVER THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 1 AM TO 7 PM PST SATURDAY FOR
ADMIRALTY INLET-EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE
FUCA-NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.
SMALL CRAFT ADVISORY UNTIL 9 PM PST SATURDAY FOR COASTAL WATERS
FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL
WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10
NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER
10 TO 60 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM PST SATURDAY FOR COASTAL WATERS
FROM POINT GRENVILLE TO CAPE SHOALWATER OUT 10 NM.
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