781
FXUS66 KSEW 210933
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
233 AM PDT MON APR 21 2025
SYNOPSIS
CONDITIONS WILL BEGIN TO DRY OUT TODAY AS A TROUGH
EXITS. HIGH PRESSURE WILL BRING DRY AND WARMER CONDITIONS
WEDNESDAY AND THURSDAY. PRECIPITATION CHANCES RETURN FRIDAY INTO
THE WEEKEND.
SHORT TERM /TODAY THROUGH WEDNESDAY/
CLASSIC CONVERGENCE ZONE
OVER KING COUNTY OVERNIGHT WITH ONSHORE FLOW AND TROUGHING
OVERHEAD. SO FAR THE CENTRAL CASCADE PASSES LOOK BARE/WET BUT
COULD STILL SEE LIGHT SNOW AT BOTH STEVENS AND SNOQUALMIE PASS
WITH SNOW LEVELS LOWERING TO AROUND 2500 FT. BUT IN GENERAL, THE
CONVERGENCE ZONE WILL FADE THIS MORNING AS THE TROUGH EXITS EAST.
TEMPERATURES WILL TRACK COOLER THAN AVERAGE WITH HIGHS IN THE 50S
TODAY. LOWS WILL DROP INTO THE 30S AND LOWER 40S TONIGHT, WITH
LOWER 30S AROUND THE SOUTH SOUND. THERE'S A LOW CHANCE (10
PERCENT) OF SEEING FREEZING CONDITIONS IN THE SOUTH SOUND. IF SO,
DUE TO CLEARING AND LIGHT WINDS, IT WOULD BE BRIEF IN DURATION.
WE'RE UNDER DRY N/NW FLOW ON TUESDAY WITH HIGH PRESSURE OFFSHORE.
TEMPERATURES ARE A LITTLE WARMER AND IN THE LOWER 60S IN THE
INTERIOR, WITH 50S ELSEWHERE. LOWS WILL BE COOL AND IN THE 30S AND
LOWER 40S AGAIN. THE RIDGE SHIFTS INLAND ON WEDNESDAY FOR SUNNY
SKIES AND HIGHS IN THE 60S THROUGHOUT. 33
LONG TERM /THURSDAY THROUGH SUNDAY/
HIGH PRESSURE BRINGS ONE
MORE DRY AND WARM DAY ON THURSDAY WITH TEMPERATURES PEAKING IN
THE 60S AND 70S. A TROUGH THEN BRINGS SHOWERS AND COOLER
CONDITIONS MOVING INTO FRIDAY. RAIN AND COOLER WEATHER FOLLOWS
INTO THE WEEKEND WITH A BROAD TROUGH OVER THE WEST. SUNDAY IS A
LITTLE DRIER AND WARMER (NEAR NORMAL) AS THE LOW CENTER SHIFTS
TOWARD THE GREAT BASIN. 33
AVIATION
AN UPPER LEVEL TROUGH IS CURRENTLY PROGRESSING THROUGH
WESTERN WA THIS MORNING WITH A JET MAX OVER THE STATE, CREATING
STRONG NORTHWESTERLY FLOW ALOFT UNTIL LATER TODAY. A FEW AREAS OF
SHOWERS CONTINUE ACROSS SOME OF THE TERMINALS THIS MORNING. THE
SHOWERS UP IN SKAGIT/WHATCOM COUNTIES CONTINUE TO MOVE SOUTHEAST
WITH LIGHT/MODERATE RAIN. DOWN IN KING COUNTY (BETWEEN I-90 AND THE
SNOHOMISH COUNTY LINE), THE CONVERGENCE ZONE CONTINUES, REMAINING
STATIONARY WITH LIGHT/MODERATE RAIN. A FEW SCATTERED/ISOLATED
SHOWERS WERE ALSO TRACKING SOUTHEAST ALONG THE PACIFIC COAST. THE
CEILINGS REMAIN BROKEN TO OVERCAST ACROSS, WITH THE LOWEST CIGS
(MVFR) ASSOCIATED WITH THE CONVERGENCE ZONE AFFECTING KSEA AND KBFI.
MOST OF THE SHOWERS WILL WIND DOWN AROUND 12Z THIS MORNING (WITH A
FEW LINGERING IN AREAS NEAR THE NORTH CASCADES THROUGH ROUGHLY 00Z).
THROUGHOUT THE DAY TODAY, MVFR CEILINGS WILL BE ASSOCIATED WITH
SHOWERS NORTH OF I-90 THROUGH THE AFTERNOON, WITH REMAINING AREAS
SEEING LOWER VFR CEILINGS WITH CLEARING TAKING PLACE THIS EVENING.
LOWER VISIBILITIES DOWN TO 3 SM WITH MIST IS POSSIBLE WITH THE
HEAVIER SHOWERS.
WINDS CONTINUE TO DECREASE ALONG THE STRAIT OF JUAN DE FUCA THIS
MORNING (WITH A FEW GUSTS TO 20-25 KT POSSIBLE THROUGH SUNRISE).
NORTHWEST WINDS OF 5 TO 10 KT WILL BE FOUND IN AREAS WEST OF THE
OLYMPICS. IN THE SOUTH INTERIOR (AROUND KOLM), THE WINDS WILL BE
MORE WESTERLY AT THE SAME MAGNITUDE. FOR THE NORTH INTERIOR (KBLI),
WINDS WILL BE OUT OF THE SOUTHWEST, WITH LIGHTER WINDS DOWN TO 5
KT TONIGHT/TUESDAY MORNING. FINALLY, IN PUGET SOUND, WINDS WILL
BECOME SOLIDLY SOUTHERLY THIS MORNING AT AROUND 4 TO 8 KT, WITH A
TURN TO THE WEST/NORTHWEST TAKING PLACE AROUND 00Z (DECREASING TO
LESS THAN 5 KT).
KSEA...CONVERGENCE ZONE JUST NORTH OF THE TERMINAL WILL CONTINUE
THIS MORNING THROUGH ROUGHLY 12Z. THE SHOWERS ARE EXPECTED TO REMAIN
TO THE NORTH OF THE TERMINAL AT THIS POINT. CEILINGS WILL LIKELY
REMAIN MVFR UNTIL THE CONVERGENCE ZONE VASTLY DISSIPATES, BUT
CEILINGS WILL STILL REMAIN OVERCAST ON THE LOW-END OF VFR. MORE
CLEARING IS EXPECTED TONIGHT/TUESDAY MORNING. WINDS HAVE TURNED BACK
TO THE SOUTH AT AROUND 8 KT THIS MORNING, AND WILL BECOME MORE
WESTERLY THIS AFTERNOON TO NORTHWEST SOMETIME AFTER 00Z. THE
MAGNITUDE OF THE WIND WILL DECREASE AT OR BELOW 5 KT TONIGHT.
HPR
MARINE
A TROUGH SITS OVER INLAND WA THIS MORNING, WITH HIGH
PRESSURE BEGINNING TO BUILD OUT IN THE COASTAL WATERS THIS MORNING.
THIS WILL KEEP THE FLOW PATTERN NORTHWESTERLY/ONSHORE THROUGH NEXT
THURSDAY/FRIDAY BEFORE ANOTHER POTENTIAL DISTURBANCE TRACKS TOWARDS
THE REGION.
POST TROUGH, A FEW BREEZY SPOTS REMAIN OUT ON SMITH ISLAND AND FAR
IN THE NORTHERN COASTAL WATERS. SUSTAINED WINDS HAVE DROPPED AT OR
BELOW 20 KT, WITH GUSTS NOT EXCEEDING 25 KT. GIVEN THE DOWNWARD
TREND IN THE OBSERVATIONS, WILL ALLOW THE SMALL CRAFT ADVISORIES TO
EXPIRE AT 3 AM THIS MORNING IN THE CENTRAL/EAST STRAIT OF JUAN DE
FUCA, AND 11 AM FOR THE NORTHERN TWO THIRDS OF THE COASTAL
WATERS/WEST STRAIT OF JUAN DE FUCA. THE WINDS WILL DECREASE THIS
MORNING, AND WILL REMAIN BENIGN THROUGH THE WEEK. THE FRONT
THURSDAY/FRIDAY IS NOT EXPECTED TO PRODUCE HAZARDOUS WINDS AT THIS
TIME, BUT MAY CHANGE AS HIGHER RESOLUTION GUIDANCE BECOMES AVAILABLE.
THE SEAS WILL DECREASE FROM 8 TO 10 FEET THIS MORNING DOWN TO 5 TO 7
FEET TUESDAY (PERIODS WILL INCREASE FROM 9 SECONDS TO 11 SECONDS
TUESDAY). EXPECT A FURTHER DROP DOWN TO 3 TO 5 FEET THURSDAY BEFORE
INCREASING BACK UP TO 6 TO 9 FEET ON SATURDAY.
HPR
HYDROLOGY
NO RIVER FLOODING IS EXPECTED DURING THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT EARLY THIS MORNING FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA-WEST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 11 AM PDT THIS MORNING 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.
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