986
FXUS66 KSEW 230320
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
820 PM PDT SUN MAR 22 2026
SYNOPSIS
A DECAYING SYSTEM MOVING INLAND HAS LEAD TO INCREASED CLOUD
COVER TODAY BUT NOT MUCH IN THE WAY OF ANY PRECIPITATION.
GENERALLY DRY CONDITIONS SHOULD PERSIST INTO MONDAY, WITH A MORE
ACTIVE SYSTEM ARRIVING BY MID WEEK FOR ADDITIONAL RAIN, HIGH
ELEVATION SNOW, AND GUSTY WINDS.
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
WEAK HIGH PRESSURE IS BUILDING OVER WESTERN WASHINGTON THIS
AFTERNOON IN THE WAKE OF A DECAYING FRONT. MILD AND GENERALLY
CLEAR CONDITIONS ARE EXPECTED THROUGH MONDAY.
THE NEXT LOW PRESSURE SYSTEM WILL INFLUENCE THE REGION BEGINNING
TUESDAY AND LASTING THROUGH WEDNESDAY. THERE HAS BEEN SOME
SHIFTING OF THE TRACK OF THE LOW PRESSURE SYSTEM, WHICH HAS
IMPACTED THE WIND FORECAST, BUT GUSTY CONDITIONS ARE EXPECTED
THROUGHOUT THE AREA, IN ADDITION TO HIGH ELEVATION SNOW AND
LOWLAND RAIN. THE GUSTIEST LOCATIONS LOOK TO BE ALONG THE
IMMEDIATE COAST AND AREAS FROM EVERETT NORTH TO THE CANADIAN
BORDER. WINDS WILL PEAK TUESDAY AFTERNOON AND EVENING BEFORE
DECREASING. SNOW LEVELS WILL BEGIN AROUND 2500 TO 3500 FEET ON
TUESDAY, INCREASING TO 5000 FEET AND LIMITING THE AMOUNT OF SNOW
THAT FALLS TO AREAS ABOVE THAT ELEVATION. SNOW LEVELS DROP
AGAIN TO 2000 TO 3000 FEET ON WEDNESDAY, WITH LIGHT
ACCUMULATIONS EXPECTED THROUGH THE CASCADE PASSES. ESTIMATES FOR
SNOWFALL ARE ROUGHLY BETWEEN 1-2 INCHES AT SNOQUALMIE PASS, AND
2-4 INCHES AT STEVENS PASS FOR THE DURATION OF THE EVENT. THESE
AMOUNTS ARE SUBJECT TO CHANGE AS THE TRACK OF THE LOW CHANGES.
ADDITIONALLY, POST FRONTAL CONVERGENCE ZONE ACTIVITY ON
WEDNESDAY COULD LOCALLY ENHANCE SNOWFALL ALONG THE US 2 CORRIDOR
IN THROUGH STEVENS PASS. THE 48 HOUR PROBABILITIES OF SNOWFALL
GREATER THAN 8 INCHES ENDING THURSDAY MORNING ARE 25% FOR
STEVENS PASS AND 20% FOR SNOQUALMIE PASS. LOWLAND RAINFALL
AMOUNTS FOR THIS EVENT ARE BETWEEN 0.5-0.75 INCHES IN PUGET
SOUND, AND UP TO AN INCH ALONG THE IMMEDIATE COAST.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
ACTIVE WEATHER CONTINUES ON WEDNESDAY, WITH THE SYSTEM FORECAST
TO EXIT ON THURSDAY. LINGERING SHOWERS WILL BE POSSIBLE THURSDAY
MORNING BEFORE SCATTERING IN THE AFTERNOON AND EVENING. THE
LATER HALF OF THE WEEK APPEARS TO BE DRIER AS THE RIDGE IN THE
GREAT BASIN AMPLIFIES, MOVING THE STORM TRACK MORE INTO SE AK.
TEMPERATURES ON FRIDAY AND SATURDAY COULD REBOUND INTO THE UPPER
50S AND EVEN LOW 60S IN SOME LOCATIONS, GIVING A MORE CLEAR
TASTE OF SPRING.
21
AVIATION
ZONAL FLOW ALOFT WILL PREVAIL ACROSS WESTERN WASHINGTON TONIGHT
INTO MONDAY. HIGH PRESSURE WILL BUILD BACK INTO THE AREA AT THE
SURFACE IN THE WAKE OF THIS MORNING'S FRONT. SATELLITE IMAGERY
CONTINUES TO SHOW CLOUDS CONTINUING TO THIN OUT SOMEWHAT,
HOWEVER THERE IS STILL A FAVORING OF MID TO HIGH LEVEL CLOUDS.
AS A RESULT, WIDESPREAD VFR CONDITIONS ARE IN PLACE AND ARE
EXPECTED TO PERSIST FOR THE TAF PERIOD.
WINDS FOR MOST TERMINALS REMAIN NORTHERLY THIS EVENING WITH SPEEDS
GENERALLY 4-8 KT. WINDS WILL BECOME LIGHT OVERNIGHT, BUT WILL
LARGELY REMAIN NORTHERLY.
KSEA...VFR CONDITIONS EXPECTED THROUGHOUT THE TAF PERIOD. HIGH
CLOUDS WILL CONTINUE TO STREAM INTO THE TERMINAL INTO MONDAY.
WINDS HAVE SWITCHED TO NORTHERLY AND PERSIST AT 4-8 KT AT THE
TERMINAL THIS AFTERNOON. THE ONLY EXCEPTION IS CLM, WHERE WINDS ARE
LIGHT AND VARIABLE. WINDS WILL EASE OVERNIGHT, BUT WILL RESUME
SPEEDS AKIN TO THIS EVENING BY 20Z.
14/18
MARINE
HIGH PRESSURE WILL REMAIN SITUATED OVER THE REGION THROUGH MONDAY,
MAINTAINING LIGHT WINDS ACROSS THE AREA. SEAS WILL HOVER BETWEEN 6-8
FT. A DEEPENING LOW PRESSURE SYSTEM WILL THEN MOVE INTO THE
NORTHEASTERN PACIFIC ON TUESDAY, SWINGING A STRONG FRONTAL SYSTEM
ACROSS THE AREA WATERS. WHILE UNCERTAINTY REMAINS IN REGARDS TO THE
EXACT TRACK OF THIS LOW PRESSURE SYSTEM, GUIDANCE CONTINUES TO
SUGGEST THAT STRONG WINDS AND BUILDING SEAS ARE LIKELY FOR THE AREA
WATERS. LATEST PROBABILISTIC GUIDANCE INDICATES A 75-90% CHANCE OF
WIND GUSTS EXCEEDING GALE FORCE CRITERIA ACROSS THE COASTAL WATERS
ON TUESDAY, AND THUS HAVE ISSUED A GALE WATCH. SEAS WILL BUILD
TOWARDS 15-19 FT ON TUESDAY, WITH LATEST GEFS GUIDANCE STILL
INDICATING ROUGHLY A 40-50% CHANCE OF SEAS EXCEEDING 20 FT FOR THE
NORTHWESTERN PORTION OF THE COASTAL WATERS. A STRONG PUSH OF
WESTERLY WINDS IS LIKELY ALONG THE STRAIT OF JUAN DE FUCA IN THE
WAKE OF THE FRONTAL SYSTEM TUESDAY NIGHT INTO WEDNESDAY. WINDS WILL
THEN EASE AREA-WIDE INTO THURSDAY AS HIGH PRESSURE STARTS TO BUILD
BACK INTO THE AREA WATERS AGAIN AND REMAINS SITUATED ACROSS THE
REGION THROUGH FRIDAY.
SEAS WILL SLOWLY SUBSIDE ON WEDNESDAY AND TOWARDS 6-8 FT
BY THURSDAY. SEAS WILL HOLD BETWEEN THIS RANGE THROUGH FRIDAY.
14
HYDROLOGY
ONE FLOOD WARNING REMAINS IN EFFECT THIS EVENING FOR THE CEDAR
RIVER AT RENTON, WHICH CONTINUES TO HOVER RIGHT AROUND FLOOD
STAGE AS WATER FROM UPSTREAM RELEASES CONTINUES TO WORK THROUGH
THE SYSTEM. THIS SHOULD CONTINUE TO TREND LOWER THROUGH MONDAY.
OTHERWISE, ATTENTION TURNS TO THE NEXT SYSTEM TUESDAY. WHILE
FLOODING IS NOT CURRENTLY EXPECTED WITH THE CURRENT
PRECIPITATION FORECAST (AIDED BY LOWERING SNOW LEVELS FOR THE
BACK HALF OF THE MOISTURE), MANY RIVERS WILL BE STARTING OFF
WITH SOMEWHAT HIGHER FLOWS. AS SUCH, THE POTENTIAL FOR
ADDITIONAL RIVER FLOODING WILL NEED TO BE CLOSELY MONITORED. THE
CEDAR RIVER AT RENTON LIKELY HOLDS ABOVE ACTION STAGE THROUGH
THE WEEK AND MAY APPROACH OR REACH FLOOD STAGE AGAIN AROUND
MIDWEEK.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...GALE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY EVENING 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-COASTAL WATERS
FROM POINT GRENVILLE TO CAPE SHOALWATER OUT 10 NM.
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