804
FXUS66 KSEW 210316
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
816 PM PDT TUE MAY 20 2025
UPDATE
SHOWERS HAVE PUSHED INTO THE CASCADES WITH THE EXCEPTION
OF ONGOING CONVERGENCE ZONE ACTIVITY ALONG THE KING AND SNOHOMISH
COUNTY BORDER. THIS ACTIVITY SHOULD LINGER THROUGHOUT A GOOD
PORTION OF THIS EVENING AND INTO THE OVERNIGHT HOURS BEFORE
TAPERING OFF. OTHERWISE THE FORECAST REMAINS ON TRACK AND NO
ADDITIONAL UPDATES HAVE BEEN MADE TONIGHT.
SYNOPSIS
COOLER AND SHOWERY CONDITIONS WILL REMAIN ACROSS THE
REGION THROUGH MUCH OF THE WEEK AS A SERIES OF DISTURBANCES CROSS
THE REGION. HIGH PRESSURE LIKELY REBUILDS OVER THE WESTERN U.S.
OVER THE WEEKEND, BRINGING A RETURN OF WARMER AND DRIER CONDITIONS
TO THE AREA.
SHORT TERM /TONIGHT THROUGH FRIDAY/
EXPECT SHOWER COVERAGE TO
DECREASE FOR MOST OVERNIGHT, BUT A DEVELOPING PUGET SOUND
CONVERGENCE ZONE WILL LIKELY MAINTAIN AN AREA OF STEADIER SHOWERS
INTO WEDNESDAY MORNING. SOME SHOWERS INCREASE AGAIN NEAR AND SOUTH
OF THE SOUTH SOUND LATER WEDNESDAY, WITH LINGERING SHOWERS IN THE
CASCADES LATE WEDNESDAY. TRANSIENT HIGH PRESSURE MOVES OVERHEAD
THURSDAY WITH INCREASED SUNSHINE, DRIER CONDITIONS, AND
TEMPERATURES RETURNING BACK TO NEAR NORMAL.
LONG TERM /SATURDAY THROUGH TUESDAY/
THE GLOBAL ENSEMBLES
GENERALLY FAVOR THE DEVELOPMENT AND STRENGTHENING OF A RIDGE
OVER THE WESTERN U.S. LATE IN THE WEEK AND INTO THE WEEKEND.
THIS IS A SUBSET, AROUND 20%, OF ENSEMBLE MEMBERS THAT SUGGEST
ENOUGH OF A TROUGH NEAR THE REGION TO MAINTAIN SOME CLOUDS AND
MOUNTAIN SHOWERS, BUT THE MAJORITY GO FAVOR A DRIER TREND. AS A
RESULT, THE FORECAST CONTINUES TO FOLLOW THIS PATTERN WITH A
WARM UP - MOST NOTABLY SUNDAY, WITH AFTERNOON HIGH TEMPERATURES
WELL INTO THE 70S AND APPROACHING 80 IN THE WARMEST SPOTS. IT'S
WORTH NOTING THAT THERE'S IS STILL A PORTION OF ENSEMBLE
MEMBERS THAT WOULD KEEP TEMPERATURES MUCH CLOSER TO (OR BELOW)
NORMAL VALUES. CONFIDENCE REMAINS LOW INTO THE START OF NEXT
WEEK WITH SOME POTENTIAL FOR THE NEXT FRONTAL SYSTEM TO MAKE
ITS WAY INTO THE REGION, BUT THE RIDGE MAY REMAIN PRESENT AND
AMPLIFIED ENOUGH TO KEEP WARMER AND DRIER CONDITIONS FOR FIRST
HALF OF NEXT WEEK.
AVIATION
NORTHWESTERLY FLOW ALOFT AS SCATTERED SHOWERS
CONTINUE THROUGHOUT THE REGION THIS EVENING. SCATTERED SHOWERS
ARE EXPECTED TO CONTINUE THIS EVENING, WHICH COULD BRING
LOCALIZED POCKETS OF REDUCED CEILINGS AND VISIBILITY BRIEFLY AT
TIMES. A CONVERGENCE ZONE AROUND KPAE THIS EVENING WILL CONTINUE
TO BRING LOCALIZED LOWER CEILINGS, BUT WILL SLOWLY DISSIPATE INTO
THE OVERNIGHT HOURS. SHOWERS WILL GRADUALLY TAPER OFF TONIGHT.
CEILINGS WILL DROP TO MVFR WEDNESDAY MORNING ALONG THE MAJORITY OF
PUGET SOUND TERMINALS (KPWT MAY DROP DOWN TO IFR) AND NORTHERN
INTERIOR TERMINALS, WITH IMPROVEMENT EXPECTED LATE IN THE MORNING.
OTHERWISE, VFR EXPECTED TO PERSIST FOR THE MAJORITY OF THE TAF
PERIOD FOR MOSTLY ALL TERMINALS.
BREEZY S/SW WINDS ALONG INTERIOR TERMINALS WILL CONTINUE THIS
AFTERNOON 10-15 KT AND GUSTING TO 20-25 KT, SUBSIDING OVERNIGHT TO 5-
7 KT. SURFACE FLOW WILL SHIFT MORE NORTHERLY LATE WEDNESDAY MORNING.
KSEA...SCATTERED SHOWERS CONTINUE AROUND THE TERMINAL THIS
EVENING. HOWEVER, ANY SHOWERS THAT DO IMPACT THE TERMINAL MAY
BRIEFLY REDUCE CEILINGS AND VISIBILITY AT TIMES. MODELS ARE STILL
IN GENERAL AGREEMENT FOR CONVERGENCE ZONE DEVELOPMENT TO STAY
NORTH OF THE TERMINAL TONIGHT. GUIDANCE IS HINTING AT HIGH-END
MVFR CEILINGS BETWEEN 12Z-17Z WEDNESDAY MORNING, WITH IMPROVEMENT
INTO VFR EXPECTED LATE MORNING. OTHERWISE, VFR IS FAVORED FOR THE
MAJORITY OF THE TAF PERIOD.
S/SW BREEZY WIND CONTINUE THIS AFTERNOON AT 10-15 KT AND GUSTING UP
TO AROUND 20 KT. WINDS ARE EXPECTED TO SUBSIDE TONIGHT. SURFACE
WINDS WILL SHIFT NORTH/NORTHEASTERLY LATE WEDNESDAY MORNING INTO THE
AFTERNOON (6-8 KT).
29/MAZURKIEWICZ
MARINE
WESTERLY SURFACE FLOW ALONG THE COASTAL WATERS WILL SHIFT
MORE NORTHWESTERLY THIS EVENING. A WEAK PUSH ALONG THE CENTRAL AND
EAST STRAIT IS EXPECTED TONIGHT. SUSTAINED WIND SPEEDS WILL BE
AROUND 15-20 KT, BUT PROBABILISTIC GUIDANCE HIGHLIGHTS A 60-80
PERCENT CHANCE OF WIND GUSTS REACHING SMALL CRAFT CRITERIA FOR A
BRIEF PERIOD, FOR WHICH A SMALL CRAFT ADVISORY HAS BEEN ISSUED. IN
ADDITION, A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE
COASTAL WATERS AND WEST STRAIT FOR HIGH SEAS 10-11 FT THIS
AFTERNOON. SEAS SHOULD SUBSIDE BELOW 10 FT TONIGHT INTO EARLY
WEDNESDAY MORNING.
WEAK HIGH PRESSURE WILL BUILD OVER THE COASTAL WATERS ON WEDNESDAY
AND THURSDAY. THE NEXT FRONTAL SYSTEM LOOKS TO ARRIVE ON FRIDAY,
WITH HIGH PRESSURE REBUILDING OVER THE WEEKEND.
SEAS 9 TO 11 FT THIS AFTERNOON AND WILL SUBSIDE LATE TONIGHT TO 7 TO
8 FT. SEAS LOOK TO REMAIN BELOW 10 FT THROUGH THE REST OF THE WEEK.
29
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 2 AM PDT WEDNESDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page