468
FXUS66 KSEW 152328
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
428 PM PDT WED APR 15 2026
SYNOPSIS
UNSETTLED CONDITIONS CONTINUE INTO TONIGHT AS AN
UPPER LOW MOVES ACROSS THE PACIFIC NORTHWEST. COOL, DRY
CONDITIONS THURSDAY AND FRIDAY. AN UPPER LOW WILL SLIDE
SOUTHWARDS ALONG THE WEST COAST OVER THE WEEKEND, RESULTING IN
THE NEXT CHANCE FOR PRECIPITATION.
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
SCATTERED SHOWERS
CONTINUE THIS AFTERNOON IN A POST-FRONTAL AIRMASS. SOME
INSTABILITY, GENERALLY RANGING 200-600 J/KG, WILL CONTINUE TO
RESULT IN LOCALIZED THUNDERSTORMS INTO THIS EVENING,
PARTICULARLY ALONG THE OLYMPIC PENINSULA, AS WELL AS IN THE
CONVERGENCE ZONE THAT HAS DEVELOPED OVER KING/KITSAP COUNTIES.
SMALL HAIL, BRIEF GUSTY WINDS, AND LIGHTNING MAY OCCUR WITHIN
ANY THUNDERSTORM. THE CONVERGENCE ZONE WILL SLOWLY PROGRESS
SOUTHWARDS ACROSS KING COUNTY INTO THIS EVENING. SHOWERS WILL
ALSO RESULT IN ADDITIONAL SNOW ACCUMULATION AT TIMES FOR THE
MOUNTAINS. SNOW LEVELS WILL REMAIN AROUND 1500 TO 2000 FEET INTO
TONIGHT, WITH SNOW FOR THE CASCADES PASSES. BRIEF, HEAVY SNOW
RATES CAN OCCUR IN HEAVIER SHOWERS AS WELL. IN GENERAL,
PRECIPITATION TAPERS OFF TONIGHT, WITH DRIER CONDITIONS
DEVELOPING BY THURSDAY MORNING.
OVERNIGHT TEMPERATURES WILL FALL INTO THE 30S FOR MOST LOCATIONS
INTO THURSDAY MORNING. IN ADDITION TO THE COLDER TEMPERATURES,
SKIES WILL CLEAR FOR THE OLYMPIC PENINSULA, AS WELL AS PORTIONS
OF SOUTH SOUND. THIS WILL HELP PROMOTE FROST DEVELOPMENT INTO
THURSDAY MORNING. HAVE ISSUED A FROST ADVISORY FOR MANY LOWLAND
LOCATIONS ACROSS THE OLYMPIC AND KITSAP PENINSULAS. THERE ALSO
REMAINS HIGHER PROBABILITIES (OVER 70 PERCENT) FOR FREEZE
CONDITIONS FOR OLYMPIA SOUTHWARDS AND ALONG THE SOUTHWEST
INTERIOR, FOR THAT REASON, UPGRADED TO A FREEZE WARNING FOR
THESE LOCATIONS. WILL NEED TO MONITOR THE POTENTIAL FOR
ADDITIONAL FROST ADVISORIES ELSEWHERE, HOWEVER, LINGERING CLOUDS
ARE EXPECTED FOR A GOOD PORTION OF THE CENTRAL AND NORTH PUGET
SOUND, WHICH MAY LIMIT ANY FROST. OTHERWISE, ANY LINGERING
CLOUDS THURSDAY MORNING WILL CLEAR FOR SOME SUNSHINE IN THE
AFTERNOON. DRY CONDITIONS THEN CONTINUE THROUGH FRIDAY WITH
RIDGING BUILDING INTO WESTERN WASHINGTON.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
AN UPPER LOW WILL
APPROACH THE PACIFIC NORTHWEST SATURDAY, AND THEN SLIDE
SOUTHWARDS ALONG THE WEST COAST EARLY NEXT WEEK. THERE REMAINS
SOME UNCERTAINTY IN REGARDS TO THE EASTWARD EXTENT OF THE
ASSOCIATED FRONT OVER THE WEEKEND, WHICH WOULD IMPACT THE
POTENTIAL FOR ADDITIONAL RAINFALL, PRIMARILY ON SUNDAY. AT THIS
TIME, THE HIGHEST CHANCES FOR RAINFALL REMAIN ALONG THE OLYMPIC
PENINSULA, BUT PRECIP POTENTIAL EXISTS ELSEWHERE AS WELL.
EITHER WAY, THIS SYSTEM WILL REMAIN RATHER FAR OFFSHORE, AND
IMPACTS ARE EXPECTED TO BE LIMITED. SLIGHT PRECIP CHANCES REMAIN
INTO MIDWEEK AS THE UPPER LOW MOVES ONSHORE, WITH THE BULK OF
THE ENERGY FOCUSED SOUTH OF WESTERN WASHINGTON. SEASONABLE
TEMPERATURES LOOK TO RETURN EARLY NEXT WEEK. JD
AVIATION
CEILINGS HAVE BEEN TRENDING LOWER THAN GUIDANCE AT SOME
TERMINALS. THEREFORE, SEEING A MIX OF VFR AND MVFR THIS AFTERNOON
AND LIKELY TO SEE SOME BOUNCING AROUND IN BETWEEN CATEGORIES AT
TIMES. LATEST RADAR IMAGERY SHOWS CONVECTION WELL UNDERWAY THIS
AFTERNOON. THE CHANCE OF ISOLATED THUNDERSTORMS STILL REMAINS BELOW
20-30%. THE TIME FRAME FOR THUNDERSTORMS IS BETWEEN NOW AND 02Z.
THREATS WITH THUNDERSTORMS MAY INCLUDE LIGHTNING, HEAVY DOWNPOURS,
SMALL HAIL, GUSTY/VARIABLE WINDS. IN ADDITION, A CONVERGENCE ZONE
HAS DEVELOPED OVER PAE THIS AFTERNOON AND IS EXPECTED TO SINK
SOUTHWARDS AND IMPACT BOTH BFI AND SEA. HIGH-RES GUIDANCE SUGGESTS
EMBEDDED THUNDERSTORMS ARE POSSIBLE WITH THE CONVERGENCE ZONE AS IT
MOVES OVER THE TERMINALS. WINDS WILL SHIFT NORTHERLY AS WELL BETWEEN
23Z-03Z WITH SUSTAINED SPEEDS OF 8-15 KT. SHOWER ACTIVITY WILL TAPER
OFF TONIGHT. LIGHT WINDS 5 KT OR LESS EXPECTED TONIGHT INTO THURSDAY
MORNING. MVFR CIGS POSSIBLE (20-40% CHANCE) BETWEEN 12Z-18Z
THURSDAY.
KSEA...CEILINGS HAVE BEEN BOUNCING BETWEEN VFR AND MVFR THIS
AFTERNOON, WITH SOME LOWER CLOUD DECKS LINGERING AROUND. ISOLATED
THUNDERSTORMS REMAIN POSSIBLE THROUGH AROUND 03Z. A CONVERGENCE ZONE
IS EXPECTED TO IMPACT THE TERMINAL THIS EVENING AS EARLY AS 23Z,
WITH WINDS EXPECTED TO SHIFT NORTHERLY AROUND 23Z AND CONTINUING
THROUGH 03Z WITH SPEEDS 10-15 KT AND GUSTS TO 20-25 KT. WINDS WILL
THEN SHIFT SOUTHERLY AFTER 03Z WITH SPEEDS AROUND 5 KT. GUIDANCE
CONTINUES TO HIGHLIGHT A SLIGHT CHANCE OF MVFR CIGS BETWEEN 12Z-18Z,
WITH CURRENT PROBABILITIES AROUND 20-30%.
29
MARINE
ISOLATED THUNDERSTORMS REMAIN POSSIBLE OVER AREA WATERS
TODAY. MAIN CONCERNS WITH THE THUNDERSTORMS ARE ERRATIC/GUSTY
WINDS, LIGHTNING, AND HEAVY DOWNPOURS. SMALL CRAFT ADVISORIES
CONTINUE IN EFFECT FOR THE COASTAL WATERS FOR THE COMBINATION OF
STEEP SEAS 8-12 FT WITH A DOMINANT PERIOD OF 9-10 SECONDS AND
WINDS. ALTHOUGH SEAS HAVE BEEN HOVERING SLIGHTLY BELOW 7-9 FT
WITH THE LATEST OBS, SEAS ARE EXPECTED TO BUILD LATER THIS
EVENING TO 10 FT AND THUS THE SMALL CRAFT ADVISORY FOR GRAYS
HARBOR BAR HAS BEEN EXTENDED THROUGH THURSDAY MORNING.
THUNDERSTORM ACTIVITY EXPECTED TO TAPER OFF TONIGHT. HIGH
PRESSURE WILL REBUILD OVER AREA WATERS ON THURSDAY AND SEAS ARE
EXPECTED TO DECREASE BELOW 10 FT, BUT STILL LOOKING TO REMAIN
STEEP THROUGH THURSDAY NIGHT. A WESTERLY PUSH IS EXPECTED
THROUGH THE STRAIT OF JUAN DE FUCA ON THURSDAY. HOWEVER, CURRENT
PROBABILITIES ARE BETWEEN 30-45% OF WINDS EXCEEDING 21 KT. HIGH
PRESSURE WILL WEAKEN ON SATURDAY AND THE NEXT SYSTEM IS
EXPECTED TO IMPACT AREA WATERS THIS WEEKEND. LATEST GUIDANCE
SUGGESTS WINDS AND WAVES WILL REMAIN BELOW SMALL CRAFT
THRESHOLDS AT THIS TIME.
29
HYDROLOGY
NO RIVER FLOODING IS EXPECTED DURING THE NEXT SEVEN
DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...WINTER STORM WARNING UNTIL 11 PM PDT THIS EVENING FOR CASCADES
OF PIERCE AND LEWIS COUNTIES-CASCADES OF SNOHOMISH AND
NORTHERN KING COUNTIES-CASCADES OF SOUTHERN KING COUNTY.
FROST ADVISORY FROM 1 AM TO 9 AM PDT THURSDAY FOR EASTERN
KITSAP COUNTY-EASTERN STRAIT OF JUAN DE FUCA-FOOTHILLS OF
THE WESTERN AND SOUTHERN OLYMPIC PENINSULA-LAKE CRESCENT
AREA INCLUDING US 101-LOWLANDS OF PIERCE AND SOUTHERN
KING COUNTIES-NORTHERN HOOD CANAL-PORT TOWNSEND AREA.
FREEZE WARNING FROM 1 AM TO 9 AM PDT THURSDAY FOR LOWLANDS OF
LEWIS AND SOUTHERN THURSTON COUNTIES-MIDDLE CHEHALIS
RIVER VALLEY-OLYMPIA AND SOUTHERN PUGET SOUND-SOUTHERN
HOOD CANAL-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY 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-GRAYS HARBOR BAR.
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