511
FXUS66 KSEW 211028
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
328 AM PDT TUE JUL 21 2026
SYNOPSIS
UPPER LEVEL RIDGE CENTERED WELL TO THE SOUTHEAST EXTENDING BACK
OVER WESTERN WASHINGTON THROUGH WEDNESDAY. SOUTHWESTERLY FLOW
ALOFT WITH HIGH CLOUDS MOVING THROUGH AT TIMES. IN THE LOWER
LEVELS LIGHT FLOW WITH A THERMALLY INDUCED SURFACE TROUGH
BOUNCING BACK AND FORTH BETWEEN THE COAST AND THE INTERIOR.
PATTERN CHANGE WEDNESDAY NIGHT INTO THURSDAY WITH REMNANTS OF
TROPICAL STORM ELIDA MOVING THROUGH PRODUCING A CHANCE OF
SHOWERS. UPPER LEVEL TROUGH OVER WESTERN WASHINGTON WITH LOW
LEVEL ONSHORE FLOW FRIDAY THROUGH THE FIRST PART OF NEXT WEEK
FOR A ROUND OF SEASONABLE TEMPERATURES.
SHORT TERM /TODAY THROUGH THURSDAY/
SATELLITE IMAGERY SHOWS HIGH CLOUDS OVER MOST OF THE AREA EARLY
THIS MORNING WITH PATCHY LOW CLOUDS AND FOG ALONG THE COAST.
HIGH CLOUDS KEEPING TEMPERATURES MILD OVERNIGHT WITH MOST PLACES
IN THE LOWER TO MID 60S AT 3 AM/10Z.
UPPER LEVEL RIDGE CENTERED WELL TO THE SOUTHEAST EXTENDING BACK
OVER WESTERN WASHINGTON THROUGH WEDNESDAY. SOUTHWESTERLY FLOW
ALOFT SENDING HIGH CLOUDS THROUGH THE AREA AT TIMES. THERMALLY
INDUCED SURFACE TROUGH ALONG THE COAST THIS MORNING WILL SHIFT
INLAND THIS AFTERNOON, RETREAT BACK TO THE COAST TONIGHT THEN
MOVE INLAND AGAIN WEDNESDAY AFTERNOON. TEMPERATURES ALOFT
WARMING WITH THE 850 MB TEMPERATURES PEAKING IN THE PLUS 22C TO
24C RANGE WEDNESDAY AFTERNOON. ALL THIS ADDS UP TO A PAIR OF
HOT DAYS FOR WESTERN WASHINGTON WITH NEAR RECORD BREAKING HIGH
TEMPERATURES AND MAXIMUM LOW TEMPERATURES. HIGHS TODAY IN 80S TO
MID 90S OVER THE INTERIOR WARMING A COUPLE OF DEGREES WEDNESDAY
INTO THE MID 80S TO NEAR 100. HIGHS ON THE COAST IN THE MID 70S
TO MID 80S BOTH DAYS. LOWS IN THE LOWER TO MID 60S INLAND AND
MID 50S ALONG THE COAST.
A HEAT ADVISORY WILL GO INTO EFFECT THIS MORNING AT 10 AM/17Z
AND REMAIN IN EFFECT UNTIL AT LEAST 11 PM WEDNESDAY EVENING.
IN ADDITION TO THE HEAT, NORTHERLY FLOW AT TIMES WILL PULL
WILDFIRE SMOKE FROM BRITISH COLUMBIA INTO WHATCOM AND SKAGIT
COUNTIES. AN AIR QUALITY ALERT HAS BEEN ISSUED BY THE NORTHWEST
CLEAN AIR AGENCY. WEAK EASTERLY FLOW TODAY WILL ALSO BRING
WILDFIRE SMOKE FROM EASTERN WASHINGTON WEST OF THE CREST. WHILE
INCOMING WILDFIRE SMOKE MAY CAUSE LOCALIZED DEGRADATIONS IN AIR
QUALITY AT TIMES OVER THE MOUNTAINS, THE SMOKE IS NOT EXPECTED
TO MIX DOWN INTO THE LOWER LEVELS AND IS FAVORED TO STAY EAST OF
THE SEATTLE METRO.
CHANGES IN THE PATTERN WEDNESDAY NIGHT INTO THURSDAY WITH
REMNANTS OF TROPICAL STORM ELIDA MOVING THROUGH THURSDAY
MORNING CREATING A CHANCE OF SHOWERS. IN ADDITION TO THE
POSSIBLE SHOWERS LOW LEVEL FLOW TURNING ONSHORE PRODUCING MUCH
COOLER HIGH TEMPERATURES. AFTER LOWS IN THE LOWER TO MID 60S
AGAIN THURSDAY MORNING FOR THE INTERIOR HIGHS COOLING TO THE
70S AND LOWER 80S. FOR THE COAST, LOWS IN THE MID 50S AND HIGHS
IN THE MID 60S.
THE RETURN OF LOW LEVEL ONSHORE FLOW WILL GET RID OF ANY SMOKE
CONCERNS IN THE LOWER LEVELS. FELTON
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
WEAK UPPER LEVEL LOW THAT IS WHAT WILL BE LEFT OF ELIDA
REMAINING OFFSHORE THURSDAY NIGHT THROUGH FRIDAY NIGHT WITH LOW
LEVEL ONSHORE FLOW. UPPER LEVEL LOW WEAKENING INTO AN UPPER
LEVEL TROUGH AND MOVING THROUGH WESTERN WASHINGTON SATURDAY.
ANOTHER CHANCE FOR SHOWERS AS THE TROUGH MOVES THROUGH THE AREA.
WEAK UPPER LEVEL TROFINESS WITH LOW LEVEL ONSHORE FLOW
CONTINUING SUNDAY AND MONDAY. SEASONABLE TEMPERATURES THROUGH
THE PERIOD WITH HIGHS IN THE 60S ON THE COAST AND 70S INLAND.
LOWS IN THE 50S. FELTON
AVIATION
HIGH PRESSURE WILL LEAD TO DRY AND STABLE CONDITIONS ACROSS
WESTERN WA TODAY. LOW CLOUDS MAY CLIP THE COAST EARLY THIS
MORNING OTHERWISE VFR CONDITIONS ARE EXPECTED WITH HIGH CLOUDS
ALOFT. WILDFIRE SMOKE ALOFT ACROSS NORTHWEST WA MAY LIMIT BOTH
HORIZONTAL AND SLANT-RANGE VISIBILITY AT TIMES.
KSEA...VFR TODAY WITH N WIND AROUND 5 KT.
MARINE
STRONG HIGH PRESSURE IS OFFSHORE WITH A THERMAL TROUGH ALONG
THE WA COAST. OVERALL WINDS ARE GENERALLY LIGHT ACROSS WESTERN
WA WITH SEAS UNDER 6 FT. THE THERMAL TROUGH WILL SHIFT INLAND
WEDNESDAY AND THURSDAY WITH STRONG ONSHORE PUSHES EXPECTED
THROUGH THE STRAIT OF JUAN DE FUCA. 33
FIRE WEATHER
ELEVATED FIRE WEATHER CONCERNS THE NEXT TWO DAYS WITH NEAR
RECORD HIGH TEMPERATURES AND VERY DRY CONDITIONS ESPECIALLY IN
THE AFTERNOON HOURS. MINIMUM RELATIVE HUMIDITIES WILL FALL AS
LOW AS 20% TO 30% BOTH TUESDAY AND WEDNESDAY, WITH DRIER
LOCATIONS ACROSS THE SOUTHERN PUGET SOUND POTENTIALLY BOTTOMING
OUT IN THE TEENS. THERE IS A VERY SLIGHT CHANCE OF
THUNDERSTORMS COMING IN FROM THE SOUTH THURSDAY MORNING WHICH
GIVEN THE WARM AND DRY CONDITIONS COULD CAUSE ADDITIONAL
IGNITIONS FROM LIGHTNING. ONSHORE FLOW WILL INCREASE LATER
THURSDAY BRINGING COOLER TEMPERATURES AND BETTER OVERNIGHT RH
RECOVERIES THROUGH THE WEEKEND INTO THE FIRST PART OF NEXT WEEK
EASING FIRE WEATHER CONCERNS. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 9 AM PDT WEDNESDAY FOR CASCADES OF
WHATCOM AND SKAGIT COUNTIES-FOOTHILLS AND VALLEYS OF THE
NORTH CASCADES-LOWLANDS OF WESTERN SKAGIT AND
NORTHWESTERN SNOHOMISH COUNTIES-LOWLANDS OF WESTERN
WHATCOM COUNTY.
HEAT ADVISORY FROM 10 AM THIS MORNING TO 11 PM PDT WEDNESDAY
FOR CITY OF SEATTLE-DOWNTOWN EVERETT / MARYSVILLE AREA-
EASTERN KITSAP COUNTY-EASTERN STRAIT OF JUAN DE FUCA-
EASTSIDE-FOOTHILLS AND VALLEYS OF CENTRAL KING COUNTY-
FOOTHILLS AND VALLEYS OF PIERCE AND SOUTHERN KING
COUNTIES-FOOTHILLS AND VALLEYS OF SNOHOMISH AND NORTHERN
KING COUNTIES-FOOTHILLS AND VALLEYS OF THURSTON AND LEWIS
COUNTIES-FOOTHILLS AND VALLEYS OF THE NORTH CASCADES-
FOOTHILLS OF THE WESTERN AND SOUTHERN OLYMPIC PENINSULA-
LAKE CRESCENT AREA INCLUDING US 101-LOWLANDS OF LEWIS AND
SOUTHERN THURSTON COUNTIES-LOWLANDS OF PIERCE AND
SOUTHERN KING COUNTIES-LOWLANDS OF WESTERN SKAGIT AND
NORTHWESTERN SNOHOMISH COUNTIES-LOWLANDS OF WESTERN
WHATCOM COUNTY-MIDDLE CHEHALIS RIVER VALLEY-NORTHERN HOOD
CANAL-OLYMPIA AND SOUTHERN PUGET SOUND-PORT TOWNSEND AREA-
SHORELINE / LYNNWOOD / SOUTH EVERETT AREA-SOUTHERN HOOD
CANAL.
PZ...NONE.
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