655
FXUS66 KSEW 190406
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
906 PM PDT SAT JUL 18 2026
SYNOPSIS
HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH
MIDWEEK. THIS WILL LEAD TO MUCH ABOVE NORMAL TEMPERATURES AND
WIDESPREAD AREAS OF MODERATE TO LOCALLY MAJOR HEATRISK LEVELS. A
PATTERN CHANGE IS POSSIBLE THURSDAY INTO FRIDAY, WITH THE
POTENTIAL FOR ANOTHER ROUND OF MONSOONAL MOISTURE REACHING THE
AREA.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
A RIDGE WILL
BUILD INTO THE NORTHWEST THROUGH MIDWEEK. TEMPERATURES TOMORROW
WILL BE IN THE UPPER 70S TO LOW 80S, CLIMBING TO THE MID TO
UPPER 80S BY MONDAY. THIS CORRESPONDS TO WIDESPREAD MODERATE
HEATRISK ON MONDAY, ESPECIALLY FROM THE SEATTLE METRO AREA
SOUTHWARD INTO OLYMPIA AND THE CHEHALIS VALLEY. VERY LIGHT WINDS
GOING OFFSHORE TEMPORARILY IN THE AFTERNOON WILL LEAD TO VERY
DRY CONDITIONS OVER THE NEXT SEVERAL DAYS.
THE COAST WILL SEE MARINE STRATUS CLOUDS TOMORROW MORNING, WITH
AN INCREASINGLY LIMITED EASTWARD EXTENT OVER THE NEXT SEVERAL
DAYS AS HIGH PRESSURE RETURNS.
LONG TERM /TUESDAY THROUGH SATURDAY/
THE PATTERN IS
CONSISTENT WITH THE RIDGE REMAINING THE DOMINANT FEATURE IN THE
REGION THROUGH THE MIDDLE OF THE WEEK. TEMPERATURES CLIMB INTO
THE UPPER 80S TO LOW 90S ON TUESDAY, AND THEN REMAIN IN THE LOW
90S ON WEDNESDAY. MAJOR HEATRISK VALUES WILL BE CENTERED ON
TYPICAL URBAN HEAT ISLANDS, INCLUDING THE BELLEVUE AREA (60-65%
CHANCE OF MAJOR HEATRISK) AND PORTIONS OF SOUTH KING COUNTY
(50-60% CHANCE OF MAJOR HEATRISK). MODERATE HEATRISK LEVELS
RETURN BY THURSDAY, BUT THE WEATHER PATTERN BEYOND WEDNESDAY
SEEMS A BIT UNCERTAIN. MODELS ARE GENERALLY DIVERGENT ON THE
SOLUTIONS WHERE SOME BRING ANOTHER INFLUX OF MONSOONAL MOISTURE
INTO THE STATE AND OTHERS KEEP THE HIGH PRESSURE IN PLACE. THIS
WILL BE SOMETHING THAT IS MONITORED AS MORE CLARITY EVOLVES AS
THE POTENTIAL FOR ADDITIONAL LIGHTNING STARTS IS STILL A RISK
AFTER ANOTHER ROUND OF HOT AND DRY CONDITIONS.
RIGHT NOW, TEMPERATURES ARE FORECAST TO BEGIN FALLING LATE IN
THE WEEK AND INTO NEXT WEEKEND.
21
AVIATION
WESTERLY FLOW ALOFT THIS EVENING AND REMAINING
OVERNIGHT. VFR CONDITIONS CONTINUE ACROSS THE AREA WITH MOSTLY
CLEAR SKIES PREVAILING ACROSS MOST OF WESTERN WASHINGTON. LOW
STRATUS WILL REDEVELOP ALONG THE COAST LATE TONIGHT AND SLOWLY
PUSH INLAND EARLY SUNDAY MORNING. STRATUS WILL GET CLOSE TO THE
PUGET SOUND TERMINALS; THERE IS A 15-30% CHANCE OF SEEING MVFR
OR LOWER CONDITIONS BETWEEN AROUND 12-17Z SUN. STRATUS SHOULD
GIVE WAY TO VFR CONDITIONS AGAIN LATE SUNDAY MORNING. WINDS ARE
CURRENTLY IN PROGRESS OF SWITCHING FROM WEST/SOUTHWEST TO NORTH
AND SHOULD BE THERE BY TONIGHT. WINDS BECOME LIGHT AND VARIABLE
OVERNIGHT BEFORE NORTH WINDS RESUME DURING THE DAY SUNDAY.
KSEA...VFR CONDITIONS THIS EVENING WILL CONTINUE OVERNIGHT.
THERE'S A 15-25% CHANCE OF MVFR TO IFR CONDITIONS AROUND 12-16Z
SUN AS STRATUS PUSHES BACK INLAND. IF MANIFEST, EXPECT CEILINGS
TO LIFT AND SCATTER AFTER 17Z SUN WITH A RETURN TO VFR
CONDITIONS. WEST WINDS WILL BECOME NORTH THIS EVENING, EASING
BELOW 5 KT OVERNIGHT. NORTH WINDS 5-10 KT EXPECTED DURING THE
DAY SUNDAY.
62/41
MARINE
THE OVERALL PATTERN REMAINS STEADY WITH HIGH PRESSURE
CENTERED OFFSHORE WITH LOWER PRESSURE OVER LAND. THIS WILL
MAINTAIN NORTHWESTERLY WINDS OVER THE COASTAL WATERS. WIND
SPEEDS WILL PICK UP TONIGHT AND THROUGH MUCH OF SUNDAY WHICH
WILL BRING MARGINAL SMALL CRAFT ADVISORY WINDS TO THE OUTER
WATERS, BUT THIS WILL ALLOW SEAS TO PICK UP AND BECOME STEEP,
WITH 6-8 FT SEAS AT AROUND 8 SECONDS. WINDS AND SEAS EASE SUNDAY
NIGHT, AND WINDS LOOK TO REMAIN LIGHT AND SEAS BELOW 6 FT
THROUGH MUCH OF THE WEEK.
AN ONSHORE PUSH IS EXPECTED LATE THIS AFTERNOON AND INTO TONIGHT,
BRINGING SMALL CRAFT ADVISORY WINDS THROUGH THE STRAIT OF JUAN DE
FUCA. ONSHORE GRADIENTS WILL EASE THROUGH THE EARLY PART OF NEXT
WEEK AS THERMALLY-INDUCED LOW PRESSURE DEVELOPS ACROSS WESTERN
WASHINGTON AND OREGON. STRONGER ONSHORE FLOW AND PUSHES DOWN THE
STRAIT LOOK TO RESUME IN THE LATTER HALF OF THE WEEK.
62
FIRE WEATHER
ANOTHER PERIOD OF HOT AND DRY WEATHER WILL
INCREASE FIRE WEATHER CONCERNS THROUGHOUT THE FIRST HALF OF THE
WEEK. TEMPERATURES CLIMBING BACK INTO THE UPPER 80S AND LOW 90S
WITH RELATIVE HUMIDITY VALUES THE DROP INTO THE 20 PERCENT RANGE
ARE EXPECTED THROUGH WEDNESDAY. WHILE WIND DOES NOT LOOK TO BE
A CONSIDERABLE FACTOR IN THE ELEVATED CONDITIONS, THERE WILL BE
PERIODS OF WEAK OFFSHORE FLOW THAT CAN STILL ACT TO DRY OUT THE
ENVIRONMENT AND MAKE FUELS MORE RECEPTIVE. BEYOND WEDNESDAY, THE
PATTERN WILL NEED TO BE MONITORED AS THERE IS A SUGGESTION OF
ANOTHER INFLUX OF MONSOONAL MOISTURE THAT COULD LEAD TO ANOTHER
ROUND OF THUNDERSTORMS LATE IN THE WEEK. DETAILS ON THIS WILL
EVOLVE THROUGHOUT THE FIRST HALF OF THE WEEK.
21
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PDT SUNDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT SUNDAY FOR COASTAL WATERS
FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10
TO 60 NM.
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