287
FXUS66 KSEW 182048
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
148 PM PDT SAT JUL 18 2026
SYNOPSIS
WEAK TROUGHING ALOFT IS MOVING TOWARD THE NORTHEAST, ALLOWING
HIGH PRESSURE TO RESUME FOR THE FIRST HALF OF THE WEEK. 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/
LOW PRESSURE IS ACTIVELY MOVING OFF TO THE NORTHEAST, ALLOWING
FOR THE RIDGE TO BUILD INTO THE NORTHWEST THROUGH THE FIRST HALF
OF THE WEEK. 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
WEST/NORTHWEST FLOW CONTINUES AS A TROUGH EXITS SOUTHERN BRITISH
COLUMBIA. VFR CONDITIONS CONTINUE ACROSS THE AREA WITH SCATTERED
CUMULUS PREVAILING ACROSS MOST OF WESTERN WASHINGTON. CLOUD COVERAGE
SHOULD SLOWLY DECREASE THROUGH THE REST OF THE AFTERNOON AND INTO
TONIGHT WITH VFR CONDITIONS CONTINUING THROUGH TONIGHT. LOW STRATUS
WILL REDEVELOP ALONG THE COAST LATE TONIGHT AND SLOWLY PUSH
INLAND EARLY SUNDAY MORNING. STRATUS WILL GET CLOSE TO THE
SEATTLE METRO AREA; THERE IS A 25-30% CHANCE OF SEEING MVFR OR
LOWER CONDITIONS BETWEEN AROUND 13-17Z 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 AFTERNOON WILL CONTINUE OVERNIGHT.
MVFR TO IFR CONDITIONS EXPECTED TO RETURN AROUND 12-13Z SUN AS
STRATUS PUSHES BACK INLAND. EXPECT CEILINGS TO LIFT AND SCATTER
AFTER 17-19Z 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
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 FROM 5 PM THIS AFTERNOON TO 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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