775
FXUS66 KSEW 202205
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
305 PM PDT TUE OCT 20 2026
SYNOPSIS
DRY WITH WARMER THAN NORMAL DAYTIME TEMPS WILL LINGER THROUGH
WEDNESDAY. A WEAK SYSTEM THURSDAY WILL BRING INCREASED CLOUDS,
NEAR NORMAL TEMPERATURES AND A FEW LIGHT SHOWERS. DRY AND
CONTINUED NEAR NORMAL TEMPERATURES FRIDAY, FOLLOWED BY A CHANCE
OF A WEAK SYSTEM OVER THE WEEKEND.
SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/
DRY WITH NEAR-NORMAL TO SLIGHTLY COOLER THAN NORMAL OVERNIGHT
LOWS TONIGHT. LIGHTER WINDS INTO WEDNESDAY MORNING WILL ALLOW
FOR MORE EARLY MORNING PATCHY FOG FORMATION IN SHELTERED
LOCATIONS. MORNING SHALLOW STRATUS/FOG SHOULD LIFT AND SCATTER
LATE MORNING WITH ANOTHER WARM OCTOBER DAY. A WEAK UPPER LEVEL
SYSTEM CONTINUES TO BE EXPECTED TO BRUSH THE AREA THURSDAY. THE
MAIN IMPACT WILL BE MORE CLOUD COVER AND NEAR NORMAL
TEMPERATURES. HIGH RESOLUTION ENSEMBLES LIKE THE REFS SHOWING
VERY LIMITED, SHORTLIVED SHOWERS MAINLY IN THE OLYMPICS AND
NORTH CASCADES THURSDAY AFTERNOON AND EVENING.
LONG TERM /FRIDAY THROUGH TUESDAY/
ENSEMBLES IN FAIR ALIGNMENT WITH THE OVERALL PATTERN FRIDAY
BECOMING MORE ZONAL BUT DRY FRIDAY. FOR THE WEEKEND, ENSEMBLE
CLUSTERS IN GOOD AGREEMENT WITH THE OVERALL PATTERN INDICATING
AN UPPER LEVEL TROUGH MOVING ACROSS THE NE PACIFIC AND GULF OF
ALASKA FRIDAY NIGHT, THEN SHEARING INTO A MORE CONSOLIDATED
TROUGH MOVING INTO BRITISH COLUMBIA SATURDAY AND A TRAILING
UPPER LEVEL LOW OVER THE EASTERN PACIFIC. THE GRAND ENSEMBLE
SHOWING GOOD AGREEMENT ON THE OVERALL IDEA OF THIS UPPER LEVEL
TROUGH MOVING SOUTH AND EAST THROUGH BRITISH COLUMBIA ITSELF OR
ALONG WEST ALONG THE BC INTO WESTERN WASHINGTON SATURDAY NIGHT
INTO SUNDAY. NEARLY HALF (48%) OF THE ENSEMBLE MEMBERS FAVOR
THE MORE DIRECT APPROACH WITH A MORE CONSOLIDATED TROUGH. THE
REMAINING 52% SHOW EITHER SLOWER MORE NORTHERLY TRACK OR EVEN
OFFSHORE TRACK FOR THE TROUGH. THE MORE CONSOLIDATED TRACK WOULD
RESULT IN A MORE ORGANIZED, BUT LIKELY WEAK SYSTEM MOVING
THROUGH THE AREA SATURDAY NIGHT INTO SUNDAY, WHERE THE
NORTHERLY/OFFSHORE SCENARIOS WOULD LIKELY RESULT IN MORE LIMITED
PRECIPITATION BRUSHING THE AREA SUNDAY OR EVEN DELAYED INTO
MONDAY. THE OVERALL PATTERN EARLY NEXT WEEK LOOKS FAIRLY EVENLY
SPLIT WITH 49% OF THE GRAND ENSEMBLE SHOWING SOME DEGREE OF
RIDGING EARLY IN THE WEEK, AND 51% SOME DEGREE OF TROUGHING.
AVIATION
AN UPPER LEVEL LOW CONTINUES TO SPIN OFF CA WITH DRY
AND STABLE CONDITIONS ACROSS WESTERN WA. THE FLOW ALOFT IS
SOUTHWESTERLY. PATCHY, SHALLOW, FOG WILL LIKELY DEVELOP IN THE
INTERIOR WEDNESDAY MORNING FOR A BRIEF PERIOD OF LIFR
CONDITIONS. FOG WILL SCATTER OUT BY 18-20Z FOR A RETURN OF VFR
CONDITIONS. 33
KSEA...VFR CONDITIONS CONTINUE THIS AFTERNOON AND EVENING. A
BRIEF PERIOD OF SHALLOW/PATCHY FOG IS POSSIBLE EARLY WEDNESDAY
MORNING FOR LIFR CONDITIONS. OTHERWISE, VFR EXPECTED BY
THE AFTERNOON. N WIND TO 10 KT, BECOMING NE 5 KT OVERNIGHT,
THEN LIGHT AND VARIABLE WEDNESDAY MORNING. WINDS WEDNESDAY
AFTERNOON WILL BE MORE W TO NW AROUND 5 KT. 33
MARINE
WEAK HIGH PRESSURE WILL LEAD TO GENERALLY LIGHT WINDS
OVER THE WATERS THROUGH WEDNESDAY. ONSHORE FLOW WILL INCREASE ON
THURSDAY AS A COLD FRONT MOVES INLAND. SEAS WILL BUILD TO 10-15
FT THURSDAY NIGHT THEN GRADUALLY SUBSIDE UNDER 10 FT ON FRIDAY.
THE FLOW WILL TURN OFFSHORE THIS WEEKEND AS A THERMAL TROUGH
FORMS ALONG THE COAST. LOW PRESSURE WILL WEAKEN OVER THE
OFFSHORE WATERS EARLY NEXT WEEK. 33
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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