949
FXUS66 KSEW 100353
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
853 PM PDT SUN AUG 9 2026
SYNOPSIS
ZONAL FLOW ALOFT AND ONSHORE FLOW WILL LEAD TO DAYTIME HIGH
TEMPERATURES NEAR SEASONAL NORMALS THROUGH THE FIRST HALF OF
THE WEEK. AN UPPER TROUGH PASSING ACROSS BRITISH COLUMBIA WILL
LEAD TO A THREAT OF SHOWERS IN THE NORTH CASCADES MIDWEEK BEFORE
WARMER CONDITIONS RETURN AT THE END OF THE WEEK AS UPPER
RIDGING REBUILDS OVER THE REGION.
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
MORE MARINE AIR HAS REACHED THE INTERIOR OF WESTERN WASHINGTON
THIS AFTERNOON WITH TEMPERATURES RUNNING 3 TO 5 DEGREES BELOW
THIS TIME YESTERDAY. THE SYNOPTIC PATTERN STAYS IN PLACE THROUGH
MONDAY AND TUESDAY WITH ZONAL FLOW ALOFT AND LIGHT LOW LEVEL
ONSHORE FLOW. THIS TRANSLATES TO MONDAY AND TUESDAY BEING
VIRTUAL CARBON COPIES OF TODAY WITH COASTAL STRATUS MAKING A
BRIEF MORNING VISIT ACROSS THE INTERIOR BEFORE BURNING OFF WITH
HIGH TEMPERATURES RUNNING WITHIN A COUPLE DEGREES OF SEASONAL
AVERAGES. MODELS ARE REACHING A BETTER CONSENSUS WITH UN UPPER
LEVEL TROUGH DIPPING SOUTHWARD ACROSS BRITISH COLUMBIA ON
WEDNESDAY. WHILE CONDITIONS WILL REMAIN MAINLY DRY FOR MOST OF
THE AREA, THE THREAT OF A FEW SHOWERS OR THUNDERSTORMS REMAINS
IN THE CARDS FOR THE NORTH CASCADES WEDNESDAY AFTERNOON AND
EVENING. THIS WILL REMAIN A PRIMARY FOCUS FOR FIRE WEATHER
CONCERNS IN THE COMING DAYS.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
HEIGHTS RECOVER TOWARD THE END OF THE WEEK AS UPPER RIDGING
REBUILDS OVER THE REGION. PROBABILISTIC HEAT GUIDANCE CONTINUES
TO PAINT THE SEATTLE-TACOMA METRO CORE IN 50-70% PROBABILITY
FOR MODERATE HEATRISK ON FRIDAY AND SATURDAY WITH WIDESPREAD
HIGH TEMPERATURES IN THE MID AND UPPER 80S. MODEL TRENDS SUGGEST
THAT THIS MAY BE A RELATIVELY SHORT WARM SPELL. ENSEMBLES ARE
HINTING AT SOME ANOMALOUS TROUGHING JUST OFFSHORE EARLY NEXT
WEEK WHICH SUGGESTS INCREASING ONSHORE FLOW AND COOLER
TEMPERATURES, BUT NOTHING TO SPEAK OF IN THE PRECIPITATION
DEPARTMENT AT THIS TIME.
27
AVIATION
WESTERLY FLOW ALOFT PERSISTS INTO MONDAY AS LOW LEVEL FLOW REMAINS
ONSHORE. MUCH LIKE THE PREVIOUS COUPLE OF DAYS, LIFR/IFR COASTAL
STRATUS WILL SPREAD PARTIALLY INLAND LATE TONIGHT INTO MONDAY
MORNING BEFORE BURNING BACK TO THE COAST MIDDAY. OTHERWISE MOSTLY
CLEAR SKIES WITH SOME HIGH CLOUDS WILL CONTINUE TO PREVAIL.
NORTHWESTERLY WINDS LOOK TO EASE TONIGHT BECOMING MOSTLY LIGHT AND
CALM OVERNIGHT. WINDS WILL INCREASE AGAIN THROUGHOUT THE DAY, WITH A
SWITCH FROM SOUTH TO NORTH ACROSS THE PUGET SOUND INTERIOR WITH A
WESTERLY PUSH DOWN THE STRAIT OF JUAN DE FUCA.
KSEA...VFR THROUGH THE EVENING. LOW CLOUDS WILL LIKELY RETURN AROUND
THE SAME TIME FRAME ON MONDAY WITH A PERIOD OF LIFR/IFR BETWEEN 13Z
AND 17Z. SURFACE WINDS W/NW 7 KNOTS OR LESS THIS AFTERNOON WILL BACK
TO S/SW TONIGHT. WINDS TURN BACK TO N AFTER AROUND 00Z TUESDAY.
27/62
MARINE
BROAD SURFACE HIGH PRESSURE WILL REMAIN LARGELY CENTERED OVER
THE OFFSHORE WATERS WITH LOWER PRESSURE EAST OF THE CASCADES
THROUGH THE WEEK AHEAD. THIS WILL MAINTAIN ONSHORE FLOW OVER
THE NEXT SEVERAL DAYS AND BRING DIURNALLY DRIVEN SMALL CRAFT
ADVISORY STRENGTH WESTERLIES TO THE CENTRAL AND EAST STRAIT OF
JUAN DE FUCA DAILY. A SERIES OF WEAK SYSTEMS PASSING TO THE
NORTH OF THE AREA THIS UPCOMING WEEK MAY STRENGTHEN ONSHORE FLOW
AT TIMES FOR ADDITIONAL RISKS OF GALES ALONG THE CENTRAL AND
EASTERN STRAIT.
SEAS ACROSS THE COASTAL WATERS WILL PRIMARILY PERSIST AT 4 TO 6
FEET AND MAY BECOME STEEP AT TIMES UNDER LOCALLY DRIVEN WINDS
INTO MONDAY. SEAS SUBSIDE TO 3 OR 4 FEET BY TUESDAY BEFORE
INCREASING TO 5 TO 7 FEET MIDWEEK.
27
FIRE WEATHER
A DRY, ONSHORE FLOW PATTERN WITH SEASONABLE TEMPERATURES AND
PERSISTENT GOOD TO EXCELLENT OVERNIGHT RH RECOVERIES THROUGH
TUESDAY. ENSEMBLES CONTINUE TO VERY CONFIDENTLY SHOW AN UPPER
LEVEL SHORTWAVE CLIPPING THE AREA WEDNESDAY, WITH SOME
VARIABILITY IN THE STRENGTH OF THE SHORTWAVE. THIS CONTINUES TO
REINFORCE THE SCENARIO OF THUNDERSTORM POTENTIAL WEDNESDAY
AFTERNOON AND EVENING FOR THE FAR NORTHERN CASCADES. THE NBM HAS
A 20-30% PROBABILITY OVER THE WHATCOM, SKAGIT AND SNOHOMISH
CASCADES THROUGH LATE WEDNESDAY EVENING. WARMER AND CONTINUED
DRY CONDITIONS REMAIN ON TRACK THROUGH THE SECOND HALF OF THE
WEEK, LIKELY RESULTING IN A RETURN OF ELEVATED FIRE WEATHER
CONCERNS FOR SOME AREAS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT MONDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
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