107
FXUS66 KSEW 120821
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
121 AM PDT SUN JUL 12 2026
SYNOPSIS
AN UPPER LEVEL TROUGH OVER THE REGION WILL WEAKEN TODAY AND HIGH
PRESSURE ALOFT WILL REBUILD ACROSS THE AREA MONDAY INTO TUESDAY
FOR A WARMING TREND. ANOTHER WEAK TROUGH OFFSHORE WILL TEMPORARILY
COOL TEMPERATURES SOMEWHAT MIDWEEK BEFORE A LONGER TERM WARMING
TREND BEGINS TOWARD NEXT WEEKEND WITH A STRONG RIDGE OF HIGH
PRESSURE.
SHORT TERM /TODAY THROUGH TUESDAY/
PERSISTENT TROUGHING JUST OFFSHORE WILL KEEP SOME CLOUDS AROUND
TODAY AND HOLD BACK TEMPERATURES TO NEAR CLIMO TODAY BEFORE
LIFTING BACK INTO BRITISH COLUMBIA AS A STRONG UPPER RIDGE
CENTERED EAST OF THE ROCKIES EXERTS A LITTLE MORE INFLUENCE ON
THE AREA. THIS WILL LEAD TO AN UPWARD TREND IN TEMPERATURES WITH
WARMER INTERIOR AREAS GETTING BACK INTO THE 80S MONDAY AND
TUESDAY AND A CHANCE FOR MODERATE HEATRISK FOR SEATTLE METRO
SOUTHWARD.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
HEIGHTS STAY RELATIVELY HIGH INTO WEDNESDAY AS AN UPPER LOW
CUTS OFF OFFSHORE. AS WITH MOST CUT-OFF LOWS, MODELS ARE HAVING
A TOUGH TIME RESOLVING HOW THIS SYSTEM WILL EVOLVE AS IT LIFTS
BACK ONSHORE AROUND THURSDAY. THIS SHOULD TEMPORARILY DELAY AN
IMPENDING EXTENDED WARM SPELL THAT IS STILL EXPECTED TO BEGIN
NEXT WEEKEND. WHILE IT'S STILL EARLY DAYS, WE'LL NEED TO MONITOR
HOW THIS SYSTEM TRACKS ONSHORE BECAUSE IT COULD TRIGGER SOME
CONVECTION...SOMETHING WE DON'T NEED IN FIRE SEASON. MODELS
REMAIN IN RELATIVELY GOOD AGREEMENT WITH STRONG UPPER RIDGING
REGAINING CONTROL BY THE WEEKEND FOR WHAT LOOKS LIKE THE
BEGINNING OF AN EXTENDED PERIOD OF ABOVE NORMAL TEMPERATURES.
27
AVIATION
AN UPPER LEVEL LOW WILL REMAIN SITUATED OVER THE CENTRAL B.C. WITH A
JET STREAK MOVING TO THE EAST. A SURFACE LOW WITH A STATIONARY FRONT
SITS IN EASTERN WA WITH A FEW AREAS OF CONVECTION POPPING UP IN THE
NORTH CASCADES THIS MORNING. THESE WILL LIKELY REMAIN OUT OF MAJOR
TERMINALS AND DIMINISH NO LATER THAN SUNRISE. STRONG LOW-LEVEL
ONSHORE FLOW BEHIND THE STALLED FRONT REMAINS ON TRACK TO BRING IN
WIDESPREAD MVFR STRATUS FOR MOST TERMINALS THIS MORNING FROM 12Z
THROUGH 18Z BEFORE CLEARING. WINDS WILL REMAIN GUSTY OUT OF THE
SOUTHWEST AT 10 KT GUSTING TO 20 KT THROUGH LATE MORNING, WITH THEM
BECOMING LIGHT AS THEY FLIP TO THE NORTHWEST IN THE AFTERNOON TO
AROUND 8-12 KT. EARLY INDICATIONS FOR MONDAY MORNING HAVE 40-60%
CHANCE OF IFR/LIFR CONDITIONS FOR THE IMMEDIATE COAST, AND EAST OUT
TO THE KITSAP AREA. PROBABILITIES FOR ANY CEILINGS ELSEWHERE REMAIN
LOW AT THIS TIME.
KSEA...MVFR STRATUS LIKELY TO ARRIVE AROUND 12Z AND BURN OFF PRIOR
TO 18Z WITH CLEAR SKIES FOR THE REMAINDER OF THE DAY. SOUTHWEST
WINDS AROUND 10 KT GUSTING TO 20 KT THROUGH LATE MORNING, SWITCHING
TO THE NORTHWEST FROM 18Z-21Z AROUND 8-12 KT BEFORE TURNING MORE
NORTHEAST AROUND 5 KT LATE.
HPR
MARINE
A TROUGH REMAINS ALONG THE COAST WITH AN UPPER LOW IN B.C.. DOWN AT
THE SURFACE, A STATIONARY FRONT WITH SURFACE LOW PRESSURE REMAINS IN
EASTERN WA, WITH HIGH PRESSURE OVER THE COASTAL WATERS. A PUSH OF
WINDS ACROSS MOST WATERS IS IN PROGRESS THIS MORNING, WITH STRONGEST
WINDS IN THE STRAIT OF JUAN DE FUCA WHERE A SMALL CRAFT ADVISORY
CONTINUES THROUGH 12Z THIS MORNING. A FEW GUSTS UP TO 20 KT THROUGH
PUGET SOUND CAN'T BE RULED OUT THIS MORNING. THE PUSHES THROUGH THE
STRAIT WILL BECOME MUCH WEAKER GOING THROUGH MIDWEEK, AND ODDS RIGHT
NOW ARE IN FAVOR OF WINDS AND GUSTS REMAINING BELOW 20 KT THROUGH
THE REMAINDER OF THE WEEK. COASTAL WATERS MAY ALSO SEE WIND GUSTS
APPROACH 20 KT TOWARDS THE END OF THE WEEK ON THURSDAY AND FRIDAY
WITH ANOTHER LOW SYSTEM TRACKING THROUGH THE WATERS.
SEAS FOR THE MAJORITY OF THE FORECAST WILL REMAIN AT 4-6 FT, WITH
THE SYSTEM THURSDAY/FRIDAY INCREASING SEAS TO 7-8 FT WITH PERIODS
AROUND 6-8 SECONDS.
HPR
FIRE WEATHER
THE LACK OF OFFSHORE FLOW THROUGH THE MIDDLE OF THE WEEK WILL
KEEP FIRE WEATHER CONCERNS AT A MINIMUM. WARMING TEMPERATURES
LATE WEEK WILL BEGIN TO INCREASE THE FIRE WEATHER RISKS GOING
INTO THE WEEKEND. AN UPPER TROUGH ARRIVING AROUND MIDWEEK WILL
NEED TO BE MONITORED IN THE DAYS AHEAD FOR POTENTIAL CONVECTION
AND ASSOCIATED RISKS OF LIGHTNING STRIKES WITH FUELS NOW RUNNING
QUITE DRY.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
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