302
FXUS66 KSEW 121556
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
856 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/
NO SIGNIFICANT CHANGES MADE TO THE FORECAST THIS MORNING. THE
PREVIOUS DISCUSSION CAN BE FOUND BELOW WITH UPDATES TO THE
AVIATION AND MARINE SECTIONS:
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
STRONG LOW-LEVEL ONSHORE FLOW HAS BROUGHT IN WIDESPREAD MVFR STRATUS
FOR MOST TERMINALS THIS MORNING BUT CLOUDS HAVE BEGAN TO SCATTER.
SURFACE WINDS ARE TRENDING LIGHTER BUT WILL 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 IS SCATTERING TO VFR AND IS FORECAST TO REMAIN
IN PLACE THROUGHOUT THE DAY. SOUTHWEST WINDS TRENDING LIGHTER THIS
MORNING BEFORE SWITCHING TO THE NORTHWEST FROM 18Z-21Z AROUND 8-12
KT BEFORE TURNING MORE NORTHEAST AROUND 5 KT LATE.
HPR/41
MARINE
A TROUGH REMAINS ALONG THE COAST WITH AN UPPER LOW IN BC. DOWN AT
THE SURFACE, A STATIONARY FRONT WITH SURFACE LOW PRESSURE REMAINS IN
EASTERN WA, WITH HIGH PRESSURE OVER THE COASTAL WATERS. NO HEADLINES
IN PLACE CURRENTLY ACROSS AREA WATERS. 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/41
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...NONE.
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