007
FXUS66 KSEW 220317
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
813 PM PDT MON APR 21 2025
SYNOPSIS
DRY AND WARMING CONDITIONS ARE EXPECTED THROUGH THURSDAY
AS HIGH PRESSURE MOVES INTO THE REGION. COOLER CONDITIONS AND
PRECIPITATION CHANCES WILL RETURN TO THE FORECAST FRIDAY INTO THE
WEEKEND.
SHORT TERM /TONIGHT THROUGH THURSDAY/
A VERY THIN BAND OF WEAK
ECHOES PRESENT ON CURRENT RADAR STRETCHING FROM SEABECK THROUGH
EDMONDS INTO MARTHA LAKE. GIVEN THE NORTH TO NORTHWEST WINDS IN THE
AREA, WOULD NOT RULE OUT A VERY WEAK CONVERGENCE ZONE, BUT GIVEN THE
LOW DBZ, ANY PRECIP THERE IS LIKELY EITHER SPRINKLES OR THE LIGHTEST
OF SHOWER. REMAINDER OF W WA GENERALLY FREE OF ECHOES. SATELLITE
SHOWS SOME MID TO LOW CLOUDS LINGERING OVER EASTERN PORTIONS OF THE
OLYMPIC PENINSULA, OVER THE CASCADES, THE SOUTHERN HALF OF SNOHOMISH
COUNTY AND MUCH OF KING COUNTY. AS THE PACIFIC RIDGE NUDGES
EASTWARD, THAT WILL HELP SKIES TO CLEAR OVERNIGHT, AS ADVERTISED
BELOW.
THAT SAID, INHERITED FORECAST LOOKS IN GOOD SHAPE WITH NO NEED FOR
ANY UPDATES THIS EVENING. FOR ADDITIONAL FORECAST DETAILS, PLEASE
REFER TO THE PREVIOUS DISCUSSION SECTION BELOW.
18
FROM PREVIOUS DISCUSSION...WEAK AND SLOW MOVING SHOWER ACTIVITY
CONTINUES ACROSS PORTIONS OF WESTERN WA THIS AFTERNOON. THIS
ACTIVITY WILL CONTINUE TO WANE AS WE GET INTO THE EVENING HOURS.
GENERALLY DECREASING CLOUDS ARE EXPECTED OVERNIGHT. FOR THE MOST
PART LITTLE IMPACT IS EXPECTED. FOR THE SOUTHWEST INTERIOR, THERE
WILL BE A BATTLE BETWEEN AREAS OF FROST AND AREAS OF FOG BETWEEN
ROUGHLY 09-15Z TUESDAY. WITH TEMPERATURES IN THE MID-30S AND THE FOG
POTENTIAL, DECIDED TO HOLD OFF ON ANY FROST PRODUCTS AS PROBABILITY
AND COVERAGE LOOK MARGINAL AT BEST.
FOR THE TUESDAY THROUGH THURSDAY TIMEFRAME, EXPECT DRY CONDITIONS
AND A GRADUAL WARMING TREND. BY THURSDAY, AFTERNOON HIGHS ARE
LIKELY TO REACH THE LOW TO EVEN MID-70S ACROSS MANY AREAS. THAT
SAID, BY THURSDAY AFTERNOON THE RIDGE AXIS WILL SHIFT EAST OF THE
AREA AND WILL OPEN THE DOOR FOR A CHANGE IN THE LONG TERM.
LONG TERM /FRIDAY THROUGH MONDAY/
TROUGHING WILL RETURN FRIDAY
THROUGH THE WEEKEND, BRINGING A RETURN OF COOLER AND SHOWERY
WEATHER. THERE ARE SOME KEY DIFFERENCES WITHIN THE RANGE OF
POSSIBLE OUTCOMES IN TERMS OF THE PATTERN OVER THE WEEKEND WITH
SOME SOLUTIONS KEEPING THE LOW MORE COMPACT AND FURTHER NORTH
IMPACTING WA, WHILE OTHERS RESULT IN CUTOFF LOW THAT BRINGS THE
BULK OF THE ENERGY FURTHER SOUTH. THE MAIN DIFFERENCE FOR WESTERN
WA WOULD BE THE AMOUNT AND COVERAGE OF PRECIPITATION.
BY MONDAY, THERE IS SOME HINT THAT RIDGING MAY TRY TO RETURN TO
THE REGION, STARTING ANOTHER WARMING TREND.
-WOLCOTT-
AVIATION
SHOWER ACTIVITY HAS LARGELY ENDED WITH JUST SOME
SCATTERED CLOUDS LINGERING OVER THE MOUNTAINS AND OVER THE SEATTLE
METRO. ELSEWHERE, CLEAR SKIES. VFR CONDITIONS SHOULD PREVAIL THROUGH
THE TAF PERIOD WITH SCATTERED CLOUDS SLOWLY CONTINUING TO CLEAR OUT
THROUGH TONIGHT AND INTO TUESDAY. SOME PATCHY FOG MAY DEVELOP IN THE
FOG-PRONE VALLEYS (OLM, PWT, PAE, ETC.) EARLY TUESDAY MORNING,
THROUGH PROBABILITIES REMAIN LOW (10-15%). TEMPERATURES MAY GET COOL
ENOUGH FOR FROST FORMATION. WINDS BECOMING LIGHT AND VARIABLE TO
CALM TONIGHT, THROUGH RESUMING DURING THE DAY TUESDAY AS NORTHERLY,
AT AROUND 5 TO 10 KT.
KSEA...VFR CONDITIONS PREVAIL THROUGH THE TAF PERIOD WITH DECREASING
CLOUD COVERAGE TONIGHT INTO TUESDAY. LIGHT SOUTHWESTERLY WINDS
BECOMING SOUTHEASTERLY TO VARIABLE OVERNIGHT, RESUMING AS NORTHERLY
DURING THE DAY TUESDAY 6 TO 10 KT. ANY LIGHT PATCHY FOG THAT
DEVELOPS EARLY ON TUESDAY SHOULD REMAIN SOUTH AND WEST OF THE
TERMINAL.
62
MARINE
HIGH PRESSURE CONTINUING TO GRADUALLY BUILD OVER THE
COASTAL WATERS THIS AFTERNOON AND THIS HIGH PRESSURE WILL REMAIN IN
PLACE. EXPECT PRIMARILY NORTHERLY WINDS OVER THE COASTAL WATERS AND
PUGET SOUND THE NEXT FEW DAYS, STRONGEST EACH AFTERNOON, AND WEST
WINDS THROUGH THE STRAIT. SEAS WILL GRADUALLY SUBSIDE THROUGH THE
WEEK. WHILE SEAS OVER THE COASTAL WATERS WILL REMAIN RELATIVELY
SHORT PERIOD FOR THE NEXT COUPLE OF DAYS, THEY SHOULDN'T BE LARGE
ENOUGH TO WARRANT AN ADVISORY. THE NEXT FRONTAL SYSTEM BEGINS TO
TAKE APPROACH THE COASTAL WATERS LATE THURSDAY AND COULD BRING
ANOTHER INCREASE IN SEAS AND STRONGER WINDS.
HYDROLOGY
NO RIVER FLOODING IS EXPECTED DURING THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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