943
FXUS66 KSEW 071620
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
920 AM PDT TUE JUL 7 2020
SYNOPSIS
AN UPPER DISTURBANCE WILL CROSS THE REGION TODAY WITH
A FEW SHOWERS AND COOLER TEMPERATURES. AFTER A SHORT BREAK ON
WEDNESDAY, ADDITIONAL WEATHER SYSTEMS WILL ROTATE THROUGH THE
REGION ON THURSDAY AND OVER THE WEEKEND FOR CONTINUED COOLER THAN
NORMAL TEMPERATURES AND A CHANCE OF SHOWERS AT TIMES.
SHORT TERM /TODAY THROUGH THURSDAY/
ANOTHER UPPER LEVEL TROUGH
IS SHIFTING ONSHORE TODAY, PROVIDING FOR INCREASING SHOWERS AND
ABUNDANT CLOUD COVER, ALONG WITH COOLER AIR SETTLING INTO THE
REGION. THE TROUGH WILL SHIFT EAST OF THE CASCADES THIS AFTERNOON
WITH WEAK UPPER RIDGING BUILDING INTO THE AREA LATE TONIGHT AND
WEDNESDAY. ALTHOUGH WEDNESDAY LOOKS DRIER FOR MOST OF THE AREA,
PERSISTENT LOW LEVEL ONSHORE FLOW WILL LIKELY ENSURE SIGNIFICANT
CLOUD COVER WITH ONLY SOME PARTIAL SUNSHINE OVER INTERIOR LOWLAND
AREAS IN THE AFTERNOON. THIS WILL HELP BOOST AFTERNOON HIGH
TEMPERATURES BY A FEW DEGREES, BUT THEY WILL REMAIN BELOW NORMAL
FOR THIS TIME OF YEAR. THE NEXT IN THE SERIES OF WEAK UPPER
TROUGHS MOVES ONSHORE ON THURSDAY FOR AN ADDITIONAL ROUND OF
SHOWERS AND TEMPERATURES REMAINING ON THE COOL SIDE. 27/12
LONG TERM /FRIDAY THROUGH MONDAY/
WEAK UPPER RIDGING RETURNS
ON FRIDAY. BY LATER FRIDAY AND PART OF SATURDAY, WESTERN
WASHINGTON WILL BE ON NORTHERN PERIPHERY OF A VERY STRONG UPPER
RIDGE EXPECTED TO DEVELOP OVER THE FOUR CORNERS REGION. THIS
BRIEFLY PUSHES 500 MB HEIGHTS INTO THE 576-580 DAM RANGE. LOW
LEVEL FLOW WILL REMAIN ONSHORE, THOUGH, SO THAT WILL TEMPER ANY
KIND OF BRIEF WARM UP WE SEE AT THE END OF THE WEEK. IF ANYTHING,
WE'LL SEE TEMPERATURES CLOSER TO NORMAL LEVELS FRIDAY AFTERNOON
AND PERHAPS SATURDAY. BUT ALL GOOD THINGS MUST COME TO AN END AS
YET ANOTHER UPPER TROUGH IS EXPECTED TO SWING ACROSS THE AREA IN
THE SUNDAY/MONDAY TIME FRAME FOR ANOTHER POSSIBILITY OF SHOWERS
AND COOLER TEMPERATURES. 27
AVIATION
CEILINGS THIS MORNING ARE LARGELY MVFR AT THE TAF SITES
AND THESE CONDITIONS WILL LIKELY PERSIST INTO THE AFTERNOON HOURS.
LOCAL RADARS ARE PICKING UP ON SOME LIGHT SHOWERS ACROSS THE AREA,
SOME OF WHICH MAY TEMPORARILY DROP CEILINGS DOWN TO IFR. ALTHOUGH
SIGNIFICANT RECOVERY IS NOT EXPECTED TODAY, CEILINGS MAY BE ABLE TO
LIFT TO LOW END VFR BY MID-LATE AFTERNOON. THEY WILL LIKELY THEN
DROP BACK TO MVFR AGAIN OVERNIGHT. WINDS WILL REMAIN OUT OF THE
SOUTH AT 8-12KTS, THO WILL LIKELY TAKE ON MORE OF A NW COMPONENT AT
CLM AND PAE AS WESTERLY WINDS PUSH DOWN THE STRAIT.
KSEA...MVFR CEILINGS WILL LINGER INTO THE AFTERNOON BEFORE
ATTEMPTING TO RECOVER BACK TO LOWER-END VFR LATER IN THE DAY. WINDS
WILL REMAIN OUT OF THE SOUTH AT 8-12KTS.
KOVACIK
MARINE
NO CHANGES WERE MADE TO THE ONGOING MARINE FORECAST THIS
MORNING AND NO HEADLINES ARE CURRENTLY IN PLACE. PREVIOUS DISCUSSION
HAS BEEN INCLUDED BELOW:
WEAK ONSHORE FLOW WILL CONTINUE INTO SATURDAY AS
HIGH PRESSURE REMAINS CENTERED OFFSHORE. THERE IS THE POSSIBILITY
OF LOW END SMALL CRAFT ADVISORY WINDS IN THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA EACH EVENING. THE DAYS WITH THE BEST
CHANCES WILL BE THIS WEEKEND.
KOVACIK/FELTON
HYDROLOGY
THE DAILY HYDROLOGY DISCUSSION HAS ENDED UNTIL THE
START OF THE NEXT RAINY SEASON; IT WILL ONLY BE UPDATED AS NEEDED
UNTIL THEN.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/SEATTLE
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