842
FXUS66 KSEW 202222
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
222 PM PST THU FEB 20 2020
SYNOPSIS
DRY CONDITIONS WILL PERSIST INTO FRIDAY. A WEAK FRONT
MAY BRING A FEW LIGHT SHOWERS ON SATURDAY, WITH A MORE ROBUST
SYSTEM EXPECTED FOR SUNDAY. THIS SYSTEM WILL BRING LOWLAND RAIN
AND MOUNTAIN SNOW TO THE AREA, WHICH WILL LINGER INTO MONDAY. DRY
CONDITIONS RETURN FOR TUESDAY AND LAST THROUGH MID-WEEK.
SHORT TERM /TONIGHT THROUGH SUNDAY/
HIGH PRESSURE AND OFFSHORE
FLOW CONTINUES ACROSS WESTERN WA TODAY FOR DRY AND MILD WEATHER.
SKIES ARE MOSTLY CLEAR THIS AFTERNOON WITH TEMPERATURES IN THE
50S. TEMPERATURES WILL BE CHILLY OVERNIGHT UNDER CLEAR SKIES AND
LIGHT WINDS. EXPECT LOWS IN THE 20S TO LOWER 30S ONCE AGAIN.
THE RIDGE WILL EXITS EAST ON FRIDAY WHILE THE FLOW ALOFT BECOMES
MORE WESTERLY OR ZONAL. A WEAK SYSTEM MOVING INTO B.C. WILL
SPREAD HIGH CLOUDS INTO WESTERN WA. OTHERWISE, WE'LL SEE ONE MORE
DRY AND MILD DAY ACROSS THE REGION.
RAIN RETURNS LATE FRIDAY NIGHT INTO SATURDAY AS A WEAK FRONTAL
SYSTEM CLIPS WESTERN WA. OVERALL, PRECIPITATION AMOUNTS LOOK LIGHT
AND MOST AREAS WILL SEE LESS THAN 0.10" THROUGH THE PERIOD.
A STRONGER AND WETTER PACIFIC FRONTAL SYSTEM IS SLATED FOR SUNDAY.
THIS SYSTEM WILL BRING MORE RAIN, GUSTY WINDS AND POSSIBLY HEAVY
MOUNTAIN SNOW TO THE AREA. SNOW LEVELS WILL REMAIN LOW, AROUND
3000 FT, WITH ACCUMULATING SNOW EXPECTED AT THE HIGHER PASSES
(LIKE STEVENS AND WHITE PASS). SNOQUALMIE PASS MAY SEE A RAIN/SNOW
MIX. WINDS WILL BE GUSTY (OUT OF THE S/SW) AS THE COLD FRONT
MOVES THROUGH THE INTERIOR SUNDAY AFTERNOON - GUSTS TO 40 MPH
POSSIBLE. SHOWERS WILL MOSTLY IMPACT THE CASCADES SUNDAY NIGHT
UNDER POST-FRONTAL ONSHORE FLOW. WILL LIKELY SEE A CONVERGENCE
ZONE DEVELOP WHICH MAY BRING MORE HEAVY SNOW TO STEVENS PASS. 33
LONG TERM /MONDAY THROUGH THURSDAY/
SHOWERS WILL LINGER INTO
MONDAY AS ONSHORE FLOW CONTINUES. AN UPPER LEVEL RIDGE WILL BUILD
INLAND ON TUESDAY FOR A BREAK IN THE PATTERN. THE RIDGE MAY
FLATTEN OVER THE PAC NW ON WEDNESDAY AS A WEAK FRONT CLIPS THE
REGION. HIGH PRESSURE WILL REBUILD LATE IN THE WEEK, PUTTING US
BACK IN A RELATIVELY QUIET PERIOD OF WEATHER. 33
AVIATION
VFR CONDITIONS WITH GENERALLY LIGHT AND VARIABLE WINDS
AT NEARLY ALL TAF SITES. HQM CONTINUES TO HAVE EAST-SOUTHEASTERLY
PREVAILING WINDS AROUND 10 KNOTS, WITH THE LATEST METAR REPORTING
3SM DUE TO HAZE AT THIS HOUR. OTHERWISE, FOG IS EXPECTED TO DEVELOP
AT AND AROUND OLM OVERNIGHT.
KSEA...VFR CONDITIONS WITH WINDS CURRENTLY OUT OF THE NW AT 7KTS.
WINDS ARE EXPECTED TO WEAKEN AND SHIFT BACK TO AN EASTERLY DIRECTION
ENE TO ESE OVERNIGHT BEFORE BECOMING SOUTHERLY AFTER DAYBREAK.
SPEEDS BELOW 7KTS EXPECTED. INCREASING HIGH CLOUDS AOA 25K FT
FRIDAY.
PULLIN
MARINE
LIGHT OFFSHORE FLOW WILL CONTINUE THROUGH FRIDAY MORNING
BEFORE GIVING WAY TO LIGHT ONSHORE FLOW DURING THE DAY. A WEAKENING
FRONT WILL MOVE THROUGH THE AREA SATURDAY, WITH A SECOND FRONT
MOVING THROUGH THE AREA SUNDAY INTO SUNDAY NIGHT. THE SECOND FRONT
WILL YIELD INCREASING WINDS AND SEAS, WITH THE POTENTIAL FOR STRONG
WINDS SPREADING FROM THE NEARSHORE WATERS INTO THE STRAIT OF JUAN DE
FUCA ON SUNDAY.
PULLIN
HYDROLOGY
RIVER FLOODING IS NOT EXPECTED OVER THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/SEATTLE
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