textproduct: Seattle/Tacoma

SYNOPSIS

An upper-level trough offshore will push inland today. A weak front will follow the trough Sunday into Sunday night. Temporary high pressure Monday before another weak front arrives Tuesday. Dry and warmer weather Wednesday into next weekend as an upper level ridge centered over the southwest builds back towards the Pacific Northwest.

SHORT TERM /TODAY THROUGH MONDAY/

Clouds are continuing to work their way inland this morning and fill in across the area. Breaks of sun and clouds remain on track for the forecast today. See below for an update to the aviation section. 62

Upper level trough offshore moving through Western Washington later this morning into the afternoon hours. Best chances for showers along the coast and over the Northwest Interior. Marine layer filling in over the rest of the lowlands by mid morning. Trough moving through will keep the layer intact this afternoon making for a mostly cloudy day. Temperatures well below normal with highs in the mid 60s to mid 70s.

Another upper level trough digging south offshore tonight. Front associated with the trough stalling offshore as the flow aloft becomes more parallel to the front. Rain developing along the North Coast with a chance of rain west of Puget Sound. Under at least mostly cloudy skies lows in the 50s and lower 60s.

Another day of much below normal temperatures Sunday as the frontal system moves slowly eastward. Rain over the Olympic Peninsula and the coast with rain likely for the Northwest Interior. Mostly cloudy to cloudy skies elsewhere. Highs only in the mid 60s to lower 70s.

Front weakening and moving through Sunday night with a chance of rain or better from about Chehalis northward. Lows in the 50s.

Another weak trough digging offshore Sunday night into Monday. This one a little further offshore allowing a weak upper level ridge to try an build over Western Washington. Chance of showers west of Puget Sound. With the upper level ridge temperatures warming a little with highs in the 70s over the interior. Under mostly cloudy skies high temperatures along the coast in the mid and upper 60s. Lows Monday morning in the 50s. Felton

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

One more weak weather system moving through Tuesday ( is it really the last week of July? ) for another chance of rain. Highs upper 60s to mid 70s inland and mid 60s coast.

Upper level ridge centered over the Desert Southwest will begin building towards the Pacific Northwest Tuesday night. Ridge continuing to slowly build and by Friday 500 mb heights in the mid to upper 580 dms. Low level flow remain onshore Wednesday through Friday keeping temperatures from getting too warm. Highs in the 70s Wednesday warming to the mid 70s to mid 80s Thursday and Friday for the interior. Highs along the coast in the mid 60s Wednesday, near 70 Thursday and Friday.

Is the current streak of Julys with above normal temperatures in Seattle ( currently at 13 ) over? Through the 24th the average temperature for the month is 66.9 degrees, only 0.2 degrees above normal. Current forecast temperatures for the next week put the July average temperature at 66.9 degrees by the end of the month. Normal for the month of July is 67.1 degrees. The last time Seattle had an average monthly temperature in July below 67.0 degrees was 2016 with 66.8 degrees ( the 1981-2010 normal for July was 65.7 degrees so this was still an above normal month ). It's going to be close. Felton

AVIATION

Southwest flow continues aloft with an upper level trough moving into the Pacific Northwest. This is producing a mixed bag of ceilings that straddle MVFR thresholds. Mostly VFR ceilings are expected for interior areas this afternoon with MVFR persisting near the coast with occasional light showers. Deeper moisture with a frontal boundary arrives on Sunday with low MVFR or occasional IFR in stratiform precipitation developing along the coast and interior areas from around KPAE northward. There's moderate confidence that ceilings for central/south sound terminals will drop to high end MVFR at times mid-late Sunday morning.

KSEA...MVFR ceilings are expected to lift to VFR by around 21z. VFR ceilings continue into Sunday morning, but recent guidance confidence is tipping the balance toward a period of high end MVFR ceilings developing 12Z-20Z Sunday. Surface winds S/SW 5 to 8 knots except 9 to 13 knots 21z-03z.

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MARINE

A stalled front offshore today will move inland Sunday into Sunday night. High pressure behind the front Monday. Another front will move into the area waters Tuesday with high pressure again building in behind the front Tuesday night and Wednesday.

Small craft advisory winds over the coastal waters today easing tonight. Diurnal westerly pushes through the Strait of Juan de Fuca in the evenings in the middle of next week could produce small craft advisory winds. Felton

FIRE WEATHER

Fire weather concerns relaxing the next few days with chances for precipitation over the weekend and again Tuesday. Good chance of wetting rains along the north coast and the west slopes of the Olympics Sunday and Sunday night. Dry and warmer conditions beginning the middle of next week. Low level flow remaining onshore for good relative humidity recoveries in the overnight hours. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 PM PDT this afternoon for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.