textproduct: Seattle/Tacoma

SYNOPSIS

Weather settling down today with upper level trough to the east, surface high pressure over the area and split flow aloft developing off the coast. Little change in the pattern tonight and Sunday. Flow aloft consolidating off the coast Sunday night but next system not reaching the area until Tuesday. Much weaker system most likely will fall apart before it gets to Western Washington Thursday. Upper level ridge building Friday with thermally induced surface trough developing along the Oregon coast.

SHORT TERM /TODAY THROUGH MONDAY/

No major updates have been made this morning. See below for an updated aviation section.

Dry weekend in store for Western Washington. Upper level trough east of the area early this morning. Surface high pressure building today. Split flow aloft developing off the coast today as well. Little change in the pattern tonight and Sunday. Patchy fog developing this morning will dissipate before late morning. A little more fog coverage Sunday morning as the air mass continues to calm down. Highs today and Sunday even with some sunshine a little below normal, lower to mid 60s. Lows tonight in the 40s and lower 50s.

Pattern changes beginning Sunday night with the flow aloft becoming consolidated off the coast. Next system well to the northwest, near Haida Gwaii. Mostly clear skies allowing temperatures to drop into the upper 30s and 40s. The forecast low of 46 at Seattle-Tacoma airport would be the coldest low since 45 degrees on May 30th.

Increasing middle and high level clouds Monday as the next weather system continues to move southeast down the British Columbia coast. Chance of rain along the north coast by late in the afternoon. Highs again in the lower to mid 60s. Felton

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Models in good agreement with rain out ahead of the system over the northern portion of the area Monday night. Slow moving front dragging through Western Washington Tuesday into Tuesday night. Not much cool air behind the front with minimal post frontal shower activity Wednesday.

Inconsistency in the solutions increasing Wednesday night through Thursday night. Operational runs are dry but enough ensemble solutions indicating light precipitation to keep slight chance pops in the forecast. Confidence in this scenario not very high. Will not be surprised if the pops fall out of the forecast in the next few runs.

ECMWF has strong upper level ridge building Friday with thermally induced surface trough developing along the Oregon coast. GFS has this scenario as well but is 24 hours behind the ECMWF. For now the general idea is dry and warmer heading into next weekend. Felton

AVIATION

Northwesterly flow aloft this morning and this afternoon as an upper level ridge builds over the coastal waters. This will turn more zonal this evening as split flow develops between this low and a developing trough off the OR waters. Surface winds south to southwesterly this morning before turning more north to northeasterly this afternoon. Speeds generally 4-8 kts this morning before increasing to 8-12 kts this afternoon. Wind speeds expected to ease tonight back into that initial 4-8 kts range.

Most locations still seeing VFR conditions this early morning although some isolated MVFR to IFR conditions are present. As winds continue to ease this morning, cigs expected to lower due to abundant low-level moisture with widespread MVFR/IFR conditions expected by 12Z this morning. Cigs expected to lift and return to VFR in the usual 18-20Z time frame and persist for the remainder of the TAF period.

KSEA...VFR conditions in place with FEW-SCT clouds around 2000 ft. VFR still expected around 18Z with skies clearing throughout the day thanks to building upper level ridge. Southerly surface winds turning northerly after 18Z with speeds increasing to 8-12 kts.

33/18

MARINE

Weak high pressure and winds turning light offshore today. On Sunday, an approaching frontal system will dissipate over the offshore waters. A stronger frontal system will reach WA Monday night and Tuesday with increasing south winds. Additional headlines may be needed for this time frame should forecast remain consistent.

Seas generally 5-7 feet and will continue to ease this morning until reaching 3-5 ft by noon today. Wave heights rebound this evening slightly this evening to 4-6 ft before reaching 7-9 ft Sunday and into Monday. With frontal passage expected Tuesday, seas may rise to 9-11 ft and may need headlines.

33/18

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.