textproduct: Seattle/Tacoma

UPDATE

No changes made to the inherited forecast. The previous discussion remains below along with an updated marine/aviation section.

SYNOPSIS

Split flow aloft with high pressure at the surface producing a dry day today for Western Washington. Flow aloft consolidating tonight into Monday with surface high pressure weakening. Next system moving down the British Columbia coast moving through Tuesday. Weak upper level ridge building Wednesday. Possible system moving by to the north later Thursday into Friday. Strong upper level ridge building Saturday with the low level flow trying to turn offshore.

SHORT TERM /TODAY THROUGH TUESDAY/

Satellite imagery shows just a few high clouds moving through the area early this morning. Temperatures were a little cool at 3 am/10Z ranging from 39 in Shelton to the lower 50s in the Seattle metro area.

Split flow aloft combining with surface high pressure for a dry day today. High clouds moving through this morning with plenty of sunshine this afternoon. Patchy fog developing in mainly in sheltered valleys will be gone by mid morning. With the cool start to the day even with sunshine highs ending up a little below normal, in the lower to mid 60s.

Another cool night tonight with mostly clear skies and light winds at the surface. Lows in the mid 30s to upper 40s.

Flow aloft consolidated Monday with surface high pressure weakening. Next system moving down the British Columbia coast between Haida Gwaii and Vancouver Island by late Monday afternoon. Increasing middle and high level clouds with a chance of rain late in the day along the North Coast. Highs in the 60s.

Front continuing to move slowly southeast Monday night with a rain developing over the North Coast and a chance of rain over the northern portion of the interior. Winds picking up over the Northwest Interior with southeast winds in the 20 to 30 mph range after midnight. Low temperatures much warmer with the cloud cover, in the mid 40s to mid 50s.

Front moving into the area Tuesday with rain spreading over the entire area from the north early in the morning. Windy conditions continuing over the Northwest Interior. There is a chance wind advisories made be needed. Highs in the lower to mid 60s. Felton

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Models in good agreement with the front moving through late Tuesday afternoon/Tuesday evening. Not much cool air behind the front with just a chance of showers overnight. Lows in the mid 40s to lower 50s.

Post frontal showers coming to an end Wednesday morning with high pressure, both at the surface and aloft, building into the area. At least partly sunny skies in the afternoon. Highs in the lower to mid 60s.

High pressure remaining over the area Wednesday night with lows in the mid 40s to lower 50s.

Models having trouble again in the day 5 and 6 period. Operational runs are dry Thursday but there remains a few ensemble solutions trying to bring a weak system over the top of the ridge. Like last night enough of solutions with light precipitation to have a slight chance of showers over the northern portion of the area. Highs in the 60s. Lows in the mid 40s to lower 50s.

Friday the operational ECMWF brings a dissipating system into Western Washington. The GFS has this feature not making it to the area. Ensembles mostly dry but like Thursday enough solutions for a slight chance of showers along the coast and over the North Cascades. Highs in the lower to mid 60s. Lows in the mid 40s to lower 50s.

Better agreement in the models on day 7 with a strong upper level ridge, 500 mb heights in the lower to mid 580 dms, building over the Pacific Northwest. Thermally induced surface trough as far north as the Northern Oregon Coast by late Saturday afternoon. Highs in the 60s. Models keep the pattern intact Sunday. If this continues could easily see some highs in the 70s next Sunday. Felton

AVIATION

Southwesterly flow aloft this morning as W WA finds itself under split flow with a ridge to the north and upper level low to the south. This will transition to northwesterly this afternoon and into Monday. Most terminals reporting light and variable surface winds this morning with speeds less than 5 kts, although terminals with faster winds reporting north to northeasterly winds with speeds 5 to 10 kts. Widespread north to northeasterly winds at these speeds expected to emerge late this morning through the afternoon before light and variable conditions emerge again this evening and tonight.

Widespread VFR conditions persist under weak high pressure, although isolated patches of low clouds can result in occasional MVFR to IFR conditions this morning. VFR area-wide expected late this morning and for the remainder of the TAF period with generally high clouds present.

KSEA...VFR conditions will persist throughout the TAF period. Northerly winds around 10 kts.

MARINE

A weak front will dissipate over the offshore waters today with minimal impacts expected for local waters. Southerly flow will increase Monday night and Tuesday with a stronger frontal system. Weak high pressure and offshore flow will follow on Wednesday.

Seas generally 3-6 ft although some locations in the outer coastal waters could see seas reach 7 ft this morning. Seas will increase throughout the afternoon before reaching 7-9 ft this evening. The front Monday night/Tuesday will boost waves up to 10-12 ft before receding quickly starting Tuesday afternoon.

33/18

SEW WATCHES/WARNINGS/ADVISORIES

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