textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low moving out of the Gulf of Alaska moving down British Columbia coast to the Washington coastal waters Thursday. Strong for early September cold front associated with the low moving through late this afternoon and early this evening bringing rain and gusty winds. The upper level low will remain in the vicinity through the weekend for cool and unsettled weather. Possible drying trend Monday and Tuesday as the low moves out of the area.

SHORT TERM /TODAY THROUGH FRIDAY/

Satellite imagery shows upper level low just southwest of Haida Gwaii with the associated cold front off the coast near 128W. Rain started on the North Coast in the last hour. Slightly unstable air mass ahead of the front with doppler radar indicating some light showers over the foothills and Cascades. Temperatures at 3 am/10Z were in the mid 50s to lower 60s.

Everything still looks on track this morning. Upper level low will continue to drop south today. Cold front off the coast becoming slightly negatively tilted. This will slow down the eastward progress of the front. Rain spreading inland west of Puget Sound this morning and over the remainder of the area this afternoon. Slight chance of thunderstorms well ahead of the front this morning with the unstable air mass. South to southeast winds increasing along the coast and over the Northwest Interior and Admiralty Inlet later this morning. Windy conditions, 20 to 35 mph, continuing into the afternoon hours. Front reaching the coast late this afternoon. The wind advisories for the coastline, Northwest Interior and Admiralty Inlet remain in effect. Highs in the lower to mid 60s.

Front moving through the interior early this evening with steady rain changing to showers. Breezy conditions just ahead and with the front. Winds easing post frontal along the coast early evening and over the interior before midnight. Lows in the mid 40s to mid 50s.

Upper level low off the coast Thursday will slowly drift inland Friday over Oregon. Relatively cool and unstable air mass over the area keeping showers in the forecast with a slight chance of thunderstorms in the afternoons with a little daytime heating. Highs remaining in the 60s. Lows Thursday night in the mid 40s to lower 50s. The last time Seattle had a low in the 40s was June 8th ( 49 degrees ). Felton

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Models in general agreement with the upper level low remaining in the vicinity through the weekend. This is not a scenario the models are going to handle very well as far as the exact placement of the low. At this point will have to keep at least a chance of showers in the forecast. Temperatures slowly warming with highs in the mid 60s to lower 70s. Lows in the upper 40s to mid 50s.

Model solutions in good agreement given the situation with the low kicking out to the east Monday and a weak upper level trough moving over the area Tuesday. This scenario would confine the shower chances to the Cascades both days. Highs remaining below normal, in the mid 60s to lower 70s. Lows in the lower to mid 50s. Felton

AVIATION

South to southwest flow aloft will continue into Thursday as an upper low digs southwards along the coast. Widespread mid and high clouds this morning ahead of a frontal system that will move onshore today. The front moves across Western Washington into this afternoon, with widespread rainfall along the coast this morning sliding into Puget Sound this afternoon. MVFR cigs for the majority of today along the coast, with lowering VFR cigs for the interior sites, briefly becoming MVFR with the frontal passage at some locations. Post-frontal showers are then expected along the Olympic Peninsula tonight. Cigs lowering to low-end VFR and MVFR Thursday morning. South winds increasing this morning, peaking between 16-21z for the coast, and 19-01z for interior sites. Gusts will be strongest along the coast and north of PAE, the exception being CLM. Winds will slowly ease tonight.

KSEA...VFR cigs are expected to continue for the majority of the TAF period with widespread mid and high clouds. Cigs may briefly lower to MVFR around 22-02z during the timing of the frontal passage. Probabilities peak at 30% for MVFR cigs during this period. Rain is expected to begin around 20-21z and continue through 00z. Increasing south winds this morning, peaking between 20-01z, with peak gusts of 25 to 30 kts. Winds slowly ease tonight. JD

MARINE

A low pressure system will continue its way across the region today as its cold front moves through W WA today while the low center moves down through the coastal waters on Thursday. Gale force wind gusts are expected across most of the coastal waters, and through the northern Salish Sea from Admiralty Inlet up through the East Entrance and into the Northern Inland Waters. Wind gusts through the Puget Sound and Hood Canal will increase this morning, reaching Small Craft Advisory criteria by afternoon and will continue into possibly the early evening hours. Portions of the central Strait of Juan de Fuca south and east of Victoria may also see Small Craft to gale force gusts, but the majority of the zone should stay sheltered from the strongest winds. The strongest winds area-wide should start to decrease following the frontal passage tonight. While winds will stay elevated over some of the interior waters, at this time it does not look like additional headlines will be needed. Broad low pressure will remain over region through the end of the week into this weekend though winds look to remain light.

Chances for isolated thunderstorms will pose a threat to the area waters today and Thursday, through probabilities remain minimal (10- 20% chc).

Seas 7-10 ft this morning increasing to 10-13 ft by noon. These heights will not linger, as seas return to 7-9 ft late this afternoon/early this evening. Seas briefly increase then towards 8 to 11 feet tonight into Thursday morning. Seas ease to around 4-6 ft by Thursday night and remain like so through the weekend.

JD/18

FIRE WEATHER

Fire weather concerns remain low through the next week. A strong for the first week of September weather system will bring significant rainfall to the coast and Olympics through Thursday afternoon. Rainfall amounts in the Olympics in the 1.5 to as high as 3 inch range with 1 to 1.5 inches along the coast. Elsewhere amounts will be lower but most areas should see a wetting rain. Rainfall may pose a minor threat to highly sensitive and brand new burn scars. Chances for showers will continue through the weekend with a slight chance of thunderstorms Thursday and Friday afternoon. The risk of new fire starts is low due to the isolated coverage and the increased fuel moisture from the wetting rains. Even with a drier pattern next week temperatures will remain a little below normal keeping fire weather concerns in check. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 8 PM PDT this evening for Island County- Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Port Townsend Area-San Juan County.

Wind Advisory until 5 PM PDT this afternoon for Grays Harbor County Coast-Lowlands of Lewis and Southern Thurston Counties-Northern Washington Coast.

PZ...Small Craft Advisory until 5 PM PDT this afternoon for Grays Harbor Bar.

Gale Warning until 11 PM PDT this evening for Admiralty Inlet- East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 11 PM PDT this evening for Puget Sound and Hood Canal.

Gale Warning 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.

Small Craft Advisory from 5 PM this afternoon to 11 AM PDT Thursday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.