textproduct: Seattle/Tacoma

SYNOPSIS

Dry conditions continue into Wednesday. A frontal system will bring a brief period of lowland rain late Wednesday into Thursday. A stronger front on Friday brings gusty winds and additional precipitation. A cold front moves through over the weekend, with additional systems next week for a continued active pattern.

SHORT TERM /TODAY THROUGH THURSDAY NIGHT/

Dry conditions for most areas this afternoon with a mix of clouds and sunshine. A few showers are moving northwards towards Mount Rainier this afternoon with an upper low well south of the area in California. These showers will dissipate into this evening, with dry conditions into Wednesday AM. A weak frontal system moves across the region Wednesday evening into Thursday bringing lowland rain, and locally breezy winds around Whidbey Island northwards. Mainly dry conditions returns for lowland areas for Thursday afternoon with lingering rain or drizzle in the mountains. Highs in the mid to upper 50s through Thursday.

LONG TERM /FRIDAY THROUGH MONDAY/

A more active weather pattern begins Friday and continues into next week as multiple frontal systems move across Western Washington. The first front arrives Friday bringing lowland rain and gusty winds. South winds will be strongest along the immediate coast and from Admiralty Inlet northwards. NBM probabilities of gusts exceeding 40 MPH on Friday range 40 to 80% in these areas, and will need to monitor the potential for any wind headlines on Friday. A warm front then lifts northwards on Saturday, resulting in continued rain at times for the Olympic Peninsula and near BC, with a brief period of drier weather for some of Puget Sound. The associated cold front then slides across the region Saturday night into Sunday for the return of additional rain and breezy winds. Due to continued foliage on the trees, localized power outages may be possible during this period. Snow levels remain higher Friday into Sunday, mainly 5000 to 8000 feet, for high elevation mountain snowfall. Furthermore, seas rise towards 15 to 20 feet Friday, and will need to monitor high surf concerns along the coast.

Ensembles suggest there may be a brief break in the heavier precipitation Sunday night into Monday, before another front moves into the Pacific Northwest late Monday. The active pattern then continues next week resulting in further lowland rain, mountain snow, gusty winds, and increased waves. Continue to monitor the forecast for additional updates. JD

AVIATION

VFR conditions persist across western Washington this evening as broken mid to high level clouds continue to move across the area. Cloud cover should continue to decrease in coverage this evening and overnight, which will open up the door for areas of low stratus and fog to develop overnight as winds remain light. Confidence is highest in southwest Washington (OLM, PWT) but other sheltered terminals (PAE, BLI) could also see some periods of fog. The biggest uncertainty will be SEA and the metro area terminals, with a 25-30% chc of seeing LIFR conditions. Fog should clear out succinctly around 18Z as southerly winds begin to increase due to an approaching frontal system. MVFR to IFR cigs as well as rain begin to move onshore along the coast by 00Z Thur.

KSEA...VFR conditions through most of the TAF period. High cloud coverage will decrease this evening, opening the door up to a brief period of low stratus/fog development. Chances are highest (25-30% chc) between 13-18Z Thur for a brief period of IFR to LIFR conditions. N/NW winds 5-7 kt decrease to 5 kt or less overnight. Winds switch to S overnight, between 06-12Z Thur, increasing back to 5-7 kt during the day Thursday.

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MARINE

Conditions remain relatively benign today as the area remains under relatively higher pressure with a front approaching from well offshore. Seas in the outermost waters may still be hovering near 10 ft but are slowly easing and should remain around 6-8 ft through tonight. A Small Craft Advisory remains in effect through 4 PM.

South/southwesterly winds will start to increase over the coastal waters early Wednesday morning as the front approaches the area. Small Craft Advisories begin across outer coastal waters first, then including the inner coastal waters by Wednesday afternoon as winds increase. Southerly winds will also increase Wednesday afternoon through the interior Salish Sea from the central Puget Sound up through the southern Strait of Georgia, but confidence is high in winds remaining below advisory thresholds. The front moves through Wednesday evening and winds slowly ease into early Thursday. In addition to winds, seas build back to 10-12 ft late Wednesday and continue into Thursday.

Conditions become more active Thursday night into Friday as another stronger frontal system traverses the area waters. Winds increase area-wide overnight, with 60-80% chances for gale force wind gusts across portions of the coastal waters and the East Strait of Juan de Fuca through Friday morning. Winds look to slowly weaken during the day Friday. Seas will also begin to increase Thursday night, in conjunction with the winds but also as a large, long-period swell group arrives to the coastal waters. Seas will most likely rise to around 15-18 ft, through ensemble guidance shows a 25-40% chance of seas exceeding 20 ft. Seas look to maximize by mid-day Friday before easing Friday night.

The next frontal system, however, will be on its heels with winds increasing once again on Saturday, with higher (50-70%) chances for gale force winds across the coastal waters through early Sunday morning. Winds remain elevated overnight before easing on Sunday. Seas rise once again late Saturday up to 16-20 ft during the day Sunday. Seas ease slightly Sunday night.

Conditions look to remain hazardous going into next week. Additional frontal systems move near or through the area waters almost every day, bringing additional periods of strong to gale- force winds. Deep low centers over the Gulf of Alaska will continue to generate and send several series of large, longer- period waves to the coast, keeping seas at least above 12 ft.

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HYDROLOGY

River flooding is not expected through the next seven days. However, a series of increasingly wet weather systems will bring rain (and high mountain snow) to the region, especially from Friday onward. While current forecasts are not expected to cause flooding, this will begin to saturate soils and raise base flows that could bring a concern with subsequent storms systems.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 1 PM to 10 PM PST Wednesday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Small Craft Advisory until 4 PM PST this afternoon 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.

Small Craft Advisory from 8 AM to 10 PM PST Wednesday 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.