textproduct: Seattle/Tacoma

SYNOPSIS

A stronger, more typical fall weather system has arrived on the coast this afternoon, and will continue moving into the area through Friday. Rain, increasing winds and the potential for isolated thunderstorms are forecast for the area through tomorrow. Drier, but cool weather is expected over the weekend with additional chances for precipitation early next week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Rain has arrived along the coast and is working its way inland to the Kitsap Peninsula this afternoon. More widespread rain is expected throughout Puget Sound this evening, which will continue overnight. The core of the low pressure system and associated front will be arriving tomorrow morning, and will increase not only the southerly winds along the coast, but the instability for afternoon thunderstorms. There is still some uncertainty as to where the center of the low makes landfall. The ensembles favor it arriving at the Columbia River Bar, but there is still a 10-15% chance that it arrives along coastal Grays Harbor County. If this scenario occurs, winds throughout Puget Sound will be stronger, with gusts upwards of 25-35 mph. Gusts along the coast in this situation would be closer to 50-55 mph. There is still considerable spread between the 10th and 90th percentile solutions for wind gusts. Conditions will be monitored and the forecast will be updated if guidance suggests the more northward track of the low. Current QPF forecasts through Friday evening suggest a half to three quarters of an inch of rain in the lowlands with over an inch along the coast, Olympics and Cascades.

In addition to the gusty conditions, snow levels drop as low as 5,000 to 6,000 feet by late Friday. These elevations could receive a dusting to few inches of snow. The airmass will be unstable through Friday, with around a 20-25% chance of afternoon thunderstorms. These storms will generally favor areas from King County north, and in the terrain of the Cascades. Any storm that develops will be capable of lightning, small hail, brief periods of heavy rain and gusty/erratic winds. Keep this in mind for any outdoor activities tomorrow afternoon.

Conditions dry out quickly overnight on Friday into Saturday morning. Highs will struggle to get much warmer than the low 60s under mostly cloudy skies.

LONG TERM /SUNDAY THROUGH THURSDAY/

Sunday will also be dry with highs again in the low 60s, though with more afternoon sunshine. Zonal flow aloft will continue into Monday, with general troughing over the NE Pacific. Additional systems bringing more rain appear possible on Monday and Tuesday, with a midweek break and more unsettled weather by late in the week.

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AVIATION

Most locations remain under VFR conditions with ceilings slowly lowering this afternoon. A low pressure system will gradually move through tonight into tomorrow. This system will bring rain across the area this evening along the coast and pushing inland overnight into early Friday. Ceilings will lower to MVFR to IFR, with periods of LIFR possible in the heaviest rain along the coast. Lower ceilings will arrive to the coast around 00Z, moving into the interior around 06-09Z tonight and persist through the TAF period. Periods of lower visibility will also be possible in the heaviest rain. There will be a slight (15-25%) chance of thunderstorms on the back end of the system, mainly Friday morning along the coast and Friday afternoon through the interior.

Winds N/NE 5-8 kt this afternoon will ease tonight. Winds will increase along the coast after around 12Z Friday morning, then across the interior after 18Z Friday. Gusts up to 15-25 kt will be possible across much of the area through 00Z Sat. Gusts may locally reach 30 kt through the Strait of Juan de Fuca and the Pacific coast.

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KSEA...VFR conditions continue through this evening with high clouds continuing to lower. MVFR cigs will likely prevail from around 09Z Fri through the end of period. Some periods of IFR may be possible through 15Z Fri in heavier rain. Expect some limitations to visibility as well in heavier rain. N winds will continue at 5-10 kt through this evening. Winds turn to the S Friday morning and increase during the day with gusts up to 20-25 kt after around 18Z Fri.

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MARINE

A low pressure system will continue to slowly make its way through the coastal waters. The low center currently sits of the coast of south-central OR but will make its way to the northwest, likely making landfall around the mouth of the Columbia early Friday morning. Winds will increase over the coastal waters tonight, with the strongest winds over the southern-most zones, especially on the back side of the low center as the winds switch from south/southeasterly to north/northwesterly. That is where the highest confidence for gale force winds will be. Winds will ease over the coastal waters Friday afternoon. Through the interior waters, winds will start to increase Friday morning. The strongest winds will be through the Strait of Juan de Fuca, where gusts may reach up to 35-40 kt. Elsewhere, Small Craft Advisory conditions are expected. Winds will peak across the interior waters Friday afternoon before slowly easing Friday night.

Conditions become calmer through the weekend as high pressure rebuilds offshore. A weak frontal system will dissipate well offshore on Sunday. A stronger system looks to move through the waters on Tuesday, which will be the next chance for gusty winds over the area waters.

Seas 6-8 ft this afternoon will rise to around 10-13 ft, locally as high as 13-15 ft under the strongest winds. Seas then ease Friday night, down to 4-6 ft through the weekend. Seas may rise back to around 10 ft as the next system moves through on Tuesday.

Lastly, there is a 15-20% chance of thunderstorms over the coastal waters on Friday.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Gale Warning from 11 AM Friday to 5 AM PDT Saturday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 2 PM Friday to 5 AM PDT Saturday for Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory from 11 AM to 11 PM PDT Friday for Puget Sound and Hood Canal.

Small Craft Advisory from 5 AM to 11 PM PDT Friday 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.

Gale Warning from 11 PM this evening to 5 PM PDT Friday for Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.