James Island to Point Grenville WA out 10 to 60 NM Marine Forecast
| Tonight...Sw Wind 5 To 15 Kt Becoming Se 15 To 25 Kt After Midnight. Wind Waves 1 To 2 Ft Building To 3 To 5 Ft After Midnight. W Swell 10 Ft At 13 Seconds Building To 13 Ft At 15 Seconds After Midnight. A Chance Of Rain In The Evening Then Rain Likely After Midnight. |
| Mon...Se Wind 20 To 30 Kt Becoming S 25 To 30 Kt In The Afternoon. Wind Waves 4 To 6 Ft Building To 8 To 10 Ft In The Afternoon. W Swell 18 Ft At 17 Seconds Subsiding To 15 Ft At 16 Seconds In The Afternoon. Rain. |
| Mon Night...S Wind 25 To 35 Kt Becoming Sw 20 To 30 Kt After Midnight. Combined Seas 14 To 17 Ft With A Dominant Period Of 15 Seconds. Rain. |
| Tue...Sw Wind 5 To 15 Kt. Wind Waves 1 To 2 Ft. W Swell 13 Ft At 14 Seconds Building To 21 Ft At 18 Seconds In The Afternoon. |
| Tue Night...Sw Wind 5 To 15 Kt. Wind Waves 1 To 2 Ft. W Swell 21 Ft At 17 Seconds Subsiding To 19 Ft At 17 Seconds After Midnight. |
| Wed...Nw Wind To 10 Kt. Wind Waves 1 To 2 Ft. W Swell 17 Ft At 17 Seconds Subsiding To 14 Ft At 15 Seconds In The Afternoon. |
| Wed Night...Nw Wind 5 To 15 Kt. Wind Waves 1 To 2 Ft. W Swell 13 Ft At 14 Seconds. |
| Thu...Nw Wind 5 To 15 Kt. Wind Waves 1 To 3 Ft. W Swell 11 Ft. |
| Fri...W Wind 5 To 15 Kt Becoming Se 15 To 25 Kt. Wind Waves 1 To 2 Ft Building To 3 To 5 Ft. W Swell 8 Ft. |
| Area Forecast Discussion National Weather Service Seattle WA 838pm PST Sunday Dec 3 2023 Synopsis An atmospheric river will impact the region Monday through Tuesday, bringing periods of heavy rain to western Washington and an increased risk of river flooding. An upper level trough will cross the region late in the week for a shift toward more showery precipitation, cooler temperatures, and lowering snow levels. A brief break in the active pattern is possible on Friday, before additional systems move through the region over the weekend. .Short Term - Tonight through Wednesday Current radar not terribly active, although there is an area of attention over central Snohomish and Skagit counties looking like a convergence zone. The trends do show this feature fizzling out and precipitation associated with it has been pretty light. Otherwise, W WA finds itself in a bit of a lull this evening and tonight before the expected atmospheric river scenario sets up Monday. That said, inherited forecast remains on track and as such no evening updates are expected. For additional forecast details, please refer to the Previous Discussion section below. 18 From Previous Discussion...Latest radar imagery this afternoon shows some light shower activity persisting along the coast and a convergence zone lingering along the King -Snohomish county border. Overall, hi-res guidance is indicative of the convergence zone lingering into the early evening hours before dissipating. Elsewhere, expect shower activity to dissipate into the evening for a brief lull in the weather in between systems. An atmospheric river is slated to impact the region Monday through Tuesday. Moderate to heavy precipitation is expected to spread northward across western Washington starting Monday morning as a warm front lifts across the region. Snow levels will rise rapidly to 7500-9000 feet through the morning hours as a result. The trailing cold front then looks to stall offshore before making its way across the region on Tuesday. The latest forecast calls for 48 hour rainfall totals between 12Z Monday and 12Z Wednesday generally ranging from 1.5 to 3 inches for the interior lowlands, 3 to 5 inches along the coast, 5 to 9 inches along the Cascades, and 7 to 10 inches across the Olympics. The combination of Quantitative Precipitation Forecast and runoff from rain falling on top of snow in higher elevations will lead to sharp rises on area rivers and an increased risk of river flooding across the region. See the hydro section below for more details. In addition to rain, breezy to locally windy conditions will develop across the region during the afternoon hours and persist through Tuesday morning. Large waves along the coast will build towards 20 feet on Tuesday and may run up further on area beaches at times. Heavier rain associated with the cold front will then gradually sag southward into Oregon on Wednesday, though conditions look to remain showery across western Washington. At this time, additional rainfall amounts look to remain light, from a couple hundredths of an inch to a few tenths. 14 Long Term - Thursday Through Sunday From Previous Discussion...Deterministic models remain in good agreement with an upper level trough shifting eastward through W WA through the day Thursday, keeping precipitation in the forecast into the long term. This system will eject Friday in favor of some long-overdue upper level ridging. Enough lingering moisture may present for some morning and early afternoon showers, but the majority of the afternoon and evening will be dry. The side effect of this ridging is that it will allow for continued cooling as daytime highs slide solidly into the 40s and snow levels continue to lower below pass levels. Deterministic models disagree by 6 or so hours as to when on Saturday to bring the next frontal system into the area, and while ensembles at this point in the forecast offer an array of solutions, the ensemble mean suggests that while some rain can be expected, amounts will be generally light. There are some hints at some atmospheric river support to the back end of this system during the day Sunday, but deterministic models disagree on both placement /GFS (Global Forecast System) favors W WA while ECMWF (European Centre for Medium-Range Weather Forecasts) leans more toward W OR/ and strength /ECMWF shows the AR connections being tenuous at best/. Ensembles however are not biting into this solution at all, suggesting a general down turn in activity at the close of the forecast period. Current forecast blend of models is currently leaning slightly more favorably in the direction of wetter solutions, but not convincingly so, doing little to shore up any confidence for this time frame. 18 Marine A series of frontal systems will make their way across the waters Monday through Thursday. Winds in the inland waters have come down to below Small Craft Advisory, and this lull in winds is expected to continue overnight. Winds will increase again Monday, first along the coast and in the Central and East Strait of Juan de Fuca in the early morning, then for the rest of the coastal waters in the afternoon. Confidence is highest for gales along the coast and for the East Strait, but is less so for the Northern Inland Waters--thus keeping the watch until the next update. The Central Strait looks to avoid headlines Monday night into Tuesday with the southerly winds along the Puget Sound into the Strait of Georgia and tapering down along the coast. While a break in wind headlines for the long term is expected, SCA (Small Craft Advisory) conditions for seas will likely remain along the coast into the end of the week. Seas at 10 to 12 ft will rise to 15 to 17 ft on Monday before reaching 18 to 20 ft Tuesday. Seas then will drop to around 10 ft by Thursday and look to remain around 8-10 ft Friday and into the weekend. LH/18 Hydrology From Previous Discussion...An atmospheric river will impact the region Monday through Tuesday and looks to bring rainfall amounts of 7 to 10 inches in the Olympics, 6 to 9 inches in the Cascades, 3 to 5 inches along the coast and 1.5 to 3 inches to the interior lowlands through early Wednesday. Snow levels will rise rapidly across the region on Monday, topping out and generally ranging between 8000 to 9000 feet by Monday afternoon. A Flood Watch remains in effect for the area through late Wednesday night. The combination of heavy precipitation and rising snow levels will most likely result in river flooding on many rivers across western Washington. Rivers currently look to reach flood stage Monday night or Tuesday. Moderate to major flooding will be possible on some of the bigger rivers like the Snoqualmie, Snohomish and Skagit as well as the lower reaches of the Chehalis. While flooding looks likely across the region, there remains a degree of uncertainty in its scope and extent. This will depend largely on the reaction of the area rivers from runoff produced from rain on snow for river basins in higher elevations and the locations of the heaviest bands of precipitation, so it will be important to stay up to date on the latest forecast developments. In addition to the river flooding, burn scars in the Cascades will have to be monitored with the heavy precipitation forecast. Elevated risks of landslide and debris flows will also be possible, NOAA Seattle WA Office: Watches - Warnings - Advisories WA...Flood Watch through late Wednesday night for Admiralty Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity-Central Coast- East Puget Sound Lowlands-Eastern Strait of Juan de Fuca-Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley Area-North Coast- Olympics-San Juan County-Seattle and Vicinity-Southwest Interior- Tacoma Area-West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes-Western Skagit County-Western Strait of Juan De Fuca- Western Whatcom County. PZ...Small Craft Advisory until 4am PST Tuesday for Grays Harbor Bar West Entrance USA Waters Strait Of Juan De Fuca. Small Craft Advisory from 1am to 1pm PST Monday for Central U.S. Waters Strait Of Juan De Fuca. Gale Warning from 1am Monday to 1am PST Tuesday for East Entrance U.S. Waters Strait Of Juan De Fuca. Gale Watch from Monday morning through late Monday night for Northern Inland Waters Including The San Juan Islands. Small Craft Advisory from 10am Monday to 4am PST Tuesday for Admiralty Inlet. Small Craft Advisory from 1pm Monday to 4am PST Tuesday for Puget Sound and Hood Canal Small Craft Advisory until 10am PST Monday 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. Gale Warning from 10am Monday to 1am PST Tuesday 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. |
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