San Juan Islands and Northern Inland Waters Marine Forecast
| Today...S Wind 5 To 15 Kt. Wind Waves 2 Ft Or Less. |
| Tonight...Sw Wind To 10 Kt Becoming S 5 To 15 Kt After Midnight. Wind Waves 2 Ft Or Less. A Chance Of Showers After Midnight. |
| Fri...Se Wind 15 To 25 Kt. Wind Waves 2 To 4 Ft. Showers. |
| Fri Night...S Wind 20 To 30 Kt. Wind Waves 3 To 5 Ft. |
| Sat...Sw Wind 15 To 25 Kt. Wind Waves 2 To 4 Ft. |
| Sat Night...S Wind 10 To 20 Kt. Wind Waves 1 To 3 Ft. |
| Sun...Se Wind 10 To 20 Kt Becoming W To 10 Kt. Wind Waves 1 To 3 Ft Subsiding To 1 Ft Or Less. |
| Mon...Sw Wind To 10 Kt. Wind Waves 1 Ft Or Less. |
| Area Forecast Discussion National Weather Service Seattle WA 318am PDT Thu Mar 30 2023 Synopsis A weak upper level trough will move across the region today, bringing showers to portions of western Washington. A seasonally strong frontal system will then move across the area Friday night into Saturday, bringing gusty winds, lowland rain, and periods of heavy mountain snow to the area. Cool upper level troughing will remain over the region into early next week for continued shower activity and below normal temperatures. Short Term - Today through Saturday Conditions remain relatively quiet across western Washington early this morning, with current temperatures ranging in the upper 30s to mid 40s across the area as of 09Z/2AM. A weak upper level trough, embedded in the northwesterly flow aloft, will move across the region today. Moisture with this system remains limited, so expect the main story with this feature to be an increase in cloud cover for the region throughout the day. Afternoon high temperatures will cool a couple of degrees from Wednesday's highs as a result - and are expected to mainly top out in the upper 40s to mid 50s across the region. Despite limited moisture, a few light showers are still possible - primarily along the coast and across any higher terrain. Overall precipitation amounts will remain quite light, with lowland locations across the Olympic Peninsula likely only seeing one or two hundredths of an inch. Areas of higher terrain may see precipitation amounts of a few hundredths of an inch to just over a tenth of an inch. A more substantial shift in the weather is then expected Friday into Saturday as a seasonally strong frontal system moves across the region and brings with it gusty winds, widespread lowland rain, and heavy mountain snow. Showers look to move into western Washington by Friday morning, with the more widespread precipitation making its way along the coast by Friday afternoon and spreading inland Friday night into Saturday. Snow levels will fall below pass level for periods of heavy mountain snow across the Cascade passes. Travel impacts will be possible - and a Winter Storm Watch remains in effect at this time. Southerly winds will pick up Friday afternoon and evening ahead of the frontal system, with gusts between 30-40 MPH possible across the lowlands at times. Afternoon high temperatures will cool a couple degrees again on Friday and will be in the mid 40s to low 50s. The upper level trough influence will then become greater over the region on Saturday, maintaining shower activity across the forecast area. Latest guidance still showing rather cold 500 mb level temperatures at around -35C for this time of year. Thus, with conditions becomingly increasingly unstable in the wake of the front, may see some isolated thunderstorm activity in any heavier showers across western Washington Saturday afternoon and evening. Snow showers will continue for the mountains and highs will trend 5 to 10 degrees below normal - only topping out in the mid to upper 40s. 14 Long Term - Sunday Through Wednesday Cool and unsettled weather will persist through much of the extended period. An upper level low looks to swing through the region Sunday into Monday, which will keep shower activity in the forecast. With a cold airmass remaining in place, snow levels will be rather low (between 400-600 ft) by early Monday morning. Should enough moisture linger for any heavier shower activity, cannot rule out a rain/snow mix for some lowland locations during the early morning hours. Temperatures will remain unseasonably cool Sunday and Monday, with highs generally in the 40s to low 50s and overnight lows expected to dip into the low to mid 30s. The upper level low looks to exit the Pacific Northwest to the south and east on Tuesday and looks to be replaced by an upper level ridge building into the region near midweek. The GFS (Global Forecast System) and ECMWF (European Centre for Medium-Range Weather Forecasts) ensemble solutions continue to show a reduction in the number of wet solutions for the period, but do still have 20-30 percent of the solutions showing some light precipitation. Thus, showers remain in the forecast for both days for now, but do not expect conditions to be as wet as over the weekend. Afternoon highs will warm a few degrees each day - and will be in the 50s. Overnight lows look remain in the 30s. 14 Marine Onshore flow continues today with strongest winds through the Strait of Juan de Fuca - a Small Craft Advisory is in effect. Southerly flow will increase on Friday as a strong Pacific frontal system moves in. Small Craft Advisory winds are likely over all waters. Winds will remain elevated through the weekend as an active weather pattern continues. 33 Hydrology No river flooding expected in the next 7 days. NOAA Seattle WA Office: Watches - Warnings - Advisories WA...Winter Storm Watch from Friday afternoon through Sunday afternoon for West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes. PZ...Small Craft Advisory until 11pm PDT this evening for Central U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 11am PDT this morning for East Entrance U.S. Waters Strait Of Juan De Fuca. |
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