Marine Weather Net

San Juan Islands and Northern Inland Waters Marine Forecast


TODAY

S
WINDS
10 - 20
KNOTS

TONIGHT

SW
WINDS
25 - 35
KNOTS

SUN

W
WINDS
25 - 35
KNOTS

SUN NIGHT

SW
WINDS
15 - 25
KNOTS

The Marine Weather Forecast In Detail:
PZZ133 Forecast Issued: 257 AM PST Sat Nov 26 2022

SMALL CRAFT ADVISORY IN EFFECT FROM 10 AM PST THIS MORNING THROUGH THIS EVENING ...GALE WATCH IN EFFECT FROM THIS EVENING THROUGH SUNDAY MORNING...
Today...S Wind 10 To 20 Kt Rising To 15 To 25 Kt In The Afternoon. Wind Waves 1 To 3 Ft Building To 2 To 4 Ft In The Afternoon. A Chance Of Showers In The Morning Then Rain Likely In The Afternoon.
Tonight...Sw Wind 25 To 35 Kt. Wind Waves 4 To 6 Ft. Rain In The Evening Then A Chance Of Rain After Midnight.
Sun...W Wind 25 To 35 Kt Easing To 15 To 25 Kt In The Afternoon. Wind Waves 4 To 6 Ft Subsiding To 2 To 4 Ft In The Afternoon. A Chance Of Rain In The Morning Then Showers Likely In The Afternoon.
Sun Night...Sw Wind 15 To 25 Kt Becoming Nw 5 To 15 Kt After Midnight. Wind Waves 2 To 4 Ft Subsiding To 1 To 2 Ft After Midnight.
Mon...N Wind 5 To 15 Kt. Wind Waves 1 To 2 Ft.
Mon Night...Ne Wind 5 To 15 Kt. Wind Waves 1 To 2 Ft.
Tue...E Wind To 10 Kt Becoming Se 5 To 15 Kt. Wind Waves 1 To 2 Ft.
Wed...E Wind 5 To 15 Kt Becoming Ne To 10 Kt. Wind Waves 1 To 2 Ft.
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Area Forecast Discussion
National Weather Service Seattle WA
301am PST Sat Nov 26 2022

Synopsis
Drier weather today with scattered showers mainly for the Cascades and northern areas. A stronger front will bring lowland rain, heavy mountain snow, and breezy winds tonight into Sunday. Convective showers Sunday afternoon into Monday morning for additional mountain snow and lowering snow levels. A much cooler weather pattern through much of next week for potential lowland snow mid-week.

Short Term - Today through Monday
A mix of clouds and fog across the area interior early this morning as shown on satellite, with the majority of fog mainly south of Seattle, with low clouds across Snohomish/Skagit counties with weak convergence and light showers. Mainly drier weather today, however, light showers will continue for Snohomish County northward, especially in the Cascades. The next system will move into Western Washington Saturday night and continue into Monday for additional impacts as highlighted:

Mountain Snow: Snow levels will initially be 3000-3500 feet this evening through tonight for the Cascades then drop to 1000-2000 feet Sunday through Sunday night. The heaviest stratiform precipitation will move southward tonight across the area for heavy snowfall in the mountains. Winter Storm Warnings have been issued for the Cascades for this front. Snoqualmie Pass will likely initially have a rain/snow mix tonight with the front before transitioning to all snow with falling snow levels. Stevens Pass is expected to remain all snow for this event. Snowfall accumulations will range 14-21" for the Passes tonight through Monday morning. Travel impacts are expected due to the heavy snow, make sure to be familiar with WSDOT pass updates through Monday.

Wind: Winds will increase late this afternoon and peak tonight with the front. HREF highligheights the strongest winds being near the water of the northern interior and Puget Sound, particularly Western Whatcom County, and towards western Snohomish/King Counties. Wind gusts of 30 to 40 MPH are expected to be widespread in these areas, as well as along the north Olympic coast. In addition, increasing onshore flow and tight pressure gradients late tonight will promote west winds through the Strait of Juan de Fuca towards Admiralty Inlet and Whidbey Island. West wind gusts of 35 to 45 MPH may be possible during this period. Will have to continue to monitor if headlines are necessary, but localized power outages may be possible. Winds will taper off into Sunday, albeit continuing to be breezy in some areas.

Lowland Precipitation: Rain will be heaviest across the lowlands tonight as the front quickly moves southward. Sunday may feature drier weather in some places, with likely convergence banding and heavier convective showers beginning during the day and continuing through Sunday night. In addition, snow levels will drop Sunday night into Monday morning to near 500-1000 feet. Due to the more convective nature of the showers during this period, snow levels may briefly be lowered to near sea level in the heaviest precipitation for possible rain/snow mix, especially late Sunday night into Monday morning. We're certainly just on the cusp of hi-res guidance for this period, but brief mixing is expected in the heaviest bands, which includes any convergence activity. Little to no snow accumulation is expected for most areas. However, the Cascade Foothills/Valleys will need to be monitored for potential light accumulations due to their higher elevation. Precipitation will taper off on Monday.

Long Term - Tuesday Through Friday
A period of brief, dry weather is expected Monday night into Tuesday morning with lows dropping below freezing for most areas. Re-freeze possible for any untreated road surfaces. The primary focus on the longer-term period will be the next system to impact the Pacific Northwest between Tuesday-Thursday. We briefly discuss a few aspects with this system below.

Guidance is in general agreement an upper trough will slide southeast along the British Columbia coast Tuesday-Thursday, and ensembles have come into a bit better agreement in the depth and intensity of the trough, but minor fluctuations of the systems storm track will greatly influence surface precipitation type during this period. As such, have focused on looking at the WPC cluster analysis (all 90 ensemble members from GFS/CMC/ECMWF) for the 24-hour period ending 00z Thurs. The Cluster Analysis tool is useful in identifying ensemble uncertainty, as well as potential extremes and the forecast. Per the Cluster 500mb heights, approximately 55% of the distribution indicates a deepening trough offshore of Vancouver Island, with a more elongated trough noted on only 21% of the cluster (primarily GFS). This would suggest a deeper, stronger system is likely. One of the main impacts from a stronger system would be increased southwesterly flow, and thus warmer temperatures both at the surface and aloft on Wednesday. This can be seen on the cluster analysis max/min temperatures, with temperatures a tad warmer than the mean with a deeper trough. With all that said, temperatures will still be below average during this period due to the previous trough moving overhead Sunday-Monday, and thus making for a rather tricky setup for potential wintry precipitation in the lowlands due to the lower snow levels. Reviewing NBM guidance for the 72-hour period ending 12z Friday shows widespread 60-90% chance of >1" of snow for the lowlands. Potential for 4 inches or more favors the Cascade Foothills/Valleys (50-80% chance). In addition to the western Kitsap County area (60-90% chance) due to colder air sticking around that area longer. As for the I-5 corridor a general theme of higher probabilities exist north of Seattle (40-70%), and less southward (25-50%). Minor fluctuations in the storm intensity/track will lead to any further adjustments in thinking for lowland snow. For that reason, it will continue to be important to stay updated on the weather forecast during this period. Finally (if you're still reading), the trough will reinforce the cold airmass for the Pacific Northwest late next week. Temperatures will be well below normal for this time period, with widespread lows in the teens/20s and highs in the 30s on Friday. JD

Marine
A strong frontal system will move across the region tonight into Sunday, bringing several rounds of headlines to the area waters. Southerly winds will start to increase across the waters this afternoon, mainly persisting at 15-25 kt. Thus, have issued small craft advisories for all area waters ahead of this next system. Latest hi-res guidance still showing the potential for frequent gusts to gale as this frontal system traverses the waters. Thus, have issued gale watches for increasing southerly winds tonight into Sunday for the coastal waters and for the interior waters of Puget Sound, Admiralty Inlet, the eastern Strait, and the Northern Inland waters. Winds will then shift westerly in the wake of the system, with a strong surge expected down the Strait of Juan de Fuca. Thus, a gale watch has also been issued for the west and central portions of the Strait. Winds along the eastern Strait will shift from strong southerly to strong westerly by early Sunday. Overall, expect winds to peak overnight and will then gradually ease again through the day Sunday. An active pattern will persist heading into next week as additional systems traverse the region, potentially bringing several rounds of additional headlines to the area waters.

Seas will continue to subside to 7 to 9 ft this morning, before increasing again to 10-14 ft by Sunday. Seas look to remain elevated, hovering around 10-12 ft, into the start of next week. 14

Hydrology
No river flooding expected over the next 7 days.

NOAA Seattle WA Office: Watches - Warnings - Advisories
WA...Winter Storm Warning from 1pm this afternoon to 7am PST Sunday for West Slopes North Cascades and Passes.

Winter Storm Warning from 7pm this evening to 10am PST Monday for West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes.

PZ...Small Craft Advisory from 1pm this afternoon to 7pm PST this evening for
Central U.S. Waters Strait Of Juan De Fuca-
West Entrance USA Waters Strait Of Juan De Fuca.

Gale Watch from this evening through late tonight for
West Entrance USA Waters Strait Of Juan De Fuca.

Gale Watch from this evening through Sunday morning for
Admiralty Inlet
Central U.S. Waters Strait Of Juan De Fuca-
East Entrance U.S. Waters Strait Of Juan De Fuca-
Northern Inland Waters Including The San Juan Islands-
Puget Sound and Hood Canal

Small Craft Advisory from 10am this morning to 7pm PST this evening for
Admiralty Inlet
East Entrance U.S. Waters Strait Of Juan De Fuca-
Northern Inland Waters Including The San Juan Islands-
Puget Sound and Hood Canal

Small Craft Advisory from 10am this morning to 4pm PST 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.

Gale Watch from this afternoon through late tonight 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.