Weather Watch Advisory for 36-48 Hours

From Brendan Cowan, San Juan County/Friday Harbor Department of Emergency Management

Info below is courtesy of National Weather Service in Seattle. Usually it’s when we see mention of gusts in the 70 mph range that we start to see more significant impacts to the islands, usually in the form of outages and downed trees.

Islanders should be prepared for possibility of power outages late Sunday and into Monday.

SYNOPSIS:
A deep low pressure system developing over the Northern Central Pacific Ocean will move rapidly eastward, reaching the area late Sunday night or Monday morning. Confidence is rather high that the low will move inland somewhere between southern Vancouver Island and Westport on the Central Washington coast.

A majority of the more reliable computer forecast models show the low moving onshore near the west entrance to the Strait of Juan De Fuca around 4 AM PST Monday, then take the low into the North Cascades by midday Monday. Another reliable forecast model has been consistently taking the low along about the same track, but about 4-6 hours faster. Some recent computer solutions take the low farther south, on a track from Westport to Seattle early Monday morning.

Local impacts will be strongly influenced by the exact timing and track of the low due to western Washington’s complex terrain and the time of the tides.

EXPECTED IMPACTS:

North Interior of Western Washington including areas around the Strait of Juan De Fuca:

South to southeast winds will develop early Sunday evening and will likely increase to 30 to 40 mph with gusts to 60 mph. Winds will shift to the southwest or west and gusts increase to 70 mph late Sunday night or Monday. the strongest gusts Monday morning are most likely near the Strait of Juan De Fuca.

Coastal flooding is possible along the shorelines of the coastal waters around the morning high tide on Monday. Astronomical tides over the inland waters Monday morning will already be nearly the highest of the year. Low pressure will likely cause tidal anomalies around 2 feet; this is 1.5 to 2 feet above maximum astronomical tide values (where tidal overflow normally begins).

Wind waves 8 to 11 feet through the Strait of Juan De Fuca may batter the western shorelines of Whidbey Island, southern San Juan Island, and areas around Rosaio Strait around the high tide Monday morning if storm force winds develop over the Strait of Juan De Fuca.