Heavy Rain, Gusty Winds and Potential Flooding Possible; Portions of Washington; October 18th - 21st

Photo byNational Weather Force

Forecast Outlook (Friday through Monday):

Over the weekend of October 18-20, 2024, Western and Central Washington will experience a protracted period of inclement weather. Anticipate significant rainfall intensifying over the weekend (periodically) potential snow in higher elevations and strong wind gusts. Key urban and rural areas including Seattle, Tacoma, Olympia, and Spokane will likely encounter urban flooding and travel disruptions due to these conditions.

Upper-Level Forecast:

A significant upper-level trough extending from the Pacific Northwest across the region. This trough is expected to deepen as it interacts with a potent jet stream, which will enhance the storm’s capability to draw in moist air from the Pacific. The jet stream, positioned directly over Washington, will contribute to sustained periods of heavy precipitation by facilitating rapid upward motion of air masses, which helps to cool and condense moisture rapidly.

As the system progresses, shortwave troughs — smaller, more pronounced disturbances in the upper atmosphere — are forecasted to move through the region intermittently. These shortwaves will likely trigger more intense periods of rainfall and could enhance thunderstorm activity periodically as well.

Detailed Forecast:

The weather event will kick off on Friday, October 18, with coastal regions expected to receive 2-3 inches of rain and inland areas around 1-2 inches. The Cascade Range, elevations above 4,000 feet, may see 2-4 inches of snow, particularly affecting mountain pass accessibility. Wind gusts could reach 40-50 mph in exposed coastal and mountainous areas, potentially exceeding these speeds in more vulnerable canyons and passes.

Saturday, October 19, will see continued rainfall with an additional 1-2 inches expected across the state, maintaining a high risk of flooding. The mountains could receive an additional 2-3 inches of snow. Winds will remain strong but are expected to decrease slightly, with gusts around 30-40 mph.

By Sunday, October 20, the system will persist, with rain accumulation forecasted to increase up to 2-3 inches, particularly on the western side. This could elevate the flood risk further, especially in areas already saturated from the previous days’ downpours. Mountainous areas might receive light to moderate snowfall, accumulating an additional 1-2 inches. Winds are anticipated to lessen to about 20-30 mph.

Timing:

The weather conditions are expected to begin intensifying by mid-morning on Friday around 10 AM PT, with peak intensity between 2 PM and 6 PM PT. Saturday will witness continued weather effects with peak times expected around midday. By Sunday, the storm system will not only persist but is expected to strengthen, with peak rainfall and wind conditions forecasted for the afternoon. The system is projected to start tapering off late Sunday night, although residual effects could extend into Monday.

Sina⚡⚡

Co-Owner/CTO and Lead Forecaster of NWF Innovations & NWF Networks

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