Rare June back-to-back atmospheric rivers hit the Pacific Northwest

A rare June weather event with two back-to-back atmospheric rivers hit the Pacific Northwest on Monday, June 3, 2024, bringing record-breaking rainfall and leaving more than 200 000 people without power.

According to FoxWeather meteorologists, the storms were fueled by the remnants of a former tropical storm in the West Pacific Ocean, with the first of two waves of rain pushing into the region on Sunday, June 2. This first atmospheric river, the more potent of the two, impacted the region on Monday, June 3, 2024, and the second one on Monday evening.

In 24 hours to 04:00 on Monday, June 3, daily rainfall records were broken in several cities. Seattle recorded 16.5 mm (0.65 inches), breaking the previous record of 12.2 mm (0.48 inches) in 2021. Olympia recorded 27.4 mm (1.08 inches), breaking the previous daily record of 17.3 mm (0.68 inches) set in 2010, while Hoquiam recorded 47.5 mm (1.87 inches), breaking the record set in 1962.

The 16.51 mm (1.87 inches) recorded in Hoquiam was the wettest June day since record-keeping began there in 1953.

As of 06:30 LT on June 3, more than 82 000 customers (~205 000 people) across the region were without power. Most of the outages were restored over the next couple of hours, except for 5 600 customers in the Graham area.

Power outages, caused by trees falling on wires and poles, resulted in school closures or delayed classes across the region.

The Washington State Department of Transportation reported several crashes on I-5 blocking lanes in the early morning hours between Tacoma and Seattle.

KING 5 reported many people went out to get food and supplies like gas for power generators.

In addition, strong winds prevented two cruise ships from docking in Seattle, forcing them to anchor in Elliott Bay for hours before tug boats could assist.

Early Monday morning, the National Weather Service (NWS) warned that rain and snow melt will produce heavy runoff over parts of the Northwest and Northern Intermountain Region. Therefore, the Weather Prediction Center (WPC) has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Northern Intermountain Region through Tuesday morning.

“The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable,” NWS forecaster Ziegenfelder noted.

In addition, a wind advisory was issued for lowland areas of western Washington into Tuesday morning. South winds up to 40 km/h (25 mph) were expected, with gusts up to 65 km/h (40 mph) possible.

Early Tuesday (LT), June 4, a front will move onshore over the Pacific Northwest and inland to the Northern Intermountain Region and weaken by Wednesday, June 5. The system will produce additional rain over parts of the Pacific Northwest and Northern Intermountain Region.

References:

¹ Seattle, Portland see record-breaking rain as rare June atmospheric river storms slam Northwest – FOX Weather – June 3, 2024

² Thousands without power across western Washington Monday morning – KOMO News – June 3, 2024

³ Several thousand still without power after strong winds in western Washington – KING 5 – June 3, 2024

Featured image: Atmospheric River slams Pacific Northwest. Credit: NOAA/GOES-West, RAMMB/CIRA, The Watchers. Acquired at 00:20 UTC on June 4, 2024