What is the location of the flooding?

As of Wednesday, November 20, a bomb cyclone struck the Pacific Northwest region, resulting in flooding, high winds, and heavy rainfall (1). About 506,000 homes and businesses in Washington State and 34,000 in Northern California have lost power (2).

Flooding is primarily affecting the Pacific Northwest region of the United States, with the hardest-hit areas being in Washington state, northern California, and parts of British Columbia, Canada. It is possible that flooding could cause rockslides and mudslides in parts of California and Oregon.

What is a bomb cyclone?

A bomb cyclone is a rapidly intensifying storm that forms when atmospheric pressure drops by at least 24 millibars within 24 hours, a process known as "bombogenesis."

These storms typically occur over oceans during cooler months and bring extreme weather, including hurricane-force winds, heavy rain or snow, and severe coastal impacts. The rapid intensification makes them particularly dangerous, as they can unleash significant damage in a short period.

Which cities or areas are affected by the flooding?

Cities across the Pacific Northwest may experience flooding, including (3):

• Bellevue, Washington
• Eureka, California
• Issaquah, Washington
• Lake Stevens, Washington
• Lynnwood, Washington
• Maple Valley, Washington
• Medford, Oregon
• San Francisco, California
• Seattle, Washington

Other areas impacted include coastal cities and towns from northern California to British Columbia.

What is the current containment status of the flooding?

Containment efforts are ongoing. Emergency crews are addressing downed trees, blocked roads, and power outages. Flood warnings and high-risk alerts remain in place, with authorities managing urban flooding, debris flows, and river overflows in vulnerable areas. Restoration of power has begun but remains inconsistent.

Are there any evacuation orders or alerts in place?

Evacuation alerts and safety advisories have been issued, particularly in the northern San Francisco Bay area and parts of Washington State. The Eatonville School District and other local authorities have canceled activities and closed schools due to power outages and safety concerns.

Blizzard warnings and flood watches also serve as indirect evacuation triggers, urging residents to avoid travel and stay in safe locations (3).

How can I protect myself from mold after flooding?

It’s important to take steps to prevent mold after a flood.

• Before entering a flooded area, make sure it is safe and free from electrical hazards or structural damage.
• Use protective gear: wear gloves, goggles, and a KN95/FFP2 mask to minimize exposure to mold spores.
• If there is still standing water, remove it as quickly as possible. Use pumps, wet-dry vacuums, or buckets to extract the water.
• Open windows and doors to facilitate air circulation and use fans, dehumidifiers, and HVAC systems to help dry the space. This step is crucial within the first 24-48 hours after flooding to prevent mold growth.
• Remove and discard any items that have been severely damaged by floodwater and cannot be thoroughly cleaned and dried. This includes carpets, upholstered furniture, mattresses, and any other porous materials.
• Thoroughly clean all hard surfaces with a detergent or cleaner suitable for mold remediation. Use a solution of 1.5 cups of bleach mixed with one gallon of water to disinfect nonporous surfaces. Never mix bleach with ammonia or other cleaning products, as the fumes are toxic.
• Maintain an indoor relative humidity (RH) of 35-50%. High humidity promotes mold growth, so consider using dehumidifiers in damp areas.
• Run a high-performance air purifier for mold, both during and after the mold removal work.
• If the flooding and mold damage are extensive, consider contacting professionals specializing in mold remediation to ensure proper cleanup and restoration.

Remember, mold can pose health risks, so it's important to take these steps promptly and thoroughly. If you experience persistent mold-related health issues or have concerns about extensive mold growth, consult with a medical professional or a mold remediation specialist.