A freezing fog advisory was issued by the National Weather Service on Sunday at 1:32 a.m. in effect until 9 a.m. for West Central Willamette Valley, East Central Willamette Valley, Benton County Lowlands and Linn County Lowlands.

The weather service states to expect, "Visibility one quarter mile or less in freezing fog."

"Low visibility could make driving conditions hazardous," explains the weather service. "If driving, slow down, use your headlights, and leave plenty of distance ahead of you. State air quality agencies highly recommend that no outdoor burning occur and that residential wood burning devices be limited as much as possible. According to state air quality agencies, prolonged periods of stagnant air can hold pollutants close to the ground where people live and breathe. Check with your local burn agency for any current restrictions in your area. People with respiratory illness should follow their physician's advice for dealing with high levels of air pollution during periods of stagnant air, especially if an Air Quality Alert is in effect for your area. Alternatively, you could also type your location into the search bar found on the top-left hand side of the homepage. From there, you will see an Air Quality Alert listed at the top if one is in effect for your location; you can click the alert to read more details if applicable."

When a freezing fog advisory is in effect, it indicates that fog is developing while surface temperatures hover at or dip below the freezing point. In such conditions, the minuscule liquid droplets within the fog can instantaneously freeze upon contact with various surfaces, including vehicles and roadways. Freezing fog poses heightened risks for driving, boating, flying, and other modes of transportation. Typically, visibilities plummet to a mile or less.

What is a freezing fog?

Freezing fog, a close cousin to ice, forms the same way as regular fog. Both fog and freezing fog start when the skies are clear, heat radiates into space, and as a result, the Earth's surface cools down. As this cooling progresses, the air's capacity to retain moisture decreases, triggering the condensation of water vapor into minuscule liquid droplets -- the essential components of fog. When this fog forms in sub-zero temperatures, its water droplets remain in liquid form, a phenomenon known as "Supercooling". In essence, supercooling occurs when a liquid, despite being below its freezing point, remains in a liquid state due to the absence of a freezing surface.

When these supercooled droplets encounter surfaces, they undergo a remarkable transformation, crystallizing into delicate ice structures known as rime. This transformation is often visible on vertical surfaces exposed to prevailing winds, as well as on trees, plants, and other elements in the environment. In fact, rime can form on a variety of surfaces, including stairs, railings, sidewalks, roads, and even vehicles.

What is black ice?

Black ice, also known as clear ice, refers to a delicate, nearly invisible layer of glaze ice that forms on various surfaces, especially on roadways. Despite its name, the ice is not black, but possesses exceptional transparency, enabling the underlying black pavement of the road, to remain visible.

The formation of black ice is frequently attributed to freezing fog, which can swiftly coat roadways with this treacherous hazard. Its near-invisibility renders black ice exceptionally perilous, as it poses a significant challenge for road users to detect.

How to stay safe?

When freezing fog blankets your surroundings, the safest course of action may entail avoiding travel if at all possible. If venturing out becomes an inevitability, exercise utmost caution and heed these essential safety guidelines:

High vigilance:

Be vigilant, as freezing fog can give rise to the notorious black ice, which remains elusive and challenging to spot.

Reduce speed:

Drive at a reduced pace, especially when icy conditions are suspected.

Visibility matters:

Ensure your vehicle is visible to others by using low-beam headlights, which also activate your taillights. If you have fog lights, use them.

Avoid high-beams:

Refrain from using high-beam lights, as they create glare, making it more difficult for you to see what's ahead of you on the road.

Keep your distance:

Keep a considerable following distance to account for sudden stops or shifts in traffic patterns.

Stay in your lane:

Use the road's lane markings as a guide to remaining in the correct lane.

For those taking to the skies, be aware that even a thin layer of ice can form on aircraft surfaces, posing significant flight safety risks. Ensure the aircraft is appropriately treated or equipped with effective de-icing systems before embarking on your journey.

In the realm of freezing fog, knowledge, and vigilance serve as your steadfast allies, empowering you to navigate these meteorological complexities with safety as your main priority.