![]() Wednesday: Cloudy and breezy with a chance for snow. Tomorrow night: Partly cloudy and breezy. Today: Areas of freezing fog in the morning, then mostly cloudy and breezy. Mild and dry weather continues through the start of next week. A breezy southwest wind will usher us back into mid-30s to low 40s on Saturday with sun. After a cooler start to the day, highs remain cooler but seasonable in the 20s. High pressure moves in Friday to supply plenty of sunshine. This are will see a localized 1-3” by Friday morning. Lows stay in single digits for the Twin Ports, and parts of the South Shore stay in the teens due to lingering lake effect clouds and snow. By tonight, temps fall to minus single digits near and north of the Iron Range under partly cloudy skies with northwest winds remaining blustery. Highs still manage to reach low to mid-30s. Fog gradually improves through the morning with mostly cloudy skies remaining.Ī cold front passing today will be responsible for gusty north northwest winds, a few flurries or light snow showers, and the arrival of cooler air. Freezing fog occurs when the air temperature drops below freezing until water droplets in the fog get supercooled. ![]() Allow time to keep plenty of distance between vehicles and have headlights on. Subfreezing temps following yesterday’s snowmelt also contributes to ice that may creep up on you this morning. Andrea Orton, Purdue University and National Weather Service Forecasting Office, Boulder, CO.Areas of freezing fog have set up this morning, leading to poor visibility and icy patches for our morning commute. Without the proper de-icing tools the airlines have, it's best to stay on the ground when freezing rain, drizzle, or fog is headed your way. The first indication that freezing precipitation might be a factor will be found on your airport's TAF or METAR. When freezing fog conditions exist, ice accumulation will increase as the wind increases. Everything becomes covered in a glass-like glaze. ![]() In most cases trees, the ground, roads, and your aircraft. But without any cloud condensation nuclei to adhere to, these super-small droplets freeze to whatever they come into contact with. Subzero temperatures supercool water droplets in the air. Just like radiation fog, freezing fog forms on clear, calm nights. What's the difference? Once the visibility drops below 1/2 mile, METARs report freezing fog (FZFG) instead of freezing drizzle (FZDZ). The process to create freezing fog is essentially the same as freezing drizzle. As soon as that happened, the freezing drizzle was replaced by light snow. Those ice crystals served as a condensation nuclei, and the freezing drizzle started sticking to the ice crystals aloft. Later in the day as the moist layer of air got thicker, ice crystals began forming aloft. Pair this with the cold surface temperatures in Colorado, and freezing drizzle coated almost everything on the ground. ![]() Recently in Boulder, northeast upslope winds kept a shallow moisture plume aloft. Inadvertent icing encounters with freezing rain can be deadly, the NTSB is still investigating a recent Cessna 210 crash in Lubbock, Texas where freezing rain is suspected to be a significant contributing factor. Clear ice can also be hard to see because of its smooth, transparent appearance. Here are the codes youll see: Freezing Rain: FZRA Freezing Drizzle: FZDZ Freezing Fog: FZFG Without the proper de-icing tools the airlines have, its best to stay on the ground when freezing rain, drizzle, or fog is headed your way. Large drops, like you'd expect with freezing rain, can form a heavy glaze on your airframe (clear ice) that can be difficult to remove, especially if ice forms aft of de-icing equipment. The first indication that freezing precipitation might be a factor will be found on your airports TAF or METAR. Why Are Supercooled Large Droplets So Dangerous? But when supercooled droplets impact a surface of your aircraft, they stick and freeze. Supercooling is a state where a liquid is below freezing but isn't a solid (in this case, ice), meaning that as the droplets fall through the atmosphere they can't crystalize. As the melted snowflakes fall through the below-freezing surface layer of air they become supercooled, creating a significant icing risk to aircraft. ![]()
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