Weekend Weather Blog: The different types of cold fronts
TWIN FALLS, Idaho (KMVT/KSVT) — I don’t mean to spoil the forecast for anyone reading this, but a cold front will be sliding through southern Idaho this week. As far as when it will happen? You’ll have to wait until my forecast at 9 and 10 PM (if you’re reading this before then).
In any case, cold fronts bring in various different kinds of weather - weather that’s always active no matter what. These are associated with areas of low pressure, known as midlatitude cyclones. These are complex storm systems that impact us here outside of the poles and tropics. However, dis you know that there are actually 2 different types of cold fronts?
The type of cold front that you experience can have an impact on the weather you see it. What are the two types of cold fronts you see then? The katafront and the anfront. If they’re both cold fronts though, what makes them different. Once again, we’ll show an example by bringing up my favorite way to look at the atmosphere - the sounding.
Above shows an example of a what the atmospheric temperature and moisture looks like going higher into the sky after a front has passed at the surface. It’s important to understand that fronts first pass at the surface and then pass aloft later on. The key to defining a katafront is the noticeable drop in moisture where the inversion (or region where temperatures increase with height) begins.
What does this mean for us on the ground? After the passage of the front, you can expect clearing skies to occur, with a thin band of precipitation and active weather (usually thunderstorms in cases of katafronts) happening just before the passage of the front. This is due to the dry air entering the atmosphere in the middle levels.
Above is an example of what precipitation ahead of a katafront can look like. Notice the thin band of heavier precipitation, with drier air behind it. The dry air above the surface, as I mentioned prevents precipitation from happening. Because dry air is heavier than moist air, it causes sinking, keeping things dry behind the front. This is also assisted by a circulation that occurs around the front as winds are thrown out of balance. The air behind the front sinks down to the ground as a result, working with the dry air aloft to keep precipitation away.
What about the other type of front? This is called an anafront. Anafronts work like a warm front in reverse. What dies that mean? Warm, moist air out ahead of the front slopes up the frontal surface, generating vertical motion behind the actual leading edge of the front.
Notice how the air stays moist throughout the entire profile. This allows precipitation to fall behind the actual leading edge of the front, mainly in the form of general rain showers or snow showers.
Above is an example of precipitation that occurs from an anafront. Notice how this is more uniform in nature, covering a much wider area, and is much lighter in nature than katafrontal precipitation.
How can you tell what type of front is going to occur outside of using soundings and radar? Simple - fond out if the front has just formed, or if it’s lasted for a while. If the front has formed recently, it typically is an anafront. If the front is in its mature stage it’s usually a katafront.
So what type of fronts form here in Idaho usually? Anafronts - this is because the mountains usually decay oncoming systems from the Pacific. As the energy from these systems reaches the western edge of the Great Plains, new systems form, creating new fronts that slide through - typically anafronts.
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