Monday's wind is coming from something called a lee side low. Let's talk about how they form.
Let's start by breaking down the name. Lee side just means downwind of the mountains. There are two sides to a mountain - the windward side (the side the wind hits and tends to get a lot of moisture) and the leeward side, which is the side away from the direction the wind flows. Since the wind over the Rocky Mountains flows west to east, the leeward side is to the east of the mountains. So a lee side low means we have a low to the east of the mountains. They form in some types of downslope wind set ups.
Downslope winds occur when strong winds flow over the Rocky Mountains. The air descends over the plains and warms up as it does so.
Lee side lows tend to form when the strong winds carry extra energy into the upper atmosphere. You may hear us refer to this energy as an upper-level disturbance.
As this energy moves from the mountains into the plains it tends to cause air to rise and move inward. As we suck air up from the ground… we end up with less air - at - the ground. That's what low pressure is.
The downslope winds themselves help with this process too. As air races down a mountain… speeding up like a bowling ball rolled down a hill… it spreads out farther. This enhances the low pressure.
Since the atmosphere wants to stay in balance... air flows from high to low pressure. When these lows develop over the plains they push the atmosphere out of balance. So the downslope winds speed up to try and restore that balance again.
To summarize… lee side lows increase wind gust speeds in downslope wind set ups. That's why it was windy Monday morning. They also increase the amount of warming we get from a downslope wind set up... which is why it was warm Monday afternoon. In summer, they can form something called a dryline, with moist air getting pulled in east of the line and producing thunderstorms.
We see lee side lows more often during spring as the jet stream frequently moves over our state. So, this may be a good time of year to move some of your lighter weight outdoor items away from the part of your home facing the mountains.
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