Why such cold nights but warm afternoons?

Suddenly this week we've gone into temperature extremes with very cool nights but nice warm afternoons.

Thanks to that strong cold front that moved through on Saturday we have seen quite the pattern change. The biggest change is the lack of humidity, so hello dry air.

Now that a large ridge of high pressure has moved in we are seeing very clear skies.

Here is a surface analysis may from Tuesday showing that High pressure pretty much centered over Virginia.

Light winds and clear skies are expected with these conditions.

During the day those clear skies are allowing us to warm up with ample amounts of sunshine. High pressure means sinking air.

Sinking air also evaporates most of the air's moisture so we end up with very dry conditions.

However at night the sky stays clear, that allows for what we call radiational cooling.

Radiational cooling is when all that daytime heating is lost.

Clouds at night can work to hold in daytime heating.

But with clear skies at night, all that daytime heat gets radiated back into the atmosphere, and radiational cooling is maximized in dry air.

So you can expect dry air to heat up and cool down quicker than humid air. That's why we are seeing such temperature extremes.If you've ever been out west to the desert you'll notice daytime highs are very warm but you need a sweatshirt at night because lows can drop into the 40s most nights! That's all because of the dry air and lack of humidity.

Tuesday morning we had cooled down to a chilly 49 degrees but managed to warm our way up to 75 degrees in Harrisonburg with plenty of sunshine and light winds. Wednesday started near 50 and warmed to about 80 for just about all areas, nearly a 30 degree temperature range! Average temperatures this time of year are right at 80 degrees for daytime highs and mid 50s for lows. So overnights have been well below average.

We're slowly starting to see a bit of moisture move back into the area so our night time temperatures will slowly start to warm a few degrees as we head towards the end of the week. Overall though, just beautiful conditions and a nice taste of early fall like weather.

Follow Meteorologist Aubrey Urbanowicz WHSV on Facebook and Twitter.

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