What's up with the clouds?

It's typical during the winter months to have cloudy days, but a little sunshine now and then would sure be nice.  Unfortunately, those pesky clouds we've had over the past few days may be sticking around a little longer through the weekend.

So, why is that?  Well, we have to look at what's going on in the atmosphere at the surface and above.  The image on the left is called a Skew-T diagram.  It's a 'snap shot' of the atmosphere taken from a weather balloon launched from the Quad Cities National Weather Service Wednesday evening.  Temperatures, in degrees Celsius, are located on the bottom and heights are located on the left hand side.  The green line shows the dew point temperature and the red line shows the temperature.  Something that often happens during the winter months is an inversion.  An inversion occurs when the temperature above is warmer than the temperature at the surface.  During the summer months, inversions can prevent afternoon thunderstorms.  In the winter, inversions can 'trap' clouds and fog near the surface making it hard for the clouds or fog to 'burn off'.

In order to weaken or break the inversion, you need the help of the sun.  In winter, the days are shorter and the sun angle is lower.  This doesn't allow us to maximize on heating during the afternoon.  Without that heating, inversions can last, and last, and last.  Now, if I've learned anything in my 10 years of forecasting it's that persistence is key.  We'll likely see the clouds linger into the weekend, but winds will begin to shift around to the south with an upper level ridge.  This should help allow a little more sunshine to peek through, but full sunshine may be hard to find.