Warning: Nerd Alert - Clouds and rain chances increase through the weekend

It looks like we'll stay stuck under a persistent upper level low for the next several days and that will keep the cool temperatures, clouds and periodic rain chances with us through at least early next week.

We've been talking about this upper low now all week and starting today and lasting through the weekend temperatures will be cool and our rain chances may in fact go up as we round out the work week.  Yesterday's high of 69° wasn't too bad, although it still was below average, and we were able to see a fair amount of sunshine for most of the day.  The reason, we were in the 'dry-slot' of the storm.  Meaning there was dry air wrapping in on the southwest side of the low pressure system.  This causes the clouds to clear, but usually increases the winds.  We are now no longer within that 'dry-slot' as the main upper low has moved into Canada.  If you were to look at a looping water vapor image you would notice these little counter-clockwise circulations moving through the Midwest.  These are actually little disturbances, or as meteorologists call them vorticity maxes, that rotate around the main system.  What's important for you to know is that ahead of these vort maxes the air is rising and behind them the air is sinking.  Where you have rising air you build clouds and typically increase your chance for rain.  Where the air is sinking there is typically less cloud cover.  So, as each one of these moves through the Great Lakes they will continue to produce cloud cover and pretty much daily rain chances.  Another thing you may have noticed today versus yesterday is the depth of the clouds (or maybe you haven't and it's just been me).  The clouds are a little thicker than they were yesterday and that's because there is a much cooler pocket of air above us than there has been the past couple of days.  Air will continue to rise as long as it's warmer than the environment it's moving into.  So if you have a pretty cold layer above your air is going to rise a little more quickly.  This creates a more unstable atmosphere - hence the deeper the cloud depth and the greater the chance of rain.  So going into the weekend we will have both of these factors, cold pocket of air and vort maxes, that will keep the cloud cover and rain in the forecast.