After a very wet, cloudy, and cool spring, more rain is likely the last thing anyone wants to hear at this point. But more is on the way. With continued southerly flow pumping in very warm and juicy air, the atmosphere is primed for heavy rain. The dewpoint is the best way we can measure the amount of moisture in the atmosphere. The higher the dewpoint, the more moisture in the air. Thursday morning, dewpoints are in the low 60's… not at all uncommon for our neck of the woods. But with southerly winds continuing to pump Gulf of Mexico moisture into the region, these numbers will continue to climb. Here is what one of our forecasting computer models is suggesting dewpoints will be Thursday afternoon:
Now take a peek at what Friday afternoon looks like:
These maps are a bit busy, but I color coated what I want you to focus on. First, forget the red lines and just focus on the yellow and orange lines. I have areas with 70°+ dewpoints circled in yellow and areas with 75°+ dewpoints circled in orange. The metro is still in the upper 60's Thursday afternoon, but continues to climb with moisture levels surging into the tropical category Friday afternoon with dewpoints from 70 to 75 degrees. It's this level of moisture that can produce tropical downpours of 2 inches or more an hour in some of the stronger thunderstorms.
With that in mind, here is a forecast that shows anticipated rainfall amounts over the next 3 days (Thursday, Friday, and Saturday) produced by the Weather Prediction Center (WPC).
This shows much of Minnesota, including the metro, receiving widespread amounts of 1 to 3 inches through Saturday afternoon. Remember, that with thunderstorms, locally heavier amounts are always a possibility.