Thunder and Heat

Is the issue of the day (A) thunderstorms, (B) heat or (C) a potential tropical storm?  Oh, wait; it's August 2010 - so it must be all three. Again.

The jet stream arcs from southern California across Wyoming to Lake Winnipeg this morning. Once again, a large cluster of thunderstorms is rolling across the north-central part of the country, leaving 1 to 3 inches of rain across portions of South Dakota and Nebraska overnight. Scattered flood advisories are in effect. The thunderstorms will be a severe weather and flood threat today and tonight to Minnesota and Iowa. Tomorrow they will be a problem for parts of Minnesota and Wisconsin.

It's hot over the middle of the country once again and the lack of airflow, typical for August, is becoming a larger and larger issue, especially for urban settings. The good news is that a cool front will mix the air on Saturday and even though there won't be a dramatic drop in temperature, at least the air will be moving. That will be the message of hope for the day.

There are two tropical systems this morning. One is just southwest of Ft. Myers, Florida. The other is 800 miles east-northeast of the Leeward Islands.

The one over the Gulf of Mexico doesn't have a lot of upper air support, so it looks like it will meander to the north-northwest as a weak low. It will either track to the Mississippi delta or head inland across the Florida panhandle at the the end of the week. Meanwhile, the one over the Atlantic will likely spin up in speed. It is questionable whether it will become TS Danielle. It will likely depend on how badly the National Hurricane Center needs another named storm.

A significant change in the weather is coming up for the northern tier of states this weekend as another push of cool air comes down out of Canada, this one farther west than the previous two (which primarily affected New England and the eastern Great Lakes).