Hot and muggy, with a side of thunderstorms

In general, temperatures are easier to forecast than is precipitation, especially in the warm season. Temperatures tend to be a product of the air mass present, while keeping in mind that rainfall can hold the temperature down.

Rain, on the other hand, is often showery and scattered in our part of the world this time of year. Showers and thunderstorms often rev up along old outflow boundaries in response to wrinkles aloft to initiate vertical motion and can be quite difficult to anticipate very far into the future.

Heat wave

So let's start with the easy part of the forecast. Our weather will be hot and rather humid from Thursday through at least Monday, Memorial Day. These next several days, weather fans, will constitute a heat wave.

High temperatures Thursday should range from the mid-80s to low 90s across Minnesota. The Twin Cities should reach about 90 this afternoon with dew points, the measure of moisture in the lower atmosphere, in the low to mid-60s.

Friday might be a degree or two less hot than Thursday, but the heat definitely will be turned up for the holiday weekend.

Thunderstorms

Thunderstorms tracked northeastward across Minnesota overnight and are lingering this morning.

At 7:07 a.m. Thursday morning, the National Weather Service issued a flash flood warning for southeastern Aitkin, Pine and southwestern Carlton counties in Minnesota and southwestern Douglas County in Wisconsin until 9:30 a.m. Radar estimates of 3 to 5.5 inches of rainfall have occurred and water is rising rapidly in those areas, including Sandstone, Willow River and Banning State Park.

Meanwhile, new thunderstorms have been arriving in the southwestern corner of Minnesota.

Scattered thunderstorms will continue to develop Thursday and Thursday night. The best chance of thunderstorms arriving in the Twin Cities will be later Thursday afternoon or evening.

A few thunderstorms might become strong or severe, mainly late Thursday. There is a slight risk for severe weather in northwestern Minnesota (yellow color below) while there will be a lesser, marginal risk of severe storms in the darker green color from southwestern to northeastern Minnesota, including the Twin Cities. The main threats will be damaging winds or hail but only the slightest chance of a tornado.

Expect a scattering of thunderstorms on Friday. Saturday and Sunday should be generally dry, but don't completely rule out stray storms forming along those lingering boundaries.

Monday might be a little uncertain as to showers and storms, but the better chance of rain probably will hold off until Monday night or Tuesday.

Much of the state could use some rain. Since the spring rainfall season began on March 1, the Twin Cities official rain gauge has measured 2.4 inches less precipitation than the long-term average.

Tropical update

The latest from the National Hurricane Center is that the disturbance currently over Mexico's Yucatan Peninsula has a 40 percent chance of becoming a tropical cyclone during the next 48 hours. That chance increases to 80 percent over the next five days.

Whether or not this storm becomes an actual tropical storm, it will be quite a rain-maker for much of the southeastern United States. Some soggy areas could pick up in excess of 5 inches of rain.