A cool front was draped over far northern Minnesota resulting in a rather larget cluster of thunderstorms early this morning. Debris clouds from the decaying storms will hold the tempreatures down in that region this afternoon.
In central and southern Minnesota and into northeast Iowa and Wisconsin, very warm temperatures with high dew points will result in heat index values approaching or exceeding 100 degrees this afternoon and early evening.
From the National Weather Service in Chanhassen:
A HEAT ADVISORY REMAINS IN EFFECT THROUGH THIS EVENING FOR MUCH OF SOUTHERN AND CENTRAL MINNESOTA AND WEST CENTRAL WISCONSIN. DANGEROUS HEAT INDICES OF 100 TO 103 DEGREES WILL OCCUR THIS AFTERNOON ACROSS THE ADVISORY AREA.
HIGH TEMPERATURES TODAY WILL CLIMB INT0 THE LOWER TO MIDDLE 90S…AND COMBINE WITH DEWPOINTS AROUND 70 DEGREES TO YIELD DANGEROUS HEAT INDEX VALUES. THIS DANGEROUS HEAT IS OCCURRING IN RESPONSE TO A LARGE AREA OF HIGH PRESSURE THAT IS NEARLY STATIONARY OVER THE MIDWEST. A COLD FRONT WILL DROP SOUTH ACROSS THE REGION TONIGHT.
For southeast Minnesota and portions of Wisconsin, the Heat Advisory extends through 7 p.m. Friday as the cool front arrives later in the day.
Follow basic heat safety. Avoid the midday sunshine if at all possible. Being in direct sunshine can add as much as 15 degrees to the heat index value.
There is a difference between the two US forecast models for the intensity and coverage of thunderstorms later tonight. It is likely that the strongest storms, with the greatest threat of severe weather, is over northern Minnesota and into the UP of Michigan.
The locally-run NWS Weather and Research Forecasting (WRF) paints a line of thunderstorms through central Minnesota at 10 p.m. this evening.
The NAM (North American Mesocale) model is not as generous with the rainfall amounts this evening and into the overnight hours.
The Global Forecast System (GFS) prediction of precipitation for later tonight shows a chance for some locally heavy rain in east central Minnesota into western Wisconsin.
The cool front is expected to lose some punch as it sags to northern Iowa and northern Illinois on Friday. High temperatures are likely to drop a few degrees in central Minnesota on Friday. Noticeably cooler temperatures are on tap for Saturday afternoon and Sunday.
Showers and thunderstorms may return as early as Sunday. We’ll sort out the details of that Sunday chance for rainfall in the afternoon blog.