Updraft® - Minnesota Weather News

Heat index values over 100 degrees possible Sunday

Afternoon pop-up cloudbursts thorough Wednesday; stifling heat, humidity next weekend

NOAA GFS model heat index
Global Forecast System model forecast heat index values for 4 p.m. Sunday, July 14
National Oceanic and Atmospheric Administration, via Pivotal Weather

Here comes the summer swelter. The hottest weekend of the year so far is on the way.

It looks like we’ll finally crack the 90-degree mark on Saturday or Sunday in the Twin Cities, and it comes with a heap of humidity with dew points in the upper 70s to around 80 degrees.

Heat index (apparent temperature) values could reach 100 degrees across much of southern Minnesota on Sunday afternoon.

Yes, welcome to Miami.

In the meantime, we enjoy a couple more days of sunny mornings followed by billowy afternoon cumulus clouds that will produce local downpours.

Monday’s cell merger over Little Canada produced 2.5 inches of rain in about an hour before drifting southeast through St. Paul and fading.

Our showery encores return Tuesday and Wednesday afternoons. In the beauty of chaotic summer air mass thunderstorms, there’s little chance of pinpointing precise locations of the tropical downpours more than an hour in advance.

The National Oceanic and Atmospheric Administration’s FV3 model still looks like it has the best handle on at least the probable extent of rainfall coverage across Minnesota Tuesday afternoon. The loop below runs between 1 p.m. and 11 p.m. Tuesday.

NOAA FV3 model
Finite-Volume Cubed-Sphere Dynamical Core model between 1 p.m. and 11 p.m. Tuesday
NOAA, via Tropical Tidbits

Highs Tuesday will run in the 80s once again across most of Minnesota, but notice how temperatures drop quickly back into the 70s after any passing showers:

Forecast high temperatures Tuesday
Forecast high temperatures Tuesday
NOAA

Warmest 3 weeks of the year ahead

We’ve just entered the warmest three weeks of the year on average for Minnesota. The normal high for the Twin Cities has reached 84 degrees where it will remain through Aug. 23.

Thursday and Friday look like beautiful, warm Minnesota summer days. If you like the upper 80s, this is your time to hit the lake or the park.

Steamy weekend ahead

The hottest and most humid weekend of the year so far looks very likely next weekend. On the map below, check out the dew point plume surging into Minnesota between Friday and Sunday.

Dew points of 80 degrees anyone? It’s possible on Sunday.

NOAA GFS model
Global Forecast System model dew point output between 7 a.m. Friday and 7 p.m. Sunday
NOAA, via Tropical Tidbits

Highs are likely to top 90 degrees by Saturday and especially Sunday.

Forecast high temperatures Sunday
Forecast high temperatures Sunday
NOAA

The combination of 90-degree temperatures and dew points in the upper 70s to near 80 degrees look likely to push heat index values to and above 100 degrees Sunday afternoon.

NOAA’s Global Forecast System model is cranking out heat index values of 111 degrees for southwestern Minnesota at 4 p.m. Sunday. The GFS is notorious for being a little on the extreme side so let’s see how this plays out this week.

NOAA GFS model heat index
Global Forecast System model forecast heat index values for 4 p.m. Sunday, July 14
NOAA, via Pivotal Weather

Some relief looks likely by Monday.