Wednesday, July 28, 2021 4:15 PM Updated For Smoke Wed Nt-Fri

Sweltering Day, Stormy Evening Ahead (Updated PM Outlook)

Morning Storms Have Left Many Clouds, So Worst of Heat in West Central, SW, S Central MN

The showers and thunderstorms that developed in the early morning hours in the eastern Dakotas and pushed across central and southern Minnesota (see Shortwave Albedo loop from Colorado State satellite slider) produced some large hail, some strong wind gusts, and a swath of heavy rainfall. More importantly, the leftover clouds from the extra moisture have kept a lot of the sun out in much of eastern Minnesota. The clouds have only allowed temperatures to climb towards 90 in the Twin Cities and points south and east (see NWS Aviation Weather Center metar map). Still, temperatures even in the middle 80's with those 70-plus dew points have produced heat indices in the upper 80's to the lower 90's. However, the extreme heat and humidity has been over west central, southwestern, and south central Minnesota. This is where the heat advisories and even heat warnings have been supported by temperatures in the low to middle 90's and dew points in the middle and upper 70's. That combination has produced the heat indices from 100 to 110 (see NWS Minnesota Hourly Weather Round-Up).

Thunderstorms Possible Late PM and Evening, Best Chance for Severe Storms North Central, NE, and E Central MN

There still is the potential for showers and thunderstorms, more of which will produce severe weather, the rest of this afternoon into the evening. The first of these stronger storms are now developing from International Falls into the Boundary Waters and the Iron Range. You can see the oval blobs rapidly developing on the College of DuPage visible satellite loop and radar echoes developing on the College of DuPage North Central radar loop. These storms have the potential to produce large hail and straight line wind damage. More thunderstorms will develop along the front in north central Minnesota and in the area clearing on the western edge of the leftover morning storms in Wisconsin. The best threat for these severe storms will be from north central Minnesota through northeastern and east central Minnesota into Wisconsin and Michigan. The storms will be scattered this afternoon in northern and northeastern Minnesota, but they will likely merge into a line near the Minnesota-Wisconsin border and produce a line of storms that is likely to produce widespread straight-line wind damage, as well as the potential for tornadoes from late this afternoon through this evening. The Storm Prediction Center rates the threat category 4 out of 5 from the St. Croix River Valley into Wisconsin.

There is a chance that a secondary line of thunderstorms could develop in central Minnesota late this afternoon. The boundary between the hottest and most humid air and the slightly cooler air to the east has the flow coming together between the southwest winds in western Minnesota and the southeast winds in central and eastern Minnesota. This is the best chance to produce widespread showers and thunderstorms in central and southern Minnesota with some storms possibly producing some large hail and damaging winds.

Previous Discussion

Not as Hot, Much Drier From Thursday On, Leading to Extreme Fire Danger

After tonight, we will be rid of the extreme humidity and even the hot temperatures will begin backing off towards average. Our air will begin streaming in from northern Manitoba and Nunavut, so we will see that much drier air come in with dew points falling back to the lower 50's and even the 40's. High temperatures will fall back to the 80's Thursday through Saturday and may not get out of the 70's on Sunday. However, the combination of dry air, warm afternoon temperatures, and strong winds, especially Thursday, Saturday, and Sunday, will push the fire danger back into the extreme category (see Minnesota fire danger map from the Department of Natural Resources for today's rating).

Updated 4:20 PM for Air Quality Alert

The Minnesota Pollution Control Agency has issued an air quality alert from Wednesday afternoon through Friday for most of Minnesota (see Minnesota air quality index from the Minnesota Pollution Control Agency for the latest readings). Behind the cold front, smoke from the large number of fires in northern Manitoba and Nunavut and even some in Minnesota and North Dakota (orange dots on the Environmental Protection Agency fire and smoke map), is expected to get to the ground as winds change to the northwest and the air begins to sink. 

Few Rain Chances Foreseeable Beyond Tonight

What we need is more chances for rain, besides late today. However, the only rain threat from Thursday through Sunday appears to be a small chance on Friday night as a reinforcing cold front moves through. The best chance for significant rain will be in the storms late today and early this evening and those may even move too quickly to produce a lot of rain. As of midnight last night, the St. Cloud Regional Airport is more than two and a quarter inches behind on rain in July (0.77 inch actual, 3.16 inches average) and about four and three-quarters inches behind since May 1 (5.70 inches actual, 10.57 inches average)..

Detailed St. Cloud, MN, and Vicinity Forecast

Confidence Level: "While Preparing a Meal I Will Drop a Slice of Bread"

Wednesday PM 7/28/2021: Very warm and oppressively humid. A 50-50 chance of afternoon showers and thunderstorms. Some storms could produce large hail and straight line damaging winds. Best chance of storms and severe weather to north and east of St. Cloud. High: between 87 and 92. Heat indices between 88 and 95. Winds: SE 10-25 MPH. Chance of measurable rainfall: 30% in the morning, 50% in the late afternoon.

Wednesday Night: Showers and thunderstorms ending during the evening, then turning partly clear, windy, much drier, and a bit cooler late at night. Low: between 60 and 65. Winds: shifting to NW 15-30 MPH with higher gusts in storms early evening, then NE 10-20 MPH from late evening on. Chance of measurable rainfall: 40% before 9 PM, 10% after 9 PM.

Thursday 7/29/2021: Hazy sunshine, breezy, not as hot and much drier. Poor air quality. Elevated fire danger. High: between 84 and 88. Winds: N 10-20 MPH. Chance of measurable rainfall: 0%.

Thursday Night: Partly clear, light winds, and cooler. Perhaps some early morning fog. Poor air quality. Low: between 55 and 60. Winds: NE 5 MPH. Chance of measurable rainfall: 0%.

Friday 7/30/2021: Hazy sunshine, not as breezy or quite as warm, but continued dry. Poor air quality. Elevated fire danger. High: between 82 and 87. Winds: NW 5-10 MPH. Chance of measurable rainfall: 0%.

Confidence Level: "The Bread Will Land on the Floor Jelly Side Down"

Friday Night: Partly clear, breezy, and warm with noticeable humidity. A slight chance for a shower or thunderstorm. Low: between 60 and 65. Winds: SW 8-15 MPH through early morning, becoming NW late. Chance of measurable rainfall: 20%.

Saturday 7/31/2021: Hazy sunshine, windy, seasonably warm, and very dry. Elevated fire danger. High: between 82 and 88. Winds: NW 15-25 MPH. Chance of measurable rainfall: 10%.

Confidence Level: "My Sock Will Not Get Stuck to the Floor Because I Won't Step in the Jelly Spot"

Saturday Night: Partly clear, breezy, and cooler. Low: between 52 and 57. Winds: N 8-15 MPH. Chance of measurable rainfall: 10%.

Sunday 8/1/2021: Hazy sunshine, windy, a shade cooler and continued very dry. Elevated fire danger. High: between 72 and 77. Winds: NE 10-25 MPH. Chance of measurable rainfall: 10%.

Extended: Continued above average temperatures through next weekend???

Forecast Confidence (10 - "The Rabbits Will Thump Even Though I Fed Them"; 0 - "The Rabbits Will Offer To Groom My Bald Spot"): 7 Wednesday, 6 Wednesday night through Friday, 4 Friday night and Saturday, 3 Saturday night and Sunday.

Today's High (through 3 PM): 87°F; Overnight Low (through 10 AM Wednesday): 68°F
St. Cloud Airport 24-Hour Precipitation (through 10 AM Wednesday): 0.05 inch; SCSU Precipitation (through 10 AM Wednesday): TBA

Next Update: Thursday, July 29, 2021 8 AM

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