Tuesday, September 16, 2025  4:40 AM 

Prepared by Bob Weisman, SCSU Meteorologist and Professor Emeritus

Trying to Time a Tortoise

Weather systems have come to a near stall across central North America, or they are moving in a rare south-to-north direction, like the low that moved from South Dakota into Manitoba yesterday (see College of DuPage North America mid-troposphere water vapor loop). That will continue most of this week. The high pressure ridge (switch of upper-level winds from southwest-to-northeast in eastern Kansas, Nebraska, the Dakotas, and into Canada to northwest-to-southeast from Manitoba into eastern Minnesota, Wisconsin and Illinois; see College of DuPage North America mid-troposphere water vapor loop) that allowed the deep clouds to shrivel over Minnesota yesterday (see College of DuPage North America clean infrared satellite loop) will slowly give way to the next low over the Pacific Northwest. That low will stall out as it reaches the Dakotas late this week.

What all of this means is that our very warm (highs in the 80's) and steamy (dew points in the 60's, producing heat indices from the upper 80's to the lower 90's; see NWS: last 72 hours of St. Cloud observations) weather of the past three days will give way to cloudier, slightly cooler weather with an increasing chance for showers and thunderstorms as the week goes on. There will only be a chance for a widely scattered shower today through tomorrow morning (with a slight chance of a storm producing severe weather to our west and north), but that chance will improve to more than 50-50 by tomorrow night. The best chance for rain will continue into Thursday. After that, the slow-moving low is forecast to stall near Minnesota. Eventually, the feed of moisture into the low will reduce, so the number of showers will reduce, but that may not happen before the weekend. Still, the most likely time for showers and perhaps a thunderstorm will be during the afternoon. The rain potential (see Days 1-5 on the NWS WPC quantitative precipitation forecast) will ease the drier conditions seen since the start of August. With all of the clouds, highs will fall back to the lower 70's by Friday and remain there at least through Saturday. Lows will range from the upper 50's to the lower 60's.

At this point, I don't see any complete drying and end to the shower chances (see that most of Minnesota is still within the chance of rainfall on the Days 6-7 NWS WPC quantitative precipitation forecast). However, we may have a shot at warmer highs in the upper 70's by Sunday afternoon.

Detailed St. Cloud, MN, and Vicinity Forecast

Confidence Level: "The Bugs Are Waiting for Me to Mow the Lawn"

Tuesday 9/16/2025: Sunny in the morning, partly cloudy in the afternoon, breezy, still very warm, and uncomfortably humid. A slight chance of a late day shower or thunderstorm. High: between 85 and 90. Winds: SW 10-20 MPH with higher gusts. Chance of measurable rainfall: 20%.

Confidence Level: "Extra Bugs Will Come From Every Home on the Block to Hover Around My Head"

Tuesday Night: Partly cloudy, continued August-like temperatures and humidity. A chance for scattered showers and thunderstorms. Low: between 63 and 68. Winds: SE 5-10 MPH. Chance of measurable rainfall: 30%.

Wednesday 9/17/2025: Mixed clouds and sun, windy, not quite as warm, but uncomfortable to oppressive humidity. A better chance for late afternoon showers and thunderstorms. High: between 83 and 88. Winds: SE 10-20 MPH with higher gusts. Chance of measurable rainfall: 40%.

Wednesday Night: A good chance for showers and thunderstorms. Uncomfortable humidity. Low: between 60 and 65. Winds: SE 5-15 MPH. Chance of measurable rainfall: 60%.

Thursday 9/18/2025: A good chance for both early morning and afternoon showers and thunderstorms. Not as warm, but uncomfortably humid. High: between 75 and 80. Winds: ESE 8-15 MPH. Chance of measurable rainfall: 50%.

Thursday Night: Mostly cloudy with scattered rain showers. Low: between 58 and 63. Winds: E 5-15 MPH. Chance of measurable rainfall: 40%.

Friday 9/19/2025: Mostly cloudy and humid with scattered showers and perhaps a thunderstorm. High: between 70 and 75. Winds: SE 8-15 MPH. Chance of measurable rainfall: 60%.

Confidence Level: "Enough Bugs Will Fly into My Mouth to Throw Off My Diet"

Friday Night: Mostly cloudy with occasional rain showers. Low: between 57 and 62. Winds: SE 5-15 MPH. Chance of measurable rainfall: 40%.

Saturday 9/20/2025: Continued mostly cloudy and humid with scattered showers. High: between 70 and 75. Winds: SE 5-15 MPH. Chance of measurable rainfall: 50%.

Extended: Continued cloudy through the weekend with a slow trend towards fewer scattered rain showers (still best chance in the afternoon) Highs in the 70's Sunday?? Eventually drying and turning warmer, but uncertain how quickly next week??

Forecast Confidence (10 - "The Rabbits Will Thump Even Though I Fed Them"; 0 - "The Rabbits Will Offer To Groom My Bald Spot"): 7 Tuesday, 5 Tuesday night through Thursday, 4 Thursday night and Friday, 3 Friday night and Saturday.

Yesterday's High: 86°F; Overnight Low (through 4 AM Tuesday): 65°F
St. Cloud Airport 24-Hour Melted Precipitation (through 4 AM Tuesday): None; SCSU 24-Hour Precipitation (through 4 AM Tuesday): None

Next Update: Wednesday, September 17, 2025 6 AM

Let me know what you think about this forecast and discussion by emailing SCSU meteorology professor Bob Weisman. Please note that I make the forecast, not the weather!

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