Friday, July 18, 2025  3:40 AM 

Prepared by Bob Weisman, SCSU Meteorologist and Professor Emeritus

Better Outdoor Activity Weekend Upcoming (Between Storm Chances)

Natural Air Conditioning Continued Through Early Morning

The 30-day graph of St. Cloud temperatures from MesoWest showed a second day of rare relief from the warm and sticky conditions we've seen most of the past month. Sunshine allowed temperatures to return to the 70's, but readings overnight are headed again towards the lower 50's (see NWS Aviation Weather Center METAR map) with pockets of 40's in north central and northeastern Minnesota. The Minnesota Pollution Control Agency had an air quality alert in north central and northeastern Minnesota ending during the early morning, as a small pocket of orange (unhealthy for sensitive groups) has pushed from western Ontario into northeastern Minnesota, but that has eased in the early morning hours.

Meanwhile, western Minnesota is already beginning the air flow that will allow the seasonably warm and uncomfortably humid air to return. The winds are from the southeast (see NWS Aviation Weather Center METAR map), so the uncomfortably humid air in southern Iowa and points south (see UCAR hourly dew point map) will arrive later today. That will be in time for the next storm system, pushing into the Canadian Rockies on the British Columbia-Alberta border (see College of DuPage North America mid-troposphere water vapor loop) to push the warm front over Missouri and Oklahoma (see latest NWS WPC North America zoom-in map) back towards Minnesota in time for the storm to move through tomorrow.

Next 50-50 Shot at Thunderstorms Late This PM Through Midnight Tonight

There aren't that many clouds near that Canadian Rockies storm (see some patches of clouds on the College of DuPage North America shortwave infrared satellite loop and an area of radar echoes moving from Montana to North Dakota on the College of DuPage north central US radar loop). The additional moisture will be in place by late today and especially tonight, so that will be our next best chance for showers and thunderstorms. The chance for severe thunderstorms is rated rather low in central Minnesota (category 1 of 5 on the NWS Storm Prediction Center convective outlook). There is a better chance for any type of severe weather in southwestern and south central Minnesota into northern Iowa. The rainfall potential will be significant (see Day 1 NWS WPC Quantitative Precipitation Forecast, with a decent amount likely in northern Minnesota, where there has been helpful rain during the past month (set NWS Water Prediction Service Minnesota map to yesterday and past 30 days), but there are still pockets of dryness leftover from the prolonged rain shortage that began about a year ago.

Warmer and Still Marginally Dry Saturday into Sunday

After tonight, we will be back in seasonably warm air (highs near 80), but humidity will be marginal (dew points in the upper 50's, possibly allowing a cool Saturday night low. However, the moisture (dew points in the 60's) will return again by Sunday afternoon. We will remain along the main belt of steering winds, bringing storms from the northeastern Pacific (see Pacific mid-troposphere water vapor loop from Colorado State satellite slider), but there doesn't appear to be any strong system due from Saturday daytime through most of Sunday.

At the same time, the Mexican monsoon flow will be active. The low pressure system in Baja California (counterclockwise circulation on the College of DuPage North America mid-troposphere water vapor loop) has worked together with the general area of high pressure (clockwise circulation near the US Gulf of Mexico coast; focus on the flow movement, not the thunderstorm blobs) to create a northward stream of middle atmosphere moisture that has fueled thunderstorms from New Mexico (where periodic flash flooding has been happening for the past couple of weeks, especially in areas with few trees to hold down soil) to Kansas. That will be the moisture supply for storms as we get into next week.

The computer forecasts have some level of agreement that Sunday night into Monday will be our next decent chance for storms (see Days 3-5 of the NWS WPC quantitative precipitation forecast). The NWS Storm Prediction Center has a small chance for severe storms getting into southwestern Minnesota by early Monday morning.

Silly Robert. 3-7 Day Thunderstorm Forecasting is For Idiots

During the past couple of days, I've tried to pick out favored days for thunderstorms during the early to middle part of next week. More idiotically, I have tried to hint at really warm days and really cool days. What I have neglected to mention is that the strength and timing of any storm pushing the nearby front either to the north or to the south changes with each day's computer runs. So, my revised conclusion about next week is that there will be uncertain chances of thunderstorms each day with some parts of Minnesota possibly seeing a better chance, but it's impossible to pin down where this far in advance. And, the only temperature-humidity trend we can count on is that at least uncomfortable levels of humidity will continue. In any case, that will continue our trend of above average temperatures on the strength of lows likely no cooler than the 60's.

You can look at the Days 4-5 NWS Excessive Rainfall Outlook or the Days 4-7 NWS WPC Quantitative Precipitation Forecast and see parts of Minnesota highlighted. The actual rain potential for someone in the North Central States is probably higher, but the small chance for excessive rain and the limited area for an inch is given because no one can pin down when and where at this point.

Maybe Some Smoke Issues This Weekend?

The southeast flow today will keep Minnesota free of smoke problems. However, our air flow will again turn to the northeast tomorrow and continue through Sunday. There are only a couple of pockets of high AQI in Manitoba and western Ontario right now (see EPA fire and smoke map), but the forecast flow over the weekend will come from the fires in those provinces (see forecast smoke movement from firesmoke.ca), and the air will be sinking, so more smoke particles could get to the ground. so at least northern Minnesota could see some air quality issues over the weekend.

Detailed St. Cloud, MN, and Vicinity Forecast

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

Friday 7/18/2025: A slight chance for an early shower or thunderstorm. Then, mixed clouds and sun, a ittle warmer, and turning uncomfortably humid. A chance for a late day shower or thunderstorm. High: between 75 and 80. Winds: SE 5-15 MPH. Chance of measurable rainfall: 20% during the morning, 40% during the afternoon.

Friday Night: A good chance of mainly evening showers and thunderstorms. Milder and uncomfortably humid. Maybe some fog by morning. Low: between 63 and 67. Winds: SE 5-10 MPH, becoming NE 5 MPH after midnight. Chance of measurable rainfall: 50%.

Saturday 7/19/2025: Morning clouds and fog, then becoming sunny, a bit warmer, and uncomfortably humid. High: between 77 and 82. Winds: NE 5-15 MPH. Chance of measurable rainfall: 10%.

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

Saturday Night: Partly clear, breezy, and not quite as warm with slightly lower humidity. Smoke? Low: between 55 and 60. Winds: NE-E 5-15 MPH. Chance of measurable rainfall: 10%.

Sunday 7/20/2025: Sunny to partly cloudy, breezy, and still a little cooler than average. Noticeably to uncomfortably humid. A slight chance for a late day shower or thunderstorm. Smoke? High: between 80 and 85. Winds: SE 8-15 MPH. Chance of measurable rainfall: 20%.

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

Sunday Night: Partly clear, breezy, warmer, and uncomfortably humid. A chance for showers and thunderstorms, especially late at night. Smoke? Low: between 60 and 65. Winds: SE 8-15 MPH. Chance of measurable rainfall: 50%.

Monday 7/21/2025: Lots of clouds with some sunshine, and uncomfortably humid with a good chance of showers and thunderstorms. High: between 78 and 83. Winds: SE 8-15 MPH. Chance of measurable rainfall: 50%.

Monday Night: Partly clear, breezy, warmer, and oppressively humid. Maybe some evening for showers and thunderstorms. Smoke? Low: between 70 and 75. Winds: SE 5-15 MPH. Chance of measurable rainfall: 30%.

Tuesday 7/22/2025: Mixed clouds and sun and oppressively humid with a chance of showers and thunderstorms. High: between 83 and 88. Winds: SW 8-15 MPH. Chance of measurable rainfall: 30%.

Extended: Uncertain and frequent chances for thunderstorms through the middle of 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 Friday, 6 Friday night and Saturday, 5 Saturday night and Sunday, 3 Sunday night and Monday, 1 Monday Night and Tuesday

Yesterday's High: 74°F; Overnight Low (through 3 AM Friday): 54°F
St. Cloud Airport 24-Hour Melted Precipitation (through 3 AM Friday): None; SCSU 24-Hour Precipitation (through 3 AM Friday): None

Next Update: Monday, July 21, 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!

Are you interested in studying meteorology? If so, go to the Atmospheric and Earth Sciences Department home page.