Friday, April 25, 2024  3:50 AM

Prepared by Bob Weisman, SCSU Meteorologist and Professor Emeritus

Friday and Sunday Best Chances for Weekend Rain

Mesoscale Convective Complex "Blob" A Sign of Rain to Come

The long-anticipated late week storms are on the way. The first of the storm pair pushed into Colorado and Kansas (see Mid-tropospheric water vapor loop from Colorado State satellite slider). With plenty of Gulf of Mexico available from western Kansas and Oklahoma southward (see 4 PM Thursday NWS WPC North America zoom-in map). That sticky air was pulled over the top of the drier air in the Dakotas and Minnesota, creating a pair of red "thunderstorm blobs," one moving from Kansas into Missouri and the other moving from Nebraska into the Dakotas, Iowa, and eventually Minnesota (set frames to at least 96 on the College of DuPage north central US clean infrared loop).

These large, quasi-oval thunderstorm masses are called mesoscale convective complexes. They tend to develop from groups of earlier thunderstorms into a blob, whose peak tends to be overnight. During the afternoon and evening, they can produce severe weather, but their main product is a large area of heavy rainfall College of DuPage north central US radar loop). If there are series of these complexes or they are slow moving, they can produce major flooding. These are primarily responsible for the late night or morning thunderstorms when we are in the cooler sector of a developing storm. They are estimated to produce at least a quarter of the growing season rainfall during the warm season between the Rockies and the Appalachians.

Morning and Late Day Wave of Rain

Of the two waves of showers and thunderstorms expected in Minnesota, the morning one will be from the leftovers of this system to our southwest (see NWS Aviation Weather Center METAR map). However, there will be another wave of storms developing in Iowa and Nebraska this afternoon, which will likely form another mesoscale convective complex pushing northeastward. Central and southern Minnesota will catch the complex earlier, so showers and thunderstorms will be likely from late this afternoon through the evening. Again, Minnesota isn't expected to have much severe weather, but there is the potential for a widespread half inch to an inch of rain in the two waves today.

Less Rain But a Lot of Clouds Saturday

The Colorado-Nebraska low will push through Minnesota tonight, then move into Ontario by late tomorrow. There won't be nearly as many showers tomorrow and the chances for thunderstorms will be slight, but we will have a lot of clouds and the cool air aloft will produce some spotty sprinkles or drizzle. Drier conditions will allow temperatures to climb well into the 50's and perhaps approach 60.

Two Waves of Sunday Rain (Favoring the Morning?)

The second storm pushing into Oregon (see Mid-tropospheric water vapor loop from Colorado State satellite slider) will take a track slightly further to the south from Sunday through Sunday night. The system will have more moisture associated with it, but the more southerly track will likely push the highest rain totals to southern and especially southeastern Minnesota, but much of Minnesota will still have a good shot at substantial rainfall. The first wave of showers may not arrive until the daylight hours of Sunday morning. The second wave of storms may favor southeastern Minnesota, so the chance for the second wave being heavy in central Minnesota Sunday late afternoon and evening will be smaller.

Clouds and a Few Showers Linger Monday

The second storm will slowly push northeastward on Monday, but the cold air pool aloft will still keep a lot of clouds around and perhaps a few afternoon showers.

Warmer, But Still Lingering Shower Chances into Mid-Week

The forecast for the middle of next week has changed. There is still some uncertainty, but a low pressure system that was supposed to stall out in the western third of the US isn't forecast to be as strong by the majority of computer forecasts. Instead, they show a parade of lows near the US-Canadian border from the Pacific Northwest into Manitoba and northern Minnesota. Weaker systems would mean less moisture available to each one, but the cold pocket of air aloft would mean a lot of midday and afternoon clouds and a chance for scattered showers. For now, I'll put highs in the 60's on Tuesday and perhaps Wednesday.

Detailed St. Cloud, MN, and Vicinity Forecast

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

Friday 4/26/2024: A good chance for morning showers and thunderstorms, then a midday and early afternoon break. More showers and thunderstorms likely in the middle to late afternoon. Breezy, but cooler. High: between 50 and 55. Winds: SE 10-25 MPH. Chance of measurable rainfall: 50% in the morning, 80% in the late afternoon.

Friday Night: Cloudy with a good chance of evening showers and thunderstorms, tapering to occasional light rain or drizzle after midnight. Low: between 43 and 48, rising to near 50 by morning. Winds: E 8-15 MPH evening, becoming NW late. Chance of measurable rainfall: 70% evening, 40% after midnight.

Saturday 4/27/2024: Mostly cloudy with occasional light rain or drizzle, especially in the morning. A bit milder. High: between 55 and 60. Winds: NW-N 8-15 MPH. Chance of measurable rainfall: 40%.

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

Saturday Night: Cloudy and breezy through the evening. A chance of more showers or thunderstorms late at night. Low: between 38 and 43. Winds: NE 8-15 MPH evening, 10-20 MPH late at night. Chance of measurable rainfall: 30%.

Sunday 4/28/2024: Cloudy, breezy, and cooler. Rain or showers likely through the morning. Occasional showers or drizzle in the afternoon. Breezy and even cooler. High: between 42 and 47. Winds: NE 10-20 MPH. Chance of measurable rainfall: 80% in the morning, 40% in the afternoon.

Sunday Night: Cloudy, breezy, and not quite as cool. A chance for occasional light rain or drizzle. Low: between 37 and 42. Winds: NE 10-20 MPH, shifting to SW 8-15 MPH late. Chance of measurable rainfall: 30%.

Monday 4/29/2024: Cloudy with spotty showers or drizzle in the morning, perhaps some sunny breaks possible in the afternoon, but still a scattered rain shower possible. High: between 50 and 55. Winds: W 10-20 MPH. Chance of measurable rainfall: 30%.

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

Monday Night: Partly clear with light winds evening. Cloudy with a chance for a late night shower. Low: between 40 and 45. Winds: SW 5-15 MPH, shifting to SE 5-15 MPH late. Chance of measurable rainfall: 30%.

Tuesday 4/30/2024: Mixed clouds and sun with a few scattered showers possible in the afternoon. Warmer. High: between 62 and 67. Winds: SW 10-20 MPH in the morning, 15-30 MPH with higher gusts in the afternoon. Chance of measurable rainfall: 20%.

Extended: Some lingering instability showers through the middle of the week?? Seasonably warm???

Forecast Confidence (10 - "The Rabbits Will Thump Even Though I Fed Them"; 0 - "The Rabbits Will Offer To Groom My Bald Spot"): 8 Friday, 7 Friday night and Saturday, 5 Saturday night through Sunday, 4 Sunday night and Monday, 3 Monday night and Tuesday.

Yesterday's High: 71°F; Overnight Low (through 3 AM Friday): 53°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, April 29, 2024 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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