Tuesday, May 30, 2023 6:00 AM

Partly Sunny, Chance of Storms (Larry King Strikes Again)

Warm Weekend So Far....

Yesterday was St. Cloud's warmest day (high of 88) since Labor Day weekend. We got rid of the patch of middle level clouds (see Shortwave Albedo loop from Colorado State satellite slider menu) when the high was also 88 degrees. Madison and Fargo made it to 90 yesterday afternoon with Rush City getting to 89. The humidity continued to be low with afternoon dew points in the 40's (see blue line on the 5-day St. Cloud observation chart from MesoWest). The very warm and dry air also came with a stiff south wind, gusting up to 30 MPH (see NWS: last 72 hours of St. Cloud observations), leading to another day of high to extreme fire danger (see Minnesota fire danger from the Minnesota Department of Natural Resources).

And, the afternoon air pollution levels again crept into the orange (unhealthy for sensitive groups) in Minneapolis, St. Paul, and Rochester, while just missing in St. Cloud.

This has been part of a very warm month, averaging 61.1 degrees in St. Cloud through Sunday (see NWS St. Cloud May high-low temperature table). That ranks as the 13th warmest May in St. Cloud records, just 0.7 degrees short of the 10 warmest Mays. As we head into the last two days of meteorological spring (meteorological summer, the three warmest months, begins June 1), the warm May is in quite a contrast to the chilly March and April (4.0 degrees colder than average).

<apology and boast> I won't have the average May and spring conditions in St. Cloud for a while, since I will be spending my annual couple of weeks staring at wildlife instead of weather maps, so this is the last forecast until June 16 or 19.</apology and boast>

Overnight Scattered Storms Producing a Few Spots of Significant Rain and More Humid Air

However, changes have occurred overnight. The slow-moving low over South Dakota drifted into North Dakota (see Mid-tropospheric water vapor loop from Colorado State satellite slider). Somewhat surprisingly, at least to me, the outbreak of showers and thunderstorms from the eastern Dakotas into much of Minnesota was stronger overnight than during the afternoon (set frames to at least 48 on the College of DuPage north central US radar loop), so scattered showers and thunderstorms have been pushing across Minnesota. The moist tongue of air that has been in the Dakotas for the past two days has drifted into western and central Minnesota, pushing dew points into the noticeable upper 50's (see yellows and browns, dew points in the 50's and 60's, from the Dakotas southward on the UCAR hourly dew point chart). That's what is at least fueling some rain reaching the ground in these thunderstorms. The totals have been mostly a few hundredths to a tenth of an inch (0.12 inch in St. Cloud), but there were locally heavier showers in Slayton (1.98 inch), Thief River Falls (0.87 inch), Canby (0.85 inch), Fairmont (0.46 inch), Maple Lake (0.41 inch), and Glenwood (0.28 inch). Even St. Cloud State University got 0.34 inch. More rain is possible during the early morning hours (see NWS Aviation Weather Center METAR map), perhaps lingering in eastern Minnesota through the morning rush hour.

Still A Good Chance for PM Storms Today

As the upper-air low continues northeastward to the junction of North Dakota, Minnesota, and Manitoba by this afternoon, there will be another round of showers and thunderstorms late this afternoon or early this evening. I'm not quite sure whether western Minnesota will be in the storms or if they will be off to the east a bit. There is a small chance, rated 1 out of a 5-point scale by the NWS Storm Prediction Center, that a few storms could produce some large hail. In between, we should break out into some sunshine today. It will be more humid than yesterday with dew points at least in the noticeably upper half of the 50's. Some leftover clouds from the early thunderstorms will cut our temperatures a bit, so I am going for a high in the low to middle 80's.

Rest of the Week: The High Who Loved Me (and Minnesota)

From tomorrow on, the high pressure area over Ontario and Quebec (see clockwise circulation on the Mid-tropospheric water vapor loop from Colorado State satellite slider) will continue to nudge westward, parking itself in western Ontario and even into Manitoba. We will be in the moist stream of air, so the dew points will rise to the uncomfortable 60's. They could get there tonight if more areas get more substantial rain late today, but you'll certainly notice the humidity increasing, especially from Thursday on. Any weak low coming from the main storm off Baja California or other systems moving from the eastern Pacific on shore has the potential for producing a more widespread chance for showers and thunderstorms, but there will be at least some chance of afternoon and evening showers and thunderstorms each day. High temperatures will climb into at least the middle 80's with a sunnier, breezy day having a shot at upper 80's or perhaps lower 90's.

For the entire period of Wednesday through the weekend, the rainfall from thunderstorms will be hit and miss with some areas getting heavier showers and some areas getting little or no rain.

The chance for overnight showers and thunderstorms will be more dependent on one of those stronger lows going by. At this point, it appears that we might have a better shot of overnight into early morning storms on Wednesday night and Thursday, but I wouldn't dare try to pin the overnight threat down later in the forecast. Otherwise, each night will have lows in the 60's, due to the uncomfortable dew points, and a shot at some dense fog.

Much of northern and central Minnesota could use the rain, since these areas have mainly seen between half an inch and a inch and a half of rain over the past 30 days (light and medium green on the NWS Minnesota 30-day precipitation chart).

Fire Potential Lower, Ozone Potential Initially Lower, But Uncertain If We Get Hotter

Having more moisture in the air should ease the risk of fires in northern Minnesota at least somewhat (see Minnesota fire danger from the Minnesota Department of Natural Resources). Having thunderstorms around will allow the pollutants to mix through a deeper layer above the ground, which would help the ozone situation. On the other hand, any day we stay storm-free could see ozone again being an issue (see current Minnesota Air Quality Index from MPCA), since we will go back to having regular rush hour traffic. At least, we shouldn't have the Canadian wildfire smoke issue, since the clockwise circulation of the upper-air high should continue to push the smoke plume towards northern Manitoba, Hudson Bay, and Nunavut (see North American smoke map from the EPA).

Again, this is the my last forecast discussion until June 16 or 19.

Detailed St. Cloud, MN, and Vicinity Forecast

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

Tuesday 5/30/2023: Perhaps a lingering early thunderstorm, then becoming partly sunny, breezy, not quite as warm, and uncomfortably humid. A chance for a scattered afternoon shower or thunderstorm. High: between 80 and 85. Winds: SW 10-20 MPH. Chance of measurable rainfall: 50%.

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

Tuesday Night: Perhaps a lingering evening shower, then partial clearing. Light winds with areas of dense fog forming. Low: between 60 and 65. Winds: SW 5-10 MPH, becoming calm late. Chance of measurable rainfall: 20%.

Wednesday 5/31/2023: Some morning fog, then hazy sunshine and warmer. Still uncomfortable humidity with a chance of a late day shower or thunderstorm. High: between 82 and 87. Winds: S-SE 5-10 MPH. Chance of measurable rainfall: 40%.

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

Wednesday Night: Partly clear evening, then a chance for a late night scattered shower or thunderstorm. Still warm and sticky. Low: between 60 and 65. Winds: SE 5-10 MPH. Chance of measurable rainfall: 40%.

Thursday 6/1/2023: A good chance of morning showers and thunderstorms, then becoming partly sunny, a bit breezier, continued warm and uncomfortably humid. A chance for a late day shower or thunderstorm. High: between 80 and 85. Winds: SE 8-15 MPH. Chance of measurable rainfall: 50% in the morning, 30% in the afternoon.

Thursday Night: Partly to mostly cloudy, warm, and sticky. A slight chance for a shower or thunderstorm. Some areas of fog by morning. Low: between 63 and 68. Winds: SE 5 MPH. Chance of measurable rainfall: 20%.

Friday 6/2/2023: Mixed clouds and sun, continued warm and uncomfortably humid with a chance for a late day shower or thunderstorm. High: between 82 and 87. Winds: SE 5-15 MPH. Chance of measurable rainfall: 40%.

Friday Night: Partly to mostly cloudy again. Continued summerlike warmth and humidity. A chance for a shower or thunderstorm. Some areas of fog by morning. Low: between 64 and 68. Winds: SE 5 MPH. Chance of measurable rainfall: 20%.

Saturday 6/3/2023: More of the same. Perhaps some early fog or a thunderstorm, then mixed clouds and sun, continued warm and uncomfortably humid with a chance for a late day shower or thunderstorm. High: between 85 and 90. Winds: SE 5-15 MPH. Chance of measurable rainfall: 30%.

Extended: Continued warm and sticky late week with some chance for thunderstorms into the weekend???

Forecast Confidence (10 - "The Rabbits Will Thump Even Though I Fed Them"; 0 - "The Rabbits Will Offer To Groom My Bald Spot"): 6 Tuesday, 5 Tuesday night and Wednesday, 3 Wednesday night through Saturday.

Yesterday's High: 88°F; Overnight Low (through 6 AM Tuesday): 67°F
St. Cloud Airport 24-Hour Precipitation (through 6 AM Tuesday): 0.12 inch; SCSU 24-Hour Precipitation (through 6 AM Tuesday): 0.34 inch

Next Update: June 16 or June 19, 2023 7 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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