Monday, August 19, 2019  3:50 AM

Chance of Late Monday Night, Tuesday Morning Storms, Then Drier and Cooler(!!??)

Nearing Record Levels in 2019 Half-Inch Events

The St. Cloud area picked up another couple of dousings in Friday night and Saturday night thunderstorms. None of the days produced half an inch of rain, but there have already been 22 days this year with at least half an inch of precipitation, including the one on August 13. That's only one day short of the 10 years with the most frequent half inch rain events. While St. Cloud hasn't already picked up the heaviest rainfall, the January through July precipitation was more than seven and a half inches above average and ranked as the 6th wettest first 7 months of the year in St. Cloud records.

Looking for Heat This Week?? Long-Range Forecasts Were Off Enough to Get Us The Opposite

Over the next week, we will actually have the opportunity to dry out a bit, but that's mainly because the long range forecast for this week will be wrong.

There were promises during the early and middle portions of last week that we would have true summer heat and humidity for the beginning of the State Fair this week. This forecast going wrong is an example of how difficult it is to forecast far in advance (even a week out). The main aspect of that long-range forecast involved that large high pressure system (see counterclockwise circulation center Mid-Tropospheric water vapor loop from Colorado State slider menu) associated with the big heat from Alabama to California (see Yesterday's High Temperature Map from NWS/SUNY-Albany). The overall forecast shows that the high will lurch westward over the southern and central Rockies during this week. This will get some of the worst heat out of the Southeast, but drive it further to the north in the Rockies and the Interior Pacific. So, the large weather pattern forecast doesn't appear to be terrible.

However, to get the heat through the Dakotas and into Minnesota, the nose of hot plume of air had to be forced eastward. That would depend on a Gulf of Alaska low pressure system driving the nose further to the east. Instead, weather systems that will cross from eastern Asia across either the North Pacific or Alaska are forecast to be stronger, which will drive the Canadian cold front expected tomorrow much further to the south and east. Even as we would head to the weekend, the forecast is to keep the main storm track in the vicinity of the Northern Plains, rather than push up into the Canadian Prairie Provinces. That means this weekend would get more humid with the potential for showers and thunderstorms, but no big heat would be in store (that is, if this detail holds up). So, that's how the computer forecasts can get much of the basic weather pattern right more than a week in advance, but still completely blow local forecasts over a wide area.

Showers and Thunderstorms Late Tonight and Tuesday Morning

The details for this scenario is that our best chance for showers and thunderstorms during the work week will be from late tonight through tomorrow midday as the cold front approaches. There aren't a great deal of clouds (see Shortwave Albedo satellite loop from Colorado State slider menu) back in Alberta where the cold front is, but we will still have a good chance of showers and thunderstorms. The potential for either severe weather or heavy rainfall isn't great in central Minnesota.

Turning Warmer With Slowly Increasing Humidity Today and Tonight

Before the late night and Tuesday morning storms, we will have a mainly sunny and warmer day with a noticeable increase in humidity as the day goes on. Even though the computers, with their cool bias that has been seen much of the summer, are hinting at temperatures in the 80's today, I am keeping the highs from the middle 70's to near 80, since yesterday's highs were only in the middle 70's in eastern South Dakota, the source of today's air (see Yesterday's High Temperature Map from NWS/SUNY-Albany). Tonight will be much milder as the southeast winds will keep up in advance of the cold front. Those uncomfortable dew points in the 60's in Nebraska (see NWS Aviation Weather Center METAR menu) will make it into Minnesota by tonight, so our lows will likely stay in the 60's.

We have a chance to see some Tuesday afternoon sunshine after the morning showers and thunderstorms wind down. That's when the drier air will begin to work its way in. The sunshine will give us one last shot (for a while) at an 80-degree high.

September-Like for Start of State Fair (Wednesday Through Friday)

The cooler Canadian air mass will take hold Tuesday night and last at least into Friday. Lows will be in the lower 50's Tuesday night with some 40's possible on Wednesday and Thursday nights. Some of the computer forecasts are trying to make temperatures September-like with highs in the middle or upper 60's, but I'll lean towards these forecasts being too cool and push highs mostly in the low to perhaps middle 70's.

Stormier(??) Next Weekend(??)

As noted above, it appears that the warm and humid air mass would be back for the weekend, but I certainly don't trust any thunderstorm forecast more than 2-3 days out, so it's too early to pinpoint potential rainfall or severe weather.

Confidence Level: "The Bulb on That Hard-To-Reach Light in the Foyer Will Burn Out"

Monday 8/19/2019: Sunny, breezy, and a shade warmer and a bit more humid. A slight chance of an isolated shower or thunderstorm. High: between 75 and 82. Winds: SW 8-15 MPH. Chance of measurable rainfall: 10%.

Confidence Level: "Every Time I Try to Put in a New Bulb, the Light Fixture Will Try to Detach From the Ceiling"

Monday Night: Partly clear, breezy, warmer and more humid. Perhaps a late night shower or thunderstorm. Low: between 62 and 68. Winds: S 8-15 MPH. Chance of measurable rainfall: 30%.

Tuesday 8/20/2019: Mixed clouds and sun, warm, and oppressively humid. A good chance of showers and thunderstorms,, especially during the morning and midday. High: between 77 and 82. Winds: S 10-20 MPH, becoming NW 10-25 MPH in the afternoon. Chance of measurable rainfall: 60% in the morning, 30% in the afternoon.

Tuesday Night: Clearing, breezy, cooler, and drier. Low: between 48 and 53. Winds: N 8-15 MPH evening, 5-10 MPH late. Chance of measurable rainfall: 0%.

Wednesday 8/21/2019: Sunny, breezy, cooler and drier. High: between 68 and 74. Winds: N 8-15 MPH. Chance of measurable rainfall: 0%.

Wednesday Night: Clear with diminishing wind and chilly. Perhaps some fog. Low: between 44 and 50. Winds: N 5-10 MPH. Chance of measurable rainfall: 0%.

Thursday 8/22/2019: Sunny, light winds, and continued cool and dry. High: between 68 and 74. Winds: E 5-15 MPH. Chance of measurable rainfall: 0%.

Confidence Level: "The Only Way I'll Be Able to Change the Bulb and Hold the Fixture in Place Will Be to Yell At It

Thursday Night: Partly clear and continued cool. Low: between 50 and 55. Winds: SE 5 MPH. Chance of measurable rainfall: 10%.

Friday 8/23/2019: Partly sunny, breezy, and more humid. A chance of a late day shower or thunderstorm. High: between 73 and 80. Winds: SE 10-20 MPH. Chance of measurable rainfall: 40%.

Extended: Warmer and more humid next weekend with better chance of showers and thunderstorms???

Forecast Confidence (10 - "The Rabbits Will Thump, Objecting to Me Yelling at the Light Bulb"; 0 - "I Will Be Hosting a DIY Show on Home Repairs"): 7 Monday, 5 Monday night through Thursday, 3 Thursday night and Friday, 1 Weekend.

Yesterday's High: 73°F; Overnight Low (through 3 AM Monday): 50°F
St. Cloud Airport 24-Hour Precipitation (through 3 AM Monday): None; SCSU Precipitation (through 3 AM Monday): None

Next Update: Tuesday, August 20 8 AM (or as needed)

Links

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 Hydrologic Sciences Department home page.