Local Forecast

Wednesday, August 24, 2016 3:35 AM
Prepared by Bob Weisman
Professor of Earth and Atmospheric Sciences
Saint Cloud State University
Earth and Atmospheric Sciences Department
Saint Cloud and Vicinity Forecast


Drying Out for the End of the Work Week

Thunderstorm Blob in SD, S MN Dominates Yesterday

The blob of thunderstorms that developed in the early morning hours yesterday (see infrared loop from College of DuPage Satellite and Radar Menu) ended up dominating the thunderstorms that developed yesterday afternoon and overnight. That blob maintained itself and regenerated as it moved through Minnesota River Valley into the Twin Cities yesterday afternoon. Then, new storms developed last evening along the southern edge of the first blob near the Minnesota-Iowa border. So the border area of southeastern Minnesota, northeastern Iowa, and southwestern Wisconsin has picked up over 2 inches and possible as much as 6 inches. That's why there's a flash flood warning in effect early this morning.

The storms to our south cut off the best lift and moisture supply along the cold front that spent yesterday moving from the western Dakotas into western Minnesota (see 24-hour loop of NWS WPC US weather maps). The only major storms that erupted along the front were mainly in Manitoba and Ontario overnight. The high clouds blowing off from the storms to our south cut down a bit on our afternoon sun, so highs remained in the lower to middle 80's (see NWS: Last 72 hours of St. Cloud Observations). Still, the near 70 degree dew points kept things pretty muggy.

Since the front is still just to our west early this morning and we haven't had any rain (see NWS Upper Mississippi Valley radar loop), temperatures have remained quite warm overnight (see UCAR Minnesota surface chart loop) with still that uncomfortable humidity (brown on the UCAR hourly dew point chart). The cold front will come through around sunrise. There might be a scattered shower or thunderstorm, but I'd only give us a 1 in 3 shot at seeing a shower early this morning.

Drying Out Today

Behind the cold front, the air isn't much cooler, but is significantly drier. There will be sunshine and a strong west to northwest wind. That air will pick up some moisture from the still moist ground in the area, but at least dew points will drop off to noticeable levels this afternoon. So, highs will climb into the lower 80's again, but it will feel a lot more comfortable than yesterday.

Some Clouds, Maybe a Shower Early Tomorrow? Better Friday!

We still have to get rid of the main low pressure system, which spun its way across Saskatchewan yesterday (see infrared loop from College of DuPage Satellite and Radar Menu). It is drifting a bit to the south as it travels eastward, so the main area of persistent clouds and occasional showers has drifted further to the south over the past day (see last three hours on Environment Canada Prairie Provinces radar loop). This certainly means that northern Minnesota will see a chance of some showers created by the contrast between the warmer air aloft and the chilly air in the middle atmosphere by late today and into tonight. This upper low is forecast to track a little bit further to the south, so central Minnesota will be brushed by it late tonight into tomorrow morning. This is similar to the weather set-up we saw last Saturday, when we had all of those rain showers during the morning and midday. However, two factors favor fewer rain showers in central Minnesota on Thursday: the upper-low is tracking further to the north (so we won't get a direct hit) and there is less moisture at the ground. Sti;;, expect late night clouds that will persist into the middle of the day with a couple of brief scattered showers. We could see more periods of sunshine by the afternoon. It will be cooler with highs in the lower 70's and a decent west wind.

After the upper-air low moves away, we will clear out Thursday night and keep the sunshine for Friday. Lows will drop into the 50's with perhaps some areas of dense fog by morning. Friday's highs will rebound to the 70's and a lot more sun than Thursday will make it feel much warmer.

After Friday, ??????

The next storm in this series is the smaller counterclockwise-rotating low moving through the chimney of Idaho early this morning (see water vapor loop from College of DuPage Satellite and Radar Menu). This system is expected to linger in the central Rockies through the end of the work week, then head towards the general South Dakota-Nebraska-Iowa-Minnesota area. This system will give a shot at some widespread rain showers when it arrives. The trouble is that the primary US forecast takes this over Minnesota early Saturday, which would means showers and thunderstorms Saturday and perhaps as early as late Friday night. The main European forecast has this system only in the Dakotas by late Saturday, which would push the chance of showers to Saturday afternoon into Saturday night. So, at this point, I'll channel my inner Jeff Locke (Mitch Berger? Greg Coleman?) and punt on making a definite forecast for Saturday through Sunday. Note the Great Divide of Uncertainty in the forecast below.

Expected Busy Atlantic Hurricane Season Perking Up

There's a huge back-up of storms in the Tropical Atlantic to central Africa (see loop of Meteosat satellite images from the University of Wisconsin SSEC), part of the reason hurricane forecasters have been bullish on the expected number of storms this season. Already the seventh named Atlantic storm, Gaston, has reached tropical storm strength with top winds of 65 MPH, so it is approaching hurricane strength. This storm is expect to take a northward turn and stay away from land. It is the eastern-most storm in this western and central Atlantic satellite view. There is another storm of interest drifting across the Lesser Antilles ahead of it. It isn't developed enough to have a name, but could as it moves into the Bahamas later this week. This could easily affect Florida late in the weekend, but that's already pushing out forecasting luck about tropical weather systems.

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Confidence Level: "I Will Still Have Dandruff Tomorrow"

Wednesday 8/24: Any showers ending, then clearing, breezy, and warm, but becoming less humid. A slight chance of a shower or thunderstorm. High: between 80 and 85. Winds: WNW 10-20 MPH. Chance of measurable rainfall: 20%.

Wednesday Night: Partly clear evening, maybe some clouds late, diminishing wind, cooler and less humid. Low: between 54 and 58. Winds: WNW 5-15 MPH. Chance of measurable rainfall: 20%.

Thursday 8/25: A sunny start, then rapidly becoming mostly cloudy, breezy, and cooler. Maybe an occasional sprinkle or shower. High: between 68 and 74. Winds: NW 10-20 MPH. Chance of measurable rainfall: 30%.

Thursday Night: Clear, light winds, and cool. Maybe some fog towards morning. Low: between 48 and 53. Winds: NW 5-10 MPH. Chance of measurable rainfall: 10%.

Friday 8/26: Sunny, less windy, and warmer with comfortable humidity. High: between 74 and 78. Winds: SW 5-15 MPH. Chance of measurable rainfall: 10%.

Confidence Level: "A Squirrel Will Squawk At Me" (they really hate me...)

(the Great Wall of No Confidence Goes Up Late Friday Afternoon)

Confidence Level: "The Cat Will Not Sit on My Grading"

Friday Night: Partly clear, breezy, and not as cool. Noticeably humid. A chance of late night showers and thunderstorms. Low: between 55 and 60. Winds: SE 8-15 MPH. Chance of measurable rainfall: 40%.

Saturday 8/27: Mixed clouds and sun with a chance of showers and thunderstorms. Some heavy rainfall possible. High: between 70 and 75. Winds: SW 10-20 MPH. Chance of measurable rainfall: 50%.

Extended: Drier Sunday?????

Forecast Confidence (10 - "Know what gas will cost next week, Bob?"; 0 - "Been a victim of road rage lately, Bob?"): 7 Wednesday through Friday, 2 Friday night through Sunday.

Yesterday's High: 83F; Overnight Low (through 3 AM): 66F
St. Cloud Airport Precipitation (through 3 AM Wednesday): None; SCSU Precipitation (through 3 AM Wednesday): None

Normal Temperatures for August 24 - High: 78F; Low: 55F
Next Update: Thursday, August 25 8:00 AM (or as needed)

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Current Watches/Warnings

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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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