St. Cloud, MN Weather Forecast

The expected stalled steering wind pattern has developed with lows off both coasts (see College of DuPage North America mid-level water vapor loop) and the main branch of weather system advance is in Canada. So, we will only see slow changes in our weather. 

We have been doing a bit better on high temperatures the past 2 days than was forecast (highs in the upper 60's; see NWS: last 72 hours of St. Cloud observations). That's after the hard freeze on Saturday and yet another morning frost yesterday. That makes 3 straight days with more than a 30 degree spread between the high and low temperatures (see graph of Saturday and Sunday temperature range, distance between high and low temperatures, on the NWS Twin Cities St. Cloud October high-low temperature graph). That makes 7 October days with at least a 30 degree spread between the daily high and low, including yesterday.

Big Daily Temperature Spread Due to Dry Air

Large differences between high and low temperatures is typical of somewhere in the interior of a continent, rather than being along the coast. The reason is having less water vapor (the gas form of water) in the air for interior places than onshore places.

That's because water vapor is a greenhouse gas:

• Daytime: water vapor absorbs some of the incoming sunshine before it reaches the ground, so the high temperature is held down a bit.
• Nighttime: water vapor absorbs some of the outgoing radiation from the ground, keeping it from escaping to space, so the low temperature is a bit warmer.

This factor becomes more extreme when we are in a drought. When there's even less water vapor in the air than usual, it is easier for the sun to heat the ground during the day, and it is easier for the ground to cool at night, so we can have an even larger temperature range than usual. The lack of clouds (see College of DuPage North America clean infrared satellite loop) also help this large daily temperature spread.

The main difference in the temperature range during this work week will be having the wind stay up overnight versus having calm winds. On breezier days, we won't cool quite as much during the day, so we will need even more daytime heating to keep up this range.

Highs Frequently Near or Above 70 Through At Least Friday, Lows No Colder Than the 40's

The forecast details are pretty much the same: highs near 70 Tuesday and Friday and into the 70's Wednesday and Thursday; lows in the 40's every night, except perhaps Thursday night (milder lows may be suspicious since even the very warm air headed here from Oklahoma and Texas has dewpoints only in the 40's; see yesterday's 4 PM CDT NWS WPC North America zoom-in map).

Perhaps Some Rain Saturday, Much Cooler Sunday Into Next Week

The weather pattern is forecast to become un-stuck by the weekend. Either the current low off British Columbia or a piece of the low to the west of Alaska (see Pacific mid-tropospheric water vapor loop from Colorado State satellite slider) will move west-to-east, but more along the US-Canadian border instead of staying well to the north. Since the warm air ahead of this system will still be quite dry, the potential rain amounts will remain small (see Days 4-7 of the NWS WPC quantitative precipitation forecast) with a chance for scattered showers Saturday. However, having the storm pass further to the south will bring much cooler air to Minnesota from Sunday into the first half of next week. The latest forecasts show a return to average high temperatures (50's) on Sunday. How cold we get early next week will depend on how far south through the Great Lakes that storm will get. At this point, the computer forecasts are having highs no milder than the 40's early next week. There might be the potential for occasional light showers, which could either produce sprinkles or flurries.