September in Minnesota: AC to heat in 24 hours?

Honey, did we get the furnace checked this year?

Yes, that chorus you hear the next few days will be a cacophony of AC units humming, sump pumps gurgling, and sleepy furnaces roaring to life as our next bout of weather whiplash slams Minnesota.

Yes, your AC unit and your furnace may both be working in the 24 hour span between Tuesday and Wednesday afternoon.

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Summer swan song Tuesday?

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Tuesday feels like summer in the Land of 10,000 Weather Extremes. Temps push the 80 degree mark in southern Minnesota and dew points climb well into the sweaty 60s by Tuesday afternoon as far north as Duluth.

Still time for one more dip in your favorite lake?

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Potent low Tuesday night

This is our weathermaker. Watch how this potent, October-like winds up over southeast Minnesota by Wednesday morning. Meteorologists call this kind of rapid intensification cyclogenesis.

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The green shades represent the developing widespread rain shield. The black lines are tightly packed isobars, meaning raw northeast winds will howl across Minnesota by Wednesday morning.

Heaviest rains favor southeast Minnesota

The heaviest rainfall should track near the surface low through southeast Minnesota. Widespread 1 inch-plus totals are likely across most of Minnesota, with the highest  potential for 2 to 3-plus inches in the southeast.

Flash flood watches are likely Tuesday night, and rivers and streams may rise rapidly by Wednesday morning in areas that get the heaviest rains.

Here's the model notion of rainfall distribution this week from the National Oceanic and Atmospheric Administration's Global Forecast System. If the storm track stays south, the heaviest band of 2 to 4 inches-plus potential sets up over northern Iowa, southeast Minnesota and western Wisconsin. A secondary maximum of 2 inches-plus totals may run through northern Minnesota.

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GFS model rainfall output via

Wednesday: Instant fall

By Wednesday there will be no doubt you live in Minnesota, and the calendar says September. In fact, the weather will feel more like mid-October.

Here's a look at temps across the region Wednesday, as the cold front pushes toward still temporarily balmy Chicago.

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Wednesday's winds will howl like the gales of October. A raw north wind gusts to over 30 mph across Minnesota, with gales that may approach 40 to 50 mph on Lake Superior.

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The premature October preview lasts into the weekend, then temps begin to moderate next week. Frost is likely to be widespread by Saturday morning outside the metro; 70s should return next week.

Here's the long range outlook from the  European Centre for Medium-Range Weather Forecasts.

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Looking way ahead, I don't think we're done with upper 70s just yet, and the long range maps may hint at more 80s by later in September.

Stay tuned.

Arizona under water: Norbert delivers flash floods

My former colleagues in Phoenix and Tucson have their hands full with the remnants of once Hurricane Norbert.

Remnant moisture from the system re-curved into Arizona Sunday, and heavy rains today turned freeways into rivers and lakes in the Phoenix and Tucson metro areas.

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Phoenix freeway under water. Image: ADOT

Phoenix set a new daily rainfall record Monday, where as much as 3 inches inundated the Valley of the Sun.

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Rainfall totals of 3 to 4 inches also pounded Tucson, including my old neighborhood in Oro Valley.

Numerous swift water rescues were in progress Monday, and one woman died as flood waters swept away her vehicle.

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Woman awaits rescue in car amidst floodwaters in Tucson. Image: Northwest Fire District

Dying Pacific hurricanes and tropical storms occasionally re-curve into the the Desert Southwest. When they do, copious rainfall totals can occur as they did Monday in Arizona.

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