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CATHY WURZER: And I'm Cathy Wurzer. This is Morning Edition on Minnesota Public Radio. What a wild run of weather we're having! In North Dakota, there are winter storm warnings. In parts of Minnesota, heavy rains, flooding, and mudslides.

There are still flood warnings up for significant parts of Minnesota this morning, and more rain is on the way. Rich Neistat joins us right now to talk about the weather. He's with the Chanhassen National Weather Service office. Always good to talk with you, Rich. How are you?

RICH NEISTAT: Good morning, Cathy. Always good to talk to you. I'm doing just fine.

CATHY WURZER: Good. Thanks for joining us.

RICH NEISTAT: You're welcome.

CATHY WURZER: Well, the question people want answered this morning-- how much rain did parts of our region get last night?

RICH NEISTAT: There is a wide swath of areas in excess of 4 inches from-- much of the Twin Cities area, across about the northern third of Wisconsin. That's a very wide swath of in excess of 4 inches. There were some isolated reports of much heavier amounts. Minnetonka, out in Western Hennepin County, had 6.2 inches. And in Isanti county, so far the winner of the rain gauge stakes 9 inches at Spencer Brook in Isanti county.

CATHY WURZER: Goodness. Wow. How does this compare to the 1987 floods? You and I were working that night. I remember that distinctly.

RICH NEISTAT: That's right. Actually, it ended up being less what we had last night. We ended up with back on July 23 of '87, which is the one that you're referring to. We set a rainfall record with 10 inches of rain falling in a 24-hour period. That was at the Minneapolis airport.

And what was interesting about that particular flood was two days earlier, there had been rains of probably close to 8 inches. I'd have to refigure it out in parts of Northern Bloomington on down toward Shakopee. So the ground was already quite saturated when the other deluge came in.

And my recollection of the July 23 storm was the rain was going pretty much horizontal. I remember that's what my kids told me when I got home. And they said it was just like a hurricane. Of course, they'd never been in a hurricane.

But I know the next morning, after I recovered a little bit from working late, I drove down to a parking lot near my house. And the parking lot is one of these low spots, and the water had to be at least 15 feet deep in that parking lot.

CATHY WURZER: Well, certainly this morning, water is still deep in many parts of the metro and then outside the metro area, too.

RICH NEISTAT: Right.

CATHY WURZER: Our friend Paul Douglas over at WCCO TV was saying that last night's storms were almost the deluge anyway, was due to what he calls a train echo. What is that?

RICH NEISTAT: Oh, boy. I should engineer a good response, shouldn't I to that? Essentially, that's where thunderstorms develop over one area. And then they might-- for example, back in July, 23rd of '87, they developed west of the Twin Cities, moved east across the Twin Cities, and then more developed west of the Twin Cities and moved east across the Twin Cities.

So it's regenerative. It's basically repeat storms going over the same area. Back in 1987, we really didn't understand the mechanism of what causes train echos. Since then, there's a lot of research that has gone into it, and we understand it quite well. And as I'm sure you and your listeners are well aware, there was talk about this heavy rain quite some time in advance of it actually occurring last night.

CATHY WURZER: Well, what's fueling all this rain?

RICH NEISTAT: Well, for any rain, what you need is moisture, lift, and instability. Instability is the difference of temperature with height. But I think the quick answer is, we're having unusually high moisture available, especially in September. It used to be that 70 degree dew points were virtually unheard of in September.

And now we've had them in September and into early October. It's the same type of thing that back in September was fueling some huge hail. There were reports of golf ball sized hail, which is not unusual. But also tennis ball, baseball-sized hail.

I've worked in the Weather Service in the Twin Cities since 1974. And I never remember reports of baseball-sized hail in September before. So it's actually the presence of this moisture-laden, very warm, humid air at this time of year, which normally is not found as far north as Minnesota.

CATHY WURZER: Well, speaking of folks in the north sections of our region, I'm looking at the radar right now, and there's some snow in parts of North Dakota. And we're looking at this cold front that's due to come through somewhere along the line. How potent is this cold front we're talking about?

RICH NEISTAT: Well, it's certainly going to bring in much cooler air. There's no doubt about that, with temperatures dropping into the 30s by morning. But it's October and that's not unusual. So I think it's not really a question of this is unusually cold air pouring in in October. It's just that we've been so far above normal that even a return to slightly below normal readings seems like an abrupt change, which it really is.

CATHY WURZER: I hear we're going to get into a fairly pleasant weather pattern for the weekend.

RICH NEISTAT: It's supposed to be dry. That's what we're thinking. And temperatures recovering should-- at this point, it looks delightful. Give a chance for people to let their things dry out for sure.

CATHY WURZER: We're going to need that opportunity. Rich Neistat, always a pleasure talking to you. Same here, Cathy, really enjoyed it.