Hoosier

The RGEM is nice but I am expecting it to be overdone on the southern end with some of those snow amounts. For every time when warm air aloft underperforms, you can probably come up with 8 or 10 times where it doesn't. So, planning on sig mixing/ice here and will be pretty surprised if it doesn't.

I think it's really going to be rate dependent tomorrow night for us. Even moderate won't be enough to get it done past a certain time... will need heavy precip to have a shot.

Then it sort of flatlined/reversed after 24 hrs. Good news.

00z RGEM looks like it's coming in a tad warmer so far.

I think it is useful to look at that 12/1/07 storm for at least one thing. I went back and checked the obs at ORD, and they had like 7 hours of freezing rain. There was fairly decent southeast sfc flow like there will be this time. It was 28 when freezing rain began, so it took a number of hours to go from 28 to above 32. Not that we're going to get a repeat outcome at ORD... that's not what I'm saying... but somebody farther south perhaps, depending on just how robust that warm layer aloft is and how much sleet cuts into the freezing rain time.

I remember it being a good ice storm in about the northern half of LOT.

Well, always have to keep the limitations in mind. Flipping through each one individually, almost none of them had a retreating 1045 mb high, so I'd have to think that is a factor in producing snow farther south. Really, anytime you can get accumulating snow with a surface low track like this, take it as a win.

#1 CIPS analog is 12/1/2007. Was in LAF back then but remember that storm. One difference is that the warm nose aloft back then was stronger/farther north, so the ice won't get as far north this time.

I-80 south somehow outsnows the metro area on the GFS. Oh yeah, keeps wisconsinwx's MKE call in play too.

LOT forecast for here sounds about right. A few inches of snow and up to two tenths ice.

Long range HRRR would be acceptable enough. Does seem to have too much diurnal warming tomorrow given widespread clouds.

That was 01-02 when he had that infamous line I think.

Have mentioned some factors which could hurt zr accretion rate, but one positive is that the warm layer is not progged to be super warm during the freezing rain window. All else being equal, it is harder to accrete when the drops are dealing with a layer of 50F aloft compared to say 38F.

To RC's point about the wetbulbs, look at this. Take Kankakee for example. Even at 6z Sat after it has been precipitating for a while, the temp/dew are 31/25. Seems a little questionable imo to have that much of a gap in temps/dews after precipitating for that long, but if it is right, then it provides a source for some cooling to slow down the rate of temperature rise a bit (this is outweighed by waa at this point so the net effect is that temperatures still rise).

Thanks

zr map?

A lot of the ice is progged with temps around 30-32 though, so not the most ideal situation for building up with moderate to possibly even briefly heavy rates. I do still wonder if the 32F line might get north faster than modeled, given the flow taking on an increasing southerly component with time.

Btw, as crazy as it seems, this storm will likely put ORD back into positive territory compared to average snowfall to date at least temporarily. What a way to run a season by getting fat off the early surplus.

Pretty much, lol There is some nice evaporational cooling early on before the waa surge kicks in, really evident looking at this.

Still holding out for about 2-3" on the front end. Will need to get into some good rates for it to happen. I just can't buy into the coldest models in a setup like this.

Don't have the ice map but that seemed like a pretty icy Euro run.

The GFS looks as good as it does in northern IL because of what happens between 54-57 hours. Right as 850 mb temps are about to go above freezing, the northward progress stops with even some minor cooling.

There's the case for not flipping over to a mix too early. But man, how many times have we sat here and watched the waa overperform. Past experience says to be cautious but hopefully enough precip gets down before the thermal profiles become more hostile.

Best climo