Nov. 25th-26th Midwest Snowstorm Potential

[Louieloy102]

7 minutes ago, CoalCityWxMan said:

Still think it’s overdone, but impressive to say the least 

Of note that's the Kuchera ratios and not 10:1, so probably even a "realistic" version of events.

[CoalCityWxMan]

Honestly concerned about the state roads could be in tomorrow, with lots of people traveling home or back to school it could get real dangerous or even impossible to travel. Even half of what the euro is showing would be bad. 

[Chicago WX]

2 minutes ago, Hoosier said:

We need road trip.  

Maybe not too far.  

[SchaumburgStormer]

Just now, CoalCityWxMan said:

Honestly concerned about the state roads could be in tomorrow, with lots of people traveling home or back to school it could get real dangerous or even impossible to travel. Even half of what the euro is showing would be bad. 

Couple that this will be the first “major” snow of any type for the year. Classic line, don’t travel unless absolutely necessary. 

[Thundersnow12]

Love where I sit here. 12z Euro looks almost as good as last night.

Going to try to have a blog post up by late afternoon/early evening. 

[Hoosier]

I have a small-ish tree in my backyard that still has 80-90% of its leaves.  Between the wind and whatever snow occurs, it should look a lot different in a couple days.

[RogueWaves]

4 minutes ago, Harry Perry said:

Unreal. The range of solutions is giving even the best forecaster a run for their money. 

 

I’d hope that GRR and DTX put out at least a SWS or WSW this afternoon. You can always go to an advisory - but with tomorrow/tomorrow night being a big travel time, it would be wise.. especially if the Euro and like models happen to verify. 

That's what we SHOULD'VE been unnder since the models were at least equally split with a south track option. BUT, good ole GRR office leans on the NA models and ignores their own am write-up concerns with their watch box placement.

[Radtechwxman]

Euro has been remarkably consistent the last several runs. I trust it more than GFS. Euro looks like it pretty much tracks the low right along I70. Would feel more comfortable if that was a touch south but still better than GFS which is north of I70 by a good bit

[OceanStWx]

10 minutes ago, Louieloy102 said:

Of note that's the Kuchera ratios and not 10:1, so probably even a "realistic" version of events.

Maybe MORE realistic, but still not realistic. The Euro will lump all frozen precip together as "snow," so in areas expected to mix even Kuchera snow ratios will be dramatically overdone. Like 8:1 instead of 2 or 3:1. 

[Sciascia]

For anyone (mostly N IL) people interested in the potential historical nature of this snow, the largest November snowstorm in Chicago’s history dropped 12 inches of snow. The date? Ironically enough, November 25th & 26th...1895!

Can’t say that it will happen, but there looks to be a chance.

[ConvectiveIA]

I can’t tell if the 12z euro placement of the low yields any QPF for us.

[Hoosier]

4 minutes ago, OceanStWx said:

Maybe MORE realistic, but still not realistic. The Euro will lump all frozen precip together as "snow," so in areas expected to mix even Kuchera snow ratios will be dramatically overdone. Like 8:1 instead of 2 or 3:1. 

Great point.  I usually prefer looking at it more than a 10:1 map since it at least tries to account for different ratios, but only when you know you're going to be all snow.  Also have to consider things like ground temp, etc that the Kuchera map doesn't know about but in this case the rates should overcome that fairly quickly.

[Malacka11]

Just now, Hoosier said:

Great point.  I usually prefer looking at it more than a 10:1 map since it at least tries to account for different ratios, but only when you know you're going to be all snow.  Also have to consider things like ground temp, etc that the Kuchera map doesn't know about but in this case the rates should overcome that fairly quickly.

Speaking of which, what type of rates are we looking at? I've seen many different things mentioned in different places thus far 

[HillsdaleMIWeather]

SE trend continues. Some of the places in IWX might end up back in the money.

[Hoosier]

2 minutes ago, Malacka11 said:

Speaking of which, what type of rates are we looking at? I've seen many different things mentioned in different places thus far 

At peak?  1-2" per hour, maybe even 3"

[Malacka11]

Just now, Hoosier said:

At peak?  1-2" per hour, maybe even 3"

Damn. I'll bite!

[Paulie21]

7 minutes ago, Hoosier said:

Great point.  I usually prefer looking at it more than a 10:1 map since it at least tries to account for different ratios, but only when you know you're going to be all snow.  Also have to consider things like ground temp, etc that the Kuchera map doesn't know about but in this case the rates should overcome that fairly quickly.

Onset rain and some places sitting at mid-upper 30s the night before it'll be tough at first but given strong dynamical cooling i can't imagine there being much of a mix, quick transition to steady/heavy snow. Thinking ratios will be under 10:1 though...weird

[CoalCityWxMan]

15z RAP has a nice band of 12-18” in northern IL with it still snowing at the end of the run. 

[hlcater]

2 minutes ago, CoalCityWxMan said:

15z RAP has a nice band of 12-18” in northern IL with it still snowing at the end of the run. 

I see that northern edge . Lets have that happen.

[CoalCityWxMan]

Just now, hlcater said:

I see that northern edge . Lets have that happen.

Yeah the RAP is trying to give some areas on the northern fringe some love. I’d agree with the general placement of the snow swath on the RAP

[Hoosier]

I wonder if Gary will pull off a 60 mph gust.  I think it's possible given their proximity to the lake.  

[OceanStWx]

5 minutes ago, Hoosier said:

Great point.  I usually prefer looking at it more than a 10:1 map since it at least tries to account for different ratios, but only when you know you're going to be all snow.  Also have to consider things like ground temp, etc that the Kuchera map doesn't know about but in this case the rates should overcome that fairly quickly.

Kuchera has the greatest differences near zero, which is obviously the hardest to predict. For max temp aloft of -2C the ratio is 12:1, which is probably optimistic with a sounding that warm (but it does depend on the depth of that -2C layer, etc.). Increase the temp to -1C and the ratio goes down to 10:1. Freezing? 8:1. +2? 4:1!

So you can see how you can still get snow out of that method, even with very warm soundings. On the other end, very cold temps aloft can dramatically increase ratios when colder doesn't always mean great ratios. 

[hlcater]

Just now, CoalCityWxMan said:

Yeah the RAP is trying to give some areas on the northern fringe some love. I’d agree with the general placement of the snow swath on the RAP

Perhaps. The RAP/HRRR are about a county or two north than the euro with the heavy snow. I think that doesn't come to fruition, but what I do think is plausible is the heavy snow right up until the edge. Seems that's often a feature in bigger storms(especially with dry air in the north) and something the globals don't handle too well. I think the area of literally nothing and 10" is going to be much tighter than current forecasts.

[RCNYILWX]

I wonder if Gary will pull off a 60 mph gust.  I think it's possible given their proximity to the lake.  

Also since their observers very frequently overdo the wind speeds, something we've never figured out what they do on those hourly obs considering that they have an AWOS.

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[Hoosier]

6 minutes ago, RCNYILWX said:

Also since their observers very frequently overdo the wind speeds, something we've never figured out what they do on those hourly obs considering that they have an AWOS.

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At least 60 would be believable in this case.  

[RCNYILWX]

I think this map looks pretty reasonable on how narrow the heaviest snow axis is likely to be given the intense fgen signal being modeled, if not the amounts. Though the ferrier correction is supposed to be good for low ratio events, so the attached 3km NAM map could be a fairly realistic representation. Similar to the 2015 storm, I buy a narrow area of 12"+ amounts. I think the Euro is too widespread with the huge amounts, but we'll see.

 

This is a good tweet from John Homenuk (former board member Earthlight) about the fgen compnent: https://mobile.twitter.com/jhomenuk/status/1066397512519610369

 

The models do a good job on picking up on the signal for intense fgen and negative epv driven banding but exact position is something that is really tough to pin down and is more of a nowcast item.

 

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[OceanStWx]

Just now, RCNYILWX said:

I think this map looks pretty reasonable on how narrow the heaviest snow axis is likely to be given the intense fgen signal being modeled, if not the amounts. Though the ferrier correction is supposed to be good for low ratio events. Similar to the 2015 storm, I buy a narrow area of 12"+ amounts. I think the Euro is too widespread with the huge amounts, but we'll see.

This is a good tweet from John Homenuk (former board member Earthlight) about the fgen compnent: https://mobile.twitter.com/jhomenuk/status/1066397512519610369

The models do a good job on picking up on the signal for intense fgen and negative epv driven banding but exact position is something that is really tough to pin down and is more of a nowcast item.

With that rime factor included, you can see how the snowfall distribution is sharpened on the southern, mix-y end of things.

[ILwxchr]

Blizzard Warnings going up in parts of SE Nebraska and Southwest Iowa. I'd expect that to continue eastward

[Powerball]

GRR went with a WWA for only 3-5". 

[CoalCityWxMan]

18z HRRR...still snowing at the end of the run so add another 1-3” atleast for the hard hit areas. Wow.