Dec 29-Jan 2 potential storm event

[Radtechwxman]

33 minutes ago, purduewx80 said:

12Z soundings from DVN and ILX do show the incredibly dry air from ~650 to 900 mb. Dewpoints below -50C in that layer are among the lowest ever observed in both locations.

 

I knew it was going to be bad but wow that's brutal. However WAA is strong so I feel it will still occur decently quick after stronger returns get overhead. 

[Gino27]

11 hours ago, StormfanaticInd said:

Looking forward to the severe weather here in Indy 

Might be a big day down in Dixie. We could get some thunder if enough instability is pulled up into the OHV. 

[A-L-E-K]

BRL probably a good one to watch for those hoping the southern guidance delivers

[RCNYILWX]

KFFL in southwest DVN CWA getting close already with scattered 3600' clouds and broken at 4700'. OTM broken clouds at 4600'. Not seeing any red flags yet that the antecedent dry air is going to be more prohibitive than expected.

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[blizzardof96]

21 minutes ago, Chicago Storm said:

It’s not going to mean too much, given ample advection from the southwest.

Virga and top down saturation has already started into DVN and ILX CWA’s.

Can see the elevated 700mb RH and frontogenesis moving ENE on mesoanalysis:

 

[madwx]

one thing for sure this will be a quick hitter.  Can see the snow winding down in Madison by around midnight with only maybe an inch or two at best after that

[A-L-E-K]

44 minutes ago, McHenrySnow said:

Glad we have at least 3 McHenry posters all in different areas. Will be interesting to see how this turns out, expect Woodstock to do better than Cary and I. 

[madwx]

Cloud bases still at 17,000 feet here.  Going to need all of the next 7 hours to saturate

[McHenrySnow]

My hope is 5". My range is 3-6". Final call. 

[DaveNay]

6 minutes ago, McHenrySnow said:

My hope is 5". My range is 3-6". Final call. 

I think it will underperform here south of I88-DeKalb. I think the SE winds will have an effect. 1"-3" final call.

[purduewx80]

1 hour ago, ChiTownSnow said:

What does this insinuate?  taking longer to saturate atmosphere, lower than expected QPF?  colder than depicted? 

I'm just pointing out with actual observed data rather than a model that the dry air is very real and significant. The initial forcing will be wasted in moistening that layer, the top down saturation others have mentioned is why we go from flurries to heavy snow in short order. No reason the Chicago area will not see a 2-3 hour period of heavy snow this evening. 

The SPC has a nice sounding climatology page that shows how dry the air over IL was this morning at 12Z compared to the past.

[McHenrySnow]

We had some very light snow early this morning fwiw. 

[hawkeye_wx]

Most models are looking good for Cedar Rapids.  The NAM continues to insist WAA aloft will surge up through the area and kill snow totals.

[CheeselandSkies]

1 hour ago, madwx said:

Cloud bases still at 17,000 feet here.  Going to need all of the next 7 hours to saturate

What else is new?

I seemed to recall an event last winter or the one before that was supposed to be our biggest of the winter and modeled/warning criteria totals were killed by dry air at the outset.

[kevlon62]

Glad we have at least 3 McHenry posters all in different areas. Will be interesting to see how this turns out, expect Woodstock to do better than Cary and I. 

Right on.

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[Chicago Storm]

TSSN in far NW MO.


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[kevlon62]

I'll get the yardstick out on the deck. But going by "official" there is always a somewhat heavier obs report out of Bull Valley that seems to often take the local microclimate cake.

We'll see if they are back in action this winter. I'll say even 8.

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[tuanis]

NAM continues to depict a quick inch or two of snow/sleet slop for the northern tier of counties and even into southern WI before a flip to freezing rain and rain. Are we just discounting that solution? Certainly not unprecedented.

[NEILwxbo]

LTG density on hrrr suggests there could be thundersnow in N IL later 

[madwx]

17 minutes ago, CheeselandSkies said:

What else is new?

I seemed to recall an event last winter or the one before that was supposed to be our biggest of the winter and modeled/warning criteria totals were killed by dry air at the outset.

We’re going to moisten up pretty rapidly this afternoon and go gangbusters for a few hours 

[Chicago Storm]

NAM continues to depict a quick inch or two of snow/sleet slop for the northern tier of counties and even into southern WI before a flip to freezing rain and rain. Are we just discounting that solution? Certainly not unprecedented.

You can totally toss the NAM.


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[madwx]

6.5” final call here with snow ending by 1 am and some patchy freezing drizzle until sunrise 

[SchaumburgStormer]

6 minutes ago, tuanis said:

NAM continues to depict a quick inch or two of snow/sleet slop for the northern tier of counties and even into southern WI before a flip to freezing rain and rain. Are we just discounting that solution? Certainly not unprecedented.

It's 100% on its own. I think we can toss it

[purduewx80]

6 minutes ago, tuanis said:

NAM continues to depict a quick inch or two of snow/sleet slop for the northern tier of counties and even into southern WI before a flip to freezing rain and rain. Are we just discounting that solution? Certainly not unprecedented.

NAM is often far better with lower level thermals than other guidance, but it is a northern outlier with the sleet/freezing rain.

That said, the 12Z HREF (ensemble of hi-res SPC models) shows the mixing getting up to a Janesville-to-Milwaukee line overnight. 

We'll have a better idea of how the mixing line is trending in a few hours.

[tuanis]

3 minutes ago, SchaumburgStormer said:

It's 100% on its own. I think we can toss it

I'll happily toss it... depending on how the radar and upstream obs look this afternoon.

[ChiTownSnow]

9 minutes ago, kevlon62 said:

I'll get the yardstick out on the deck. But going by "official" there is always a somewhat heavier obs report out of Bull Valley that seems to often take the local microclimate cake.

We'll see if they are back in action this winter. I'll say even 8.

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Yardstick?.  Let's start with one of those plastic 6-in rulers first

[Natester]

4 minutes ago, SchaumburgStormer said:

It's 100% on its own. I think we can toss it

Not quite sure to toss it just yet since we all know what happened on 2/11/19.  All the models severely underdid the WAA and as a result southeast Iowa and much of northern Illinois got a major ice storm instead of several inches of snow.  Just my take on it.

In other news, 12z UKMET has wave two southeast of 0z and slower.

[mimillman]

Don't worry, in case you can't get enough of part 2 of this event, the GFS has a redux in 12 days

[Chicago Storm]

NAM is often far better with lower level thermals than other guidance, but it is a northern outlier with the sleet/freezing rain.
That said, the 12Z HREF (ensemble of hi-res SPC models) shows the mixing getting up to a Janesville-to-Milwaukee line overnight. 
We'll have a better idea of how the mixing line is trending in a few hours.

The mixing issue is just one of many issues it has. Being overly dry and well too far north on placement of the heaviest QPF are also big issues.

The NAM is a complete toss, and that’s an understatement.


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[ChiTownSnow]

2 minutes ago, Natester said:

Not quite sure to toss it just yet since we all know what happened on 2/11/19.  All the models severely underdid the WAA and as a result southeast Iowa and much of northern Illinois got a major ice storm instead of several inches of snow.  Just my take on it.

Every storm is unique though and has unique scenarios. IMHO, i think we tend to associate storms with the outliers that we remember from the past too often.