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December 28-31 Snow Systems

Hoosier

By Hoosier,
in Lakes/Ohio Valley

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cyclone77

cyclone77

Posted
Posted
40 minutes ago, hawkeye_wx said:

I picked up an inch today from 0.05" liquid.  A similar ratio Friday could get me 5 inches.

Yeah this is a good sign for tomorrow.  Picked up 0.8" today, with very nice dendritic action during some of the heavier bursts.  Feeling pretty good about a good 4" of feathers tomorrow.  

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michsnowfreak

michsnowfreak

Posted
Posted
17 minutes ago, cyclone77 said:

Yeah this is a good sign for tomorrow.  Picked up 0.8" today, with very nice dendritic action during some of the heavier bursts.  Feeling pretty good about a good 4" of feathers tomorrow.  

Glad you guys are finally getting in on the action! Temps will really tank with the fresh snow. Hoping we can add another 2" to the pack here the next few days, but clearly the best snows will be south. Considering it's already a winter wonderland here and we have done very well this month, I am not complaining. Laying down an expansive area of snowpack in an arctic airmass is winter gold.

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Hoosier

Hoosier

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3 forecast soundings off the 18z NAM valid 18z Friday.  The first one is from south of Champaign, the second is near Joliet, and the third is south of Rockford. Can see the differences in DGZ depth across the region, with the sounding from south of Champaign having the smallest.  

Also note there isn't complete saturation on here.  Perhaps the NAM will be incorrect about that, but we had that issue with the 12/24 event.  Maybe I'm just a little paranoid with looking for possible fail modes regarding ratios. Will be checking out the HRRR/RAP forecast soundings.

nam_2017122818_024_39.88--88_41.thumb.png.b3a7fbf7f21238fbfe996a2f2bf45663.png

 

nam_2017122818_024_41.54--88_14.thumb.png.87d811c84acf2ced43e3e3a78a11d1c0.png

 

nam_2017122818_024_42.1--89.2.thumb.png.9bd8d8ffd09b78942d3064b4c77ef999.png

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cyclone77

cyclone77

Posted
Posted
12 minutes ago, Hoosier said:

3 forecast soundings off the 18z NAM valid 18z Friday.  The first one is from south of Champaign, the second is near Joliet, and the third is south of Rockford. Can see the differences in DGZ depth across the region, with the sounding from south of Champaign having the smallest.  

Also note there isn't complete saturation on here.  Perhaps the NAM will be incorrect about that, but we had that issue with the 12/24 event.  Maybe I'm just a little paranoid with looking for possible fail modes regarding ratios. Will be checking out the HRRR/RAP forecast soundings.

nam_2017122818_024_39.88--88_41.thumb.png.b3a7fbf7f21238fbfe996a2f2bf45663.png

 

nam_2017122818_024_41.54--88_14.thumb.png.87d811c84acf2ced43e3e3a78a11d1c0.png

 

nam_2017122818_024_42.1--89.2.thumb.png.9bd8d8ffd09b78942d3064b4c77ef999.png

Went back and looked at NAM vs GFS soundings for today's little event.  Chose areas where it was precipitating and it seems the NAMs have issues with full saturation vs GFS.  At least on the pick and choose soundings I did.  I'm gonna bank on full saturation given what happened today.  Tomorrow's DGZ is extremely nice for the northern half of that snow band.  Even though some of the forcing is above the DGZ, the majority of it seems safely inside.  Honestly wouldn't be surprised if LSRs end up above 20:1 in any enhanced bands that develop.  I'm usually pretty conservative with forecasting LSRs, but I'm all in on a high ratio jackpot tomorrow somewhere along the main axis.

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Hoosier

Hoosier

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9 minutes ago, cyclone77 said:

Went back and looked at NAM vs GFS soundings for today's little event.  Chose areas where it was precipitating and it seems the NAMs have issues with full saturation vs GFS.  At least on the pick and choose soundings I did.  I'm gonna bank on full saturation given what happened today.  Tomorrow's DGZ is extremely nice for the northern half of that snow band.  Even though some of the forcing is above the DGZ, the majority of it seems safely inside.  Honestly wouldn't be surprised if LSRs end up above 20:1 in any enhanced bands that develop.  I'm usually pretty conservative with forecasting LSRs, but I'm all in on a high ratio jackpot tomorrow somewhere along the main axis.

Agree that the main axis has higher confidence on better ratios.  Question is whether the northern/southern areas get in on the good dendrites.

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OrdIowPitMsp

OrdIowPitMsp

Posted
Posted

Ongoing flurries all day here which was a little unexpected. Officially finished with 1.1" If the DGZ had been a little bigger today would have been a nice event. Might sneak another 0.5 in tomorrow with the northward trend.

 Hoping for a big overpreformer for the Iowa crowd, lived out there for some nice winters. I'll never forgot the Dec 2009 blizzard. 

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Radtechwxman

Radtechwxman

Posted
Posted
12 minutes ago, Hoosier said:

00z NAM looks like it tightened the snowband.  The southern end in particular had a noticeable reduction.

I'm sure I'm partially wishcasting but I'm just not buying it. NAM has been flip flopping each run. The other models have shifted north but only small changes and overall consistent. Now if 0z gfs follows suite then I will be legit concerned 

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Baum

Baum

Posted
Posted
32 minutes ago, Hoosier said:

00z NAM looks like it tightened the snowband.  The southern end in particular had a noticeable reduction.

For those trying to track without model access that's tough to read. Although based on afternoon AFD's it almost seems like enough lift exists irregardless of model swings for a widespread area of 1-4"

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SchaumburgStormer

SchaumburgStormer

Posted
Posted

LOT extended the WWA North a row of counties to account for 2 to 4" accums. 

Edit: My mistake, LOT had not yet issued any. DVN had.  

URGENT - WINTER WEATHER MESSAGE
National Weather Service Chicago IL
833 PM CST Thu Dec 28 2017

ILZ008-011>014-INZ001-002-291045-
/O.NEW.KLOT.WW.Y.0004.171229T1800Z-171230T0600Z/
Ogle-DeKalb-Kane-DuPage-Cook-Lake IN-Porter-
Including the cities of Oregon, DeKalb, Aurora, Elgin, Wheaton,
Chicago, Gary, and Valparaiso
833 PM CST Thu Dec 28 2017

...WINTER WEATHER ADVISORY IN EFFECT FROM NOON FRIDAY TO MIDNIGHT
CST FRIDAY NIGHT...

* WHAT...Snow expected. Plan on slippery road conditions,
  including during the evening commute on Friday. Total snow
  accumulations of 2 to 4 inches are expected, with the highest
  amounts likely to be across southern portions of the counties.

* WHERE...Portions of northwest Indiana and north central and
  northeast Illinois.

* WHEN...From noon Friday to midnight CST Friday night.

* ADDITIONAL DETAILS...Be prepared for reduced visibilities at
  times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Be prepared for snow covered
roads and limited visibilities, and use caution while driving.

$$
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cyclone77

cyclone77

Posted
Posted
7 hours ago, StormChaser4Life said:

This system today is kind of priming our atmosphere for tmrw. So hopefully we won't waste a ton of our precip shield into saturation. The air is so dry here. Would be seeing moderate to heavy snow today if it weren't for it. Strong returns on radar but RH is barely over 60%

This is a great point, and I think it could be a big factor in beefy ratios.  Very light snow continues to fall over much of the northern half of Iowa, northern IL and surrounding areas.  It's not adding up, but it's keeping the lower 3km fairly saturated as we await the incoming clipper.  

If the 3km NAM is correct and 0.3" of precip falls near the QC, a low-end warning criteria event is possible there.

BTW, lol at the DVN sounding from tonight.  Surface temp/dew isn't correct, and resulted in some beefy cape.  Also of note, the DGZ extended from the surface all the way up to near 3km.

9hj8r5.jpg

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hlcater

hlcater

Posted
Posted
23 minutes ago, cyclone77 said:

This is a great point, and I think it could be a big factor in beefy ratios.  Very light snow continues to fall over much of the northern half of Iowa, northern IL and surrounding areas.  It's not adding up, but it's keeping the lower 3km fairly saturated as we await the incoming clipper.  

If the 3km NAM is correct and 0.3" of precip falls near the QC, a low-end warning criteria event is possible there.

BTW, lol at the DVN sounding from tonight.  Surface temp/dew isn't correct, and resulted in some beefy cape.  Also of note, the DGZ extended from the surface all the way up to near 3km.

 

Yup, these flurries are doing a huge favor.

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Hoosier

Hoosier

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1 hour ago, cyclone77 said:

This is a great point, and I think it could be a big factor in beefy ratios.  Very light snow continues to fall over much of the northern half of Iowa, northern IL and surrounding areas.  It's not adding up, but it's keeping the lower 3km fairly saturated as we await the incoming clipper.  

If the 3km NAM is correct and 0.3" of precip falls near the QC, a low-end warning criteria event is possible there.

BTW, lol at the DVN sounding from tonight.  Surface temp/dew isn't correct, and resulted in some beefy cape.  Also of note, the DGZ extended from the surface all the way up to near 3km.

9hj8r5.jpg

That's what you call super superadiabatic lapse rates. :D

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Hoosier

Hoosier

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7 minutes ago, michsnowfreak said:

Over an inch of what appears to be solid 20-1 ratios. We may get 2" tonight. Was not expecting this! The snowpack is glistening from the fresh fluff. Deep winter.

I wouldn't doubt if Wyandotte starts finding a way to snow in summer. 

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cyclone77

cyclone77

Posted
Posted

The higher the LSRs the more important every hundredth of precip becomes when trying to nail down snowfall amounts.  It's looking like the QC may be close to ground zero for the heaviest band of precip accumulation.  Model precip generally ranges from 0.2-0.3" there.  I'm gonna assume 20:1 is going to be pretty attainable in the banding that will set up along that band of max precip.  That should put the QC in a nice 4-6" range, with the possibility of 6"+ if ratios end up a bit higher than 20:1 in that main band, or precip ends up a few hundredths north of 0.3".  Here the precip will be a touch less, but we should be close enough to benefit from the northern edge of the better banded precip.  3-5" would be a solid forecast for here, with 4" being about what I expect.  

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