Feb 16-17th Winter Storm

[ILSNOW]

Southward bound 0z GEFS

[WeatherMonger]

5 minutes ago, ILSNOW said:

Southward bound 0z GEFS

[ILSNOW]

3z RAP which is prolly the most correct model at this point!!!!

The RAP and HRRR are great for entertainment purposes

[Jim Martin]

Growing concern about potential for significant icing during the transition period Thursday evening. Also, the forecast models tonight have snow ranging from near zero in Mercer and Auglaize County to over a foot in northern Williams and northern Fulton County here in Northwest Ohio.

[Hoosier]

28 minutes ago, Thundersnow12 said:

That early stuff is probably a mirage so toss that but yeah still a respectable hit across the metro. Better off using 12hr totals to get rid of that weird initial fake snows. 

Those weird initial fake snows are showing up on various guidance.

[Chicago Storm]

0z GEM a slight bump NW and wetter.

[Chicago Storm]

34 minutes ago, Thundersnow12 said:

That early stuff is probably a mirage so toss that but yeah still a respectable hit across the metro. Better off using 12hr totals to get rid of that weird initial fake snows. 

That's mostly sleet on the RAP, which it is trying to show as 3-6" of snow.

[chuckster2012]

This heavy rain I'm getting should at least wash the salt off my car so it's not a total loss for me down here. Snow's mostly gone anyway.

[SolidIcewx]

[Thundersnow12]

13 minutes ago, Hoosier said:

Those weird initial fake snows are showing up on various guidance.

Yeah more so on newer runs it seems. 3z RAP with advisory level amounts across northeast IL from that alone 

[Chicago Storm]

9 minutes ago, Chicago Storm said:

That's mostly sleet on the RAP, which it is trying to show as 3-6" of snow.

 

1 minute ago, Thundersnow12 said:

Yeah more so on newer runs it seems. 3z RAP with advisory level amounts across northeast IL from that alone 

 

[Thundersnow12]

1 minute ago, Chicago Storm said:

 

 

I don't know what I would do without you 

[Radtechwxman]

03z rap ate its spinach tonight 

[WeatherMonger]

5 minutes ago, Thundersnow12 said:

I don't know what I would do without you 

 

 

[Hoosier]

11 minutes ago, Thundersnow12 said:

Yeah more so on newer runs it seems. 3z RAP with advisory level amounts across northeast IL from that alone 

Obviously how quickly it changes over remains to be seen, but even putting 1-3" in the bank would be a nice little start given the uncertainty after that.

[Thundersnow12]

2 minutes ago, Hoosier said:

Obviously how quickly it changes over remains to be seen, but even putting 1-3" in the bank would be a nice little start given the uncertainty after that.

Joe said it's all sleet so not allowed to be snow. 

[Hoosier]

Pulled this NAM forecast sounding for northwest Indiana on Thursday afternoon.  This is some pretty impressive stuff.  

The pink bars on the left are omega, and there is a lot extending through a deep portion of the atmosphere.  Also note a layer of steeper lapse rates aloft.  All this in the presence of pwats in excess of 0.7", which is excellent for a snow system.  All of this should add up to the potential for a period of 1-2" per hour snowfall rates, if not briefly/locally a tad higher in heaviest banding.

[CheeselandSkies]

Just now, Hoosier said:

Pulled this NAM forecast sounding for northwest Indiana on Thursday afternoon.  This is some pretty impressive stuff.  

The pink bars on the left are omega, and there is a lot extending through a deep portion of the atmosphere.  Also note a layer of steeper lapse rates aloft.  All this in the presence of pwats in excess of 0.7", which is excellent for a snow system.  All of this should add up to the potential for a period of 1-2" per hour snowfall rates, if not briefly/locally a tad higher in heaviest banding.

Thanks for this post, I'm a severe wx guy so I had no clue how to use soundings to forecast winter wx.

[Radtechwxman]

4 minutes ago, Hoosier said:

Pulled this NAM forecast sounding for northwest Indiana on Thursday afternoon.  This is some pretty impressive stuff.  

The pink bars on the left are omega, and there is a lot extending through a deep portion of the atmosphere.  Also note a layer of steeper lapse rates aloft.  All this in the presence of pwats in excess of 0.7", which is excellent for a snow system.  All of this should add up to the potential for a period of 1-2" per hour snowfall rates, if not briefly/locally a tad higher in heaviest banding.

Look at dat hodo. 1000+ SRH. Can we say snow wedges? :p someone call SyFy. Movie incoming. All jokes aside really impressive snow sounding

[WeatherMonger]

1 minute ago, StormChaser4Life said:

Look at dat hodo. 1000+ SRH. Can we say snow wedges? :p someone call SyFy. Movie incoming. All jokes aside really impressive snow sounding

I'm actually rooting for you with this one. Don't want to shovel snow and GHD3 proved using the plow on 4 wheeler sucks for my drive. Pulled the carb off the snowblower I bought 5 years ago and never ran right and it's a chit show at best.

I can't win over the next 60 hours no matter what I do. Last result is a big rosebud and a few 20lb propane tanks.

 

 

 

[Chicago Storm]

0z GEM ENS mean




.

[Radtechwxman]

7 minutes ago, WeatherMonger said:

I'm actually rooting for you with this one. Don't want to shovel snow and GHD3 proved using the plow on 4 wheeler sucks for my drive. Pulled the carb off the snowblower I bought 5 years ago and never ran right and it's a chit show at best.

I can't win over the next 60 hours no matter what I do. Last result is a big rosebud and a few 20lb propane tanks.

 

 

 

Try a flamethrower. Lol. How much did you end up with btw? 

[Radtechwxman]

5 minutes ago, Chicago Storm said:

0z GEM ENS mean




.

Slowly creeping north. But pretty dry like euro

[Hoosier]

10 minutes ago, Chicago Storm said:

0z GEM ENS mean




.

A lot of turds, a lot of spread, or both to have numbers that low.

[RCNYILWX]

If you've been following the CAM runs since they've gotten into range, they're modeling extensive warm sector convection which they explicitly forecast (hence Convection Allowing Models).

The operational models and ensemble members parameterize convection, which is simulating the combined effects of convective clouds that might exist based off other elements being explicitly modeled. One of the pitfalls of higher resolution operational models and ensemble members is that the convective effects applied to many more grid points can result in a high resolution garbage in, high resolution garbage out phenomena.

We had an internal call with WPC last night and a forecaster from one of the offices on the call made the point that it's possible the GFS and NAM were being affected by convective feedback.

The thing about handling convection is that it's hard to be confident if the mass fields will be impacted in a negative way, if models are over deepening a key short wave due to simulated convection, or if some guidance members are overemphasizing negative effects. There's plenty of examples of the all of the above occurring with mid latitude cyclones modeled to have a large convective footprint in the warm sector.

I've been thinking about that point made last night and wondering if it helps explain the lingering high uncertainty in the guidance. Even the CAM solutions are struggling, given the large difference between the members of the 00z HREF.

My thinking is that since there's reasonable agreement in a sub 1000 mb low tracking north of the Ohio River, this has historically been a good track for sig snow into Chicago metro. So while I certainly can't ignore the possibility warning snows miss us south or that the whole system is weaker due to destructive interference from convection, holding with the thinking that the central (including western burbs) and south metro and points south do well.

This is based off pattern recognition, favorable jet dynamics (left exit and right entrance of jet to our north) to allow for more expansive precip shield than some of the stingier guidance on north end, and the antecedent strong downstream ridging (possibly enhanced by latent heat release).

I believe that some of the above factors (minus sfc low track), while unfortunately not overcoming the dry air for the far north and northwest metro and points west for GHD III, enabled the big dog type totals to get up to the I-55 corridor and solid warning snows decently north of that.

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[WeatherMonger]

15 minutes ago, StormChaser4Life said:

Try a flamethrower. Lol. How much did you end up with btw? 

No clue, have to ask Capital Airport here in Springfield. ILX says our official total was 12 inches, reported by Capital Airport. 

 

Capital Airport on Thursday reported 11.4" as an Official NWS OBS. Then for the Official storm tally Capital Airport took it back to 9.7" for some reason.

 

I've disputed some of their tallies before, but never like this one. They actually reported the 11.4" to ILX for recording.

 

 

 

 

[Hoosier]

8 minutes ago, RCNYILWX said:

If you've been following the CAM runs since they've gotten into range, they're modeling extensive warm sector convection which they explicitly forecast (hence Convection Allowing Models).

The operational models and ensemble members parameterize convection, which is simulating the combined effects of convective clouds that might exist based off other elements being explicitly modeled. One of the pitfalls of higher resolution operational models and ensemble members is that the convective effects applied to many more grid points can result in a high resolution garbage in, high resolution garbage out phenomena.

We had an internal call with WPC last night and a forecaster from one of the offices on the call made the point that it's possible the GFS and NAM were being affected by convective feedback.

The thing about handling convection is that it's hard to be confident if the mass fields will be impacted in a negative way, if models are over deepening a key short wave due to simulated convection, or if some guidance members are overemphasizing negative effects. There's plenty of examples of the all of the above occurring with mid latitude cyclones modeled to have a large convective footprint in the warm sector.

I've been thinking about that point made last night and wondering if it helps explain the lingering high uncertainty in the guidance. Even the CAM solutions are struggling, given the large difference between the members of the 00z HREF.

My thinking is that since there's reasonable agreement in a sub 1000 mb low tracking north of the Ohio River, this has historically been a good track for sig snow into Chicago metro. So while I certainly can't ignore the possibility warning snows miss us south or that the whole system is weaker due to destructive interference from convection, holding with the thinking that the central (including western burbs) and south metro and points south do well.

This is based off pattern recognition, favorable jet dynamics (left exit and right entrance of jet to our north) to allow for more expansive precip shield than some of the stingier guidance on north end, and the antecedent strong downstream ridging (possibly enhanced by latent heat release).

I believe that some of the above factors (minus sfc low track), while unfortunately not overcoming the dry air for the far north and northwest metro and points west for GHD III, enabled the big dog type totals to get up to the I-55 corridor and solid warning snows decently north of that.

Sent from my SM-G998U using Tapatalk


 

Appreciate the post, RC.  

[WeatherMonger]

15 minutes ago, WeatherMonger said:

No clue, have to ask Capital Airport here in Springfield. ILX says our official total was 12 inches, reported by Capital Airport. 

 

Capital Airport on Thursday reported 11.4" as an Official NWS OBS. Then for the Official storm tally Capital Airport took it back to 9.7" for some reason.

 

I've disputed some of their tallies before, but never like this one. They actually reported the 11.4" to ILX for recording.

 

 

 

 

 

 

Looks like somewhere along the line a correction was made. Now shows it corrected, but not sure when they did it.

 

 

[Hoosier]

00z Euro is a little underwhelming.

[Thundersnow12]

Euro is not pretty and SE of the 18z run.