FCST: 12/18/08-12/19/08 Central Plains / Upper Midwest Winter Storm

[David Draun]

SPC has expanded 40% convective probabilities into basically all of northern IL after 3Z. Seems like a thundery winter storm is becoming quite possible for many of us. It will be interesting to see how much conditional symmetric instability (CSI) is realized tonight and if banding will occur.

I wanted to look at a thundersnow-specific forecast, but the site that was doing them discontinued their work on Jan 31st of this year.

As you can see: http://weather.missouri.edu/ROCS/forecasts.html
No forecasts.

Is there a site that is doing them now?

 

[Dennis Sherrod]

David,
Check out this site. They may have some useful info that will help you.
http://wintercenter.michiganwxsystem.com/

 

[David Draun]

That's cool, but it doesn't talk about convective snow potential. I'm looking for a map with the thundersnow parameters on it.

 

[rdale]

What did they use to create it? I may be able to duplicate with GEMPAK and upload...

 

[Robert Dewey]

GRR said 6-9 inches in their latest conference call... saying that the moisture and temperature profile aren't really conducive to much more than 6 inches.

Hi-Res NAM is in, a little stronger than the operational with much higher QPF values (but a slightly colder thermal profile).

 

[rdale]

They said 6-9, but they don't think we'll see more than 6? Something lost in translation... Still sitting on 4-8" for Lansing - Jackson, all snow, in my forecast.

Not sure what you mean by hi-res NAM, it only runs at one resolution (12km)

 

[Robert Dewey]

They said 6-9, but they don't think we'll see more than 6? Something lost in translation... Still sitting on 4-8" for Lansing - Jackson, all snow, in my forecast.

Not sure what you mean by hi-res NAM, it only runs at one resolution (12km)

Yep, that's what they said. The guy didn't really make too much sense... especially when he said he expects the heaviest *rain* to make it up to Isabella county

They also said precipitation should start around 1am... we'll see about that.

Here's the NMM WRF run (sorry about calling it the NAM). But it's very consistent with it's 00Z run. I don't know how well it performs (moist bias, etc).

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/hiresw/12/model_l.shtml

 

[Mike Kovalchick]

They said 6-9, but they don't think we'll see more than 6? Something lost in translation... Still sitting on 4-8" for Lansing - Jackson, all snow, in my forecast.

Not sure what you mean by hi-res NAM, it only runs at one resolution (12km)

Why so low for Lansing considering the current model outputs for QPF for the storm? Even a 10 to 1 ratio would spit out at least 8". However, I do realize that storms in the Lansing area almost always disappoint on the low end!

 

[Robert Dewey]

Cobb shows ratios averaging around 12:1 for the event.

Barring the high QPF NMM WRF... it still looks like a 6-12 inch event to me. It will be interesting to see what the 18Z NAM shows.

 

[rdale]

I'm going with 9-10:1 ratio after talking with Mr Cobb, I am mentioning double-digits possible but won't dare put up a 5-10 because all people will remember is the 10!

 

[Robert Dewey]

I kinda agree with Rob...

If I was making a public forecast (throwing numbers on a forum are nothing), I'd be way more conservative... and adjust upward as needed (i.e. when I actually see the stuff on radar, and here spotters reporting 2 inches / hour).

 

[Mike Kovalchick]

Cobb shows ratios averaging around 12:1 for the event.

Barring the high QPF NMM WRF... it still looks like a 6-12 inch event to me. It will be interesting to see what the 18Z NAM shows.

18Z NAM is coming in higher on QPF (at least in the Lansing area).

 

[rdale]

18Z NAM sucked yesterday - I'd never change a thing based on that run (especially of the NAM in the first place )

 

[Mike Kovalchick]

18Z NAM sucked yesterday - I'd never change a thing based on that run (especially of the NAM in the first place )

Your favorite Tamdar version of the the RUC is look good too suggesting about 10" at the airport

http://ruc.fsl.noaa.gov/disp2.cgi?/w3/rapb/plots_20km_dev2/.//+snowacc+gl+24

 

[rdale]

I like how it goes from 0" at 4am to 3+ at 7am! Fun drive to work...