December 11-13 Snow Systems

[Hoosier]

Well, a little risky to get overly confident with the model depictions in this fast flow regime, but we have general agreement on a couple of systems in this timeframe.  At this point, it looks like they may not quite take the same track, although some zone of overlap could occur.  

[bud2380]

There are so many disturbances moving through this NW flow, it's difficult to track them all as models are fairly varied, but both the GFS and the Euro and some other models seem to have Thursday and Saturday as the two bigger ones in this time frame, with Saturday looking the strongest.

Here is the 12z ICON for Thursday

 

And then Saturday.

[bud2380]

GFS for Thursday,  sharp cutoffs with this one.

[bud2380]

Saturday, clearly a weird glitch in the run as the snow hits a brick wall in western IL and then starts up again, but if you smooth that out, a solid 3-6" for a wide area. 

 

[bud2380]

Impressive two system totals

[bud2380]

Canadian Thursday is really juiced.

 

Saturday too

[bud2380]

UK for Thursday

[bud2380]

UK weaker on Saturday.

[Hoosier]

The second system in particular looks like a fairly cold one.

[bud2380]

Euro - Thursday

I'm right on the line of the heavier snow band.  Might need to thread the needle on this one.  It's gonna be a tough forecast with that tight of a gradient, a 20 mile shift will include or exclude an entire row of counties. 

[bud2380]

Euro for Saturday has a lot of similarities to the storm this past Saturday.

 

 

[bud2380]

Total for both in IA.  I live right about where that red dot is, so in the heaviest band, but not far from much lighter totals.  A sag south would be welcomed by me.  

 

[Hoosier]

Quite cold while it's snowing.  Have not dug into forecast soundings to see what the dgz and omega profile looks like, but hopefully there are some good dendrites.  These cold airmasses are not a guarantee of super high ratios as sometimes they produce small/sugary kind of flakes.

 

 

[Hoosier]

Followed up by this in the wake of the storm.  Should be fun times on the roads.

[bud2380]

I'm no expert on soundings, but is this where you would look for the DGZ?

This is Thursday showing -9.6C, which is outside the listed -12 to -17C.  

 

This is Saturday showing -13.2C, so would this indicate potentially larger flake size?

 

[Hoosier]

Those images are cropped.  Really have to look at the whole column of the atmosphere to see how the dgz and omega lays out.  It would be on the left side of the sounding.

[bud2380]

Here is the entire image, I was specifically look at the data under the Dentritic Growth Zone, hoping it was as simple as reading the text there, but I guess not.  Again I'm no expert at reading soundings.  This is Saturday's storm in eastern Iowa at noon.  

 

[Niko]

There will be alotta wind behind this system and frigid temps. Anyone in the path should bold real well w this one (4-8inch snowfall on the tables) and during the duration of this storm, the air will be very cold. That is my fav during a snowstorm.

[Tom]

12z GEFS for the THU-FRI wave...

 

[Hoosier]

5 minutes ago, bud2380 said:

Here is the entire image, I was specifically look at the data under the Dentritic Growth Zone, hoping it was as simple as reading the text there, but I guess not.  Again I'm no expert at reading soundings.  This is Saturday's storm in eastern Iowa at noon.  

 

Seems like the Euro doesn't depict omega on the Pivotal soundings.  That's a bummer.  It would show up as horizontal salmon color bars.  On that sounding, the dgz is ok, but a bit of warming around the 700 mb level prevents it from being super deep.  

[Tom]

12z GEFS for the weekend wave...

 

 

[Clinton]

12z EPS 

[hawkstwelve]

Looks like the weekend wave will be the stronger of the two if things hold as they appear now. Hoping others can score with the Thursday system and then the Saturday wave absolutely dumps once I'm back home. The Saturday snowstorm rule might just remain intact!

[Hoosier]

Ok, so here's a forecast sounding from the 12z Euro for Saturday.  It's from northern IL in an area that is kind of on the northern end of the better snowfall rates (you can see exactly where it is by looking at the red dot on the little map).  

The red line is a plot of temperatures through the atmosphere.  The dendritic zone is characterized by the zone where temperatures are roughly between -12C to -18C.  I've drawn on this image below to illustrate some things.  This forecast sounding has a very deep dendritic growth zone that runs from a bit above the 600 mb level (say, 575 mb or so) all the way down to basically ground level.  I've circled the part of the red line that roughly lies between -12C to -18C.  The diagonal lines that are highlighted in yellow are the -10C and -20C isotherms (-20C is the left line, -10C is the right line), so you obviously kind of have to estimate where the zone of -12C to -18C would be.  Assuming there is decent omega in that layer, which there would almost have to be somewhere, then it should result in good snowflake growth.  The omega bars are not plotted on here for some reason.  The ratios are something that we can try to nail down better as this system gets closer.

Hopefully nobody is even more confused by this post, lol.  Would probably be easier to explain on a video.

[gosaints]

This is like a fast flow january or february pattern.  These patterns will drive you nuts if you model watch for days prior.

[Clinton]

Some changes on the 18z Euro, mostly the 2nd clipper is further south vs 12z run

Clipper 1

Clipper 2

Total

Ensemble mean 

[Hoosier]

I'm gonna refer to Thursday as the snowpack fixer, for those of us who are watching it melt right now.  

[ChiTownSnow]

13 minutes ago, Hoosier said:

I'm gonna refer to Thursday as the snowpack fixer, for those of us who are watching it melt right now.  

Then Saturday is the snow gods apologizing for their mishap

[bud2380]

The ICON nearly got rid of the weekend system. 

[MI Storm]

8 minutes ago, bud2380 said:

The ICON nearly got rid of the weekend system. 

The Icon flops like a fish out of water. It seems like the weekend system needs space. The better runs seem to have a wuch weaker system over southeast Canada. 

[bud2380]

GFS combined systems 

[Hoosier]

I don't think the Canadian is going to look like the ICON does.  lol

[Hawkeye]

The last four Euro runs have trended weaker, narrower, and south with both waves. 

[ChiTownSnow]

Whoever gets both clippers back to back could cash in with the much higher ratios on the weekend.

[MMike]

NAM farther SW this run for the SaturdaySunday clipper? 3 inches of snow 60 miles from KC. KC does see some flurries/light snow out of it. I just want some white stuff with the very cold airmass this weekend. I know clippers most likely fall to our N and NE, but you just never know in this fast pace pattern. AND, it’s the 80-84 hour NAM! 
 

Hey Iowa, can you share some of the snow? LOL
 

 

[bud2380]

12z models are shifting south for the Saturday system. 

Here is the RDPS for both.  

[Hawkeye]

The GFS has now shifted the Saturday clipper southwest of my area.

[bud2380]

Saturday for sure is trending further south.

Here is Thursday though.  It's hard to understand what DVN is looking at with their snow map that is showing the heaviest snow in spots that the GFS and Euro show little to no snow.  They seem to be weighting their forecast very heavily on the NAM.  DVN has been mostly clueless on the first two storms up until the day of or day before as well.  I'm not sure what forecast techniques they are using, but they need to reevaluate.  

 

[Hoosier]

If you want a farther north track for the weekend, this guy (blue arrow) needs to relax/shift north.

[bud2380]

Canadian is much further north than the GFS on Saturday.