12/8/08-12/10/08 FCST KS/NE/IA/SD/MO/MN/WI/IL/IN/MI/OH

[Joel Wright]

Well, looks like we have the biggest winter storm of the season on the way for much of the central CONUS if the latest suite of models is correct. The GFS and NAM model have recently caught on to the same idea the Euro has had for the last several days. A much stronger and further north solution, as compared to a faster and more progressive storm system initially forecasted.

This system will have all the tools necessary for a big winter storm. Very cold air knifing in on the cold side, and rich moisture laden gulf air injesting into the storm. Jet support looks fantastic as well. The basic consensus takes the surface low from northern OK into southern MO/IL, then into central IN, and eventually up into northern OH. Most of the models keep the surface cyclone below 1000mb during this period.

With a snowpack already in place across much of the cornbelt, a narrow area of icing is definitely a possibility. The cold air that will already be in place will be hard to displace and could result in a zone of freezing rain. It's about impossible to tell where this would set up exactly at this point, but an early guess would place it in southeast NE, southern IA into northern IL.

It sure looks like a band of heavy snow will be possible just north of this area. An early guess would place that from northern KS, much of NE, about the northwest 2/3 of IA, possibly nipping SE MN, southern WI/northern IL, and eventually into lower MI. Judging by the amount of moisture and forcing this system will have, it looks like a wide swath of 6"+ would be possible in those regions. Probably a band of snow accumulations even heavier than that somewhere in there, but obviously too early to tell.

Severe weather will probably be ongoing with this storm too, but I'm sure that'll be covered in the other forum section...

 

[Scott Weberpal]

At this point it initially looks like the rain/snow line should end up somewhere along the WI/IL border. Anywhere north that gets all snow could potentially get anywhere between 8-12".

 

[Robert Dewey]

Models look like they're trending further to the west with the track - looks like IA, northern IL, WI, and northern lower MI. Lots of QPF to be had, that's for sure.

 

[Michael O'Keeffe]

The 12z GFS is looking interesting for E Kansas/Nebraska/W MO and even Iowa on Tuesday. Here are some links to the projected accumulated snowfall totals based off the 12z.

The total accumulated shows 12-15" in NE Kansas/SE Nebraska with 5-8" across the KC metro.
http://204.2.104.196/gfs/WINTER_GFS0P5_SFC_ACCUM-SNOW_96HR.gif

Now here are a few plots of the 3hr. accumulated snowfall totals from the GFS once again. As you can see the heaviest band of snow looks to setup near the KS/NE/MO border. It also looks like we could see fairly strong winds on the backside of this system which could create some very interesting and dangerous conditions across the region mainly the Missouri River Valley eastward.

http://204.2.104.196/gfs/WINTER_GFS0P5_SFC_SNOWFALL_81HR.gif
http://204.2.104.196/gfs/WINTER_GFS0P5_SFC_SNOWFALL_87HR.gif

 

[Jeff Miller]

I've been keeping an eye on this and think I will jump in with my thoughts on this.

First, a look at the GFS0P5 snowfall model indicates a large spread of accumulating snowfall. The bullseye, as Micheal mentioned above, certainly looks to be the area of NE Kansas and SW Nebraska with greater than a foot of snow possibly, and general 6" or greater accumulations for much of SD, NE, IA, extreme lower MN, WI, and NW Illinois, through Michigan.

Again, this is only the GFS model, which is slower and deeper, placing a 995 low right over Tulsa. In the same timeframe, the ETA model has a weaker (1000 mb) low and more progressive storm just east of Columbia, MO. Both models have copious preciptation, the GFS stronger and more widespread, the ETA with a more narrow swath over much of Iowa and Wisconsin.

Of note in forecast prediction are a couple of things:

First, the HPC/NCEP called the 12Z GFS an outlier storm. They said that they are using the 12Z nam, the 9Z SREF and the ECMWF models. So for now, it doesn't look like they are favoring the stronger and slower GFS run that looks so impressive. ECMWF has the low on day 3 a little farther south than the ETA, and the ECMWF has been the first model to really latch onto this. One forecaster said a few days ago that he didn't see why the ECMWF somehow brought the baja low up "this way" but that's what appears to be happening.

So what should I deduce from these reasonings.

1. These storms have a tendency to shift farther north and west if they are stronger than models indicate. Therefore, my prediction for heaviest snow will, due to historical bias on these storms watching these models greater than 60 hrs out, will be shifted a little farther NW than models and forecasters are indicating. This is purely historical bias.

2. I see no reason for no significant snowfalls based on the projected path and available moisture. Cold air is certainly not lacking in all levels.

3. The other big issue will be wind - if the storm is stronger than anticipated, expect winds to be higher - the GFS would have a near-blizzard with the isobar pack. Again, HCP and even local offices like OAX have discounted GFS for the time being - so I think winds of 15-25 MPH and gusty would be common, I dont see it wrapping up to a blizzard at this point.

Accumulation projections are tricky. If I take into effect my personal belief the storm is going to shift farther NW than models show, I think the storm will be a little stronger and precipitation will be a little greater due to precipitation efficiency. I am going to estimate, this being way early, and way out in the timeframe, a general 3 to 7" snowfall total. I think the foot or greater snow depth is over done and premature. I think most areas will have a 4" to 5" average snowfall. This is just based on what I am presently thinking, and I also think the heavier snow bands will be from Omaha and NE through central and northern Iowa.

This is subject to change, this is only my first *general* look. I'll be keeping an eye on this all weekend.

 

[Robert Dewey]

As of right now, I'm also siding with a further northwest solution. Latest 18Z NAM did weaken the system some, with a SE push in the isotherms... but the GFS ensembles show a westward trend between 12Z and the 18Z run.

 

[Scott Weberpal]

Latest WRF has the strongest QPF signal further south than the previous run. I'm sure it'll jump back and forth the next day or two. I love snow, but with a system like this, I'm all about it tracking to the south.

 

[Robert Dewey]

Yeah, I see the 00Z NAM made a liar out of me in a big way. I wonder if the GFS will be somewhat more consistent.

NAM outputs upwards of an inch of QPF on the cold side... but the thermal profiles aren't as cold as previous runs, so snow ratios should stick around 10:1 or 12:1 at best.

Still looks like a 6-12 inch snowfall to me, location being the main problem.

 

[Joel Wright]

I'm not buying the latest NAM at all. Gee big surprise there, eh? It is fun to laugh at though.

Can't wait to see what the GFS has to say. I'm banking on a similar solution to it's earlier 12z run...

 

[Chip Redmond]

I have been watching this carefully at work. I nearly made a forecast thread Thursday but decided that I would wait since it appears we in Ohio will be in the warm sector of this major storm and no major accumulations will be had here. That seems to of been the right decision as I expect the GFS to fall apart and weaken greatly with this system by Mondays 0z run (as it has done alot of recently).
The NAM seems to bring much, much colder air than the GFS behind the system and I think will play out Fridays system to be more of snow storm than this system.
Its still a ways away, we shall see what happens.


Chip

 

[Joel Wright]

Wow, what a complicated storm this one is to forecast!

The latest NAM is out on a lunch break, as previously mentioned. The new GFS just in is very similar to it's last two runs, which of course is a good sign. It is in fair agreement with the Euro.

The GFS seems to develop a secondary surface low in extreme northern AR early Tuesday, and then tracks it northeast into Ohio. At the same time a secondary (and possibly even stronger) deformation zone develops and takes over from eastern KS into northwest MO before spreading northeast into southern WI and lower MI Tuesday night. This deformation zone may end up being a bit stronger/wetter than what models currently show. Definitely gonna have to watch this. It will be associated with a stronger surface low pressure, and have even more moisture available than the earlier def. zone.

So to me it's looking like a broad area of significant snows will evolve out of KS/NE into IA late Monday night and early Tuesday morning. It then weakens as the second deformation zone takes over as the new surface low over extreme northern AR deepens and moves northeast. This second deformation zone could lay some heavy snow from St. Joseph MO up through eastern IA/NW IL, and into southern WI. This is all dependent on whether this second surface low develops as shown by the GFS. This would seem a likely scenario though, as it is quite common for that to happen. Usually in a situation like that the second deformation zone is a bit stronger than the first one.

 

[Robert Dewey]

00Z GFS much more consistent, but a little further SE. I'll go with something between the NAM and GFS... GEM isn't as strong as the GFS either, but also vouches for the further W track.

 

[Chad Cowan]

Latest WRF has the strongest QPF signal further south than the previous run. I'm sure it'll jump back and forth the next day or two. I love snow, but with a system like this, I'm all about it tracking to the south.

I like a good snow too, but my new shoes would appreciate if you didn't send the highest totals down here. thanks.

 

[Robert Dewey]

12Z NAM pretty consistent with the 06Z and 00Z runs. Perhaps a tad-bit further W and a little bit stronger. GFS held strong on the 06Z run... The 12Z regional GEM is quite a bit stronger and further W... Rain/snow line back into central IA, extending up through northern lower MI.

 

[Joel Wright]

GFS appears a bit more bullish than the other models with the strength and associated QPF. Given the strong baroclinicy and good jet support, not to mention a very good supply of gulf moisture this seems to be a believable scenario. The GFS really deepens the surface low by Tuesday night as it moves into Ohio. If this scenario plays out there could be a pretty significant band of snow developing from IL to lower MI.

I think it all depends on the timing of the main shortwave energy arriving Tuesday as to how fast this whole situation develops. Obviously if it arrives later the surface low will remain much weaker and scoot quickly to the northeast as a few other models indicate. However, if the shortwave arrives a bit earlier it could really deepen the surface low even more so than what the GFS would indicate. In that scenario a band of very heavy snow with near blizzardlike conditions would be a possibility over the Lakes area. Of course that possibility is quite remote; but considering the baroclinicy, jet support, moisture supply, and the time of the season it remains a possibility. The main energy that will drive this storm system is just now reaching the west coast, so there could still be some substantial changes in surface low placement and intensity.

I think the only real certainty at this point is that there should be a broad area of decent snowfall accumulation from northern KS, much of NE into the NW half of IA and possibly southern MN by Tuesday morning from the first part of this storm system.