3/16/2006 FCST: Midwest snowstorm

Looks like a late season winter storm will pummel the midwest this week. A low pressure coming out of the plains will track across Northern Illinois Wednesday night into Thursday.

The GFS and NAM are painting almost 1" QPF for Southern MN, Northern Iowa, and Southern Wisconsin. With 12:1 snow to liquid ratio, we could be looking at almost a foot of snow by the time Thursday evening rolls around.

Midwest snowlovers, any comments?
 
The NAM has been a bad model for this system for quite some time, although it has come around in the latest runs. Previous runs it had a very small, yet defined snow band over the northern plains. It has a much broader band of snowfall as of tonights runs and just slightly north of the current NWS thinking on the storm. GFS has done a good job keeping this system in control and has had the best handle on the strength of the system. Although the GFS the last couple of runs has also trended south now and is quite a ways south of the current Winter Storm Watches that have been issued.

As for myself, I'm currently only looking at 2 or 3 inches from this system as of its current track. But, its' possible that the GFS may be onto something and slowing this system down just a bit. That would allow the low pressure to dig south and pick up a bit more moisture. That could be why it is showing the snow further south and keeping the strength right up there around that 1" QPF.
 
I think it should be more ho hum than most of the chatter would indicate. Heaviest snow in WI should be SW corner as low will be weakening with time...and convergence and other ingredients will become much less favorable. I'm thinkin I'll probably fall short of the 6 inch mark again, but you never know.
 
I think the NAM might be showing the mesoscale features alot better than the courser models. If you look at other high resolution models (namely the 12Z GEM), you'll notice heavier output as well.

The un-interrupted stream of moisture, very good overrunning, good lift, decent instability, and system movement parallel to the snow band should combine to provide a nice mesoscale band of 8-12 inches. Right now, it looks like the best ingredients will be located in SE MN into SW WI. I think the NAM might be a little too widespread with QPF amounts, but it has the right idea (stationary mesoscale banding).

Personally though, unless I'm at the center of the heaviest snow axis (particularly this time of year), I'd rather not deal with the 2-3 inches of crap we're expected to get. But for those in MN/WI/IA... Enjoy.
 
Haven't done a lot of looking into the latest models and what they showed, but I noticed that the snow amounts have been bumped up for northern Iowa. Maybe showing signs of slowing? Or system just further south a bit... Either way I've been put into a 2-5 inch snowfall range instead of the previous 2-3 inch snows. Winds aren't expected to be high with this system, especially compared to this weekends. But, we could see a little bit of blowing snow. Should start to see the snows in around 6 hours or so for me...
 
Givning my few cents worth as I'm looking at models, central Indiana is only suppose to get less than a inch(I'm going to call it a dusting) of snow for our area. On the other hand its looking have way descent for severe weather in TX/OK region, but I don't think this system would amount to much.
 
Another late winter storm will affect much of the Upper-Midwest over the next 24-36 hours. Following are some specific area forecasts:

Rochester, MN:
Snowfall starting at 10PM tonight, with total accumulations of 10 inches.

Minneapolis/St. Paul:
Snowfall starting at 9PM tonight, with 6 inches total accumulation in the northern portions of the metro, and 8 inches across the south.

St. Cloud, MN:
Snow starting at 8PM tonight, with 5 inches total accumulation.

Iowa City, IA:
Light snow and rain starting 9PM, changing over to all rain by midnight, and then back to snow after 3 AM. Total snowfall accumulation: 1 inch or less, mainly on grassy and raised surfaces.

Cedar Rapids, IA:
Light rain and snow starting 9PM, and changing over to all snow by 3 AM. Total snowfall accumulation: 1 inch across the south (Eastern IA Airport) and 2" in the north (Marion, Hiawatha).

Discussion:
Interesting late winter storm is shaping up in the Upper-Midwest. It appears that this system will tap into a generous amount of moisture, despite the fact that the low is not based in the TX/NM/OK region which is often associated with large moisture transport winter systems. In the upper-levels, trough in the WRN CONUS will deepen through the next several days. In the near term, Lead impulse in SERN CO and secondary wave lifting through NWRN MN will affect the WX in the Upper-Midwest for the next 24 hours. By 12Z tomorrow, shortwave axis will be aligned along the IA/NE border. Meanwhile, SFC low pressure will track through SRN IA while the H85 low tracks from the Sioux Falls towards Chicago. Isentropic upglide of high theta-E/mixing ratio airmass on the 285K to 292K surfaces around to the NERN and NRN side of the low will commence in NERN IA and SERN MN by late afternoon as 50kt LLJ noses into the area. Examination of the H7 VV fields along with -10C to -15C isotherms indicates impressive UVV's in zone of maximum snow production. It also appears that banding with enhanced snowfall rates will occur across SRN MN with negative equivalent potential vorticity along with strong GQ-forcing. Concerning model performance, GFS has been most consistent from run to run; while the NAM's has been trending back to the S more in line with the GFS.

- bill
 
Looks to me like the heaviest axis of snow will be centered from the NW tip of IA to about Maquoketa IA, through dekalb IL, and right through Chi town. There should be a narrow axis of heavy snows of 6"+ with a sharp gradient south of the heavy band, and a slower drop off north of the heavy band.

This is another nail biter for us here in the QC, but it looks like the heaviest will stay just north.

The UKMET and the GFS have been the most consistant models lately so I've been generally following them.
 
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