Snow Event 1-6-2010 for Illinois?

[Joe Schaub]

Anyone seen any models covering the forecasted snow for that night and the next day?

Not sure where you guys get your GFS and all those models at so I am winging it off of the NOAA site for Central IL.

All they say is a few inches of snow are possible on their long term forecast.

 

[Ryan Wichman]

Anyone seen any models covering the forecasted snow for that night and the next day?

Not sure where you guys get your GFS and all those models at so I am winging it off of the NOAA site for Central IL.

All they say is a few inches of snow are possible on their long term forecast.

There has been snow in the forecast for the past few days, but it is not limited to Illinois. Iowa, Nebraska, Kansas and Missouri will come out of this with some decent snowfall accumulations as well.

This will be a classic clipper system with limited mositure and fast moving features. While the moisture and dynamics are not overpowering, the dry arctic airmass firmly in place over the Upper Mississippi river valley will allow for some high snow to liquid ratios. 15-20:1 will be common but would not be suprised to see reports of even higher ratios. Looking at .1 to .25 QPF over a large area that means an advisory or possibly low-end warning snowfall for select locations (exactly where is TBD).

As far as good places to find data on winter weather there are a few good locations...

Earl Barker always has good site to provide:http://www.wxcaster.com/models_main.htm

HPC provides great discussions to learn about upcoming winter weather: http://www.hpc.ncep.noaa.gov/wwd/winter_wx.shtml

Not limited to winter weather, but wx data in general: twisterdata.com

If you do a google search and put in some time looking around stormtrack you will find many, many more...

 

[MatthewCarman]

The local news here in Central Iowa is saying we will not get much in the way of accumulating snow. I am more worried about the winds that could follow this system. Chance of blowing snow come Thursday.

 

[Joe Schaub]

There has been snow in the forecast for the past few days, but it is not limited to Illinois. Iowa, Nebraska, Kansas and Missouri will come out of this with some decent snowfall accumulations as well.

This will be a classic clipper system with limited mositure and fast moving features. While the moisture and dynamics are not overpowering, the dry arctic airmass firmly in place over the Upper Mississippi river valley will allow for some high snow to liquid ratios. 15-20:1 will be common but would not be suprised to see reports of even higher ratios. Looking at .1 to .25 QPF over a large area that means an advisory or possibly low-end warning snowfall for select locations (exactly where is TBD).

As far as good places to find data on winter weather there are a few good locations...

Earl Barker always has good site to provide:http://www.wxcaster.com/models_main.htm

HPC provides great discussions to learn about upcoming winter weather: http://www.hpc.ncep.noaa.gov/wwd/winter_wx.shtml

Not limited to winter weather, but wx data in general: twisterdata.com

If you do a google search and put in some time looking around stormtrack you will find many, many more...

Thank you Ryan. I will check those out. I would love some more snow but the cold air can go. Barely getting 10 degrees here today kind of sucks.

 

[Justin Griffith]

We're forecasted for 2-4" on Wednesday evening into Thursday.

It's going to be COLD, the lows dropping to -3 on Thursday with strong winds and blowing snow, those wind chills are going to be COLD!

 

[Jeff Miller]

NWS Sioux Falls stating 2 to 5 inches of snow - Omaha stating a little more, up to 7 inches of fluffy snow.

Of note, ground blizzard conditions will be possible wed night into Thu so NWS Sioux Falls is considering Blizzard Watches for the area for the time frame for low visibilities.

The big story with this will be the extreme cold to follow - windchill WARNINGS are likely to follow this system.

Will be an interesting system to follow.

 

[Chris Heater]

Snowfall expected upped to 3 to 4" of snow. Local amounts of 5" possible. May see blowing snow advisories/blizzard watches for blowing snow later on? That i'm not too sure on yet

 

[Jeff Miller]

Chris,

The product of "Blowing Snow Advisory" is over. This advisory was discontinued beginning with the 2008-09 winter season.

You will find if there are advisory level conditions for Blowing Snow that this will likely be a Winter Weather Advisory for Blowing Snow issued for your area. Winter Weather Advisories have replaced quite a few of the older products including Snow Advisories and Snow and Blowing Snow Advisories.

If enough loose snow falls, and winds are sufficient enough to produce visibilities under 1/4 mile as well as winds exceeding 35 MPH for a period of 3 hrs or greater, the Weather Service will consider Blizzard Watches instead of Winter Weather Advisories. In the Sioux Falls forecast area, this may be the case due to winds that may approach or exceed 35 MPH with significant loose snow, hence the possible Blizzard Watch - even though falling snow will be greatly reduced by that time. Blowing snow and low visibilities with extreme cold, however, IS a life threatening situation and will make this in itself a dangerous event.

As for your area, with less snowfall on the ground and low end accumulations of 3 to 4 inches, I would probably venture to guess you will be under a Winter Weather Advisory for the majority of the event - unless sufficient snow falls and visibilities are low enough for a warning criteria upgrade. Time will tell on that.

As a sidenote, people are taking this event seriously - more seriously then usual - perhaps to the intense few storms that have bulls-eyed us lately. Stores are almost out and/or low of bread, milk and meat (was out yesterday).

 

[Joel Wright]

This looks like a fairly impressive system coming in ahead of the next arctic blast. If the gulf wasn't as choked off there'd be some pretty impressive snowfall totals with this. Even with limited gulf moisture the vigor of this system will squeeze out every available amount of moisture it can. Seasonally high snow to water ratios will also favor decent accumulations. These inverted trough setups this time of year drop a very large swath of snow normally, and this one looks no different. Should be a wide swath of 4-7" snow from the Dakotas to the Ohio Valley.

All of this fresh, dry snow on top of existing snowpack will lay the foundation for an extremely cold late week/weekend. Parts of northwest Iowa already have over 2 feet of snow on the ground, and after this dump of snow some areas could have over 30". Wouldn't at all be surprised to see a few -40 degree readings being reported from northwest Iowa Friday or Saturday morning...

 

[Mark Sefried]

Agree with Joel on this one that a good swath of 4-7 inches will occur with the storm and locally higher amounts. With around 18:1 ratios the snow is going to be fluffy so it should blow around nicely. I Imagine that winter storm watches will go out this evening for late Wed night into Thursday for at least the northern half of IL and possibly IN with an upgrade to a warning likely eventually. Watches are already out for IA, Eastern NE, and NW Mo.

 

[Chris Heater]

Winter Storm Watches in going in effect. There is even a batch of them in southern Illinois, Kentucky, etc.? I'll assume all of central IL will go under one soon too unless i'm wrong. This will be our first WSW this winter

 

[Danny Neal]

As Mark said watches are out in E IA (DVN) and I look for at least an advisory out for LOT maybe northern areas of ILX too. 6-8 inches look like a good bet per the 12Z NAM http://wxcaster.com/gis-snow-overlays.php3?STATIONID=LOT. I have just stumbled up on this "localized WFO" total forecast so I am not sure what to make of it. LOT AFD seems to paint at least an advisory later today.

 

[Jeff Miller]

Quick look at various models and updates:

GFS TO 66: Heaviest snowfall totals should be easy 6 to 8" total storm accumulations from ND SE through Northern Missourri to Central Illinois. Also concurs with off run GFS.

NAM using Snow To Liquid Algorithm: If this run (time sensitive) is to be believed, accumulations would be in the 8 to 12" range. I believe this is overdoing it though the dendretic layer will be pretty much saturated and snowfall production will be extremely efficient. Though, I wouldn't doubt that some locations may receive isolated 9 or 10" snowfall totals.

WRF Northern Plains painsts a nice stripe of 8 to 10" snowfall from ND SE towards Iowa.

With these models in general agreement, I believe snow production will be extremely efficient and I do not think higher total accumulations with this kind of dendretic fluff will be unreasonable - though might be overdone a tad. 7" will probably be the going totals in the highest stripe of accumulations in my best estimate. Check the 2 Day HPC Guidance that seems to concur with this reasoning with at least 4" highly likely.

Regardless of all, with the likelihood of warning level criteria, extreme cold windchills and low visibilities, believe the winter storm watches are warranted and would not be surprised to see these watches be upgraded to warnings. I have noticed here in Sioux City area that most forecasts for snowfall have been followed by noticably higher snowfall totals with each storm due to snowfall ratios. For instance, a forecasted half inch was nearly 2 inches of fluffy snow a few days ago - and the same thing happened a few days before that with somewhat higher than forecasted totals. I believe the same thing is possible to happen here generally speaking throughout the event and would not be at all surprised for 1-3" greater accumulations then forecast by models with this type of an event in some areas.

Of note from Des Moines:

MOST OF THE AREA IS PARTICULARLY PRIMED FOR
SIGNIFICANT TO SEVERE DRIFTING IF THE SYSTEM PANS OUT AS
EXPECTED...WITH A STRONG DEEP SNOW PACK IN PLACE AND ALL DITCHES
BANK FULL.

 

[Ryan Wichman]

As has been the case with the last few systems, this clipper-hybrid is making for a very tricky forecast here in Quincy. A broad swath of 5-8 inches appears likely over much of IA, extreme northern MO and northern IL. Add in the 20-30 mph winds to create blowing and drifting in locations where many of the ditches are already full of snow and you are looking at a very dangerous situation (esp when you add in the sub-zero temps). This is why the forecast for an exact amount is tricky and it is easy to get burned...

When temperatures are as cold as they have been and are expected to be during the duration of the event, it allows snow to accumulate at a higher rate than it normally would be able to. So throw the old 10:1 snow to liquid ratio right out the window. Now you have to decide what the ratio will actually be....18:1? 15:1? 25:1? It looks like many locations will be pushing 20 to 1 if not even a bit higher. So pinning down your snowfall accumulations can actually come down to the HUNDREDTH of an inch in QPF (good luck pinning down exact snow amounts for any given location).

I have attached a sounding from near Quincy during Thursday morning, look at how long the snow will be falling through the favorable snow growth zone...nearly 250 mb! If a band of snow sets up over one location it would not take long at all to really pile on the totals especially considering the column is saturated to nearly 600hPa. All of that happening while nearby locations only report flurries.

PHEW!....With all that said I still feel that a good swath of 5-8 inches is likely over the previously mentioned areas with isolated amounts approaching a foot not coming as a surprise. But good luck measuring with all the wind.

BTW...good discussion earlier Jeff and all others who didn't just tell us the NWS has issued a watch/warning.

 

[Bill Schintler]

Eastern IA forecast

A winter storm will bring several inches of “light, fluffyâ€￾ snow to the area starting early Wednesday afternoon. Snow will be light during the day Wednesday, and will become moderate to heavy Wednesday night. Light snow will continue through the day Thursday, and winds will increase, resulting in considerable blowing and drifting of the snow. Thursday will be the worse day for travel conditions. Below is time of arrival and total snow accumulation for tonight’s event for specific locations in central and eastern IA:

Cedar Rapids, IA (Eastern IA Airport):
Snow will start at 1 PM Wednesday and accumulate to 6.7 inches by Thursday evening.

Iowa City, IA:
Snow will start at 1 PM Wednesday and accumulate to 7.0 inches by Thursday evening.

North Linn Co., IA (Paris and Coggon):
Snow will start at 1 PM Wednesday and accumulate to 6.3 inches by Thursday evening.

Marengo, IA:
Snow will start at 12:30 PM Wednesday and accumulate to 7.1 inches by Thursday evening.

Union, IA:
Snow will start at 10:30 AM Wednesday and accumulate to 7.8 inches by Thursday evening.

Discussion:
Models agree to intensify an H5 shortwave embedded within NWRLY flow into a closed system through early Friday
The GFS appears quite slower with precipitation onset then the NAM and SPC SREF.

Regarding snowfall amounts, a snow to liquid ratio of around 20:1 or even a bit higher seems reasonable given FCST temperature structure. This should offset the limited moisture capacity of the arctic AMS, with most MDLs indicating 0.3 to 0.4 inches of storm total QPF over a widespread area. Latest model trends indicate increased QPF trends with a fairly long period of forcing. Starting Thursday, winds will increase as an inverted trough shifts to the east and high pressure builds to our west.

- bill s
8:00 PM CST, 01/05/10