WINTER STORM FCST 12/07/07-12/12/07: KS, MO, IA, IL, MN, WI, NE, MI

[Jeff Miller]

Des Moines, where's your advisories?

While the threat of a severe ice storm situation is quite plausible in the central plains, I wanted to bring up some reasoning discrepencies in the FSD/DMX areas...

Woodbury County, Iowa is under a Heavy Snow Warning for 6-8" of snowfall accumulation. However, if you go one county southeast to Crawford County, Iowa, there is absolutely no warnings, watches, or advisories, even though 3-5" of snow is forecast, at least putting the area and counties directly northeast in a Snow Advisory criteria. I dont often see such a sharp cutoff from a Warning to absolutely nothing like this is. Since accumulations to 6" are certainly possible, I would imagine at the least a Snow Advisory is warranted - but the AFD shows no signs of a warning issuance. I would expect a little better reasoning or collaberation - it seems senseless to forecast up to 6" and not have some sort of advisory up since criteria at least has a chance of being met.

 

[Mike Hollingshead]

Hoping KC dodges the worst of this one - -

Day 2 HPC ice probabilities puts the majority of icing to the east and south, but it looks too close to call.

Day 3 shows more icing over Oklahoma, with the same areas in Missouri continuing to receive accumulation.

Both NAM and GFS seem to generally agree on the precip outlines, though the timing looks to be varying a bit.

I've seen enough of these now to know that they can easily become a much bigger, or much smaller event than predicted. And that areas riding the forecast boundaries are totally up in the air until it happens. What concerns me is the extended period of precip that looks to be setting up, with the same areas getting several fresh coats. Not good.

Looks like St. Joe could get some love from this one...at least the 18z gfs thinks so.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_090m.gif

Since they are just north of the sfc freezing line.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_096m.gif

It really doesn't move it 6 hours later either.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_096m.gif

Or during the following 6, lol.

That'd be a big difference between this and that last "ice-storm". It doesn't look to surge anywhere and should actually have some converging sfc winds out of the ne along it, trying to keep it there/below freezing.

 

[Mike Peregrine]

Hmmm - I was looking at Earl Barker's GFS page. I wonder if it hasn't updated yet or something? If the ones you posted play out, it would be a different story, looks like. Those make it look like NC-NE Kansas into NW Missouri is going to get pounded, which contradicts what we're seeing out of most NWS offices right now. Winter weather just makes me scratch my head. I'm convinced that it's totally a wait-and-see thing. I'm pretty sure somebody is going to get it, though - will be interesting to watch and see who.

 

[Michael O'Keeffe]

Well Mike I think the NWS is looking at the WRF which is making the areas between 1-70 and I-44 looking to be in line for a major ice storm which has already been said I think.

 

[Jeff Snyder]

While the threat of a severe ice storm situation is quite plausible in the central plains, I wanted to bring up some reasoning discrepencies in the FSD/DMX areas...

Woodbury County, Iowa is under a Heavy Snow Warning for 6-8" of snowfall accumulation. However, if you go one county southeast to Crawford County, Iowa, there is absolutely no warnings, watches, or advisories, even though 3-5" of snow is forecast, at least putting the area and counties directly northeast in a Snow Advisory criteria. I dont often see such a sharp cutoff from a Warning to absolutely nothing like this is. Since accumulations to 6" are certainly possible, I would imagine at the least a Snow Advisory is warranted - but the AFD shows no signs of a warning issuance. I would expect a little better reasoning or collaberation - it seems senseless to forecast up to 6" and not have some sort of advisory up since criteria at least has a chance of being met.

Jeff, what is the timeline for the snowfall up there, though? Most of the time, advisories (winter weather, dense fog, etc) are not issued much more than 12 hours ahead of time (many times issued ~6 hrs before the event starts, sometimes issued after an event starts). For significant events, though, winter storm watches may be issued ~24 hours ahead of time, especially for particularly dangerous events (big ice storm, first major winter storm, big storm over a holiday when lots of people will be traveling, etc). In this case, the heavy snow warning doesn't actually start until 9 am tomorrow, and it may be a bit premature for a winter weather advisory to be issued if it doesn't start for 15 hours. If ~6" snows look likely after tonight's models, I would expect to see at least a snow advisory issued with the morning forecast package (i.e. issued with the 3-4am forecasts).

 

[Jeff Miller]

Jeff, what is the timeline for the snowfall up there, though? Most of the time, advisories (winter weather, dense fog, etc) are not issued much more than 12 hours ahead of time (many times issued ~6 hrs before the event starts, sometimes issued after an event starts). For significant events, though, winter storm watches may be issued ~24 hours ahead of time, especially for particularly dangerous events (big ice storm, first major winter storm, big storm over a holiday when lots of people will be traveling, etc). In this case, the heavy snow warning doesn't actually start until 9 am tomorrow, and it may be a bit premature for a winter weather advisory to be issued if it doesn't start for 15 hours. If ~6" snows look likely after tonight's models, I would expect to see at least a snow advisory issued with the morning forecast package (i.e. issued with the 3-4am forecasts).

I totally agree with you on the timing aspect. I guess my concern is the public who would look at that (on a TV graphic) and see a heavy snow warning to the west and nothing for them potentially making them think "it's going to miss us" and be lax about the system. Of course we know that weather knows no man-made criteria, however I would think at least a mention of potential advisories or warnings should have been included in the evening AFD.

 

[rdale]

That's why we NEVER show NWS information on our forecast maps... It's my forecast - why would I advertise one made by another entity that only adds confusion! People understand "6 inches of snow coming" -- not "heavy snow warning" :>

 

[Mike Hollingshead]

http://weather.cod.edu/forecast/ECMWF/ecmwf_850_temp_96.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_850_090m.gif

Check out the 850 0c line on both of those for 12z Tues. The last one, the 18z gfs was a nudge north from earlier thoughts. The 12z ecmwf however is a lot further north than that. ecmwf has it just south of Sioux City while 18z gfs has it down near Nebraska City.

 

[Bill Schintler]

Winter weather FCST, 12/08/07 - 12/09/07

An extended period of light mixed winter precipitation will affect eastern Iowa beginning Saturday afternoon and lasting through the day Sunday. Below are forecasts for specific locations:

Cedar Rapids:
Light snow will start at 5:30 PM CST Saturday and continue until 6 PM Sunday. Total snow accumulation through Sunday evening: 3.0 inches.

Iowa City:
Light snow will start at 5:30 PM CST Saturday, change to sleet and snow at 9:30 PM, and continue until 6 PM Sunday. Some freezing rain may mix in with the sleet and snow Sunday morning. Total snow and sleet accumulation through Sunday evening: 1.5 inches.

Marengo:
Light snow will start at 5:00 PM CST Saturday, change to sleet and snow at 8 PM, and continue until 5 PM Sunday. Some freezing rain may mix in with the sleet and snow Sunday morning. Total snow and sleet accumulation through Sunday evening: 2.0 inches.

Paris, IA:
Light snow will start at 5:15 PM CST Saturday and continue until 6 PM Sunday. Total snow and sleet accumulation through Sunday evening: 3.0 inches.

Synopsis:
Analysis indicated H3 height falls over the WRN CONUS with 140kt H3 flow from UT through the SRN Great Lakes. H7 WAA had commenced in SWRN KS, while at the SFC, high pressure was established from MT into ERN SD and STG NERLY flow was pushing into KS and NE.

Discussion:
A continuation of the very active winter WX pattern is in store for the next several days. First, SFC high pressure will shift slowly off to the N as SRLY flow aloft increases ahead of developing SFC low pressure in the WRN high plains. Winter WX FCST is challenging for the weekend as high-amplitude SWRN CONUS trough will eject a succession of compact ULVL SHWVS towards the CNTRL Plains and upper-Midwest. Each piece of ULVL energy has varying degrees of isentropic lift, frontogenetical forcing, and TROWAL features. Precipitation should develop over the area Saturday afternoon as a lead H5 wave approaches the area. Precipitation rates will be strongest late Saturday evening within the right-entrance region of a 120kt H3 jet, isentropic lift, and H8-H7 frontogenesis. Following a lull in the precipitation Sunday morning, a second impulse will affect the area Sunday on a more SRLY trajectory. Looking ahead, yet another piece of energy will affect the area Monday evening.

One FCST certainty is that an arctic airmass is becoming entrenched at the LLVLS across the area, maintaining a NWWRD slanting baroclinic zone oriented parallel to the ULVL flow. This frontal SFC will shift very slowly SERD over the next few days as the cold dome expands and the jet stream shifts slowly SWRD, Meanwhile, moisture in parcels that is running well above seasonal norms will follow isentropic SFCS NW of this feature in response to ULVL forcing. MDL confidence (GFS, NAM, UKMET, and NGM) remains low with regard to handling of kinematic details of the aforementioned ULVL waves and a coupled H3 jet structure, as well as to the thermal profile of the atmosphere, therefore weighted ensemble PROGS were favored except for SFC/LLVL temperatures where the cold GFS was favored. Latest trends have indicated a delay in the precipitation onset as well as less QPF. MDL soundings suggest primarily snow N of I-80, while some sleet will mix in further S. Cold layer appears sufficiently deep so that liquid precipitation should refreeze before reaching the ground. MDL confidence is also low with QPF, and may be too high as banded or convective features and strong omega in DGZ will be short lived if at all. In summary, it looks like an extended period of light snowfall and sleet in the area Saturday afternoon and again Sunday.

- bill
8:37 PM CST, 12/07/07

 

[Mike Hollingshead]

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/images/gfs_p60_090m.gif

Yikes. That second shot Wednesday morning really helps crank up the precip totals.

Interesting that through 84 hours NAM has a more northerly precip track.
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/nam/00/images/nam_p60_084m.gif

It's much different than the GFS with the system at 84 hours. Shearing it out pretty good while the GFS continues a stronger storm.

http://www.rap.ucar.edu/weather/model/eta84hr_500_wnd.gif
http://www.rap.ucar.edu/weather/model/gfs084hr_500_wnd.gif

I have no idea which is more likely to be correct. I guess the old 12z run of the ecmwf leans towards the nam's more sheared system by 12z Wednesday.

 

[Michael O'Keeffe]

Here is an image of the latest QPF model for the Monday night into Tuesday night timeframe. It is indicating over 2.5" of precip for my area and points west. I think anywhere between I70 and I35 from KC to Topeka south to Emporia and back to KC area in for a VERY damaging ice event. The latest forecast from the NWS EAX is saying there is a 100% chance of freezing rain Monday night and Tuesday before tapering off late on Tuesday.

 

[Joel Wright]

Someone's going to get hammered tomorrow night into Tuesday morning. Look at all the QPF forecasted right in the area where forecast soundings indicate freezing rain. There may be areas from northeast KS, into northwest MO, and into extreme southern IA that receive over an inch of glaze by noon Tuesday. Some of that may extend further east into north-central IL too.

To me it looks like Salina, up through the St. Joseph MO area, and up towards Lamoni IA is going to be in the midst of the heaviest glaze band.

 

[Joel Wright]

The 00z models seem to slow the monday night system just a bit, but other than that I don't see too much of a difference from previous runs. Maybe just a slight nudge northward of the heaviest QPF.

It's sure looking like a very damaging icestorm with ice accumulations/glaze approaching 1" in a band from northeast Kansas, through northwest MO, through southeast IA, and into northern IL.

Here in the Quad Cities area of NW IL, we're looking to receive 0.50-1.00" of glaze depending on what model you look at. That would rival and possibly exceed the last icestorm we just had last weekend.

The only saving grace with this particular storm is the lack of wind associated with it. The storm system on December 1st brought 40mph winds during the event. This one will have considerably less wind. On the flip side, unlike that icestorm which was quickly followed by thawing temps which helped melt ice off of everything, this one will actually have colder air surging in after the precip quits...

 

[Mikey Gribble]

Wichita may end up dodging a bullet on this one if the NAM is to be believed. The last few runs have been keeping us barely above freezing. The 00Z run only has us dipping below freezing for a few hours early Tuesday morning.
The system does look like it slowed down a bit from previous runs, but I haven't been watching it that closely. The NWS has been keeping our temps well below freezing in the forecast. I haven't forecasted nearly enough to second guess them, but right now I'm thinking that if ICT gets below freezing then we are just barely going to get there. Aside from the surface temperatures being slightly to warm the ICT sounding is definitely going to be freezing rain. We got pretty much all sleet out of the storm that just exited our area, but the cold air in forecast sounding for ICT in this event should be shallow enough to keep the precip. in liquid form. I always feel like sleet is a waste of a winter storm. I just don't like it for some reason. Ice sucks too, but it makes things a little more interesting (so long as I don't have to drive in it). Anyways, I'm hoping our temps drop a bit more than the NAM is forecasting because I want a good winter storm.

 

[Jim Zandonai]

Looks like late tonight and Tuesday is going to be another Icy event in N.IL.
Here in RFD looks like we will be on the north edge of the significant precip again.
At this time KLOT has held off with the warnings probably due to timing and any slight shift to the south or north would make a big difference.
I wasnt worried about Ice last time but our power was out for 15 hours..although it was windy then too. This time its going to be close again. Just south of us though is going to be a mess.