1/13/07-1/15/07 FCST: OK / KS / MO / IA / IL / WI / IN / MI (WINTER PRECIP)

Model Ensembles have been consistent enough lately in advertising a significant low pressure system to eject NE out of the Four Corners Region... A strong arctic cold front will stall out somewhere in the Midwest and impulses of energy will tipple northward along the front.. Projected path and timing, as well as placement of the front, would begin to spread precipitation starting in the SW portion of the outlooked area around Thursday. Precip should fall as rain for about the first 36-48 hrs. Thereafter a period.. possibly an extended period of frozen precipitation may fall.. Most likely along and 20-30 miles either direction of a SLX through EAX line.. By Saturday Night low should be E/SE of the outlook area.. And the arctic air should be able to turn majority of the WA precip to all snow... With less confidence of a period of all snow with further southward extent.. Precip associated with the low.. and the wraparound.. apear to be lighter than suggested in the last model runs.. With PWAT' s hitting .40 - .50 max throughout the period... Main threats throughout the event could focus on heavy rain and flooding potential and then a freezing rain threat.. ATTM I could see minor accumulations.. but dont look for anything like what our poor friends in Denver, Co have seen lately..;) Hopefully a couple more model runs can clear up freezing lines, and QPF..
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Potential Winter Storm!

The Desmoines NWS is stating in its HWO that there could be strong winds and between 6 and 12 inches of snow across portions of Iowa starting late Saturday and lasting into Monday! http://www.crh.noaa.gov/dmx/?n=outlooks So with the strength of this system and the amount of cold air that will be available it looks to me like my area (east central Iowa) will be blanketed with the white stuff come Monday morning, its about time! :)
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Not a lot to add yet, given all the model and ensemble spread, but I don't think accums will be minor (wherever they do fall.) I imagine parts of IL/IN/MI will pick up a half-foot or more, which doesn't sound like much but for many of us it'll be more than we've picked up all season long!

EC probably a little too warm yet, I'm pretty happy with the 18Z GFS overall.
GFS pulled the system a little farther south on the earlier 00z run and it certainly has the moisture and (finally) arctic air to work with this run. If we are to believe GFS (which is being leaned on at this point by many), it would appear Kansas City to Des Moines to Davenport (and maybe Detroit down the road?) will have the heaviest precipitation in the form of snow with this one... with lighter snows north and west of this main area. I am concerned about the massive convective potential to limit snowfall amounts... (108 12z)...and Canadian puts it a little farther north.

Im personally thinking it will track a little more north again...just based on historicals, and also, a little bias. ;)

Safe to say we have the moisture AND the arctic air to work with on this one. Now the question is where, and how strong. Any guesses on as to the path of this this far out?

I'm not relying just on GFS for this, it's a long ways out...looking for consistency on the majority of models of course...I am just wondering the opinions on if it is MORE likely to be on course, swing left or swing more to the right...and also if anyone else is concerned about convective energy robbing the life out of this. Ahh, the joys of winter storm predictions!!!
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sorry about the long time no update.. internet server lost power and had problems getting back up..

About The Weather... A more southern track had been sneaking into the picture in the last few runs.. This could spell heavy snow amounts over IA/IL/MO. And I do believe the ice threat is still there as well.. Cold canadian air already diving into the western us... storm path still pretty up in the air.. Obviously a more southern track would mean less ice more snow. And vice versa. PWATS a little mroe impressive. GFS seems to be my model of choice as NAM is a clear outlier.. Again just have to wait until the track of the low is cleared up. With is vital to the evolution of the system.. Also, as Mr. Miller correctly addressed, I am somewhat concerned of the moisture robbing potential..
Well, the Bears game on Sunday (at noon) in Chicago could be very interesting. A strong wind off the lake combined with waves of snow moving through, if current forecasts hold.

The GFS has been very consistant (which is very nice to see) with the major features for quite some time now. One thing that's become more apparent is it looks like the ice threat is much lower compared to the way it was looking a few days ago. Because the storm is taking so long to evolve out of the rockies, the cold air will have had time to become deeper out ahead of it. There still may be a zone of ice in the transition zone, but not nearly as widespread as it was looking a few days back.

Another nice thing about this storm system is how large the zone of heavy precip in the cold sector is. Unlike some previous storms which had fairly narrow swaths of heavy snow, this one looks to lay out a nice wide band covering a lot of territory.

For folks on the western side of the heavy snow band, say western IA, eastern NE; you guys will have much higher snow ratios, so it won't take too much precip to fluff up a lot of snow. Of course, with the tight gradient that will develop, the wind will really whip that around.

With the storm still almost 100 hours out things will likely be tweaked as the weekend approaches, but it does look like someone will end up with a good 8-12" of snow by Monday...
00Z GFS slows things down so no snow affecting the football game, Cobb method comes up with some ice at the onset for ORD then finishing up with 8-10" of snow (that was from the 18Z run though.) If the EC starts getting a little colder I'll start getting more excited, but I can't go too hard against old faithful until it or the ensembles come more in line...
I was looking at the 00z runs myself just a few minutes ago and one trend I did notice was increased coverage of precipitation over NE/IA/SD. Also, an area of moderate QPF is now indicated in central and NE Nebraska early in the evolution of the storm (84 00z run). Central Iowa still looks to be without change and continues to likely receive heavier snow (but not as heavy as the last run indicated). Overall, GFS still remains quite consistent, but trending a bit farther north and also a little weaker in intensity it appears. I'm becoming quite pleased with the consistency of GFS but far from ready to call this one. Is the Northern stream or southern stream gonna win out? This is the fun part....the challenge.

Regardless, Im pretty sure that winter storm watches will be hoisted probably from an area from Omaha CWA to Des Moines to Davenport CWA...probably within the next 24 to 36 hrs, bounded by winter weather advisories a few county tiers north later down the road I think. I was also liking the wording from Sioux Falls saying "Big trouble" for the southern CWA if the southern stream wins. Keeping tuned!
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I think the title of this thread needs to be expanded to include more of the Midwest/Great Lakes.

Anyway, this system is barely into the NAM model now, which is when the REAL fun will begin. I'm sure we'll see some pretty big model spreads coming out with the typical NAM vs. GFS battle. Although, the medium range models seem to be in excellent agreement and have been rather consistent, so I'd eventure to say the NAM won't be much different. That in itself weighs more heavily than a single model-specific ensemble (at least IMO), but we shall see.
Not sure if this belongs in this thread or not as it pertains to a different region, so mods please feel free to move or delete. Anyway, the 00z NAM shows a rather significant trend towards a faster cold frontal passage over the Southern Plains on Friday and a corresponding shift southward of the 32F isotherm during much of the precipitation over the weekend. This now looks like a potential ice storm threat for a lot of Oklahoma, especially north and west of I-44 (but hopefully at least down to Norman too ;)). Taking the 00z NAM QPF fields literally would paint a very ominous picture on Saturday night into Sunday morning with copious precipitation centered along the I-44 corridor, and surface temperatures solidly below freezing at the same time 850 mb temperatures are still well above.

Definitely something to watch for the Oklahoma posters, I think - I know I'd been second guessing the TV mets and NWS the past few days with all the models showing relatively warm solutions, but with this run and the evening OUN AFD, I'm getting a bit more excited.
Its Coming

As someone mentioned earlier diffs. come out in the GFS and NAM.. Only variable seems to be mostly with the timing of the system.. With the NAM surprisingly being slower.. With the setup appearing more and more likely.. Look for the watches to be popping out. Believe OUN already issued.. As well as some other southern WFO's. Snow amounts lookng more and more heavier with time.. More depth of cold air intruding the area sooner. I cant say as I'm too terribly concerned about the MCS/Squall killing the moisture flow.. The system should be able to gather its strength and dynamics pretty well. Again, wouldnt be surprised to see watches posted in next 24-48 hours..
Last nights 0z and this mornings 12z WRF are painting an ugly picture for most of Oklahoma. It appears that the initial wave will provide a fairly significant layer of ice for most of the state (~1/4 inch), with the exception being in the SE part. As the trough approaches towards the latter half of the weekend, a band of significant icing looks to occur along the I-44 corridor.

I feel that the local TV stations have grossly under-estimated the impact that this storm could have on Oklahoma. I am advising relatives, friends, and co-workers to plan on being at home for at least 3 days and possibly up to a week. I'm not as good at forecasting winter weather as I am at forecasting severe weather, but I have enough experience and knowledge to know that this type of set-up can produce copious amounts of freezing rain.
I can already see the differences between the NAM and GFS, and they are pretty big. NAM is quite a bit further north and deeper (like the previous GFS runs), while the 06Z GFS lost the system almost completely, with the 12Z showing at least something. I'm interested in seeing what the GEM shows, and hoping the GFS is simply the odd-man out playing it's "lose the system" game.
One thing I'm not liking at all with this storm is the southwest/northeast oriented band of heavy rain near the boundary. This type of setup usually cuts off a good deal of moisture from the cold sector. This is very evident by the rather wimpy QPF amounts in the deformation zone through the period. Very good upper level dynamics will help overcome some of that, but to what extent remains to be seen.

However, like I said last night, the snow ratios will be relatively high with this storm. Particularly deeper into the cold side of the snowband, so it won't take as much moisture to "make" a lot of snow.

As for ice, the north part of OK on up into southeast KS look to have the best chance at ice accumulations the way it's looking now.
OUN is upgrading most of their area to an Ice Storm Warning toe the Friday night event, interesting because the 06Z NAM is much warmer than the 12Z run (which drops 3/4" freezing rain.) EC is also fairly warm in that area - seems surprising to go with a warning this far ahead on a situation with plenty of questions yet. I find it hard to believe enough cooling will work in once the precip starts to cause a dramatic situation.

GFS looking a little weaker with the system as it moves through the Ohio Valley, Euro continues a slower / warmer track which doesn't bring me much snow at all...
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If in fact that a SW/NE oriented band of heavy rain does fall near the boundary, wont that actually support more active severe weather come saturday through monday across AR,TN,KY,MS,AL?
Pretty sure there's no such office as SLX, and a reminder that this section is for talking about your forecast (or using NWS forecasts to make a point, we all know how to read NWS discussions and watches.)

Warmness of the Euro still has me worried around MI, 18Z NAM has a little wave now that kicks off some snowfall Saturday night into early Sunday (apart from the main system) but I'm not ready to buy that. Yet.
He probably meant LSX....

The 18z WRF remains consistent with the last nights 0z and this mornings 12z runs for the significant icing potential over Oklahoma. The only discrepency that I can see lies in the timing/strength of the main wave. Of course, 33 degree surface temps could destroy this entire forecast, but it looks like we won't have too much trouble getting the cold air in place at the surface. I'll be interested to see if the WRF and GFS come into any sort of agreement at 0z. FYI, OUN has issued an ice storm warning for all of C. and W. Oklahoma with the mention of a significant icing along and either side of I-44, with amounts ranging from .5-1.5 inches of ice accumulation.
He probably meant LSX....

The 18z WRF remains consistent with the last nights 0z and this mornings 12z runs for the significant icing potential over Oklahoma. The only discrepency that I can see lies in the timing/strength of the main wave. Of course, 33 degree surface temps could destroy this entire forecast, but it looks like we won't have too much trouble getting the cold air in place at the surface. I'll be interested to see if the WRF and GFS come into any sort of agreement at 0z. FYI, OUN has issued an ice storm warning for all of C. and W. Oklahoma with the mention of a significant icing along and either side of I-44, with amounts ranging from .5-1.5 inches of ice accumulation.

Which WRF run are you looking at? I'm assuming you mean the NAM WRF. Interestingly, both the 12Z and 18Z runs raise the surface temperatures over much of southern OK even with northerly surface winds between 6Z and 12Z on Sunday, concurrent with the onset of precipitation with the second round. However, both show categorical freezing rain throughout the entire event. I imagine the warming in the model is from latent heat release due to freezing at the surface, which would tend to try to raise the temperature toward freezing while CAA tries to keep it down.

Depending on where the main precipitation bands end up (NAM wants to paint a lot of it north of the frontal boundary, while GFS wants to keep most of it in the warm air), we could be looking at a real mess.
What seems plausible to happen at the onset of the precipitation is that the above freezing temperatures may fall towards the surface with the rain, raising the surface temperatures by a degree or two, before the arctic air really establishes itself. If this happens, the amount of ice accumulation may be reduced slightly, but will still be significant, and enough to cause damage to trees and powerlines.

Looking at the 0z soundings, DDC has a deep enough layer to melt the precipitation prior to its reaching the ground, but that layer is cooling off significantly after the passage of the front. I would suspect we see the same thing after the front passes through OUN closer to 12z.
It seems with a significant ice event one needs the freezing line to stay in one location for a good/long duration of the event...otherwise several locations are getting a bit of each type as it progresses, instead of one area getting all one type. It'll be interesting to see how that unfolds. It almost seems like it might want to at least keep sagging south.

The reason southern NE got so much that event was two nights of it and the line pretty much not budging at all for the whole deal(very little wiggling to it at all). That time the cold air feeding into the region was not nearly as cold as what is around now. I'd say once it is below 32 in areas of OK it's not going back above. The model forecast sfc temps were blown on the NE one, even 12z the day of. They wanted to raise it as the freezing line moved back west, but it never happened. And again, that time had a weak push of cold air, which was not nearly as cold as what is around for this one. Best of luck if you get 2+ inches of the stuff.
Another quick look at the models.. WRF/NAM still slower and a touch weaker than the GFS. Lots of snow and ice still looking good up here in IL. lots of precip could possibly fall as ice pellets.. Im gonna have to wait till tommorows runs..
Latest 00Z NAM is in and it's quite a bit stronger than the GFS. The 18Z GFS had a decent system, but we lost it again with the 00Z run. The previous GEM runs have been pretty consistent as well, so I guess I'll wait for those to come out.

Perhaps the GFS will beef up the system again by the next 12Z run, then I'd be a bit more confident. Either way - plenty of cold air to work with, so I guesstimate snow ratios to be in the 15 or 20 to 1 range... Rob Dale - what are you getting as far as snow ratios north of the boundary across areas like IL and southern MI? GFS has us pretty cold, as does the NAM.
I'm really hoping the GFS is out to lunch on this latest run. It paints a very unimpressive snow system for the midwest and great lakes.

Both the NAM and GFS refuse to close the low pressure above 700mb. This is largely why the cold side of the system seems to lack intense precip. Previous runs from a few days ago had a closed low up to 500mb making for a much heavier band of snow in the cold sector.