11/30/2006 FCST: IL / MI / IL / MO / KS / OK (WINTER PRECIP)

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Latest model runs continue to indicate a possible winter storm setup on the 29th through the 1st. Critical thickness data shows a favorable setup for accumulating snows. Thermal profiles show freezing temps at BG level, thus any precip that could fall would be able to be all snow. Post frontal precip would be changed to snow as low pressure builds into the area. Still a ways out, and models can't really agree, couple of hundred miles of deviation would have a big effect. Also, passage time and strength of the front in the day 2-3 period will impact the possibilities. Have to wait it out. But we wouldnt complain if we got a big one.
 
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First major winter storm still looks to be on track for the 29-31. Kansas city first to pull the triggger and issue the winter stomr watch. Both surrounding offices are mentioning the same possibility. Latest HPC outlooks place a narrow band from MO-IL in the risk for .25 inches of ice accumulations. Also, HPC does have the area in the slight chance of snow>12 inches. Based on timing and models threat would most likely begin as significant ice accumulations, until precip can make the complete change over. Wouldnt be surprised to see new watches come out with this evenings shift or tommorow morning.
 
This looks like the first major winter storm of the season. I'd expect to see a good 6 inch swatch from Tulsa, Oklahoma northeast to Chicago, Illinois. The way the dynamics are setting up and the timing of the cold air it looks like the northern half of Illinois will see the greatest accumulations. I'd go for 8-12 inches in Chicago, but some isolated areas in northern Illinois, northeast Missouri and eastern Iowa will probably see well over 12 inches.
 
Latest 12Z NAM still has the system considerably eastward. This is in line with the previous SREF runs, and a "middle of the road" solution when compared to the GFS's no-show system. I'm thinking a SFC low will eventually track from AR to just east of CLE. The models should be getting a pretty good sample of the system now, and I expect the 12Z GFS to come back to its senses with a system probably similar to what the NAM is currently showing.

What I really like is the very tight baroclinic zone. The 850MB T's are in the -8C to -10C region within 50 miles of the front / 0C isotherm, so some pretty good snow growth should occur. I also suspect that snow ratios would be bumped up to 10:1 or 12:1 in those areas.
 
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Well, I'm going to stick with the NAM for now... The past three runs of the GFS have been absolutely horrible.

00Z - Farthest west with the system.
06Z - No system at all - open wave
12Z - Weaker system, much further east

The NAM has at least some continuity, but SREF is all over the place. With such a tight baroclinic zone, I can't help but think at least something will develop - whether it's a NAM or a GFS system remains to be seen.
 
I agree with rdewey. i think a sfc low should develop somewhere
along the front and move into the tn valley by 01/12z. warm
advection patterns ahead of the low would set up conditions
favorable for snow...freezing rain and/or sleet in the transition
zone from srn mo north into il...with a risk of lesser amounts of
snow extending up into the wrn great lakes. Agree with rdale too. Soo much spread in the models, its hard to stick my neck out.:) But do think it will be a big event somewhere
 
FWIW... The latest 12Z GGEM is pretty consistent with it's 00Z run. It also has an easterly track, completely bypassing everything from CLE westward... The 12Z run is just a *touch* deeper at 500MB, but otherwise it's very close to the previous run. The 12Z UKMET has a similar track to the NAM but is about 6 hours slower.

Not sure what's up with model continuity, but I would say odds are going against a strong winter storm right now.
 
FWIW... The latest 12Z GGEM is pretty consistent with it's 00Z run. It also has an easterly track, completely bypassing everything from CLE westward... The 12Z run is just a *touch* deeper at 500MB, but otherwise it's very close to the previous run. The 12Z UKMET has a similar track to the NAM but is about 6 hours slower.

Not sure what's up with model continuity, but I would say odds are going against a strong winter storm right now.

which model proves to be most accurate normally??? like i said in another thread im new to all the models and im trying to learn so i was wondering what proves to be most accurate 9 times out of 10 if any?
 
which model proves to be most accurate normally??? like i said in another thread im new to all the models and im trying to learn so i was wondering what proves to be most accurate 9 times out of 10 if any?

That's the problem... There isn't one specific model that's more accurate than the other. Usually, you go with the "majority"... If 3 out of the 4 major models are showing a strong storm, then you can bet that there will be a strong storm (often middle of the road between the two extremes). However, when you have 4 models showing 4 different solutions with each run, it's pretty complicated.

As you can see from the link Rob Dale posted above, even the various runs of the same model (ensembles) aren't lining up.
 
probably can pull the plug on the ws watch for any wild winter wx in much of the Pleasant Hill CWA. It does look interesting in the I-44 corridor, but even that window is pretty short as progressive as things have changed up over the 00z runs last night.
 
probably can pull the plug on the ws watch for any wild winter wx in much of the Pleasant Hill CWA.

I think you may have jumped the gun going with a watch this early - in these preseason events, especially those with such a large variety of solutions, you should hold off until you're more certain.

Not saying your forecast is a bust yet ;> as we still have a few more runs...
 
just watched the 1230 skilling forecast, he points out all the models except the "navy" one point the "major winter storm" as being a bust and if one does form it would pass south of chicago, still aways out but it went from being nothing to something and now back to nothing, looks like more of a severe weather event
 
just watched the 1230 skilling forecast, he points out all the models except the "navy" one point the "major winter storm" as being a bust and if one does form it would pass south of chicago, still aways out but it went from being nothing to something and now back to nothing, looks like more of a severe weather event

I think he means bust for his forecast area... The NAM certainly isn't a bust for the Great Lakes, and the GFS isn't a bust for areast further south and east.
 
well thats what i meant im sorry i wasnt more specific on that, although he didnt use the words "major winter storm" anymore for anyone in the midwest, thats usually something he does is emphasize the fact that sometimes chicago "misses a major winter storm" hmmm....sorry for the confusion
 
As with all threads in the Chase Forecasts forum, let's try to keep the S/N ratio as high as possible. Hugely in-depth analyses and discussion is not necessarily required, but try to formulate your own forecast and provide insight into your forecast process. Everyone is encouraged to participate, but let's all try to keep this forum of high quality. Just a friendly reminder.... :)
 
Now im really confused. The latest WRF, would lead you to think, little if any frozen precip, at least for my area in west central Il;based on timing, and thermal profiles. GFS indicates a brief period of SN/ZR over the area. And the SREF shows an extended period of snow with significant accums, begining with a period of freeaing rain. Note NWS in St. Louis did post a Winter Storm Watch. Also, the models are TRYING to indicate a more southern path for the highest snow amounts. Looks like snow accumulations could have a REALLY sharp cutoff with northward extent. NAM model seems to have had the best handle on things lately. So, maybe that will be the model that will verify.
 
00Z models starting to flow in... NAM has made another adjustment to the west and really bombs this system out with near blizzard conditions to the northwest. The NAM has a 988MB low near PA by 12Z FRI with 20-30knt sfc winds along and to the northwest of the system.

The heaviest swath of snow is displaced further northwest than the 18Z run, stretching from MO through IL, IN, and MI. QPF on the snow side is generally widespread 1.25 to 1.50 inch amounts, with isolated 1.50 to 2.00 inch amounts. The baroclinic zone is very tight and mid level VV's are beyond impressive - I would expect most areas from MI southwestward to switch to snow by 06Z FRI or shortly after, with extremely heavy snowfall.

Okay, that's the NAM version and we're talking 60 hours out - a nice wishcast. We will have to wait and see what the new Canadian and GFS models bring us. Right now, I'm thinking the system won't be as intense at what the NAM is showing, and will end up a bit further east. It should be noted that "weaker" (cutting QPF by 1/3) still yields 12-18 inches over a pretty large area.

Even so, my confidence has been boosted slightly with this run of the NAM. If the GFS can show something even remotely similar (or deeper / further west on the 00Z), then I would up the chance to "good".
 
You won't believe this but a short term forecast was issued for our area saying that the arctic front will be in KC by 10PM!!!!!!

THE ARCTIC COLD FRONT HAS ACCELERATED SOUTHEAST SINCE 6 PM...
SURGING SOUTHEAST AT AROUND 20 MPH. THE FRONT IS NOW EXPECTED TO
REACH A PRINCETON TO PLATTE CITY TO JUST EAST OF A LAWRENCE KANSAS
LINE BY 9 PM...AND A CHILLICOTHE TO INDEPENDENCE TO OLATHE LINE BY 10
PM. TEMPERATURES WILL PLUMMET A FAST 15 DEGREES WITH THE PASSAGE OF
THE FRONT.
 
With the horrendous performance by almost all the models over the last 36hrs, even this close I wouldn't bite into anything just yet....

Be that as it may, they all still show some very heavy wet snow in the cold sector in a pretty compact swath. Chicago may not be out of the woods yet, and much of MI is really looking to get nailed by this one by Friday. Flow has been from the gulf for days now, so moisture availability is going to be very impressive. It even looks like there's a deep tropical feed coming up from way down south of Mexico.

Still a bit far out, but there's no question someone is going to post a very hefty amount of snow, just a matter of who at this point.
 
You won't believe this but a short term forecast was issued for our area saying that the arctic front will be in KC by 10PM!!!!!!

I'd have to say EAX was right on that one...I just stepped outside and it has dropped about 10 degrees from what it was an hour ago. Anyways, I just finished reviewing some of the hpc data, and it appears that Central, Eastern, Southern MO and Central IL could get blasted with the freezing rain tomorrow and snow by Thursday.

Day 1 Freezing Rain Outlook: http://www.hpc.ncep.noaa.gov/wwd/day1_pice_gt_25.gif

Day 2 Freezing Rain Outlook:
http://www.hpc.ncep.noaa.gov/wwd/day2_pice_gt_25.gif

Day 2-Snowfall Probability >4"
http://www.hpc.ncep.noaa.gov/wwd/day2_psnow_gt_04.gif

Day 3-Snowfall Probability >4" (for you folks in IN, MI, and OH)
http://www.hpc.ncep.noaa.gov/wwd/day3_psnow_gt_04.gif

Day 3-Snowfall Probability >8" http://www.hpc.ncep.noaa.gov/wwd/day3_psnow_gt_08.gif
 
00Z GFS and RGEM now on board with the NAM. The 00Z FSL RUC is also digging pretty deep at FH30. The 21Z SREF is also tightening up slightly with the SFC low positions spread out across much of OH and PA.

My confidence level is quite a bit higher that a major winter storm will develop... The threat region right now is pretty broad, but I think we can start narrowing it down to an area between ORD and CLE.
 
Severe Storms of Two Kinds

WOW! System that was no more at last nightss 06Z runs, in now very alive!

My first item of interest is the severe storms threat this afternoon.....

SFC front should lowly traverse the area today and provide a focal point for shower and thunderstorms. Already a strong storms noted on WSR 88-D for NWS Quad Cities. Expect initiation in OK/AR/TX/MO this afternoon. Weaker lapse rates with northern extent of the front will preclude higher instability. 50 F dewpoints and daytime heating should be able to put MUCAPE aoa 500 j/kg in illinois, with greater amounts with southward extent. Supercell potential is there, but the greatest threat should be in central texas where low level shear can be maximized.. Storms, once intitation will develop and move northeast along the front.

Now the Snowstorm...

Moisture fields become somewhat depleted where after the cold front treks across the area. This would mainly happen the areas in Northcentral IA and Northcentral Mo, which would have an effect on the amount of post frontal winter precip. If moisture is meager then ice accums in these areas would obviously lesser. Gulf moisture comes quickly into the area right in time before the next system, is forecast to glide northward along the front, early thursday morning. Timing shows favorable for significant ice accums, some spots possibly over .5 inches!!:eek:This would most likely AT THIS TIME, occur from an area around 100 miles any direction of St. Louis, by early thursday morning, the precip should be able to turn to light snow. Depending on how long WA precip can last, amounts could be as high as 4-8 inches, from a Jefferson City,MO -Springfield, IL axis. With Sharply lesser amounts on either side. Evolution of the Low is still at question. Thus timing, amounts, and location are still at question.. Models are coming together better. So we'll have to see. It's gonna be an interesting next few days. :cool:
 
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Latest 12Z NAM is slightly weaker than the 06Z, but it's further west. The RGEM just came in and it's also a touch further northwest than it's 00Z run. The 00Z ECMWF and UKMET are further east with the system, in line with the GFS. Right now, I'm thinking a track more along the lines of the GFS with a strength in between the two.

Just for kicks, I'm thinking about merging the GFS and NAM grids to create a weighted average, but I'll wait and see what the 12Z GFS shows.

As for the storm - The NAM snow output across IL is impressive. Widespread +20 inches with a few isolated spots up and over 30 inches at a 10:1 ratio. There also appears to be a pretty good icing event between the rain/snow area as the system pulls in mid level warm air (particularly across IN and parts of MI). It should be noted that NCEP reports the NAM is not deep enough with its initialization at 500MB over the west - off by about 30M. I'm not sure what impact that would have on the system, other than the NAM may not be far enough west (i.e. deeper equals farther west).
 
"There also appears to be a pretty good icing event between the rain/snow area as the system pulls in mid level warm air (particularly across IN and parts of MI). "

One thing to note though is we need a nice area of high pressure to the north to keep the cold Canadian air coming south... That's not the case here, so odds are it would stay rain or transition to sleet but I don't see an icing event as a big deal.
 
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