11/20/07-11/22/07 FCST: NE/MN/IA/WI/IL (WINTER PRECIP)

[Jeff Miller]

**Model is still out over 96 hrs and frequent changes are likely as the path and strength of this winter event is highly uncertain. This forecast is subject to rapid change.**

GFS is maintaining the system is back and on track, looking at this time to affect Iowa with moderate snows and cranking up to quite a heavy snow maker over central and lower northern Michigan up to the UP.

A look at the GFS model holds on to cyclogenesis - with a potential swath of heavy snow - **at this time and subject to change** - from Omaha, NE through Davenport, IA northeast through central wisconsin to northern lower Michigan. If - If - IF - this model holds - 2 to 5" of accumulating snow would not be an unreasonable guess. If the storm is more intense then this model indicates I would expect the storm to pull a little more left of the track then indicated here.

Chances are better tonight of this event materializing and creating hazardous winter weather driving conditions for thanksgiving holiday travel.

 

[Craig Maire II]

Snow

As I stated in my other post it looks like Old Man Winter knows that I've got to travel 120 miles to my girl's house for ThanksGiving! So you can bet we will have HEAVY snow here (Iowa) and it will be my fault! My dad has to plow snow for the Waterloo street department so he is not happy about this!

 

[Brandon Sullivan]

Things coming more into line tonight, in many aspects of the forecast. Model sounding thermal profiles show temps supporting snow!! Moisture return/availability is looking much more promising tonight than it has for a while now. Tonights model progs forecast the low bottoming out at 996 mb.. Heaviest snow axis progged by the models, seems to have shifted somewhat SE... SE of DMX-DBQ (Dubuque) line.. I cant wait to see what HPC says tommorow. Here is the GFS forecast snowfall image. From 12z and 18z.. THe 12z showed more snow further NW.. And the 18 advertised less accumulation further SE.. Right over me! This axis of heaviest snow will change alot in the next few days..

 

[Robert Dewey]

NAM seems to be pretty progressive in pushing the front through with no development. Meanwhile, the 18Z GFS ensembles are more aggressive than the 12Z run... although a bit further southeast; this is evident by the deeper 500MB trough, and more members depicting a sub 996MB low over the eastern Great Lakes area.

The 18Z operational GFS shows a nice swath of QPF on the cold side, which would translate into a decent area of snow.

Still lots of time for changes...

 

[Jeff Miller]

Robert, you and I are on two different pages. I'm hoping for a push NW and you're hoping for a push SE. Perhaps the both of us will counterbalance and keep it right where it is

Agreed, still time for lots of changes, and with many winter storm situations, the exact path may not be realized till cyclogenesis begins.

 

[Joel Wright]

Yep, the brand new NAM and the ECMWF are very progressive. Still waiting on the new GFS. The 18z GFS had nudged things a bit further to the east, so it'll be interesting to see if that trend continues.

A majority of the energy/shortwaves that will play a major part in all of this are still not being sampled very well, so we'll see how it all plays out as we go on in time. Tomorrow will be crucial. The models will hopefully all converge unanimously on a solution by this time tomorrow night.

I would not be at all surprised to see a very progressive forecast by many of the models tonight, only to have them all reverse that way of thinking tomorrow on the 12z or 00z run and bring back a stronger/more westward tracking storm...

 

[Jeff Miller]

Yep, the brand new NAM and the ECMWF are very progressive. Still waiting on the new GFS. The 18z GFS had nudged things a bit further to the east, so it'll be interesting to see if that trend continues.

A majority of the energy/shortwaves that will play a major part in all of this are still not being sampled very well, so we'll see how it all plays out as we go on in time. Tomorrow will be crucial. The models will hopefully all converge unanimously on a solution by this time tomorrow night.

I would not be at all surprised to see a very progressive forecast by many of the models tonight, only to have them all reverse that way of thinking tomorrow on the 12z or 00z run and bring back a stronger/more westward tracking storm...

Exactly, tomorrow will be the crucial day - and if any snow advisories or possible winter storm watches are issued for this event (due to the holiday season, many NWS offices may go for winter storm criteria even though it may be marginal) it will likely be issued tomorrow night. I don't expect anyone to jump the gun anywhere until there is a decent model agreement. This is just one model, but it's becoming quite the persistant bugger (I'm saying that before the 00z comes out, watch that show absolutely nothing)

I am just glad I don't live in Davenport. I'd be quite dissapointed if this was to fizzle based on the above potential outcome

 

[Robert Dewey]

Robert, you and I are on two different pages. I'm hoping for a push NW and you're hoping for a push SE. Perhaps the both of us will counterbalance and keep it right where it is

Agreed, still time for lots of changes, and with many winter storm situations, the exact path may not be realized till cyclogenesis begins.

Just by comparing the 18Z GFS ensembles to the 18Z operational run, it looks like the operational run is actually one of the weaker solutions. In fact, the 18Z operational GFS isn't as deep with the 500MB trough, with about 50% of the members showing a deeper solution. In addition, the 18Z GFS ensembles suggest a deeper and further west SFC low than the 18Z operational run.

I'm thinking the 00Z GFS might actually end up a bit further west and stronger... but now that I said that, I'll be wrong.

 

[Jeff Miller]

Robert, you had to go there.... now the storm is tracking farther southeast and the 00z has you, Robert, actually in the frozen precip..... definately a farther south and east run with this model.

 

[Robert Dewey]

...well, at this rate I think we'll all be missing the storm if it keeps trending farther east with each run.

 

[Joel Wright]

Meh. The further east trend continues. I'm not buying it.

Expecting the flop back to less progressiveness tomorrow.

If I'm wrong I guess the only bird I'll be eating on Thanksgiving will be crow.

Seriously though, a bit early. We'll see what tomorrow's runs bring.

 

[Robert Dewey]

Man... Talk about a bummer. Today's 12Z GFS is even more progressive, looking more and more like the NAM.

I guess I can only pray that we'll see a surprise Thanksgiving Day snowstorm, kind of like those "sneak-attack" storms back in the 70's. But, I'm not holding my breath.

 

[Brandon Sullivan]

A White Thanksgiving?

Just looking at some 12z Models and 9z SREF. Things looked to have sped it up again.. With the system out of the area by Thursday Afternoon. WRF shows a somewhat slower cold air intrusion, as compared to the GFS which switches precip over to snow very early.. It seems to me, that these winter systems always tend to slow down, when the event draws nearer.. It will be interesting to see the 18z and 00z data.

I saw HPC does have the 10% 4 Inch Prob over SouthEast IA/NorthEast MO/Western IL. They said low probs only warranted due to model uncertainty.. Should be an interesting next 24 hours to watch this thing.

 

[rdale]

If you're banking on HPC to give you better odds - you won't like this afternoon's Winter Weather Graphics...

 

[Mike Kovalchick]

Seems that there is still some hope of a significant storm as the models still haven't well samplied the system. I note from the APX forecast discussion there was model ingest problems in the NAM and GFS in the 12 Z runs.

http://kamala.cod.edu/mi/latest.fxus63.KAPX.html

...."ESPECIALLY IN LIGHT OF DATA INGEST
PROBLEMS WITH 12Z MODEL RUNS AND 00Z AND 12Z MODEL PROJECTED 6 TO 12 HOUR TIME STAMPS WHICH APPEAR TO BE ROUGHLY 100 MILES OR SO TOO FAR NORTHWEST WITH SYSTEM OF INTEREST DROPPING SOUTHEAST OFFSHORE OF THE WASHINGTON COASTLINE."