12/08/2009-12/09/2009 Winter Storm

[jshields]

after a brief return to a little more southern path, the 0Z GFS is back north again. also upped the qpf for sunday/sun nights little wave that comes through ahead of the main show on tuesday. the new cmc is also in and has roughly the same track across kansas into northern illinois and southern michigan. it drops the pressure from 994mb at 0Z wed to 986 at 12Z wednesday. waiting for the european model....

time sensitive for 0Z 12/5:
http://204.2.104.196/gfs/CONUS_GFS0P5_SFC_ACCUM-SNOW_120HR.gif

 

[Chris Carter]

I think the GFS is a bit bullish. It deepens the low over southern CA brings it northeast into Northwestern CO, then turns southeast towards the OK panhandle?

It pretty much takes a roller coaster ride before it comes out into the plains!

Looking at that link. 20" of snow from Kearney to Omaha?! Looks like i might not be able to go to my doctor's appointment on Tuesday.

Euro looks a little further south than the previous run, but still fast on the timing. Canadian and NOGAPS have roughly the same track as the 0Z GFS. Which is good because the previous run of NOGAPS had the low streaking across Northern Nebraska into Wisconsin.

 

[Chris Carter]

http://www.weatheroffice.gc.ca/model_forecast/global_e.html

Latest Canadian run now indicating a northly track that takes the low through central nebraska.

Seems like the GFS/CMC/WRF/NOGAPS and the ensembles are slowing the system down a little bit, which could pose a problem for snow lovers like myself, could see more warm air work itself into the system and create more rain/snow in areas that would more likely see snow right now. Good news is most of the models are developing that parallel low after the low works into the Ohio Valley.

Waiting for the 12Z Euro to come out...

 

[Ryan Wichman]

Latest Canadian run now indicating a northly track that takes the low through central nebraska.

I just looked at the UKMET...don't you mean through central Kansas, not central Nebraska? I know it's hard to see on those little maps so I won't even bother posting the map on here.

This low is starting to take shape of a Colorado low rather than a panhandle low. Still at least 3 days out, plenty of time to bang our heads against the wall trying to figure the exact track out.

 

[Robert Dewey]

12z ECMWF pretty similar to 12z GFS; although a tad further SE and 8mb deeper @ 96h. As mentioned, the 12z GEM is stronger / further NW... GEM ensembles show pretty equal chances for a northern operational track vs. a southern track. Still 84-96 hours, but it's fun to analyze the models (and add notes here, like this, for future reference).

 

[rdale]

I just looked at the UKMET...don't you mean through central Kansas, not central Nebraska? I know it's hard to see on those little maps so I won't even bother posting the map on here

The Canadian model is the GEM model. Don't look at little maps The big ones are in the links I added to the previous winter thread. But no need to post in the first place, we all know where to find them.

 

[Robert Dewey]

Not sure what link you're grabbing it from, but it takes the low at F132 over the OK/KS border to near STL at F144.

In any case - the GEM ensemble says "Don't even think about worrying over tracks"

http://www.weatheroffice.gc.ca/data...4_E1_north@america_I_ENSEMBLE_pnm@moy_144.png

Notice a few of the ensemble members even have high pressure centered right on top of where the rest have a strong low!

Best bet for hi-res Canadian is at http://www.weatheroffice.gc.ca/vizaweb/vizaweb_home_e.html

Ensembles at http://www.weatheroffice.gc.ca/vizaweb/vizaweb_home_e.html

Rob, these appear to be password protected. It would be nice if we didn't have to look at the "little maps"

 

[rdale]

Ahh - I didn't know that. Let me double-check, I think it's an open password. In the meantime, this is a good source http://meteocentre.com/models/ And my ensembles link was wrong, what you have is the best source I know of too.

12Z GEM takes the low from central Kansas, to Ft Wayne Indiana, and then wraps it up more and drifts towards Saginaw Bay.

 

[Robert Dewey]

Ahh - I didn't know that. Let me double-check, I think it's an open password. In the meantime, this is a good source http://meteocentre.com/models/

12Z GEM takes the low from central Kansas, to Ft Wayne Indiana, and then wraps it up more and drifts towards Saginaw Bay.

Got it - it's open. Username & password: vizaweb

 

[Robert Dewey]

18z NAM had to make things much more difficult. While it's trending towards the GFS and other models (for the most part), its solution would mean mainly rain for SE WI / all of IL / lower MI. Meanwhile 15z SREF mean 850mb T at 87h keeps the 0C isotherm south of LOT to CLE. Interesting that GRR AFD states

PRECIPITATION SHOULD BE ALL SNOW WITH THE SYSTEM AND ACCUMULATIONS MAY BE SIGNIFICANT.

 

[Chris Carter]

Really liking how the GFS and NAM are dumping around 2-4 inches of snow Monday night alone from North Platte to Omaha from the insentropic lift before the main event moves out of the morning. The main area of snow moves in around midday Tuesday and doesn't let up until early Wednesday morning. Looks like 4-8 inches or more during this stage of the storm on top of the earlier snow, pushing totals around 12-14" of snow. SW Iowa may see the heaviest snow amounts with amount of moisture and maybe the possibility of thundersnow. All depends on how much warm air will get worked into the system.

 

[Ryan Wichman]

18z NAM had to make things much more difficult. While it's trending towards the GFS and other models (for the most part), its solution would mean mainly rain for SE WI / all of IL / lower MI. Meanwhile 15z SREF mean 850mb T at 87h keeps the 0C isotherm south of LOT to CLE. Interesting that GRR AFD states

I was reading earlier that the HPC has thrown out the NAM today as an outlier. Seemed reasonable. Kansas City had an excellent discussion in their afternoon AFD.

Seems like much of Southern Iowa will be under the gun for the heaviest accumulations and as Chris mentioned SW Iowa will likely see some significant accumulations when you combine both of these events.

 

[rdale]

18z NAM had to make things much more difficult. While it's trending towards the GFS and other models

The NAM at longer ranges continues to be useless in the winter. I'd hesitate to bother looking at it - let alone using an offhour run - until something changes in its performance.

 

[Chris Carter]

I was reading earlier that the HPC has thrown out the NAM today as an outlier. Seemed reasonable. Kansas City had an excellent discussion in their afternoon AFD.

Seems like much of Southern Iowa will be under the gun for the heaviest accumulations and as Chris mentioned SW Iowa will likely see some significant accumulations when you combine both of these events.

NAM has been thrown out for Sunday's snow in the Central Plains.

The NAM and EC are being used for mid-week systems, even though they are just now able to get a hold on it.

Currently coming from the Des Moines, IA discussion.

"PRESENTLY THE MODELS ARE SHOWING A
DEEPER SYSTEM THAN 12 HOURS AGO AND STILL SHOWING A RANGE OF QPF
VALUES OF .80 TO JUST UNDER 1.10 WITH THIS RANGE FROM NEAR I80 SOUTH
TO ABOUT I70. CURRENT COBB OUTPUT FOR THE GFS MODEL IS SHOWING
ROUGHLY 6 TO 10 INCHES OVER THE REGION WITH THE AXIS OF HEAVIER
SNOWFALL ACROSS THE SOUTH...ALONG AND SOUTH OF I80 TO THE BORDER. AS
WITH ALL GUIDANCE...THIS MIGHT CHANGE OVER THE NEXT SEVERAL
DAYS...BUT THERE HAS BEEN BETTER CONSISTENCY OVER THE PAST FEW RUNS"

 

[Robert Dewey]

The NAM at longer ranges continues to be useless in the winter. I'd hesitate to bother looking at it - let alone using an offhour run - until something changes in its performance.

Good idea. 18z GFS reaffirms that thinking... it's pretty consistent with it's 12z run.