ILSNOW

9z plumes just shy of 5 at ORD which includes both events.

12z NAM going to be south

0z UKIE assuming ratios north of 20:1 would not be bad (actually includes a .1 or .2 form saturday night wave)

03z RAP

thanks my bad

I am guessing the the 18z Euro was not impressive?

started here as snow

The wave train seems to be temporarily derailed we need to trend back to the 12z and 18z runs from yesterday. There are certainly going to be many opportunities over the next 5 days or so. Lets reel em in. EDIT And 12z GEM comes in with something in for the monday/tuesday time frame with a nice hit for C IL,N IN and western MI. Gives northern IL about .3 to .4 precip with ratios north of 20:1.

0z GFS wave#2 weaker but north of 20:1 ratios still bring it (snow totals for both waves)

0z GFS wave #1

snow depth via 12Z Euro that would be truly unbelievable

ratios of 15-17:1 wont hurt either.

yes but it is going to be 36 degrees here today and i am concerned.

i use pivotal and it hasnt updated the GFS para since 6z where are you seeing it?

yep on the 12z we had a deepening low in central wisconsin on the 18z we have a weakening low going thru southern IL.

Interesting that 18z NAM has more snow via both Kuchera and 10:1 closer to metro Chicago and less and NW and west which is against the KLOT forecast. Just happy that the system went away from a rainer and snow eater.

KLOT not impressed with snow chances and agrees with Hoosier The jet core will continue to strengthen as the system treks eastward which should be able to drum up a decent surface low via cyclogenesis along the developing baroclinic zone as lead dome of colder air funnels into the trough axis. As the system nears the Great Lakes, the increased strengthening evidenced via the negative tilting of the trough and increased frontal strengthening should lead to a significant deepening of the associated surface low. We will be maintaining a southeast surface wind over the snowpack as warm south/southwest flow off the surface pumps in some warmer air aloft. This suggest there could be small window for brief freezing rain at onset Thursday morning, though it does not look to be long lived. Precip type appears to be snow north initially and rain south, with a generally changeover to a mix or rain for most areas except for northwest of Chicago which could remain as a wet snow. The period of highest confidence for precipitation is Thursday afternoon with the left exit of the upper jet in place, maximized isentropic lift, and strong q-vector convergence fields with the increased height falls. This would be the wild card period if snow remains dominant near and northwest of Chicago, but with system strengthening/deepening the pattern of maintaining warmer air aloft suggests the layer would warm enough unless precip rates were to remain sufficiently strong. There are some model differences in the strength of the low, but all generally show a stronger system with a deepening low with a fairly significant pressure rise on the back side as colder air funnels on in. This is the period of continued upper low strengthening combined with the strong surface cold front. Bitterly cold air accompanied by a "wall of wind" behind the front should result in a rapid changeover to snow if it had not occurred already. QPF should be starting to taper, but there appears a window time where forcing, decent lapse rates aloft, cold air, and strong pressure rises could result in a brief period of moderate snow and wind gusts in excess of 40 mph Thursday later in the evening and dangerous travel conditions. This does appear to be well after the evening commute. At this time model guidance has not changed much with the overall snow forecast, maybe slightly higher for snow near Rockford and less farther south and east, with the highest probabilities of a few inches of snow (maybe several north central IL) northwest of Chicago. The combination of snow and wind could certainly warrant some kind of winter weather alert.

yep it backoff it 0z run here locally and has 2-4 for the northern tier of counties in IL. It is quite clear that the GFS and GEM have a much better handle on this event (haha). Lets see how it plays out.

GFS,RGEM,GEM and Euro vs. NAM and Ukie and you can get 4-8 inches of snow and Hoosier can get 1-2 from this setup. We shall see!!!!!!

12z GFS

Agree there are now 2 precip maxes 1 which did jump nw and 1 over chicago metro which the 6z had .2 the 12z now has .5 to .7 (i am not sure that all of the 12z precip would be snow)

KLOT The main story though looks to be the arrival of a true arctic airmass over the weekend. Timing differences in the global guidance remain, but the signal in the deterministic and ensemble output for a period of significant cold is impressive at this range. The heart of the arctic airmass may not arrive until later on Sunday into monday, but lingering breezes and high temperatures that may not rise much above 0 result in wind chill values during the overnight periods that may fall below -20 F.

12z GEM coming on board also