Chicago Storm

12z GEM with a solid bump north and drier.

One thing that we have seen change over time is for the storm system to end up further northwest in the Plains, as it ejects out and gets caught in a bit of ridge that extends back up into the Rockies and BC/Alberta. This allows the storm system to peak sooner while out west, before hitting the wall and quickly shearing off to the east.

12z GFS keeping with the trend of going drier.

12z RGEM bumping south and drier.

That has been a large part of it, especially with how much the confluence over the Lakes/Northeast has been changing with time. There have also been some changes with the main southern wave with how far north/south it ejects out, as well as changes with ridging ahead of it. Another thing to watch, is the next trough coming into the West Coast, as that is actually somewhat acting as a kicker for our ejecting southern wave.

There were 3 soundings missing in the Southwestern US, which is significant given that is where the main southern trough/wave is located. At the same time, soundings occurred as normal across most of the rest of the US and Canada, which allowed for the open field ahead of the southern wave and the northern stream to be fully sampled still. So probably have some caution, but don't overthink it too much. Edit: Also, some Mexico soundings were missing at times yesterday, but were available this morning.

12z NAM .

Parts of IA went from 13" 6z run to 0" 12z run.

12z NAM is much drier.

Confluence in S Canada/N Lakes/Northeast is further south and the southern wave ejects out a bit further south.

12z NAM coming in with a big bump south.

Very much has been the case over the years.

probably on point there.

3rd main cycle that have been missing them, unfortunately.

this must be the new model run total snow map thread.

T both at ORD and here.

6z Euro bumped back north as well. .

Add the GFS and para GFS to the 6z bump north group. .

0z Euro .

Indeed. In the end it ended up ~0.10” drier. .

That’s not because it’s drier. It’s due to the shift south. .

Heaviest axis in LOT CWA is actually south of most other guidance now. .

0z Euro bumping a bit south. Not significantly drier or wetter. .

0z UKMET bumped north and was a bit drier, as seen above.

Like the RGEM, the GEM is coming in weaker and drier.