Chicago Storm

0z GEM .

0z GEFS mean...

0z GEM appears to have bumped north with both the overrunning and main storm.

Some of the positives we saw, such as with the 12z run, stepped back. PV in Canada was further SW, along with associated area of confluence. Heights also steadily lower ahead of the main ejecting wave.

It did, by about 6hrs+.

you had to pay for the derecho years prior.

0z GFS...

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Confirmed.

Looks like 0z GFS will bump south with at least the overrunning portion. Edit: And likely main storm too.

COOP observer and NWS OBS sites are more the official route. CoCoRaHs is supplemental.

There were only ~3 EPS members that had the main storm this far north.

It does, but the 18z EPS goes out to 144hrs.

Cross referencing COD, looks the same as WxBell… .

18z GEFS mean...

Would hope that we have the overrunning portion sorted out by tomorrow at some point, and the main storm on Monday hopefully.

It has been exceptionally bad this season.

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Fairly large changes on the 18z GFS.

you moved to cedar rapids?

well, that’s a wrap for here. .

The latter one is the correct one in this case. .

-D. .

The main storm potential has many factors involved, all of which obviously can make for a north/south shift. Some of the players involved are; The PV in Canada, ridging out ahead of the Western US trough, additional waves diving into the West later in the period, the quality of the main wave (elongated/strung out vs not), timing of the main wave ejection and more. The GFS for example is north due to the quality of ridging ahead of the main ejecting wave, as well as a much more consolidated Western US trough, with a main wave that is actually able to take on a negative tilt as it ejects into the Plains. On the other hand, one reason the Euro is much further south with the main storm is due the much slower timing and a much more elongated/strung out trough. .

12z EPS mean .