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Pre-Christmas (Dec 21-23rd) Winter Storm


Chicago Storm
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4 minutes ago, Malacka11 said:

There has to be a windshield wiper pattern here because what's the alternative? If the east/weak trend continues for 72 more hours in any capacity there literally will not be a storm

Same windshield wiper pattern happened with GHD 3 as well.

Seems to be the SOP with potentially major winter storms these days.

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Some perspective is in order I think, and this doesn't apply to all areas and how much snow might fall. The ECMWF did shift in the direction of the other models related to changes over Canada at h5. However, it adjusted less and still shows a 980 mb low over south central lower MI at 12z Friday. That's still a powerhouse low given the very strong high pressure over the Plains.

The changes that have been described here may or will hurt totals depending where you're at. It does not mean storm cancel for everyone or that there can't be adjustments back somewhat as the mid and upper pattern evolves over Canada, and some of the features still over the Gulf of Alaska this evening get sampled by the RAOB network.

24 hours ago there was perhaps some concern based off some of the models and mid and upper evolution they were showing that the system would be more amped and track far enough NW to bring rain even into Chicago. Given that this setup is fairly complex but essentially involves the PV lobe piece and the developing main wave over northwest Canada and not some exotic phase (think the failed Feb 2020 storm).

If the models are a little bit wrong in the interaction between these and changes in 500 mb height fields, the strength of the main wave, the strength of the intensifying upper jet rounding our main wave, etc, there can be adjustments that oppose what we've seen tonight, just as last night it seemed like everything (except the Euro) was going much more amped.

There are valid meteorological reasons why the PV lobe tracking to James Bay might destructively interfere with this setup, but imo it's still too early to feel confident that the changes seen tonight are directional changes that will continue unabated in subsequent model cycles. Even though it is drawing closer and the NWP should have more skill in this part of the forecast, there's still time for meaningful changes. I am not saying that the changes seen tonight won't continue unabated, but that this range before winter storms can and certainly has had shifts back in a positive direction for snow enthusiasts.

Describing what the models are showing isn't the same thing as what will actually happen. I don't think if I was analyzing the data tonight at the office (I'm working the day shift today/Tuesday) that I'd have enough info to be completely confident yet. We can see some of the key features on water vapor imagery, but there's not really much observationally right now that can tell you affirmatively the 00z models are on the right track.

This still looks like a high to very high impact event for the Chicago area and points south and east at this time due to the wind and snow combined with extremely cold temps. Really, anywhere that gets at least 3-4" of snow will have blizzard conditions in open areas.

Finally, as a snow enthusiast myself, hopefully the shifts on Tuesday are back in a positive direction.



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As another note, re. questions about the earlier than usual watch issuance today, a bit of a domino effect took place. That is a challenge we sometimes face in collaborating headlines. In the case of the Monday day shift, most offices we border (and the offices some of our neighboring offices border) preferred to hold off on a watch because we were still well outside the typical 48 hours out before the event issuance timeframe.

However, a few offices preferred to issue the watch Monday PM. So with that, and challenges associated with only including portions of CWAs (ie. only western half of LOT, MKX, ILX), ultimately it was decided by most (except GRR and IWX) to issue the early watch. Plus we had to consider what the perception of public safety and media partners and the public would be if we didn't issue and neighboring offices did, also contributing to my office joining in.

Ideally we would have waited, because we were gonna hit the messaging hard anyway, and beyond 48 hours, there can be pretty big changes still.



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40 minutes ago, Stebo said:

Yeah I dont blame you guys for going with a watch given the time of year the travel impacts and the high impact potential. Plus it is a watch not a warning anyways. 

 

Yep. Agree. And I don't blame GRR for waiting either. I admit I would be hesitant to issue one with the morning update. If they do go with one I wouldn't blame them either. I just am not trusting anything yet. Alot can change with this sort of thing still 72hours out as we have all seen before. 

 

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06z NAM has the center steadily deepening to 970 mb tracking up western L Huron to near APN MI by end of run 18z Friday and would give sw MI possible 2-3 feet of lake effect snow with 60 mph wind gusts. From that track I think ORD would see 5-8" and that would increase around southern L Mich to 24 inches by Benton Harbor, probably about 18" for SBN mostly lake effect. Storm pulls in Atlantic moisture but probably too late if this model verified, heavy snow for ne ON. Lake Erie squall potential looks high after fropa and could give BUF another heavy fall late 23rd into 24th. Could all change on later guidance of course, but there seems to be no plausible track that would fail to dump very heavy snow in sw MI and n IN. Given the likely temps and wind speeds, long-lead warnings were certainly justified and even 1-3 inches of snow blowing around in those conditions would be very dangerous. 

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4 minutes ago, Roger Smith said:

06z NAM has the center steadily deepening to 970 mb tracking up western L Huron to near APN MI by end of run 18z Friday and would give sw MI possible 2-3 feet of lake effect snow with 60 mph wind gusts. From that track I think ORD would see 5-8" and that would increase around southern L Mich to 24 inches by Benton Harbor, probably about 18" for SBN mostly lake effect. Storm pulls in Atlantic moisture but probably too late if this model verified, heavy snow for ne ON. Lake Erie squall potential looks high after fropa and could give BUF another heavy fall late 23rd into 24th. Could all change on later guidance of course, but there seems to be no plausible track that would fail to dump very heavy snow in sw MI and n IN. Given the likely temps and wind speeds, long-lead warnings were certainly justified and even 1-3 inches of snow blowing around in those conditions would be very dangerous. 

 

Well for GRR atleast they have passed on issuing a watch with this mornings package. Strong wording in afd but that's it. I would have waited for the 12z runs so yeah I am guessing that is what they may be doing?.

Btw.. With the stronger winds the heavier Les should be inland a bit like we saw in November. I love the snow but those damn winds. Have lucked out with the wind part so I guess my luck may have run out on that atleast.. 

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