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New Years' Weekend Snow Potential


Rainman

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A low is forecast by the full suite of operational models, with strong signals also in the GFS/EC/GEM ensembles, to cut off from the flow over or near the Great Basin in the middle of next week. The low is then forecast to shear northeast toward the Great Lakes as it is absorbed by broad large scale troughing developing over the northern CONUS. It is shown to remain rather steady state as it approaches, and has the potential to pick up a load of Gulf moisture on its way.

What I like about this system (that has led me to go weenie and start a thread 180 hours out):

1. Large features are the ones predominantly at play: A cutoff low and a broad continental scale height fall region. Also see: No wave phasing dependence and no northern stream shortwaves of major importance

2. Minimal system evolution. At this time, the low is shown to just shear northeast and that's about it. No big time wave amplification means no collapsing in scale of features during intensification and no huge model variability regarding strength and subsequent low placement.

3. I think there is a relatively small corridor of possible tracks, probably from one that bisects Michigan to one that bisects Ohio. Op and ensemble models all have a prominent southeast ridge which should help steer the low northeast in this fashion. This is just as important as anything at this stage, because we aren't talking about a big, longwave-altering baroclinic wave. This low should simply ride along in the prevailing southwest flow for the most part. It could get suppressed, and I'll feel better once we see where the low cuts off, but I like how it looks so far.

I recently made the comment that I like the potential in this setup, and since then all of the guidance has come on board. Consensus and continuity are outstanding, especially at this time range. Even the NOGAPS has come to play. Of course, that could also mean that when the models change course at all, they do it all at once.

Regardless of the ultimate outcome, the potential for accumulating snow in the forum is there, and we are slowly filling up then medium range thread with discussion about it, so let's do it here instead. Also, I've never started a storm thread before and I wanted to. Forgive me :)

The 00z GFS just came in. Yet again, no changes.

Discuss:

Image courtesy of Tropical Tidbits

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0z PGFS is a little farther south.

The 00z GEM suppresses it due to cutting off the low just off the west coast. Such variability can be expected with a low cutting off like that. For this type of pattern, you generally like the ECMWF and GFS more than the GEM though.

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Euro looks way south... guess this thread is off to a good karma start :(

Awesome. Yeah, it cuts the low off too far west and it takes just a hair too long to get picked up. Thankfully, NWP tend to close off lows a little differently with every run. There are a number of places the low could cut off it would work. Tonight's Euro did not show one of those places.

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Awesome. Yeah, it cuts the low off too far west and it takes just a hair too long to get picked up. Thankfully, NWP tend to close off lows a little differently with every run. There are a number of places the low could cut off it would work. Tonight's Euro did not show one of those places.

My bigger worry is the northern stream being too fast and instead of it sliding this way it gets suppressed and out to sea. Considering the -EPO is supposed to be going gangbusters it isn't that surprising the northern stream is going strong into the US.

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THE GFS ENSEMBLE MEAN STANDARD DEVIATION

WOULD SUGGEST THE H5 LOW TRACK WILL BE FARTHER SOUTH.

THUS...CONFIDENCE IN A WIDESPREAD SNOW EVENT CONTINUES TO BE LOW

AND HAVE KEPT POPS IN THE 15 TO 25 RANGE THROUGH FRIDAY AFTERNOON. - per Quad Cities AFD

Might be DOA

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While many solutions are on the table (even the elusive MSP special), I would definitely lean the direction of a Ohio Valley-southward storm,

As you said, many solutions on the table, and as long as the storm doesnt vanish (very unlikely), some snow starved folks will be happy. Wondering why you say south though? If anything rainmans analysis in the OP makes me like where we sit over those north or south of us.

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Tough to say what the 12z GFS is going to do. But I do like how the PV (in this run, as well as in other runs/models) is poking over Hudson Bay. I would say this increases the chances that, even if the storm cuts a bit, it could still be a candidate for a front-end thump solution.

500mb pattern resembles the ice storm last year.
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Are you sure? It would say there's better jet interaction this time, if anything...

 

12z GFS

 

gfs_namer_165_200_wnd_ht_s.gif

 

00z GFS

 

gfs_namer_177_200_wnd_ht_s.gif

 

You can see that string of PVA on the H5 plots around 156 running from near Seattle to the northern Plains. That's the bulk of the northern stream energy and it never really gets entrained into the main storm.

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As you said, many solutions on the table, and as long as the storm doesnt vanish (very unlikely), some snow starved folks will be happy. Wondering why you say south though? If anything rainmans analysis in the OP makes me like where we sit over those north or south of us.

 

Models in these setups tend to always be too quick to send those orphaned shortwaves in the SW eastward, and usually the extent of northern stream interaction needed to allow for the non-suppressed solutions is just missed.

 

Just a slightly faster ejection of the SW shortwave or the northern stream shortwave setting up just a bit further west will allow for the non-suppressed solutions though.

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Looks like 12z Euro will be a more southern track again.

 

it's a crappy setup for our area.  There's a low to our north and one to our south.   Very little cold sector precip.   No one gets much snow.   Even so, assuming there was a high to our north, the southern storm takes a track to southern Ohio, which would be WTOD for most of the Ohio crowd anyways.

Looks like another messy, complicated, need-too-many-things-to-come-together, type of system.

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