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Pattern Fail or Fab February 2023 Pattern Thread

rburrel2 said:
Let's punt the first s/w and role with the 192hr GFS.View attachment 131613
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If I was a betting man, I'd place my bets entirely on the 2nd system & ignore the first one.

There's almost no realistic chance the cold/dry air gets way out in front of the moisture on arrival with the first system, which is usually a death sentence for CAD/overrunning events.
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Webberweather53 said:
If I was a betting man, I'd place my bets entirely on the 2nd system & ignore the first one.

There's almost no realistic chance the cold/dry air gets way out in front of the moisture on arrival with the first system, which is usually a death sentence for CAD/overrunning events.
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wow, yea I didn't check the 00z EPS for the day 9 threat but dang it has a nice wedge signal for sure.
 
Webberweather53 said:
If I was a betting man, I'd place my bets entirely on the 2nd system & ignore the first one.

There's almost no realistic chance the cold/dry air gets way out in front of the moisture on arrival with the first system, which is usually a death sentence for CAD/overrunning events.
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Yeh definitely agree. It’s honestly pretty simple & really doesn’t need any deep explanation in any way. (Not a knock).. you simply get the cold air in place & let the overrunning take place, and there just isn’t any indication that is going to happen. Hopefully that second system starts showing up everywhere. Maybe VA can get a thump from the first. But I think it’s a fight with them also between extremely wet snow or either a cold 35° rain.
 
Mitch West said:
Yeh definitely agree. It’s honestly pretty simple & really doesn’t need any deep explanation in any way. (Not a knock).. you simply get the cold air in place & let the overrunning take place, and there just isn’t any indication that is going to happen. Hopefully that second system starts showing up everywhere. Maybe VA can get a thump from the first. But I think it’s a fight with them also between extremely wet snow or either a cold 35° rain.
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We're having an entirely different conversation if this is a cut-off upper low &/or coastal cyclone. Having the cold air already is nice in those cases, but it's not the end of the world because the precipitation formation processes are totally different.

In overrunning/CAD, it is absolutely necessary to have the cold show up before the moisture does, because the entire time the column is warming from warm advection aloft that's generating large areas of light-moderate stratiform precipitation.
 
Webberweather53 said:
The 12z GEFS looks pretty decent to me for a potential CAD next weekend following this coming week's overrunning event.

Just need to see the SE Canada vortex slow up/dig a bit more here & we'd have something worth talking about.


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Hopefully the Euro throws a bone with this. Guess we are about to find out.
 
All I see on these model maps are warm solutions for the Eastern Half of the nation with little mirages that occur in the long-range due to the transient positive PNA appearances that sometimes pop-out within the progressive, sometimes split-flowed, pattern. The entire Northern Hemisphere from Siberia to Bermuda looks terrible for major winter storm chances all the way into the I95 section of Mass. When I lived in NJ and PA, the only events I could look forward-to in this type of pattern would be some thread-the-needle/over-running event, but most of the snow would fall in the Ohio Valley and Appalachians. That's where snow may fall Northern Alabama/Mississippi to Western Apps, which is something I called in my forecast. The source of most of the cold air is coming from Eastern Russia/Alaska Arctic regions, and that usually favors cyclones in the Western/Central US and Newfoundland to Central Atlantic.

Yick. This warm vortex looks ready to phase over the Atlantic to create some fish storm.
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This is about the only thing that needs to change on the ECMWF Ensemble in 7-8 days to yield a strong CAD/ice storm next weekend.

Screen Shot 2023-01-28 at 12.53.18 PM.png



Very workable setup here, with cold air already well established by the time any moisture could overrun it from the W-SW. The only issue of course is the vortex over Atlantic Canada gets out of the way just a tick too soon, favoring CAD erosion &/or more of an in-situ vs classic CAD. That kind of thing isn't difficult to change this far out though.

I certainly can see some potential here, particularly for the western piedmont & foothills


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Webberweather53 said:
This is about the only thing that needs to change on the ECMWF Ensemble in 7-8 days to yield a strong CAD/ice storm next weekend.

View attachment 131640



Very workable setup here, with cold air already well established by the time any moisture could overrun it from the W-SW. The only issue of course is the vortex over Atlantic Canada gets out of the way just a tick too soon, favoring CAD erosion &/or more of an in-situ vs classic CAD. That kind of thing isn't difficult to change this far out though.


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Step for step just like it’s OP. Well established CAD for 48-72 hours but moisture doesn’t start overrunning it until 12-24 hours too late.
 
iGRXY said:
Step for step just like it’s OP. Well established CAD for 48-72 hours but moisture doesn’t start overrunning it until 12-24 hours too late.
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That's certainly something we can live with 7-8 days out.

Slow/dig the trough over Quebec + Atlantic Canada more and the upstream trough + ridge will slow/dig, amplifying the surface high over New England and causing overrunning precipitation from the W-SW to be stronger & sooner on arrival/more likely to intersect the low-level cold air mass.

A few other encouraging signs for CAD at day 7-8:

✅ The coldest air in the entire Northern Hemisphere will also be over our CAD source regions of Quebec + Atlantic Canada next weekend.

ecmwf-ensemble-avg-nhemi-t850-5468800.png


✅ As much as I think this week's overrunning event may not do much for us thru Friday of this coming week, some fresh snow cover may be laid down to our north, keeping this arctic air mass refrigerated on its way southward into VA & the Carolinas next weekend (and will encourage it to persist longer too).


We have some of the right basic ingredients in place to make something happen around day 8 & the changes we need see to make something happen between now & then are pretty small in the grand scheme of things.

ecmwf-ensemble-avg-east-snow_depth-5533600.png
 
Middle Tennessee better hope the nam is wrong. I love snow but I’ll pass on the ZR. I’d rather have a 33 degree rain then no power. This is just round 1. Another round is about to come in after the first round drops this down starting early Tuesday morning.
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Webberweather53 said:
That's certainly something we can live with 7-8 days out.

Slow/dig the trough over Quebec + Atlantic Canada more and the upstream trough + ridge will slow/dig, amplifying the surface high over New England and causing overrunning precipitation from the W-SW to be stronger & sooner on arrival/more likely to intersect the low-level cold air mass.

A few other encouraging signs for CAD at day 7-8:

✅ The coldest air in the entire Northern Hemisphere will also be over our CAD source regions of Quebec + Atlantic Canada next weekend.

View attachment 131643


✅ As much as I think this week's overrunning event may not do much for us thru Friday of this coming week, some fresh snow cover may be laid down to our north, keeping this arctic air mass refrigerated on its way southward into VA & the Carolinas next weekend (and will encourage it to persist longer too).


We have some of the right basic ingredients in place to make something happen around day 8 & the changes we need see to make something happen between now & then are pretty small in the grand scheme of things.

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The Atlantic Side looks terrible. I think you need is a solid PNA that holds for a couple of days instead of this Alaska Ridge that is trying to dig a trough over the western United States, which causes things to slip further east. I'd argue that things are trending in the wrong direction with the NW CONUS Storm.

Bad Pattern.gif

It's looking something more like this 2016 image.
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olhausen said:
Middle Tennessee better hope the nam is wrong. I love snow but I’ll pass on the ZR. I’d rather have a 33 degree rain then no power. This is just round 1. Another round is about to come in after the first round drops this down starting early Tuesday morning.
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Yeah I have no excitement for freezing rain here either which is what I'm afraid is what a lot of this is gonna be image3 (7).png
 
Myfrotho704_ said:
Lol View attachment 131651
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That would be really close. Verbatim, I'd estimate another 36 hours before CAD could establish.

icon_mslp_wind_us_41.png
 
I thought the 18z RDPS looked interesting at hour 84. There would be CAD building down from the north with dew points in the teens as close as the Mason-Dixion line.

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I know it's hard to believe but we do have some members from Tennessee, Arkansas, northern Mississippi. I might fire up a thread for those folks for the system early to mid next week. Just wanted to let everyone know before areas to the east start posting nonsense about it not happening
 
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