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Feb 3rd - 5th Potential strong stm threat


Brian D
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12z GFS with a 985  at south tip of lake michigan at 87 hours a step in the right direction
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nice hit for northwestern areas 
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On the range of possible outcomes, certainly an interesting solution to add into the mix. That run has a sharper digging northern s/w able to phase with more southern routed energy and the whole thing quickly goes neutral to negative tilt.

I'd place it on the lower probability end of the spectrum to get that well timed phase, though we'll see shortly on the rest of the incoming 12z operational and ensemble cycle if that idea gets any more than minor member support.

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Just now, RCNYILWX said:

On the range of possible outcomes, certainly an interesting solution to add into the mix. That run has a sharper digging northern s/w able to phase with more southern routed energy and the whole thing quickly goes neutral to negative tilt.

I'd place it on the lower probability end of the spectrum to get that well timed phase, though we'll see shortly on the rest of the incoming 12z operational and ensemble cycle if that idea gets any more than minor member support.

Sent from my SM-G965U using Tapatalk
 

Just need it a bit further east and game is on. An awful lot to ask for, though. 

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It's a pretty interesting scenario on the newer guidance for this storm, but as others have mentioned its still on the lower confidence side given so many huge changes that are still ongoing. It looks like the north Atlantic block is slowing down the remnants of our storm off the East Coast, which doesn't allow the ridge to build as much. The trough out west is now splitting on most guidance, with a cut off developing west of Baja and the northern stream trying to dig in. All of this essentially could allow for a more southern track to the low. There are subtle timing differences with all the waves that are important to exactly how this evolves.

From a pattern recognition perspective, having a strong 500mb jet exit region (left front quad) going by to the south, with a passing surface low and steep mid-level lapse rates is all a good recipe for thunderstorms in the cold season. 12Z GFS jet below:

548411325_ScreenShot2021-02-01at10_49_28AM.thumb.png.607546e9e60ac4f45f5cf0a8d56abc97.png

12Z NAM Chicago area average sounding valid midday Thursday (7.2 mid-level lapse rates and some modest CAPE, with an isothermal sounding just below freezing in the lowest 3km would = giant wet aggregate snowflakes):

921098521_ScreenShot2021-02-01at10_56_49AM.thumb.png.6f19d31bd73f90ad7b0d76968df4ce82.png

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See the GEFS 500mb height trends for the changes mentioned above. Notice the Rex block off the West Coast (cut off upper low under the ridge), block north of Alaska that is delivering the frigid air, heights trending higher in eastern Canada and lower in the Southeast US. trend-gefs-2021020112-f084.500h_anom_na.gif.ae6154ac7458885431d46bc558f92a94.gif

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Interesting setup.  Not everyday that you are able to snow right out ahead of a deepening sub 1000 mb surface low, and it's not like we'll be coming out of a partucularly cold airmass.  Does raise concerns about the magnitude of boundary layer warming and how much snow could be junky in the "warm" sector.  I guess we'll see.

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1 hour ago, purduewx80 said:

It's a pretty interesting scenario on the newer guidance for this storm, but as others have mentioned its still on the lower confidence side given so many huge changes that are still ongoing. It looks like the north Atlantic block is slowing down the remnants of our storm off the East Coast, which doesn't allow the ridge to build as much. The trough out west is now splitting on most guidance, with a cut off developing west of Baja and the northern stream trying to dig in. All of this essentially could allow for a more southern track to the low. There are subtle timing differences with all the waves that are important to exactly how this evolves.

From a pattern recognition perspective, having a strong 500mb jet exit region (left front quad) going by to the south, with a passing surface low and steep mid-level lapse rates is all a good recipe for thunderstorms in the cold season. 12Z GFS jet below:

 

12Z NAM Chicago area average sounding valid midday Thursday (7.2 mid-level lapse rates and some modest CAPE, with an isothermal sounding just below freezing in the lowest 3km would = giant wet aggregate snowflakes):

 

The plume of steep mid level lapse rates shares some overlap with the arctic front/cold sector immediately behind the low as well. Pretty nice soundings for snow all and all...

gfs_2021020112_081_41.75--91.5.png

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3 minutes ago, McHenrySnow said:

The idea of some snow from this before the arctic blast was nice while it lasted. 

looks good for areas up north. Can't over react too much too any one model run. Seen these set ups surprise many times as the front races in and squeezes out any residual moisture. And yes, were talking an inch or two in a flash freeze type set up and not a large scale moderate event. But I like those type events as a winter weather fan. They can't all be 10" snowstorms. 

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11 minutes ago, Baum said:

looks good for areas up north. Can't over react too much too any one model run. Seen these set ups surprise many times as the front races in and squeezes out any residual moisture. And yes, were talking an inch or two in a flash freeze type set up and not a large scale moderate event. But I like those type events as a winter weather fan. They can't all be 10" snowstorms. 

None of them have been here.

I wasn't expecting a snowstorm and was happy when guidance strayed from the mega cutter idea. Even if the low passes overhead, it's better than going through Iowa and we get to save most of the snow cover. I just hope we can squeeze an inch or two out to freshen things up for the bitter cold to follow. We'll see how it turns out. Went above freezing today actually, so definitely ready for the cold. 

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1 minute ago, McHenrySnow said:

None of them have been here.

I wasn't expecting a snowstorm and was happy when guidance strayed from the mega cutter idea. Even if the low passes overhead, it's better than going through Iowa and we get to save most of the snow cover. I just hope we can squeeze an inch or two out to freshen things up for the bitter cold to follow. We'll see how it turns out. Went above freezing today actually, so definitely read for the cold. 

Didn't you just get several inches of fresh snow?

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9 minutes ago, McHenrySnow said:

The RGEM run looks nice if you just look at the snow map. Conceptually, it doesn't make a lot of sense. 

It does because there is a wide expanse of a snow pack to the south and there is a pretty cold air in place ahead of the system. The WAA will produce precip and a good portion will be snow.

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