Chris's Corner - Active March into March

[lunchladyd]

If there is going to be severe weather overnight, I hope NWS issues a watch of some sort before people go to bed.

[Snowstorm920]

A 10:1 mean of almost a foot will get your attention

[bdgwx]

There are some "good" members in there. 920 can you post the 10:1 member breakdown for KSTL. I think even 99 would have to concede that a couple of three of them would be acceptable for his backyard.

[BRTNWXMAN]

This thing is an absolute beauty to look at in the upper levels, BUT the near-surface temps are definitely marginal and one concern I have after looking at the runs from today is the strength of the TROWAL and overall intensity of the storm. If that pans out, it would likely be a cold or slushy rain until the mid-level front pushes through and cools the column. That would make the difference between a storm that drops double digits or one that drops a few inches on the backside like the last storm we had. A weaker storm and less intense TROWAL would probably be better for us. This is a much better organized and potent storm though, so the dynamical cooling and precip intensity should be more efficient at helping snow break through.

[BRTNWXMAN]

We need to maintain the flat height field out front of this, and it looks like the developing -NAO block is helping out with the vortex lobe up near James Bay pressing in as the storm ejects. That's a textbook setup for winter storms here, as it forces confluence aloft and surface ridging over the Lakes. But if the SE ridge flexes a bit more and the storm is deepening rapidly, it may trend further N with a warmer column.

[Snowstorm920]

Feb 26, 2023 17:40:07 GMT -6 bdgwx said:

There are some "good" members in there. 920 can you post the 10:1 member breakdown for KSTL. I think even 99 would have to concede that a couple of three of them would be acceptable for his backyard.

eh, i guess some of these are ok

[Worldserieschampions (Chicago)]

Not sure I can ever recall seeing multiple ensemble members showing 2-3 feet for the metro inside of 5 days.

Top end potential is sky high if we get the marginal thermo profile to play ball.

Obviously, melting/compaction would mean you would never actually measure those amounts. But, a foot is very possible from this setup.

Edit: Not saying anyone will get a foot. I’m just referencing the upside. 0 inches is still far more likely.

[Chris Higgins]

Feb 26, 2023 17:50:43 GMT -6 BRTNWXMAN said:

We need to maintain the flat height field out front of this, and it looks like the developing -NAO block is helping out with the vortex lobe up near James Bay pressing in as the storm ejects. That's a textbook setup for winter storms here, as it forces confluence aloft and surface ridging over the Lakes. But if the SE ridge flexes a bit more and the storm is deepening rapidly, it may trend further N with a warmer column.

Brtn is on it with -NAO block. That is very important. But we really need to get this system through the pipeline tonight and tomorrow to see how that changes the playing field. The very marginal temperatures have me playing very conservative on this... especially after the fiasco last month. That being said, it's weird how sometimes March storms do sometimes make the changeover faster than mid-winter storms.

[bdgwx]

One thing that could be problematic with both 10:1 and Kuchera methods is how the post processing is applied. For example if it uses the thermal profile at the end of the period to estimate snowfall for the whole period it may overestimate if in reality only a small portion of the QPF in the period would be snow. We've seen problems like that before with borderline temperatures.

[Snowstorm920]

Feb 26, 2023 18:30:45 GMT -6 bdgwx said:

One thing that could be problematic with both 10:1 and Kuchera methods is how the post processing is applied. For example if it uses the thermal profile at the end of the period to estimate snowfall for the whole period it may overestimate if in reality only a small portion of the QPF in the period would be snow. We've seen problems like that before with borderline temperatures.

Yep, I’m leaning heavily on positive snow depth for this event. It should capture the mixing/melting/compaction factors that other methods can’t.

Here is the positive snow depth mean from the 18z GEFS off Tomer Burgs site. Much more realistic than the 10:1 map. 

[BRTNWXMAN]

I think 3-6" is a good start for expectations of the high end at this point. That could still go way up or way down though.

[STGOutdoors]

Seems like another narrow band of heavy stuff with much lighter on either side, like the last one. Funny how systems in a given winter season tend to be of such a similar nature to each other.

[landscaper]

I agree with everyone on being conservative, we’ve had to pretty big busts this year. I’m sure Mets and NWS will definitely be going the conservative route.

[jmg378s]

Being 5 days out, wherever models are showing the potential narrow heavy snow band now probably isn't where it'll end up.

[snowjunky]

I’ll take “why do I get sucked in only to have the weather models give me the middle finger in the end?” for $1000 Alex

[BRTNWXMAN]

Feb 26, 2023 19:03:17 GMT -6 jmg378s said:

Being 5 days out, wherever models are showing the potential narrow heavy snow band now probably isn't where it'll end up.

This is very true. That said, the main synoptic features are starting to come into much better focus and consistency with a consensus track that is very favorable for heavy snow in the Metro. You have to love how rock solid the GEFS has been...hopefully it's leading the pack.

[jmg378s]

Feb 26, 2023 19:35:03 GMT -6 BRTNWXMAN said:

Feb 26, 2023 19:03:17 GMT -6 jmg378s said:

Being 5 days out, wherever models are showing the potential narrow heavy snow band now probably isn't where it'll end up.

This is very true. That said, the main synoptic features are starting to come into much better focus and consistency with a consensus track that is very favorable for heavy snow in the Metro. You have to love how rock solid the GEFS has been...hopefully it's leading the pack.

Yeah I like where we stand at moment.  If we think of all the models and ensembles as a game of darts they're all landing around us.

[jmg378s]

I will say this, I don't think I'm quite as skeptical of the marginal temps (and they are very marginal if we're being honest with ourselves) as I should be. There just doesn't seem to be a good connection with the cold air to the north.  But I suspect a system that strong, if it turns out that way, is going to be very effective at dynamic cooling. I mean the surface low, as modeled, is deepening at a rate of almost 1mb/hr as it approaches...not surprising given the incredible lift in the atmosphere between a coupled 150+kt upstream jet and a 200+kt downstream jet.

[jmg378s]

The 210-220kt 250mb jet in the eastern Great Lakes region that the GFS is forecasting (see 18z hours 102-114) is top tier according to SPC sounding climatology. It may even be record breaking for some of those stations.

[BRTNWXMAN]

Feb 26, 2023 20:22:28 GMT -6 jmg378s said:

The 210-220kt 250mb jet in the eastern Great Lakes region that the GFS is forecasting (see 18z hours 102-114) is top tier according to SPC sounding climatology. It may even be record breaking for some of those stations.

The magnitude of jet energy across N America going into this week is astonishing.

[Snowstorm920]

Feb 26, 2023 20:26:02 GMT -6 BRTNWXMAN said:

Feb 26, 2023 20:22:28 GMT -6 jmg378s said:

The 210-220kt 250mb jet in the eastern Great Lakes region that the GFS is forecasting (see 18z hours 102-114) is top tier according to SPC sounding climatology. It may even be record breaking for some of those stations.

The magnitude of jet energy across N America going into this week is astonishing.

Making up some lost ground from all the sheared out crap the last several years 

[BRTNWXMAN]

Feb 26, 2023 20:06:57 GMT -6 jmg378s said:

I will say this, I don't think I'm quite as skeptical of the marginal temps (and they are very marginal if we're being honest with ourselves) as I should be. There just doesn't seem to be a good connection with the cold air to the north.  But I suspect a system that strong, if it turns out that way, is going to be very effective at dynamic cooling. I mean the surface low, as modeled, is deepening at a rate of almost 1mb/hr as it approaches...not surprising given the incredible lift in the atmosphere between a coupled 150+kt upstream jet and a 200+kt downstream jet.

Yeah, as it's modeled currently it's way more potent than the last storm that struggled. Cyclones of that strength pull winds in and coax the cold air closer to the center with time. We may loose a good chunk of the precip to liquid if that takes too long. But dynamic cooling and heavy snow rate should overwhelm the warm layer pretty efficiently I would think.

[bdgwx]

18Z EPS is north of our benchmark.

[bdgwx]

Just for funsies I looked at GFDL's 3km version of the GFS. It is showing several of those bean shaped supercells in AR and is maxing out the updraft-helicity scale for a couple of them on Thursday.

[Snowstorm920]

Feb 26, 2023 20:59:11 GMT -6 bdgwx said:

Just for funsies I looked at GFDL's 3km version of the GFS. It is showing several of those bean shaped supercells in AR and is maxing out the updraft-helicity scale for a couple of them on Thursday.

Some of the soundings I’ve seen for Thursday are pristine long track tornado soundings 

[Worldserieschampions (Chicago)]

00z Icon is too far south for the metro.

Really gets cranking over Ohio.

Next.

[landscaper]

Icon first model out , shifted south, swing and a miss for the metro.
Model count for the night 0-1

[ajd446]

Its ok, theses are swings you expect, but if you all keep expectations tamed when we get nothing it will be no big deal if we expect no snow lol.

[Snowstorm920]

01z NBM is out and looks pretty dang good

Wind gust are also 40-45 mph

[Worldserieschampions (Chicago)]

Another wild run of the gfs.

979 low just southeast of STL, but it wraps the cold air in generating a blizzard for the metro verbatim.

In reality, hard to believe it would be that stacked.