Winter Storm Threat *Technical* Discussion. No Op Run PBP or Snow maps

[CAPE]

Lets discuss upcoming potential storm threats. No pissing and moaning, emotional pendulums, and no snow maps until guidance converges on a clear, specific storm threat within 7 days. 

Hopefully mods won't mind moving noncompliant posts to the appropriate threads.

@psuhoffman @WxUSAF @MillvilleWx @brooklynwx99

[CAPE]

Favorable upper levels and surface leading into the next weekend potential. Need to keep an eye on wave spacing, any minor wave(s) moving east in the flow midweek vs the bulk of the energy being ejected from the southwest later, and the strength/ position of NS energy near the 50-50 region.

Good surface and upper level depiction leading into a potential winter storm-

[Terpeast]

Good call. I’ll start. Focusing on 0z EPS.

Next window of interest, s/w running into confluence thanks to 50/50 low:

Keeping cold air in place:

While area of low pressure stays to the south of us:

And precip distribution looks good:

 

[CAPE]

1 minute ago, Terpeast said:

Good call. I’ll start. Focusing on 0z EPS.

Next window of interest, s/w running into confluence thanks to 50/50 low:

Keeping cold air in place:

While area of low pressure stays to the south of us:

And precip distribution looks good:

Yes. I hit on some of that in my intro post. As you said, that 50-50 low is vital for this to work out, but we don't want it displaced too far south as has been depicted on some recent op runs. Weakens/suppresses the shortwave southward without enough space.

[Terpeast]

1 minute ago, CAPE said:

Yes. I hit on some of that in my intro post. As you said, that 50-50 low is vital for this to work out, but we don't want it displaced too far south as has been depicted on some recent op runs. Weakens/suppresses the shortwave southward without enough space.

I think that scenario is less likely based on ensembles, they don’t really support the suppressed scenario. Agree timing is vital, 6z Euro AI ensembles show something similar to 0z EPS with undercutting energy under the block but ridge bridging happens immediately after passing us. 

[CAPE]

Good look on the 12z GEFS leading into the potential weekend storm. Energy in the 50-50 region is in a good spot with surface HP underneath in the convergence/confluence zone.

Energy is ejecting from the southwest with surface low development. 

[bncho]

Getting a sense of the discussion over the last few days, isn't this setup a lot about timing (as is with lots of our other setups)? Correct me if I'm wrong, but we need the wave to a delay a little bit so it doesn't get strung out/suppressed, and we can't have it delay too much or else it turns into a cutter, right? It feels like we need to balance lots of these factors out.

[CAPE]

1 minute ago, bncho said:

Getting a sense of the discussion over the last few days, isn't this setup a lot about timing (as is with lots of our other setups)? Correct me if I'm wrong, but we need the wave to a delay a little bit so it doesn't get strung out/suppressed, and we can't have it delay too much or else it turns into a cutter, right? It feels like we need to balance lots of these factors out.

Pretty good synopsis.

[CAPE]

Gonna be a cutter on the 12z ens mean. Was more of a Miller B at 6z.

[Terpeast]

5 minutes ago, CAPE said:

Gonna be a cutter on the 12z ens mean. Was more of a Miller B at 6z.

you mean EPS? Or GEFS?

[Terpeast]

Just now, Terpeast said:

you mean EPS? Or GEFS?

Just looked at gefs, and you’re right on that one. But 12z EPS doesn’t cut and is actually better for us than 0z or 6z. Still sticking with the undercutting the block idea, while 12z gefs links up ridging preventing the s/w from undercutting 

[WxUSAF]

29 minutes ago, bncho said:

Getting a sense of the discussion over the last few days, isn't this setup a lot about timing (as is with lots of our other setups)? Correct me if I'm wrong, but we need the wave to a delay a little bit so it doesn't get strung out/suppressed, and we can't have it delay too much or else it turns into a cutter, right? It feels like we need to balance lots of these factors out.

 

27 minutes ago, CAPE said:

Pretty good synopsis.

Yea we need the lead wave to be near enough to generate sufficient confluence to force our potential storm underneath us and keep our airmass intact. With a big -PNA we’re relying on the Atlantic side.

[CAPE]

24 minutes ago, Terpeast said:

Just looked at gefs, and you’re right on that one. But 12z EPS doesn’t cut and is actually better for us than 0z or 6z. Still sticking with the undercutting the block idea, while 12z gefs links up ridging preventing the s/w from undercutting 

Yeah the GEFS. EPS comes out slow on WB, but the 6z EPS was even better than the GEFS- had a bit of a suppressed look which I will take at this range.

[CAPE]

26 minutes ago, WxUSAF said:

 

Yea we need the lead wave to be near enough to generate sufficient confluence to force our potential storm underneath us and keep our airmass intact. With a big -PNA we’re relying on the Atlantic side.

We are relying on the NA, but there isn't really a true block to slow the flow, so timing really is critical with these features.

[CAPE]

12z EPS has the same general idea as the op with this 'frontrunning' midwestern wave Friday into early Sat-

Then here later with energy ejecting from the SW. They don't play well together like the op. That said there is some precip for our area on the mean.

Still a week out and given the likely errors with wave timing at this point, it will evolve/morph into something else.