40/70 Benchmark

First Major Winter Storm Potential Friday with Minor "Primer" Event Monday Monday Primer Impact Mainly West The synopsis from Wednesday regarding this storm threat remains largely the same. The shortwave is currently careening to the east and towards a compressed flow between the fledgling NAO block to the north, and mature southeast ridge to the south that is in response to the deep west coast trough. In fact, that southeast ridge has been so pervasive this week that it has been causing the fledgling NAO block to conjoin with it, which both acts to negate the influence of the negative NAO and cause a very compressed flow. This compressed flow acts as a source of deconstructive interference for the shortwave that is very reminiscent of this past December 2021. At present, the shortwave is continuing to struggle in the compressed flow and will attentuate to an open wave over the Ohio valley by late tonight and early Saturday AM. Note the absence of a notable gap or area of lower heights between the south east ridge and NAO block. However, by Monday AM, the southeast ridge begins to relax as the west coast trough matures, which creates separation and falling heights in between the two ridge nodes in a more traditional configuration. This in conjunction with the strengthening NAO block that is becoming better positioned to exert enough of an influence to reduce the compression to the flow , which allows the storm to quickly begin to re-amplify and close off as it exits the coast. However, note that the system does not close off in the mid levels quite as fast on latest guidance. This is due to the powerful Maritimes low acting as an inhibiting force by not allowing it to amplify as much and compressing precipitation to the southeast as it enters the region: This is important because it was explained on Wednesday that the proximity of this low was one of two factors that would determine just how quickly this system would be able to amplify. The other being the strength of the NAO block and where is the ridge axis in the plains located. A weaker NAO block allows the ridge axis to progress further to the east, which will force the redevelopment of the storm later/ downstream and further off of the coast. However, a stronger NAO block will tend to slow the flow down, which causes the plain ridge axis to be further west, and accordingly, the downstream coastal also amplifies further to the west/closer to the coast. The Newfoundland low dictates to a large extent how far north the system does or does not get and the NAO block determines whether or not the flow is too fast to allow the system to amplify close enough to the coast for the northern extend to matter. This continuum of possibilities was categorized into two distinct group. Option #1 Means Limited Impact Here are the two options as presented on Wednesday: OPTION 1: One possibility is on the benign end of the continuum of possible outcomes. If the Maritimes low near New Foundland on Monday ends up slightly closer to the region (further south) and the NAO block weaker, then the developing coastal will be develop later (further east and off of the coast) and not allowed to amplify (squahsed to the south). This represents wither no storm of a very minor impact. OPTION 2: However, if the Newfoundland low is slightly further to the north and the NAO ridge stronger, than the storm develops faster and amplifies more to the north. This would represent the first major winter storm of the season. It is now clear the the pattern is evolving much more similarly to option 1 with respect both the position of the Maritimes low and the ridge axis in the plains, which means a minor system is on the horizon early next week. Be that as it may, there remains potential for the first measurable snowfall of the season for a relatively large portion of the region on Sunday night into early Monday. MONDAY FIRST CALL: A Final update on Sunday regarding Monday, especially since this evolution may have an impact on what transpires on Friday. Option #1 Means Limit There is the potential for the development of another major coastal storm (get used to this) on or around Friday, December 16th, which, is signaled well via teleconnector convergence. Thus the degree to which the Monday system can amplify and just how quickly it can do so may play a role in how much resistance it can provide to the Friday system taking an inland track. OPTION 1: A more intense and slower to exit first storm acts as a "50/50 low" to work in tandem with the resistance provided by the NAO block to induce a more rapid and proficient transfer of energy from the primary tracking through the Great Lakes, to the secondary coastal development. This results in (another) major winter storm with a potpourri of mixed precipitation that would produce major travel headaches to end the work week. These type of systems are referred to as SouthWestFlowEvents (SWFE) due to the prominent southwesterly flow aloft that results from warm air advect in he mid levels of the atmosphere due to the dying primary low. OPTION 2: The first storm is less and intense and faster to move out, which while this is still likely to force the ultimate development of a "triple point low" at the surface near the coast (limits low level warmth), most of the precipitations falls as rainfall after perhaps a very brief bout of wintry precipitation near the onset. Travel impact is limited. W While it is now clear that option 2 is going to materialize, which favors a warmer outcome in the absence of a more pervasive 50/50 low, a major winter storm remains a distinct possibility due to guidance continuing to adjust to the strength of the negative NAO block. As of now, transfer to the coast somewhat later if the most likely scenario, which would result in a wintry mix of precipitation across the region with the heaviest snow amounts likely across the interior. First Call with respect to Friday likely on Tuesday.

https://easternmassweather.blogspot.com/2022/12/first-major-winter-storm-potential.html First Call for this will be Tuesday

Yea, I am not worried about the 12z GFS given the pattern.

NBD

Kind of, but not entirely. It depends on the exact positioning. There is a general relationship...

Not entirely.....the block plays a role, as well.

You may have runs that, to use your term, "overmagnify" said dampening, as well. Like this one. Obviously is more runs consistently depict this, then it warrants more considerations, but toss it attm.

Ensembles will probably be north. Don' buy that at this stage.

Which is why I was excited for SWFE, but if it becomes a coastal that tracks too close, then I'm screwed.

Just so sick of it....can't win. And don't give me the BS about it being December because its been going on for years....just picks up where one season left off with the rusty screw-driver right up the rear.

If I get skunked Monday to the sw, then get killed by easterly flow Friday, then I am going to really put on a show.

Not necessarily.....guidance is still adjusting to the block.

I let go of this 2 days ago.

Really? Okay, let me rethink things. Still blows.

Hopefully we can keep Friday waaaaaay NW of where I live.

Oh boy...between the circle jerk waaaaay se of where I live, and the instability waaaaaaay sw of where I live, I feel a very comforting sense of continuity from the past several years. Why? Because its Ground Hog Day.

Yea, you can always drop the "B" bomb once it is clear within a day or two...going there at one week lead is inviting large error...especially in a situation that has and continues to be in such flux.

I feel as though its a 50/50 proposition that we are all buried alive

Gotcha. Figured I was missing something...so you don't mean similar in terms of evolution, but rather the similarity with respect to that particular point in the respective lifecycles.

Yea, that's right.

No...that was 12/13/2007. 12/9/2005 ripped a whole in the earth near the Buzzards Bay/canal. I jacked in that with like 16".

I mean crappy posts lead to 5PPD

That was a Miller A that came out of the GOM.....not sure I agree....

I got it along with a second covid booster in like October.