psuhoffman

For people asking about this one thing or that. Getting a big snow here is like a golf swing. There are 20 parts and any one can screw the whole thing up. It’s never just one thing. And these variables play off each other. Stronger 50/50 can offset a less ideal upper low track. That same 50/50 and a further south upper level pattern and it suppresses the storm to our south. I could do this with a dozen other factors and variables. Unfortunately there isn’t one thing you can say..that’s it. Just look at that. It’s how they all play off each other that matters. The upper level longwave patter (high latitude blocking) put us in the game but those details determine big hit v close miss.

The upper level low associated with the primary system to our west starts to go neutral and lift a little too far west for an ideal h5 track. But we can do fine in that scenery if we have great confluence locked in by a 50/50. But if the 50/50 were to weaken or lift out sooner we would need that to change or an icon type solution is possible.

It is but also a slightly slower more amplified system out west so other variables could offset. We will see. Minor changes have significant impacts when your worried about a 50 mile shift at 5 days.

Heavy rates needed to mix cold down stay to our SE. but it’s trending to everything else.

Gfs doesn’t quite get the heavy qpf far enough NW to intersect where it’s cold enough NW of the fall line. But it’s been clueless on this wave (as it was the wave last week that gave some light snow to southern VA).

Yea icon is way weaker and further north with the confluence. Less 50/50

@PhineasC icon says you should stay Monday then head back to NH

@Amped honestly the whole h5 track of the initial system is not ideal even on runs that show a big hit. We need that monster 50/50 to offset that. Or we need the system to trend south with the track of the initial system.

Icon h5 isn’t that significantly different from other guidance. But it never cleanly transfers energy so the h5 keeps lifting with the primary v turning east to consolidate with the coastal. But up until that last part the h5 track looks similar imo.

@losetoa6 @Ji root for the NAM solution. More amped wave but south/colder also. Better confluence at 84hr then the 18z Gfs same time.

You can’t tell by QPF or snowfall in a specific location. Have to look at mslp and h5. On the euro runs all are juiced up but colder and snowier runs here were from a less amped wave that allowed the cold to press more. But...after checking 18z eps the correlation between waves wasn’t as clear as 12z. Could be due to the other factors out west I noticed on the 18z op mitigating. And this Monday wave is trending colder with more upside. So whatever. I’m done. Bring on the Monday snow. Then we roll the dice. Not worried about the correlation. ETA: until it kills us and I write a 12 page document saying I told ya so...kidding not kidding.

Ok I fold. If I get 10” Monday I can live with whatever happens after.

Yes but the more amplified solutions also tend to be further north and warmer because we’re on the wrong side of the boundary. It’s not universal. It’s possible to get a more amplified colder solution but that’s a razor thin margin on this. I’m being specific to the majority of guidance. The clueless Gfs can obviously get more amplified and colder since it’s still drastically underestimating the wave compared to other guidance.

There are ways to get snow on snow. The main correlation with Monday being south was to a less amplified 50/50. But there are other variables that could offset. Or the Monday wave could walk the thin line. Be amplified but colder also. There were a few snow on snow solutions but that’s playing with fire. Get a weaker south wave that doesn’t produce the heavy rates needed and we get snow TV and give up the better setup 48 hours later. This is also a preference thing. I’m a big dog hunter. I’ll gladly give up a guaranteed 3” for a 25% chance at 12”. Part of that is where I live. 3” snows are kinda common. I totally get having a different attitude when you haven’t seen an inch in 2 years. So I don’t begrudge anyone’s different opinion. This reminds me of a setup in 2015. 2 waves. In this case we had too much cold and confluence. But the chance to amplify was better for wave 2. And runs that had a weak front runner had a gorgeous bomb for wave 2 a couple days later. Wave 1 ended up a 4-6” snow in DC and about 3.5” up here. Most were happy but HM and me were lamenting the lost chance as an east coast monster for a mundane progressive wave.

It’s annoying because they come true. But that’s our climos fault.

she had been joking around some lately...what's wrong with a casual comment now and then? When things get really nasty and its nothing but a litany of attacks and complaints is when we need to reign it in a little...some fun is harmless.

The other day when I looked at the GEFS I did NOT notice the same correlation. But the GFS in general is much less amplified on EVERYTHING next week...and imo its wrong on that. So if I think its mishandling the longwave pattern I would not put much stock into its handling of the details of how the two waves are playing off each other. But that is just my opinion. Just affirming your observation regarding the GFS is correct but explaining why I didn't put much weight into it.

You are 100% right. There are other variables that could make snow on snow a possibility here. One would be if the Monday starts south but still amplifies...but that one is kinda difficult since its washing out and being absorbed into the developing vortex to our north. If it starts de-amplified it probably ends up even more so. Another option would be a more amplified NS system that bombs out regardless of a less amplified monday wave. So far those 2 features seem to be acting in conjunction but that does not mean they will continue to do so. Or the 50/50 could be less amplified but move out slower. Most likely way to mitigate would be like I discussed on the 18z plot at 90 hours. There are some things out west that could offset a less ideal 50/50. One would be a more positively tilted system that goes neutral later. A flatter flow on top. Even with an obviously less ideal 50/50 its not apparent from that 90 hour 18z euro that the storm would end up north. Those other 2 factors could end up making it further south...who knows. So it's not a 1;1 correlation. But I do think its fair to say...a colder monday solution PROBABLY increases the chances that we have a less amplified 50/50 low and that is a net negative if we think the bigger risk Wednesday is a warm/north trend.

somehow several posts didn't load when I updated the thread...

nevermind i see the other thread...I am ok with that too...I am not the superstitious type.

with it being only a few days away why don't we just move the Monday stuff to the obs thread unless it becomes worthy of its own thread in the near future. Discussion of how that wave effects Wed can stay here.

That's just our christmas blizzard.

@Ji That isnt a crazy scenario... the 10 or so 12z EPS members that managed to give our area pretty much no snow next week did it that exact way. A suppressed monday wave that was just too warm to snow anywhere...then a crazy far north wednesday system where the snow started north of the mason dixon line. That is how this all falls apart. I would argue that its not JUST the monday wave though...the monday wave is acting in conjunction with the more significant wave on top of it...and that is what becomes the 50/50...so a weaker monday system is indicative of a weaker wave that turns into the 50/50. The pattern is good...but its still only mid December, with an only ok antecedent airmass, and a block that is a little north of ideal, and a pacific that is only mediocre...if you remove the ideal 50/50...this is probably an interior northeast storm.

That is the total fail scenario

My gut tells me it is way too soon to be making detailed predictions for a storm 5 days away. I don't like to pretend I am confident or know something when the truth is I don't know. I am comfortable admitting when I don't know. But...this is a pretty good setup in terms of the longwave pattern. I would like that block to be centered a little south of where it is...like CAPE has said. But we have snowed with a similar H5 look often. I would like that 50/50 hanging around a few hours longer and the system coming from the west to go neutral just a little further east. I would like a slightly colder thermal profile in front of it but its December...is what it is. But there is a reason big all snow events are VERY rare in DC this early in the year. I do think this ends up pretty amplified when its all said and done...and that in a way reduces the chances of an all snow south track some. My "gut" says this is probably going to be DC's first accumulating snow of the season and break the snow drought...but the really big totals are going to be further north/west. Even up here...if you asked me what I am more worried about...a north trend and rain is a way bigger concern for me att then missing heavy snow to the south. Now watch 0z come in suppressed lol.