ILMRoss

Whatever next week is fits neatly into the same category of the Monday system. It has upside, may be worth some token stuff, but a lot of things need to break in the right direction for it to be anything more than that. I would pay attention to how much the associated S/W digs/cuts off and if it keeps the integrity of that cut-off through the SE on today's model runs- some positive developments there would be cool. Generally anything progged to put snow down in Oklahoma and moving laterally warrants at least a lazy eye for our Carolina folks.

I thought it was fun but I really doubt it will be replicated in future runs. Happy to be proven wrong.

It has the potential to be a cute little appetizer. The upper air temps are there, surface temps are kinda blah. Rates dependent set-up. What’s new? A lot of things still have to break right. If that shortwave diving in from the lakes comes in further from the rest/digs a little more, there might be some healthier precip. We’ll see. Winter!! We’re back baby!

Had a friend that said Birmingham got some flakes today. MPING has the Atlanta suburbs seeing some flakes. Wouldn’t be surprised some pretty widespread token flake action in the Carolinas tonight but if you want to see it time to get that coffee brewing.

Tbh probably the first time in a while I’m rooting for a warm winter If we’re going to be in lockdown 2 at least let me get some more golf in.

Ok, thank you, it’s been too long since I’ve taken thermo and my old textbook is an an attic somewhere so I’m in not much of a position to rebut. That dents my argument, although I’m still weary of low level buoyancy issues (that was a better-than-the-median sounding of the ones I glanced at)

We really don’t know if the high ceiling will be realized until this time tomorrow. Every CAM has a different technique on how they render boundary layer mixing, which dictates how warm it gets at the surface. 3km NAM still displays a “mild” solution, in this case meh surface temperatures never get past the mid 70s and rising parcels don’t really have a ton of difference between their temp and the background temp until they rise to about 700 MB, according to this sounding I pulled. If the 3km is right, expect to see a lot of shallow, ‘baby’ supercells that struggle to stay alive amongst the strong low level shear. This solution would keep the SPC from slapping a high risk onto things. Once again, all about boundary layer with this limiter, and other models (looking at you HRRR) will scare a lot of people because they have a tendency to overdue temps and therefore, CAPE.

Couple of thoughts; -A weird wildcard to keep in mind is that model accuracy has gone down because of the COVID-19 outbreak. Why? Commercial planes are equipped with sensors that collect data that is fed into models. We're not talking hurricane hunters grade stuff here, but enough to increase our sampling to improve model outputs. Model verification has dipped significantly since the onset of the outbreak, and less air traffic is probably the reason why. Now- obviously models are still robust and should be trusted, but they may swing a little more/have a bit less consistency than usual. Some NC specific things: 850MB winds will be whipping- the default to expect is a squall line with some embedded spin-ups. There are two ways this becomes something fiercer: -The model trend has been ticking this thing slower and slower. The slower this goes, the more juiced the atmosphere can get ahead of the storms, and put far east places (New Bern, Edenton, E-City) in range for stronger storms/stronger tornado risk. -The flip side to the above is Sunday's storms evolving into an MCS that rockets past guidance, and is offshore the NC Coast by midmorning Monday, allowing the atmosphere over Eastern NC to recover. I think that the ceiling for NC on Monday is an enhanced risk; but keep an eye on things. Not a good idea to take your eye off the ball in high-ceiling events like this.

Stating the obvious, extremely high ceiling with this event. The 'best case' scenario is forcing coalescing the warm sector into a 'mega-squall', where you have one of those days that rack up 1000+ wind reports and a smattering of EF0-EF1 spin-ups on the line. A baked in source of good news is that on Easter Sunday, a shining candidate for our first high risk of the year, stay-at-home orders due to COVID-19 will make it much easier to communicate to people what's going on.

I love coming in here to say “I don’t know if a NW trend is possible” then logging back on to see the NAM has kicked a solid 80 miles north. NAM is a best case scenario where the energy out west *isnt* held back. Stay tuned to see if this becomes a globals vs high resolution situation

Some things I’m seeing; Starting with the bad: - I don’t know how much of a northwest trend is really *possible* given that the shortwave is coming from the northwest. A shift north could mean a flatter system overall and could mean less precip. - Euro + UK combo saying no is a tough hand to bet against - Betting in a late blooming coastal always scares me, a lot can go wrong with transporting moisture that far away from the LP Now the good: - Hi-Res models haven’t gotten a good crack at this yet. They’re not just good for thermals, they’re *much* better at rendering topography. Can’t emphasis enough how much of a night and day difference a mountain range looks on the gfs compared to the nam 3k. I mention that because any shortwave gets stretched and contracted in the mountain west and that has implications downstream. Our shortwave is being held back in dang Utah may look a little different in the hi-res stuff - We have a wildcard I haven’t seen mentioned yet: this shortwave. It’s currently between Oregon and Hawaii and flies into Cali in 3 days like a bat out of hell. Pay attention to this storm; if it holds on some more of its integrity it could be a nice little boost to our Rockies shortwave I’m pretty neutral on this storm, I’m not completely optimistic but it still has a lot of upside.

To me it’s pretty solid that the CMC had a worst case scenario in how it handled the the Rockies energy (held it back) and the run still popped a coastal that gave NE NC a respectable event.

While this is on the table I recommend fast forwarding a couple of days before we analyze exactly *what* the snow corridor will look like

Pretty much this. With a 1040 parent high I think this is the pre-eminent feature to pay attention to in model runs going forward. I don’t think temps will be *that* much of an issue but I’m also ready to eat crow on that statement given this is still below the mason Dixon line. .

The reason for the change is an eastward trend in the shortwave that drops in to help create lift. Compare: The 24 hour change in the gfs shows a 500 mile shift East. Because of this, the shortwave has a more positive tilt and produces less moisture transport. Still a very potent setup and I don’t think it would take too many tweaks to show snow again, but this is a setback.

While you are correct for the heavy precip core, I want to emphasize that *people on the fringes* of events like this still will have to worry about BL issues. In a hypothetical where the I-40 corridor gets an E-W spanning streak of the heaviest rates, places N of that (South Hill, Danville etc in this scenario) would still deal with mixing.

Focus on Thursday. Thursday is a no frills, overrunning event where the atmosphere is hair trigger sensitive to disturbances due to the thermal gradient. The closing coastal needs a lot more to go right. Focus on Thursday.

Tbh the big, smothering 1040 high is one of the most promising features of this setup thus far .

Some thoughts; This is an uncommon, although not unheard of, setup that exists because of the thermal gradient. Check this out: There is a very intense thermal gradient here with a trough in the NE and a strong ridge poking in from Florida. The general mechanism for winter mischief is that any blip or impulse riding this gradient will be able to kick up precipitation from frontogenesis and general warm air advection (which sounds scary but in pure scientific terms is another way to produce lift. WAA = lift!) The high pressure also helps. I’m not really focusing on the potential coastal closer the euro has until a few more days pass. The issue here is the high 500mb heights; it may not be very cold throughout the entire atmosphere and *whatever* this is may evolve into a delicate mix forecast as cold air still has potential to undercut things at the surface. Synoptically, I think a similar event is 1/28/14 (which eventually brought a moderate snowfall along a wave riding a big thermal gradient) although not a perfect analog. It’s an imperfect setup but there’s a higher ceiling than most events due to the potential duration/moisture supply.

The system on Thursday very much has legs. Let's be clear- Not a very high ceiling system! The best case scenario is probably a 1-3 inch event on the northern half of the state! But, beggars can't be choosers. The difference for the last few runs of the GFS is a much healthier merge between the two parent jet streaks on the shortwave. when it's exiting Texas.

Thursday definitely has the potential to be a meat and potatoes, flat, light to moderate snow event. CMC solution is pretty tame and reasonable given the pattern. That other models don’t show a big snow i think is more indicative of how noisy/unpredictable to field of shortwaves is coming in after that. Short wave interaction is what could kill this opportunity and I think we’ll see inconsistency for one more run cycle or two before we know for certain this is worth keeping track of. The storm next weekend will be interesting, although unless something In the mid levels/high arrangement changes I don’t think the cold air will be robust enough for anything outside of a Acela corridor snow. Would love to be wrong though!

I wouldn’t overlook the system coming next Thursday. The shortwave takes a nice track; it just gets sheared apart and just loses its integrity. Otherwise, it’s heading into a nice modeled air mass. If future runs begin to maintain the shortwave a bit further, Thursday gets more interesting.

It wouldn’t take a lot of repositioning to make this shortwave on the euro a bigger deal. Perfect high. Something to keep track of.

I would not write off some token flakes on Friday night, but those curling edges of the “front ends” are hard to predict 12 hours out, not just 5 days. Whatever falls would then have to be beefy enough to not evaporate in the residual dry air mass. So I wouldn’t put hard money on that. Next week looks cool, with ample opportunity if the structure of the pattern holds, but most veterans here know how quickly that can sour. Would not yet focus on any particular time period.

Keep an eye on Tuesday. If the shortwave nudges a little deeper/stronger keeping with previous trends, I-40 corridor could be in for a quick treat.