ILMRoss

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. 

Here’s why I and other mets aren’t trusting the HRRR; this is a pretty unrealistic profile for an overcast day; with a super adiabatic lapse rate at the surface this is a sounding you’d usually get if it were sunny! Sometimes even short term models struggle with the boundary layer and potential solar radiation.

I like your optimism and hope that map verifies, but I’ll be shocked if everyone receives half of that.

Heard y’all like snow maps here’s what I made for my friends on Facebook

I've been impressed with how consistent the NAM has been with modeled precip.  Even during the big storm in Dec 18, it had various runs where it was splotchy here and there with the QPF output....not this time.  I'd expect the radar to look good and consistent tomorrow.

Literally every zone this guy forecast is basically exactly the same “a few or a couple or several inches” ...why is the UNCC Grad student held in such high regard by some here, but real, actual meteorologists are not.

Warm nose crawling in on the 3k nam. I think that somebody curled a monkeys paw when they asked for a North trend.

You are correct, the synoptics are completely different this time though. Nothing in the upperlevels supports a extreme heavy snow event. More likely light to moderate. 

I can’t argue that but with that sounding, I’d imagine the only way we’d sleet is if our moisture got too shallow, right?

How on earth do we get sleet at RDU with this sounding?

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.

The way things are modeled right now, could this end up just being a thin strip of snow where the best rates and cold 850's overlap but rain on either side? 

With regard to precip, as others have alluded to, we need the northern stream shortwave to drop down farther to the west.  We need it to drop from Montana down thru the spine of the Rockies as opposed to dropping down east of the Rockies.  This improves the flow over the southeast for moisture return...specifically, it opens the door for more interaction with subtle subtropical waves that can inject moisture from Baja>Texas>Carolinas and VA.  Here's the shift west with the wave shown in this loop of the last 2 runs of the Euro Control.

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.

Surface temps are a non-issue with this storm for most folks, as modeled.
  Let me explain:
If per say, the models were showing a profile with -4c 850mb temps, 0c 925mb temps, 1c 950mb temps and 3c surface temps. We would be in trouble in that scenario as we would be dealing with lots of white rain and a thick boundary layer that wouldn't want to give up the fight.
That is not what any of the models are showing for this storm. There are (on average for mby) showing -4c 850mb temps, -2c 925mb temps, -.5c 950mb temps, and 3c surface temps.  As a result, the above freezing layer is only a few hundred feet deep at most on the globals, and any decent precip rates in that profile will quickly get the surface to 32/33.  The globals never pick up on this, especially at this range. So it's no surprise they are showing 6 straight hours of 37 degree rain/snow. In reality,(if their thermal profiles are right). that would mostly be 32/33 snow for everyone fortunate enough to get good rates, assuming your location has the good thermal profile I described above.
 
 

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.

No worries on the question, but the reality is that it wouldn't be a fruitful exercise to ponder on that type of detail this far in advance.  The most important thing IMO is for us to see a big, sprawling high pressure drop down out of Canada, delivering cold air.  Most likely, the high isn't going to stick around very long, but the bigger/stronger it is, the slower it will be to exit.  If we can get the good high pressure in place, then we look down south to see if we can time some SW flow and/or a wave in the southern stream to deliver moisture into the cold air

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.