csnavywx

Heavy snow now, ripping big dendritic aggregates.

Looking for 6-10" over for Lowershoresadness in the 'bury and eastern shore. 2-6" for the western coast of the Bay (slanted higher southwest). 1-3" west of there. The western side will pick up half or more of their snow from the pre-storm frontogenesis-driven event. I expect that to overperform a bit due to the fact that the lift is co-located across the DGZ and persists for hours before the coastal blows up. Those kinds of events are often a bit sneaky: they start early and can produce healthy dendrites and aggregates. Surface temps will start a smidgen warm, but ground temps are cold. It won't take long to get the boundary layer to cool off, unlike last week. Subject to some revision due to where the coastal actually ends up setting up. If the 850/700mb lows end up a bit further NW and we stay SSE/SE at 500mb, totals will get bumped.

I'd take those odds. It's not going to do a whole lot for DC on west perhaps, but on the western side of the Bay, yep.

Voting against that sub-72 hour NW/W walk on the GFS is a dangerous bet. Edited: It's usually 72, but strongest under 48.

Still working out some issues with storm genesis location and time to "ramp up", which will make all the difference in the world. Still, a nice floor for S MD and Ern Shore of 2-4" so far. Considerably higher (6-8") with even a partial phase for the Eastern Shore and gangbusters if we can get the genesis location and speed right (8-12"). Blizz conditions not off the table either (for the coastline), but somewhat lower probability. Will know more by 12z. Will issue a forecast here tomorrow afternoon after I get done doing stuff at work.

He's on the level. Was (correctly) poo-pooing the events last week because of the missed phase (among other issues). Personally, I want to see a continuation through 12z and no more "diurnal rocking" before committing.

Ha, that's the first thing I thought when I saw those progs a few days ago. Looks just like a PRE setup, but in January. They can persist for some time and it's that kind of setup (mid-level f-gen max across the DGZ) that can overperform pretty nicely. Might end up being the thing that "saves" the event for most of the subforum.

Lotta despair in here for well -- not much of a good reason yet, from what I can see. Maybe the west side folks, but even that is going to cash in on high-ratio fluff from the long duration f-gen event ahead of the low. GFS is doing its typical gradual, but noisy walk NW in the short range. Does nobody remember last week?

I spy a deathband at 81/84 on the frontogen maps. Going to break out some bufkit and cross sections some time tonight and have some fun with that. The 700mb low closes off between 78-81, so I would expect there to be an especially intense band setting up N and W of that.

Surface cyclogenesis starts considerably earlier on this run, too. By tau 60-66.

Ah, good stuff. Hopefully you cash in on this one too. Fingers crossed that you don't get into the mix zone.

Right, genesis is off central FL coast and no discernable inland low. Not a Miller B.

You got 11" and a blizzard warning a few years ago, right? '17/early '18 was it? Or am I misremembering that one.

It does look like we're going to get another swing at it in this pattern later this week. The chance of a repeat "phase-miss" is lower this time. Regular reminder not to get too carried away with any one run or model. I want to see this trend stick through the 12z guidance tomorrow before I start investing.

Sorry, but a low that has a genesis off of FL is not a Miller B. Not in any book I've ever read or studied. Wish we'd stop with that.

The phase is still a pain point, but that seems to be working out as the northern stream wave has trended slower. There's room for improvement on both ends, so long as the phase is still on the table.

Who honestly believes, that after the typical block breakdown mishandling, that it won't also display the sub 72-hour slow NW walk? So long as the phase holds, I posit that it will. Also, better horizontal resolution absolutely does improve handling of all of these interactions. Take a look at H5 vort on the NAM 12km vs 3km at tau 60 on this run and tell me that the 3km wouldn't be even better. Block is slightly stronger and phase is slightly better.

Hey, that omega block is breaking down slower than forecast a few days ago. What a shocker....

Yep, did some scoping on west coast initialization, they're a dead match. Good against RAOBs too. GFS was a touch weak out there (10-15m) at 500mb on the ridge.

Yep, we are pretty dependent on that ridge with a lack of a downstream block to slow it down (as @wxmvpete) mentioned.

CMC demonstrating nicely exactly what I was referring to earlier. Cutoff/omega combo breaks down slower, allowing the downstream to amplify more. That's good for us. Don't worry too much about the "tail" vort streamer. We want one there. This wave is big enough to scoop that out and give strong advection vort to spin up the low faster. Now the next question is -- are the models demonstrating the typical bias in blocking breakdowns and simply correcting for it over time now? It's always been my experience that there's a tendency to break blocks down too quickly. Some of that probably has to do with the limitations of horizonal resolution on a global. Smaller scale eddies are important for maintaining blocks.

Need that upstream omega to break down a bit slower. That cutoff offshore of CA being slower helps this run as it doesn't dampen the ridge as quickly. Lots of run to run variability until that piece settles down.

The rolling and demise of that upstream omega block is going to be key. The cutoff well off of CA is a sticking point. The primary reason the GFS shifted was due to the ridge axis being distorted as the upstream cut-off opened up into a wave and destructively interfered with the ridge axis, causing our downstream trough to be less sharp and ultimately less vort advection. Takes a bit too long to get going. That said, we're in a good spot and the fact that all 3 OPs are flagging something to watch at this distance is also a good thing.

Still not dead yet. Though it looks like LS over in Salisbury has a better chance than the rest of us on Fri night into Saturday. Front is slower than originally forecast and I expect the northern edge of the precip shield to clip us. The northern cutoff between virga and accumulating snow will be sharp. You will either be in it or not, generally speaking. Not the big storm I'm sure everybody was rooting for earlier this week, but never take your eye off a southern slider. They can sometimes bite at the last second.

If these changes carry over to the 12z runs, then I'll be on board. I want to see it survive a few initializations. Everything was slower on this run, and not just the main players. Could be running into the same issues again tomorrow -- and that matters when it comes to the NS wave being able to amplify instead of getting impinged on by the upstream NS kicker.