csnavywx

Bit of a catch-22 going on with the 3km, and a few reasons to take issue with using it over the 12km right now. The 3km has a tendency to overdo convection in marginally unstable profiles like this, which in this case, is feeding into a latent heat bias and thus -- and likely an overamplification of the surface low. Latent heat release from convection and surface pressure falls *can* work in tandem, but there's reason for this forecaster to believe that it's overdone here -- mainly experience with the NEST in this environment. The signal for some elevated upright instability being trained in is strong enough that it wouldn't surprise me to see some weak convection and a few strikes (particularly to the south), but probably not to the ridiculous degree we see here. One thing I *do* believe is that the warm nose will be tenacious in this kind of setup. P-type and rates will be very dependent on each other near the max accumulation line. You're gonna have to smell the mixing to get the most accumulation on this one. Also, weak instability combined with intense f-gen means intense bands, and subsequently a lot of subsidence around those bands. Some folks are going to get skunked and some will get jackpotted. Nature of the beast. Basically, when there's this big of a difference between the 2 resolutions of the same NAM, take note. There's some important details that can be gleaned from it.

The 3k and 12k being different is important. 3k phases a bit better and there's a significant band of instability that is entrained ahead of the system, along with quite a bit of convection, which will definitely have an effect on precip and track placement.

Nice belt of unstable air being drawn up from the Caribbean and Gulf on the latest runs. Substantial ribbon of elevated CAPE showing up that could get entrained and make things interesting.

That warm nose around 800-700mb showing up on the NAM is worrying me a bit about a sloppy p-type. Rain to wet concrete and a band of sleet mix in there somewhere. Will have to dig in on BUFKIT tomorrow and check it out. The Euro is a significantly better scenario for snow, where it starts in the wee hours and diabatic cooling keeps the column from warming up too much. Edit: The 06z NAM is a total weenie run for Lowershore. Plasters him with probably 10-12" of wet concrete. On a more serious note, that's a perfect slider track for SoMo and the lower shore. Last couple of runs were a hair north. Still ~48 hours to go, so no guarantees of course, but having the Euro and NAM sniffing out the exact same scenario is great stuff at this range.

Careful using straight 10:1 here. It's more likely to be 6-8:1 or more like the consistency of paste or wet concrete.

While it would be fun to see the deep cold at the end of the run, I think I'd rather see a Para-type scenario where the PV doesn't shear out into a huge positively tilted mess and instead rolls up into a nice storm on the way out -- as the pattern concludes. The deep scouring into the Gulf on the Euro kinda puts the damper on moisture return for a while after that scenario.

That slider is still on the table. And the TPV can stay right there just north of the border as long as it wants. Sets us up nicely to catch any southern sliders.

Notable shift in the GEFS mean and members towards the Euro on the 18Z run.

I mean... if you're not honking with these LR maps, you're in the wrong business:

Some actual accumulations with snow tv in between a few bands. Nothing heavy or earth-shattering. That's more likely next weekend or as the big vortex starts to move out in 10d or so.

This pattern has the potential to produce multiple times. The end-week wave has some explosive potential (pending timing and phasing ofc), but there's plenty of room for a follow up as the big honking vortex starts to pull away too. That's some export-quality Arctic air to work with and generate WAA/upglide on with the Gulf still open.

Starting to look like some light snow late tonight/early tomorrow morning and into late tomorrow afternoon is a decent bet. H5 low and H7 trough pull a decent loop-de-loop on the Nest and NMM (and the latest GFS), which will allow for some gentle lift in/near the DGZ. Throw in some leftover moisture and we could see some fluff.

Gonna laugh if we all end up getting more than DCA, especially you.

Looks like you've got about 1-2 hours left before mixing.

All sleet now. Looks like I'll end up right around 3" of snow+sleet by the time this is over.

Don't look now, but there's a fat slider starting to show up ahead of a true arctic airmass next weekend.

Well now, you're making out pretty damn well today, aren't ya? WAA stuff always seems to deliver the goods. Just have to be willing to hump the mixing line to get the good stuff.

Can confirm here at Pax. Just started getting some sleet mixed in. Smaller stuff melts, bigger aggregates making it through fine. Kind of a mix of fatties, singed flakes and small ice pellets.

Ripping now. Been sitting between 1/4 and 1/2 mile for a bit. 1.5" otg.

Not really seeing that. Better chance of something after it cools down Mon night -- but even that would be freezing drizzle.

Euro throwing us a bit of a bone with the coastal and gets some wraparound in here late Monday into Tues. Not a ton, but seeing it cave towards the GEM isn't something I really expected. Might be able to eek out the butt end of a ccb band after all.

Yeah, primetime between 14 and 21z, shift that up an hour or two for places further east/north. Thermals get shaky from south to north after that, though it might rip right up through changeover. I'm thinking diabatic cooling keeps the warm wedge at bay until the rates relax and the dry slot starts to nose in and then the changeover will be really fast. Key question will be how quick the morning stuff gets going. Earlier the better, as that sets us up nicely for column saturation and gives a decent powdery base to accumulate on.

Still can't count on the coastal actually doing anything for us. It's a very chaotic/sensitive setup where popping the low and closed H5 circulation a bit earlier and further south like the Euro and RGEM allows us to cash in on some of it -- or a little later and further north where it can't help us (like the NAM).

There will probably be some drizzle and freezing drizzle once the dry slot rolls in. Could be an extended period of it too. The reason is that cloud top temps warm above -10C as the dry slot erodes it away, leaving no very few ice crystals available for snow formation. Still plenty of moisture underneath that and some background lift though, so there will be drizzle. That's going to be an issue until/unless the coastal low can set up a reasonable def. zone and ccb to remoisten the column.