jm1220

Relieved that it's pretty much just the NAM that torched like crazy. Both have plenty of QPF too.

UHI won’t be a problem with temps in the low 20s. It will stick everywhere right away.

Also if we have a lousy broken up snow shield that will mean that we have inconsistent/lousy lift and saturation which means crappy snow ratios as well. We need strong lift, saturation and snow growth in the -12 to -18C layer.

The ratios will be good when we get started but they will lower as more warm air moves in aloft. We need temps from -12 to -18C in the layer where snowflakes are made for the best ratios. As we get warmer than that in the clouds the ratios will get lousier. Inland where it’s all snow will do well with ratios but wouldn’t surprise me near the city that we average 10:1. Thing is though that the sleet counts in the accumulations, so if we get 6” with 0.6” liquid then another 0.6” liquid as sleet, that adds up to almost 8” total since sleet has a 3:1 ratio. Time to concede near the city that a good chunk of the liquid that falls will be in the form of sleet. Hopefully it’s more like 20-30% but the NAM would be something like 60% and primarily a sleet storm.

It gets sleet from a line from Port Jervis to just south of Boston. If sleet really gets that far north it's hard to see how the immediate NYC area and coast do well.

20" here and 0 in Montauk. Let's goooo

The other hi-res guidance seems to be better with the great front end thump. So the NAM is by itself so far with such a lame outcome.

We need the snow shield to be heavier/steadier. In 3 hours that NAM run surged the sleet line from Wilmington DE to Staten Island. The heavy precip is when it's sleeting. It would be varying snow rates for a few hours then all out sleetstorm for 60-70% of the precip that falls.

They weren't better. People forget the massive shift within 48 hrs for the 12/26/10 blizzard for example. I thought that one was lost OTS.

It's overdone it at times. The first Dec clipper this year it overdid it. Hopefully it backs down at 6z or 12z tomorrow-the sleet line advances like bonkers probably because the front end thump sucks and would be shredded up.

Yep and make it all the more sad when it turns to pelting sleet. Hopefully it's wrong. Might not even make it to a warning event south of I-80/city and coast with that outcome.

Love how from 15 to 18z the NAM just absolutely books the sleet line up to Staten Island from Wilmington DE. Must be crappy rates and shredded precip.

21 here. Dropping like a rock.

Yep, and I think Pivotal maps don’t count sleet as snow, so I could imagine there being up to a couple inches of sleet on top since sleet is a 3:1 liquid ratio. 0.6” of water as sleet would be almost 2”.

Yep, can definitely start to feel it. We still have some snow on the ground here so I guess this will count as snow on snow. Still a couple inches in my backyard.

Something's off here-it gives me 7" of snow at 10-1 ratio but 0.5" liquid. CT coast 0.4" but same snow. Again weird precip hole.

I definitely think we pound heavy snow for a while on Sun morning/afternoon. That's a ton of moisture coming north and being lifted.

That's about what I'd go with.

We need for the big coastal storms to come back-we had plenty of great storms/outcomes when we had those. This will be fine and I highly doubt it plain rains anywhere away from maybe Montauk but this type of system will always relatively suck for us here.

RGEM looked like it held serve. Bottom line is we're going to be paying close attention to the oncoming snow shield early Sun morning and hoping it comes in like a wall. Shredded crap and we might barely make it to the low end of forecasts (I'm talking for I-80, city and coastal areas). The wraparound stuff on Monday to me looks like a longshot and again something that would favor SNE. if the primary drives that far N and wrecks the mid levels, we just get the dry slot and whatever coastal redevelopment would be too far north. It's very unlikely this will be the lame usual SWFE but if you're expecting 12"+ in the city I'd start preparing for disappointment.

It was going to cave eventually. This type of storm doesn't jackpot NYC to Philly. These do best along I-90. This is the storm where Boston catches up and probably surpasses us at least along the coast for seasonal snow-wouldn't be surprised if they get 16-18". We're lucky we have this high pressure dome in place to provide an overrunning surface so we get the initial thump of snow down into VA, otherwise this would be the usual SWFE couple inches to rain/sleet. But is something like the NAM possible here with a stronger primary low-sure. Even that though would probably be 4-6" snow then a couple more inches of sleet-however it would also bring the dryslot in quicker.

If you add 1-2" of sleet that counts as accumulation too but I always thought 12" for NYC which they have now and 14" yesterday was too aggressive. I'd go with 12" maybe in Yonkers and 8" in SI/Rockaway.

Maybe the eastern tip of LI changes to rain but I highly doubt anyone else does unless we see prolonged onshore winds given the severity of the cold air coming in. I could see freezing rain happening if we get a shallower cold layer at the surface. Bottom line is hopefully this NAM run is wrong.

I’m not very concerned about it on its own but there’s definitely still time for late north bumps. The confluence needs to hold to force it south. We’re also definitely getting sleet at least up to I-80 and maybe even up to the CT coast eventually, it’s just a matter of how big the initial thump is and how long it can hold back the sleet line.

Yep pretty much back to 6z where mixing gets to almost all of CT and RI. Thankfully it’s on its own pretty much and other models got colder at 12z but a SWFE like system such as this will take any chance it can get to nudge north unless confluence stops it.