jm1220

I said it's a possible outcome that I'm not taking too seriously yet and the hi-res RGEM is another possible outcome lol.

That outcome might make it a high end advisory event here, maybe we barely scrape it to a warning event with added sleet on top while Boston gets possibly 18". Would go into the long list of SWFEs that suck absolute donkey balls.

I take it as the worst possible outcome and the hi-res RGEM as the best because of the front end thump that still drops 10-12" despite changing most of us over. That said if sleet really makes it to I-84 those of us down here are screwed for anything major and we might struggle to make it to a warning criteria event. We're not there yet but by tonight if the NAM still totally sucks I'll take it more seriously. I didn't like the GFS cutting back at 6z either. NAM has been too aggressive with the warm layer in the past but it will probably be more right than other models close in. We should also monitor obs in the South/TN Valley for how far the warm layer is advancing vs what models have.

The real story from this storm will be the icing down south vs the snow we get here. Austin to San Antonio is expected to get up to about 0.25" ice and there are winter storm warnings all the way to almost Corpus Christi. That would be like us getting 2-3 feet of snow in terms of disruptiveness.

The heavy rates will be key. If those shred up or let up the warm air will advance fast. We saw this in last Feb's SWFE and back in Dec.

Closer to the high pressure/cold source region. I'm confident 80% of us mix at some point. The I-84 crew will probably avoid it-I hope anyway.

Yeah.... much as I would love that it's not going to happen. I think something like the RGEM is the high end for this. I'm not sure if these maps show sleet as snow so the 10-1 snow maps that are lame in general for us, you can probably add up to 2" of sleet on top so if it shows 6" for you, sleet could end up with 8" total.

We're still long range for that model, we're not within 24 hours of most of the event yet, more like 30 hours. If other guidance at 12z trends toward it then sure.

I don't use kuchera maps, 10-1 when in doubt. We could manage a little better than 10:1 since we're starting so cold but ratios will lower as the mid levels warm up.

RGEM still looks really good with a huge front end thump.

HRRR is probably too cold at this range and will come into line with other guidance. I'd love for it to verify too but it's still a little outside of where I'd use it. GFS was always going to cave. NAM getting a little better is somewhat encouraging although losing the GFS to this degree is a little concerning. It's going to sleet a decent amount into the city with this, we just have to hope the heavy snow rates can hold it back as long as possible. SWFEs will just try to screw us over in any way they can and gain the last possible inch north. This is the exact storm type where Boston will get buried.

That isn't ice accumulation. That's sleet that falls, so half an inch of sleet roughly which would be about 0.15 liquid.

NYC 9.3" Boston: 18.1" (E MA probably jackpots) Philadelphia: 7.2" DC: 6.7" Hartford: 14.6" Albany: 15.1" My backyard: 10" (8.5" snow, 1.5" sleet)

Early-mid afternoon big time fun, flip to sleet by 7pm-ish but by then the vast majority already fell. Euro got wetter too, went from about 0.9" liquid last run to 1.2 now.

Hellacious. That's exactly what we need to max out the potential from this.

Hopefully you're right. I highly doubt we jackpot around here in this type of system, I can definitely see it for I-84 corridor to Boston.

GGEM looked good, not as good as RGEM but solid. IMBY it has 10" of snow at 10-1 then probably 0.3" liquid as sleet so that would add another inch.

There's been something off with the snow maps and precip totals. It has 1.01" liquid in Montauk for example but 12" of snow on the 10:1 map. It looks cold to me which is great but 18z had the same problem.

RAP 3z is an absolute crusher at this range, but it's still beyond where we can really use it. Tomorrow it'll probably come into line with the other guidance.

Down to 15. Brutal.

Yep it finally got off the idea that the jackpot will be from here to Philly. In this type of storm that ain't happening. We hope for the hellacious 6 hours or so that can hold the sleet back as long as possible. But the sleet will eventually come, that was clear 48-60hrs ago (for the city).

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.