RitualOfTheTrout

This is the criteria for an advisory: A winter storm event (sleet, snow, freezing rain, snow and blowing snow, or a combination of events) is expected to meet or exceed local winter weather advisory criteria in the next 12 to 36 hours but stay below warning criteria. Criteria for snow is 4 inches or more in 12 hours or less covering at least 50 percent of the zone or encompassing most of the population. Use "mid-point" of snowfall range to trigger advisory (i.e 2 to 5 inches of snow = advisory). Criteria for ice is any ice accumulation less than 1/2 inch over at least 50 percent of the zone or encompassing most of the population. Winter Weather Advisory can also be issued for black ice. This is optional. Given the significant NW cutoff will create a steep gradient that will bisect Allegheny county I wouldn't be confident that 50 percent of the county sees 4 inches or more based on current guidance would you? Now my understanding is these rules aren't absolute, they can for example take into account time of day (evening / morning commute) or be more likely to issue an advisory for the first snow of a season etc. Based on the text in the discussion and the fact we probably see the biggest amounts overnight into the morning commute and it's likely the city gets at least 3 inches they will probably expand to include Allegheny unless as we draw closer the short term models lower totals further. I don't get all riled up over what the NWS posts for any area in terms of warning / advisory etc. It doesn't affect what we actually get and usually they err on the side of issuing something to raise awareness over doing nothing.

Also of note, from a quick glance it looks like all the 6z runs at least halted the South trend, if not a very minor subtle improvement. I don't think it would take much to increase the qpf a bit more on the NW edge with a few slight adjustments. f we can squeeze another 5in or more storm out of this that would be a win. Overall it looks like the bigger totals out east are also coming down somewhat, where the good qpf is it's also mixy so..

The trend continues 00z GFS.

It tries to calculate based on temperature at various levels, in a borderline scenario it would likely give you a truer outcome as it will assume less than 10:1 or if it's colder it would assume higher ratio. It also tries to take into account melting / compaction as you mentioned. Here's a good read from pivotal about the slr calculations: https://home.pivotalweather.com/guides/snowfall Snow maps are also flawed in that they use the temperature at a given forecast period then assume all qpf that falls after it will have the same conditions until the next interval. So image hour 3 all layers are below zero, then hour 4 850 goes above but the next interval isn't until hour 6, your going to have 2 hours of qpf assumed snow that is a mix.

18z Euro is ugly, 1-2 inches tops. I agree the South trend needs to stop, all the models have gone further and further in that direction consistently one run to the next. Another move like that in the Euro is partly cloudy skies.

I think if we are going to see any NW trend it will be now that yesterday’s storm is lifting out. If models are overdoing confluence associated with its departure we should see hints of that soon.

March can average above but still produce, how many stories are there of it being 50 degrees then a huge storm the next day. Rates will always overcome warm ground and sun angle. You just have to be ok with it melting 10 minutes after the storm ends. That’s why I change gears to really hunting a big one that time of year. Ill also add the blocking looks to reload one more time end of Feb, so first 2 weeks of March might have some tracking. Usually once the effect of a SSW wane it’s not uncommon to go above average, but if that’s the third week of March who cares?

I was going to say the same, we probably pulled off a sneaky inch so far today for padding stats and a moderate burst outside my window now. I do love these steady light snow days with imbedded moderate to heavy bursts especially when it’s cold. Makes radar watching fun. It’s even better when you are refreshing an existing snow pack. I’m definitely one of those that want to keep the snow pack going so I’ll take these 2-4 type snows with endless overcast sub 32 days all winter. As we close in on March though I start to gravitate towards more big game hunting as snow pack retention is pretty difficult.

Maybe I’m just pessimistic after this last storm but this one is still trending the wrong way. Everything is SE again on all 12z guidance vs the previous cycle. Weaker storm, stronger confluence, more progressive trough (basically everything we needed to save the last storm). Until any of those things reverse or at least stop there’s no reason to feel it’s going to come back. That’s what I kept looking for on this last storm and it kept going the wrong way all the way to game time.

Yeah I went out to check the cars to see if anything needed cleared off before refreezing and noted the breeze. That's one thing our storms have lacked this year is a wind component. I don't recall any that really created any drifts etc.

Lol.. just give me a few hours and I'll be back to form. I don't see any threats after the Thursday deal, going to be weird not having 3 different storms to keep track of, not sure if I'm depressed or relieved over that fact. No real signs of ice here, guessing most of it melted off. Still have some snow on the ground, will probably glacierize throughout the day. I'd be curious after it all refreezes today what the liquid content is, not sure I have the tools to do a core sample on hand and melt it down though lol I'm a bit surprised by the NWS map with 6-8.. That would make up for this last event.

Yeah, I've been reading obs threads and seeing video / pictures posted. Single digits, thunder snow, huge drifts / sleet bombs etc. Not going to lie, feeling jealous. Certainly wouldn't mind feeling some of that "hurt" especially looking out and seeing our 32.1degree downpour.

Seeing reports of freezing rain as far NW as beaver county already on the NWS Facebook page. Read the comments at your own risk though, certainly some gems in there that will make you further lose faith in humanity...

NWS trying to do FB live when they launch weather balloon at 6pm to get current observations if anyone else is interested in that.

Same here, not even a sleet pellet. One other thing that will boost zr is that it's happening after sunset.

Honestly the crews have been out, any pretreated road should be fine. Now untreated will probably get dicey quick. If temperatures are really in the mid to upper 30s overnight I’d even be willing to bet conditions aren’t to bad tomorrow morning. If that’s wrong though then all bets are off.

Yeah looks good, the South trend can end now lol

So the trend with today’s storm was a continual tick NW around 72 hours, this ones been going SE, so just based on putting money on the current trend that’s what I’d say. No real scientific evidence though.

Watch this one miss to the SE.....

I hope you are right on this, I can see a scenario with heavy plain rain that would really decimate the snowpack. Not saying I expect this, but I think it’s a possible outcome if things break in the wrong direction.

It’s also showing no snow with round 2 tonight. I know it’s not a 1:1 comparison but it will be interesting to see how that plays out. May give some hints for Thursday especially considering (as of right now) we should have colder air in place ahead of it, the high is a little stronger to the north and the low is tracking further South.

Coming down nicely right now, I’ll just enjoy this as I whistle past the graveyard with regards to round 2.

At the end of the day all the meteorologists can do is use the tools they have at their disposal. Sure you can apply local / regional climatology and outcomes of past similar storm evolutions but if all that’s based on incorrect variables from guidance used as your initial base state you don’t stand a chance. Thats why you see more seasoned folks reluctant to jump head first into forecasts depicting big events. As we have just witnessed even with a solid consensus it’s still possible to be wrong enough to dramatically effect the outcome. Then your left with trying to explain what happened to a general public that has little to no understanding of how anything in the process works let alone even a scrap of atmospheric science. It’s all a bunch of H and L graphics on a map with pretty colors to most.

I think a lot of what you are saying is in the works. Look into the UFS (Unified Forecast System) Its goal is to use same simplified code across all agencies and allow Private and Academia development too. https://ufscommunity.org/ The other goal is to improve ensemble forecasts as they are superior to a single model. https://www.hpcwire.com/2020/09/23/noaa-announces-major-upgrade-to-ensemble-forecast-model-extends-range-to-35-days/

In theory a stronger more NW storm could serve to suppress heights in the east and boost confluence allowing the Thursday storm to track under us.