psuhoffman

I’ll feel better about everything if we clear 0z tomorrow night without major changes.

12z was really south though. 850s never get north of the northern neck

I don’t expect it. Just that’s the only way I can see this going completely devastatingly wrong.

the do sometimes but there is still a tendency to amp more the final 36-48 hours so we need this to stop stat and get maybe a bit of a south trend to give us room for what is likely to be a bit of bleeding north at the end.

Nothing shows this right now so this is purely me thinking “what could go wrong” and the only way I see Maryland not getting at least a warning level event from this would be if the wave splits and there is a front runner WAA wave that targets VA south of us then the main wave amplifies and cuts and we end up in between.

Looks similar to 12z ggem

so far 18z (NAM/ICON) coming in with slightly better confluence in front of the system and a flatter flow over the top. Not major changes but we don't need major changes. These changes are showing up at 48 hours which is a pretty believable range...if we see this continue across 18z guidance it would be a significant step in the right direction of avoiding the over amplified solutions.

one is simulated radar and the other is the previous time period precip, different things tend to show...different things

The 18z NAM is better than the 12z and was about to obliterate us...and that is the end of my analysis of the NAM at 84 hours.

it's super light... DC starts to lose thermals at 1pm and only gets like .15 QPF after that. 95% of the precip falls before the thermals get problematic then hours and hours of very light freezing rain

Once it's in range...I would trust the NAM over other guidance with the thermals and precip type zones associated with that. Not at 84 hours...but once were close. Especially the 3k. It's the only thing I do trust the NAM with over other guidance.

Chuck was comparing the 18z NAM to the 12z GFS, which is apples to oranges IMO but he isn't looking at what the rest of us are looking at...which explains the "what is he seeing" stuff. The 18z NAM is less phased and has more confluence in front than the 12z NAM through 60 hours.

FYI, when you do analysis of a model run, everyone assumes you are comparing it to its previous run. If you are comparing it to a different model you have to say that or no one will know what you're talking about...even more than normal.

heavy precip is over there...they go to mix during the light precip that lingers after the WAA thump...the dryslot stuff. DC doesn't actually lose much QPF to mix on this EC run...it was close...but they held the thermals through the crazy heavy precip then warmed immediately after...which is common.

Yea we won't see those 18-1 crazy ratios...BUT...QPF tends to overperform in those crazy WAA driven thumps so it actually tends to be a wash (in terms of snowfall performance compared to modeled QPF. In one case we overperform due to rations in the other because of QPF.

Thanks... heavy precip holds off the warming...which is normal in these type setups...so we don't actually lose that much qpf to the mix...the thump is mostly snow even in DC according to that

This doesn't have that kind of upside IMO. The trough phasing as far west as it is does introduce some issues...to get the kind of prolific qpf necessary for those kinds of totals (30"+ in many areas) would require an amplitude that in this case would take the primary to our west...and mean we would miss out on the snowfall from the upper level passage. No second part of the storm. We'd get the prolific WAA thump but now that last 12" you need to reach those 2016 epic totals. If the storm were to revert to a less amplified solution which could keep the track under us (like the prolonged cold smoke euro solutions of 24 hours ago) we could max out the second half of the storm but would not get the prolific WAA snows needed to reach those 30" type totals. 2016 was absolutely perfect in that the storm was amplifying in the perfect locations to maximize everything. We don't have that here. I think a 20" event is on the table somewhere if we max out THIS SPECIFIC setup...not saying that is most likely...but possible...and I will leave it to you all to debate what a 12-20" type event falls under in terms of classification...but it's short of that biblical 2016 1996 type level. I don't see this as having that upside for the reasons mentioned above. But anyone who kicks a foot of snow out of bed given the last 10 years...needs their head examined.

we really should use the median more than we do, I find it more indicative than the mean.

HRRR at range is pretty useless

EPS 50% snowfall, this is an under utilized tool. Often when we see high snowfall means the 50% is much lower...indicating totals are skewed by outliers. That is a red flag that the high snowfall outcome is not necessarily the most likely outcome. In this case the 50% is higher than the mean, which is unusual, and a good sign.

This but also the trough amplifies and phases pretty far west...combo of those two things causes a strong southerly mid level flow as the trough approaches which facilitates the surface (but more importantly the mid level) low tracking a bit further NW than we want on some of the guidance.

to be fair his observation about the mid level low tracking too far NW for what we typically want is not wrong. But there are more variables than just that. The depth of the cold in front makes this a situation where a further NW track than typically ideal might not hurt us as much. Remember February 2015 when a storm tracking into OHIO gave us 8-14" across our area before mixing with sleet/freezing rain, because there was arctic air in front...and there was absolutely no 50/50 or blocking with that setup...it was simple that a departing arctic high had left a shit ton (borrowing this from Randy) of cold air in place in front of it and the WAA needed to scour it out produced a ton of snow before we lost thermals. And that would be kind of a worst case scenario here given the setup is even better. So on the one hand I get what he is saying...he isn't wrong about that one thing being an "issue" but I think on the whole there are factors that offset that. Hopefully I don't get schooled by a legend here.

but day drinking is the best

This could end up being the bigger story when it's all over

I was in Herndon VA for that, got about 18" of snow followed by several inches of sleet.