psuhoffman

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.

I definitely am more worried about over amped than suppressed BUT that seems a bit of an exaggeration. Chicago has a 1045 high right over it as the system is organizing to the south in just 60 hours...that would take a pretty freaking radical failure (models are much better inside 100 hours than they used to be) for this to end up THAT much further NW than say the GGEM run this morning. The mid level track is troubling...but we've seen things offset that before...look at last February when the upper level trough was back over OHIO and the VA capes got a big snowstorm. There is an arctic high in the way here and a 50/50 with a TPV lobe right over us as the system starts to develop, that does change the equation somewhat.

Moderate snow moves into the Annapolis area around 6z and mixing doesn't really become an issue until 15z. That is 9 hours of snow before you lose mid level thermals.

I don’t think the ec P type output is correct. The freezing rain along 95 should be sleet This is toward the end of the thump period and the biggest risk of losing qpf to non snow. surface is plenty cold and so is 925. The warm layer is somewhere around 850 and slightly above. That depth would indicate sleet imo along 95 not freezing rain. During the dry slot it looks like freezing drizzle. Surface 925 850 700

is that a technical term?

It did come on board though for one day...then backed off, but it was less enthusiastic for as long as other guidance. I don't have time to watch squirrels, but please feel free to let us know

My take: It's actually been the best op model in terms of verification scores over the last 6 months or so...and it was the one model to never tease us with that disaster last February. It's new but so far its been impressive. Having it on our side here is a big deal.

GEFS is better than the GFS op but still pretty far down on the list of things I care about I would rank importance in terms of what I weight this way 1)EPS 2)EC AIFS 3)Euro Op 4)UKMET 5)GEPS 6)GEFS 7)GGEM 8) tea leaves 9) wooly bear caterpillars 10) the almanac 11) Op GFS

I won't tell anyone what they should think. But what I think when presented with a scenario like this is that the potential is there for an HECS level event... but there are 3 caveats we have to acknowledge. 1) the setup here does support the possibility of a major event...the key components we need are all in place, blocking, 50/50, arctic high. But those things don't guarantee a max potential outcome...we sometimes have all that and the details don't fall our way and an event fails to reach HECS level. I am not talking about a total fail but plenty of times we have the potential for an HECS and only get a SECS or MECS because some minor details didn't work out 2) the guidance has never universally shown HECS results, not like 2016 when across the board EVERY DAMN THING showed 20" totals. This time each run we've had 1 or 2 peices of data showing that...but we've also had some less enthusiastic output. The GFS showing some deamplified wave, the UK or GGEM with some over amplified mixed event. We have not had run after run of across the board uniformity agreement on a HECS. That indicates there is still variability to this and an HECS is not necessarily the most likely outcome 3) Even if the guidance did show 100% agreement on an HECS at 100 hours out...we have to acknowledge the limitations and faults in this guidance. Yes our models are flawed, we don't yet have the scientific ability to model the atmosphere accurately at 100 hours. It's possible the guidance is wrong in some way and things will shift by this weekend. It's ok to admit this. But it's also important to also admit without the models we would have no freaking idea there was a big storm even possible on Sunday. So there is a benefit...that benefit is not that we can know for sure what is coming 4 days out though.

Odd change to the mean... didn't trend north or south...just "less"...but we are in the midst of an amplification trend across all guidance...so I find it hard to believe the decrease is due to a less amplified system. I would have to look under the hood but that change is just odd given when else we've seen from 12z data.