Moderately Unstable

00z nam maintains snow at least a bit longer over Philly. Also moves the low a touch closer to the delmarva. 540 line unchanged ish. Colder ll air in place though so more snow.

Glen Okono trail was closed several years back. Too many folks getting hurt. I had to help 2 last time I hiked it. Just an FYI in case you didn't know. Not sure if you can still access the parking lot and such or if they blocked it off.

We must find the observer!! *grabs pitchfork*. Jk. I'm embarrassed I didn't know that. I've been to the mt holly office several times...years ago when a friend worked there, and no one ever told me that. Tried to find info on Google but there's nothing. The inquirer itself reported this jan no less that totals were taken from the airport. NjHurricanes point jives with what I was trying to get at though..airport or NJ, there is often some material difference btwn airport and cc. Not hugely so, but it can be a couple inches in bigger storms. The inquirer article pointed out that many areas of phl see significantly more snow than phl airport. Even some inland parts of nj. Only the nj coast sees less. So as to my earlier comment--if I forecasted for the airport, my numbers would be lower than, say, Roxborough, even though both are "in the city". https://www.inquirer.com/weather/snow-weather-philadelphia-winter-phl-measure-20200121.html

Interesting. You're saying the measurements are done across the river...Delaware or Schuylkill? You're saying they *are not* measured at the airport? Sep: confused at what you are pointing out here. Do you mean that phl totals are reflective of reality, or aren't?

Thanks guys, appreciate the words of encouragement/inclusion. Wasn't trying to go emo there, just have been feeling rather self conscious haha. Sometimes I overanalyze things... like when I say something on here and then no one posts for 30-40 minutes I go "is that because I just stopped the conversation or because no one has anything to say right now". Not specifically this thread, just on the site in general. Happened when I was talking in tropical about Iota and internally I was screaming, even though most likely there just wasn't any update to add for awhile. You know how you feel when you go from being the one who knows a lot about something (most on here when talking to other people irl off forum) to someone who is very much NOT at the top of the knowledge tree and your peers can blow your skills to shreds? It's like that, kinda like going from HS to college. Makes me much more reserved.

Welcome back! I hope so too. I know not everyone loves snow, but most folks are working remote these days, its the holidays, it could bring some extra joy to folks who haven't seen snow in a long time. I hear ya on the statistics. One thing to factor in there is that kphl is almost always on the bare low end of the forecast estimates. You have the heat island effect from the city + moderating effect a touch of being next to the Delaware+ farther south + basically sea level. So for every storm in the top rankings list for the city that says, say, 8-9 at the airport, you could realistically have gotten 10-11+ further up but still in the metro area. I also think that from an impact standpoint--you're 100% on the money. Even with sleet or freezing rain, that still causes power outages and makes travel dangerous, perhaps more so. It's just, objectively, cool to have a big full snowstorm with no messy ptypes, in ones own area. I live personally close to the city/burbs line, so I'm especially cognizant of these setups and their gradients. I'm sure my childhood hometown will see 3"+ than me even though the distance is not too far. Either way, fingers crossed.

Posting on here stresses me out sometimes. Trying to "read the room" when you can't see people is nervewracking. Constantly editing and second guessing what I write to avoid saying something dumb & no one mentioning and just ignoring me.

Yeah, lol, if that happens I'll streak through the city. I'm still expecting 8-12" total where I'm at, north western part of town. 6-10 cc. Waiting for 21z sref. Attached 15z plumes for PHL. At this point short range models start being more useful and accurate on avg. Sref trended up btwn 9z and 15z. Still think sref is a bit low--dragged down by members predicting 0. Gfs is la la land high. There is low chance of Philly staying all snow, almost 0. Warm nose too big--needs surgery. I don't see 12+ in that scenario. Enough total qpf here though that I still find the range 8-12 most sensible for city. More in the burbs as usual. 3km nam snowfall map seems reasonable given the storm still in progress at hr 60. DT went surprisingly high.

I don't buy 14 with that much mixing for the city. If that verified, it's going to significantly cut down the totals. Perhaps 14" of snow will fall...mixed with rain, mixed with sleet, etc. I would go with 6-8" for the city if that ended up happening accounting for overrunning and back end. But that puts the city in a dicey situation if the dry slot precludes some of the back end potential. Models vary run to run, still time, fingers crossed. Also note that the ratio there is 1:10. We should expect 1:7. This will be a wet snow. Note that the euro run suggests 6.7" of snow will fall in Philly in the 6 hour interval in which the precip pane shows a mix. That means (a) it is counting snow in that, (b) that seems questionable. I'm turning in, later folks.

No I know they're used to indicate a pause or other sort of trail off. More in the context there where the statement was, there will not be 40" of snow (reasonable thing to say given qpfs, you'd need it to be very VERY cold), was more noticing bc that was the second time today I saw Mr. Birds using them in a post and it felt like it diminished the valid statement of fact. I'm realllly splitting hairs here and this is ot, I'm just pointing out the idea of, ya know, if you have a good thought or fact, a full stop period is good. Helpful content either way. The last post there "the euro will save the day", made sense with the ... I'm fun at parties.

I agreed with your post more was asking why you used the ellipses instead of just stating it as a fact.

Why ... and not .

I'm genuinely confused. Why does everyone say 5-10 in the city when none of the models say that? Even the cmc yields 11, and that's the low estimate. There's lots of precip, and it's cold. What am I not understanding? Not trying to be aggressive or wishcast--I genuinely do not see 5-10 being shown on anything. Models have stayed very consistent. That means, the maps are not clown maps: they agree with each other more or less. Like if someone wants to explain why all of the guidance is wrong, I'm all ears. But if it isn't, Philly gets 8-12 as I said earlier today, and stand by now. I'm happy to lie in that grave if I'm wrong, it isn't a bold prediction. It is true that most of the time the burbs see more than the city. That doesn't mean the city gets 6" though.

You're right on less vort org. Less than both the last several model runs of the gfs & the latest runs from the other models. Interesting that it lingers as well, that is significant but needs to be matched with the other models. So far that's an outlier...most runs of stuff' have been progressive. Could that be the "why" for its subsequent theory of lingering snow?

Could you tell me, where does the ICON rank in terms of performance versus the gfs euro and ukmet for Philly? Not super familiar w/ICON.

Lol, I believe you. It isn't a crappy model a la no gaps and co, I don't even know if they still run that. So many gaps. Just tends to be wet, over amped, and wild, vs the other contenders. Nam is the place to go if you like things wet and a bit crazy. Sometimes that's a winning combo though. . I mean, the main reason not to buy it, to my non expert eyes, is that it disagrees with everything else. Same reason you don't believe one ensemble member that says 30" when the rest say 3" or vice versa.

Well, will be interesting to compare to other short range guidance. Sref etc. I just took a peek at the rpm model, can't post that, but it doesn't have the sleet pocket at the 72 hour mark (end of run). It does have a small sleet pocket over western VA similar to the NAM, but then that line doesn't extend out into PA as the NAM does. Perhaps suggests a potential for a brief period of sleet or ice in a mostly snow event. Definitely does not echo the NAMs craziness though.

Why is it so strongly set on the inland solution?

You know, looking at the model consensus here, 3 days out, I'm really struck by how far forecasting science has advanced in the last 30 years. The fact we can, with some reasonable degree of confidence, say right now, when it's in the high 40s in Philly, that we'll get crushed in the middle of the week by a storm that hasn't EVEN FORMED YET, is pretty dang cool. Everyone always jokes to me that meteorologists have the only job where they're allowed to be wrong. But frankly, when I see stuff like this, it makes me really appreciate all of the professors and researchers and forecasters that have advanced us to this point. Ask a 60s meteorologist to predict this using a paper map of the current weather. Another thing I like about systems like this is, they're not "easy" to forecast per se, but unlike marginal events, where you have to hunt around for tiny kinks in the height lines trying to read the tea leaves, the big systems follow some basic rules vis a vis how strong mid lat systems form and operate, and have clear boundaries, so it's less hair splitting and more actual meteorology.

18z euro agrees with the gfs, high qpf, cold. Yay! Re WSA: quite true, but they seem on point. 5"+. 5 is the abs worst case I wrote down earlier. The fact is, no model, no ensemble member, says Philly et al gets advisory snow. May as well give folks more notice so they can get salt or what have you early, instead of all crowding in a store the day before the event..mid-covid surge. We know it will be a WSW, we just don't know the precise amounts yet.

^^agreed. It is nice to look at. The bulk of the guidance is not on the GFS amounts train, though I don't think it's out to lunch per se. I think a lot of the gfs's progging relates to thinking super heavy precip rates will overcome all else. For Philly CC, my gut instinct at this point for a first call is, 5-8 if we see a snow-mix/rain-snow, 8-12 if mostly snow, 12-16 if phl stays mostly snow, and everything aligns just right. I'm a bit concerned about the dry slot timing on the backend. That's screwed the region in the past and is showing more of an issue in recent runs. Thus if I had to choose a single range, I'd go 8-12, with the (*) that more is possible.

Double check to make sure it's actually accumulating (if it is, that is indeed interesting). For example, tomorrow, the NAM says 2-3" of snow could fall (snow accumulation graphic), but precisely 0 of that will accumulate (change in snow depth graphic). Also, remember that unless otherwise noted, rain:snow ratios are 1:10...since temps here are so close to freezing, ratios won't be 1:10, they'll be 1:7, 1:8...which is why Kuchara totals are lower than the non-kuch totals. Machine learning models are great, sometimes they don't pick up on big changes quick enough.

The NAM has in various thermal profiles across the NE a warm layer between anything from around 700/725mb to around 800mb. I could show more, but if you want to see why a model is progging fzra/sleet over your house, just pull up the forecast sounding for the hour in question. Sometimes the fixed pressure surface maps don't tell the entire story (whether or not it's a true story is another matter).

Ok, euro brings me back from the brink lol. I've been writing up an analysis (see below), but I'm taking a break now to go exercise, so this is incomplete. Also, I was mainly writing this for myself so it may be full of errors. On the off chance I say something helpful, posting below. /////////// Current Analysis (please take with giant grain of salt): Setup: Miller B type-ish cyclogenesis under a negative NAO, weak La Nina, PNA approximately neutral, may be trending slightly negative. A low currently over the eastern pacific ocean will traverse and be disrupted by the rockies, progressing into a trough over the southern and central US. Canadian high pressure builds over Quebec. Cold air damming occurs as cP air mass moves SE...Canadian high pushes and traps cold air against the apps. Trough/sw amplifies and move NE along the NE coast becoming a closed sfc low. Recent trends focus more on a developing low east of FL to phase with the low ejecting from the rockies which is more akin to miller A than B. Vertical Velocity Position and causes: S of Philadelphia primarily...NAM disagrees and thinks omega is higher further N, reasoning: 700mb low position (eh), 850 mb position, jet streak (UL divergence), LL convergence. Strength of WAA/CAA f(wind S, wind Dir, T gradient)....solenoids: ##todo Positioning of the low/rain-snow line: SE along a line between 20 miles SSE of Philadelphia to 5 NNW of Philadelphia depending on model run specifics. All runs indicate sfc temps sub freezing due to either precip rate or myriad other factors. Precip components: Overrunning Y/N--> Yes Central Y/N--->Yes Wrap-Around Y/N---> Unclear. Dry slot vs deformation banding. Model comparison: (to finish) GFS--> 12z Sun run weaker. At 06z Thurs, has the low up by 6mb vs previous run, and slower. Compared to runs over the past day, the 06z run low position appears to be an outlier, most of the runs keep the storm closer to the coast, and differ with strength and direction from there. The decrease in QPF seen in the 12z run (and thus, total potential snow) appears to be a function of less 6 hr QPF forecast at 00z Thursday vs earlier runs, which is itself due to the low being further south of the Philly metro at that timestamp. Despite these changes, the rain/snow line has been quite consistent since the 00z run. 00z, 06z, and 12z, all depict a virtually identical rain/snow line at 00z Thurs. This is not as true at 06z Thurs--earlier runs, including 00z Sun, had heavy snow reach further into NJ due to extreme dynamical cooling and FGEN effects, however, the 12z and 06z run are in fair agreement with a rain/snow line towards coastal NJ and DE. ECMWF-->Has the best positioning right now of the 700mb low in terms of maximal snow potential. 06z Euro brings storm further north than 00z, poss ptype implications. UKMET--> 00z run splits the difference in terms of southeast ridging between the 12z GFS solution and the 06z ECMWF solution with respect to possible temps during the storm's projected peak (around 21z Wed-09z Thurs). 12z run warmer, lowers snowfall totals in PHL from 13 to 8 or sig less (to finish). NAM--> Brings the low further north and closer to DE at 84 hours vs other models due to positioning the Canadian high further NE. Has the closest SFC low approach to Philly of any current or recent model run across models. As a result, projects much more of a mix than other models--the 12z run would bring a mostly freezing rain type event to the Philly metro, with up to 0.5" of freezing rain forecast to potentially fall by 00z Thurs. Pulling up a sounding, this is due to WAA between 850 and 700mb. In fact, the NAM actually suggests that the surface temps will be colder than other models suggest--but is so aggressive with the mid-level conveyor belt WAA that it makes much of the event FZRA. I agree with earlier analysis suggesting the NAM is too amplified. EPS vs GEFS--> EPS slightly closer to coast. Edit: NAM time stamp.