Moderately Unstable

I was wondering how long the pds on that was going to take.

Watching that one. I always focus on the lonely duckling away from all the other storms. It's in a good spot.

Okay I was gonna say ...holy gradient batman! We've done well but in line with expectations as best I can tell haha. I consider that a win given how tough this forecast has been. Well, that's impressive and qualifies, but not "Philly". If you hear someone say Philly got X, people think center city+ 5 miles. Higher elevations N&W often do better so while notable Philly folks wouldn't empathize with the sensible weather in Conshy (in this type of setup).

Honestly despite the modeling flaws and the forecast complexity I've been pleasantly surprised by how this event is going. We came in expecting a super messy setup and it has been. Depends where in Philly. My staff in Fairmount report around 4". Here at city ave we got around 5" rather quickly (as expected) and now over to sig sleet. If someone got a golden shovel foot mazeltov to them. Where are the reports of 1 foot?

Mount Holly's writeup also mentioned the sun angle, so it isn't just Glenn. Here's the website I use (both for meteo and other pursuits) plotting solar azimuth for basically any location on earth on any given day (but here linked to Philly): https://www.timeanddate.com/sun/usa/philadelphia. We're up to 38.7 degrees tomorrow at 12:14pm, vs Decem when our angle maxes in the upper 26 degree range. We're heading into the part of the year where the sun angle, day length delta (etc) are all rising rapidly day-to-day. I don't think it matters much for "the thump" but it matters later in the day--so it isn't just cya messaging. They're not wrong. Fun fact: 50 degrees of azimuth is about what you need for UV-B light to reach the surface, and thus, for your skin to produce vitamin D.

Well, of course surface temps are going to be a bit colder. But the thing is, with the track of this system and the LLJ orientation, the sleet line will probably move SW to NE, not S to N. So at least from a timing standpoint...you're not going to stay snow much longer than Philly. A bigger delineator of time would be drawing lines W-E, or ideally NE to SW as I said above. However, I think FZRA is less of an issue for you...so you'll see sleet longer, and may actually get through the entire event without any change to FZRA. From a totals standpoint, since most of the accumulations being progged are based on the front end, I think you might be a touch higher than Philly...so instead of 4-7 I'd say perhaps 5-8 for you guys particularly given the lack of fzra. Ok that's the end of my point-forecasting for now, I have to go back to work hahahaha.

It's aggressive on the changeover...it blasts us with WAA in the mid levels as the coastal approaches. The 12z run held us in the snow camp a bit longer than the 15z run...but on the order of 30 minutes: 1800 vs 1830z. I do very much think FZRA will be a bigger deal--I agree on the impacts...BUT that sort of also depends on the time of day it's falling. Messy-yes, but at 30/31 degrees in the late afternoon it won't be as bad as if it fell overnight with temps in the 20s. If you compare the SREF probabilities for us for ptypes... https://www.spc.noaa.gov/exper/sref/srefplumes/ Or you look at the HREF's probabilities for heavy snow, fzra etc: https://www.spc.noaa.gov/exper/href/?model=href&product=snowfall_001h_prob01&sector=conus And for me combined with the RPM, GRAF, and other guidance...it's really all different flavors of the same thing that we are being told. We know that models have had a cold bias this season, and it would be quite hard to believe in this setup, with the position of the coastal and the 850....that this isn't a "mess" type of event. That doesn't mean the front end won't be fun though. I don't necessarily think we'll see a quarter inch of ice, but looking back at the history this season when it comes to mid level warmth, my money would be on the warmth winning relative to expectations.

At the moment, my thinking is the Philly area sees 1-2" rates between 10AM-1PM. We may pick up 1-2 inches before that time but that's really the "main" period I'm focused on. As we head into the mid afternoon sleet becomes much more likely.

My current call for the city is 4-7", including a fair amount of sleet, and .1-.2" of ice. This is based on a blend of the RPM and other model guidance (and history of model performance this season wrt mid level warmth). I don't buy all snow. RPM does show a consistent change to sleet and then FZRA on every run. How much the snow total ends up being hinges on how fast mid level warm air comes in...but we will enjoy at least a couple hours of good rates. And I will abs take that.

It is an in house model. It's WSI's (the weather channel's parents') internal convection allowing high resolution model. They're also, fun fact, the one's developing deep thunder (aka graf)--which once operational will use a 15km grid, BUT, will have a 1 way 3 km upscaling in the conus--which they are suggesting will let them do away with convective parameterization (so that they can actually model individual thunderstorm cells). One way because those 3km cells won't then feed back out to the larger domain. Basically the small cells get initialized by the boundary conditions of the larger domain (15km), then, operate independently. Now, if they're successful--this would be fantastic for mesoscale forecasting because it could (theoretically) enable one to almost predict in advance which cells would have sustained rotation with high accuracy and locational precision (SPC and NSSL toolsets allow for meso tracking already but it's more of a general "idea" than precise here at this time type of data...even though the output simulated radar sorta acts as though that isn't the case). But color me skeptical. They're working with IBM on this--I believe with a machine learning type of approach...in any case from what I've seen of the large domain GRAF so far, looks promising. Neither is available to the public (frankly it isn't even available to everyone in the private sector), and they're EXTREMELY protective of access to it, which is why I don't post the maps here. You can get in some actual trouble doing that. Like any model, it's guidance. But for whatever reason, it really is "worth" WSI's protectiveness...it's good. I've used it to chase individual thunderstorms before by using it to time out to a half hour interval where a particular cell would be and where. For mesoscale enhanced setups like this one, it tends to do a good job. WRT the || Euro, keeping up to speed on the rapid-fire-changes of the operational and ensemble guidance while checking model verification and current obs, and doing my day job...haven't had time to look at that today haha. Link?

I love a good finale, don't you? 00z RPM keeps the trend of the 18z and 21z runs....corridor mostly snow, gives 12-16 widespread totals. Places like BAL & IAD are modeled at between 20-24" (outside of our domain but notable). Gotta keep watching this though. There's a sweet spot here for the track of the sfc and 850 low centers. The models have hit that place now. My internal sense here is, the whole 12+" thing...we've been down this road many times. Models a couple days out provide clown like totals. I think we're reaching consensus now that impacts are going to be enough here--in the form of snow--to most likely at some point down the road req a WSW for the corridor and areas NW. Exactly what the totals are...probably too soon to say, but I sure do love the 00z runs coming in now. If I were a TV met this is when I'd start talking more substantively about the "potential".

I was so close to saying something in the 18z time frame...the rpm and graf both supported an insane overrunning banding setup. Clown totals for the corridor and nw, hellish gradient though. They were supportive of 12+ as well on the corridor...down to nothing SE of around Lindenwold. I considered that a good sign bc in earlier storms the rpm picked up on warmth earlier than the globals. That it hasn't here is good. I want to see the full 00z suite before I make further comments. You could tell at 18 from the 3k that the 12km was too amped. Fwiw iirc the 21z rpm had a stripe of 20" totals in the harr ne towards the LV area. I am super hesistant to invest this season given the model insanity but I like this setup. I'm much more bullish about this than I was about the weekend or today. Objectively, not as a weenie--we have good odds here. Buckle up folks.

Sleeper event wrt wkend storm. I told my friend who was supposed to visit this weekend to reschedule. RPM suggests there could be problems and I buy it. Don't think it'll be major, but .1" seems likely...I'd give it 70% odds. With cold sfc temps, that as iceman correctly notes have been cold for awhile, and existing snowpack, this is bad news. You don't need much freezing rain to make travel dangerous. The most deadly winter wx events are the minor ones. Advisory snows etc. People tend to go faster and pay less attention, encounter slick spots they don't see, and then, wham. Bigger events generally cause more people to hunker down and stay home. You don't need 1994 to make for a bad day.

I get a kick out of this forum hahaha. RPM has trended N. Gives the corridor marginal warning level snow. See if that holds. Have been busy w scholastic stuff this week so I haven't followed this one to closely. That said I think a good rule of thumb with the currebt pattern is..if a model shows a medium range hit, ignore. If a model shows a lr hit, pay attention. For a given sfc low, expect a South bias. If a model says big hit, prolly a small hit. Model says small hit, get big hit. A lot of mets suspect lack of airplane data is hurting models. This winter has been interesting in that the model biases have been glaring and obvious. Would be a good year to use if teaching a fcsting class and wanted to give model bias examples. Not subtle. Wrt watch advisory warning...it wouldn't make sense to issue a watch (imho). A watch is a timing issue. A storm is expected to occur, but not certain yet, couple days away. Same as other nws watch types. Bc they've issued an advisory step one would be ammending advisory to mention high end potential. If model and nowcast trends this pm suggest warning crtieria are more likely they would prolly then upgrade to WSW. If you took curr guidance verbatim it would qualify as a wsw in spots. Since models are not infallable, may see later tnght. Folks have already noted earlier precip onset vs short range models. Ratios will work in our favor. (I'm partly joking on the long range vs medium range remark but gosh does it feel that way!).

La niña who?

Hi. Philly guy here. We have more than 0. I don't provide storm updates on here bc I live in a high rise building and have no place to put a snow board. I am 3 NW of CC. We had heavy, 1.5-2" snow rates for an hour or so while a band translated through..around 15 mins of which I'd characterize with the charming euphamism of "puking snow" (note: if that happens to you, see your doctor). Was very fun to watch. My place looks out over Fairmount park. The trees and surfaces have a solid few inches. I can't say exactly how the roads are as I haven't been out but I expect looking out that at least 3" has fallen on grassy surfaces and previously snow covered surfaces at least where I'm at. It is still snowing lightly now. Temps have been 32-34 the last few hours so I'd be very unsurprised if roads are just wet in the lower elevation areas. I'll take it.

First off, *congratulations*. Getting into a post bach meteo program isn't easy, and securing funding isn't a guarantee. I'll give you my two cents. Unlike in ugrad, grad school is all about your advisory-professor and how well you can fit into the program. I'm not the smartest person in the world, in fact I was often envious of my classmates for being so much faster than I was all the time! But I know how to communicate well, and I know how and where to get data. That is what you need to be successful. In stem you'll find many folks are great with numbers but can't speak or write to save their lives. Be a good communicator. Know how to explain what you do to others. Profs, potential employers etc. Where you go should depend on where you want to work. Choose a school where you can work with a prof that matches your specific interests. That's going to be important to keep you going when you're cranking out 16 hr days and yelling at code on your comp. Research the profs at MSU, see if they align with your goals. Read their papers. Write down intelligent questions, and then email those profs and ask them about those papers. If the convo goes well, ask them about your concerns. You're going to be there, you've been accepted, they won't kick you out for asking. When you go apply for a job--at noaa or wherever, your hiring manager will want to know about your research. What you did, why you did it, what you learned. Where you went to school comes up low on the list, same deal with course grades. They matter-- but they aren't what your hiring manager cares about. They do care that what you studied and know how to do matches their job needs though. I cannot stress enough that it isn't like ugrad. Realize that as a masters student, you are considered a professional student. As such, it isn't about prestige...it's about what YOU do, and how. You're in the driver's seat. You get to decide what you learn and what you put into the world. Choose the school that let's you do what you want to do. MU

I mean, as I said last night in reply to Ralph's post asking if anyone thought there was room to bust...I'll repeat, there is. That said, for a modest event like this, really the absolute lowest snow amount that qualifies for a WSW (5"): https://www.weather.gov/phi/WinterWx (Note-- above map is for a *12* hour event)...your low end estimate is going to be low somewhat often. It's unlikely the region on the whole sees <1". It is quite possible we end up with more spots getting advisory level snow totals though than warning. This will be a dynamics battle: cooling from the strong fgen, versus marginal bl temps and an eh airmass. Round 1, ding ding.

So, first, water vapor is actually a ghg, in the sense that it blocks outgoing lw radiation. In fact, water vapor is our MOST important ghg. Look it up on Google. The reason we talk about CO2 & CH4 is because we produce those en masse and they have a long lifetime. The reason earth's avg temperature is 287 K instead of 255 isn't due to the lapse rate. The lapse rate defines how temperature changes but doesn't cause the changes. The dry adiabatic lapse rate is a conceptualized rate of temperature change in which heat is not added or released to an air parcel. Using the ideal gas law, changes to the parcel temperature depend on changes to volume and pressure. Convection, the process of warm air with higher internal energy rising, expanding, and cooling, is responsible for the dry adiabatic lapse rate. As air rises and expands, it does work (1st law of thermo), and cools as it loses internal energy U. The IGL has a different constant for dry air vs moist air which basically is to say, moist air has more interal energy and therefore requires a moist parcel do more work to cool, hence the lower moist adiabatic lr. Ok so onto the skew t. Earth's sfc T avg is 287.15 kelvins. For both of these measures it seems you are off mostly because of a calculation error. For the dry adiabat to me it looks like around -34, perhaps you followed the wrong line...the 30 degree line perhapsas that appears to intersect at -24? If you plug that in, we have a delta of 47 (14.15 sfc, ~-34 @5km). 47/5=9.6. Close enough to 9.8 that I expect the plot likely is showing a 9.8 lapse rate and I just can't see that fine grained of a resolution. Let me know if this helps.

This is an easy answer: yes, I am. Can't speak for others. The biggest thing I've learned being on amwx is that a large number of folks pile onto the extreme bandwagon whenever something is progged to happen. Tornadoes, winter storms, hurricanes. Then a couple runs look bad and everyone screams bloodly murder. Then, almost always, something between "nothing" and "the best possible scenario" happens, everyone vows to be more rational moving forwards, and then apparently get amnesia and repeat the process for the next storm. In this case, the basic facts are that the models have objectively been sh*t this winter when it comes to cold, particularly in the PBL. They have consistently, with every storm we've had, suggested a rain snow line farther S&E than what actually happened. This has happened the last several years more generally. In addition, the models clearly didn't have a great handle on this storm until recently. We all thought it was headed out to sea and needed to thread the needle. Welp, it looks like it threaded the needle...it hit the phase with the northern stream. But almost every run of every model so far has moved the sfc low further N. That trend has to stop, soon, or this WILL be an issue for a lot of folks...and I don't think the forum is appreciating that risk adequately. The RPM keeps trending farther N, last I checked it had the heaviest axis up in the LV with philly just getting a couple inches...and 0...nada near the shore. Frankly I think that's more likely than the opposite with a big blast along the corridor, due to the pattern, and the model trend. As of the 00z run, it is now also showing 0" in PHL, and an axis NE to SW near Allentown gets over a foot. Now, that's one model, and I have seen it be **spectacularly** wrong before. Sometimes it picks up on things earlier than other models though. So, carry on looking at the other models. Nevertheless, I'm nervous, that trend has to stop. Otherwise by 12z tomorrow the models will all be tucked in with it. At the end of the day, my objective sense is, this could bust entirely...we could get nothing, or, the rpm could cave and move back south. It's already too late in terms of messaging now if this busts. People expect 3-6. The weenie in me hopes for the best. The meteorologist in me has questions.

Insane omega values in that FGEN band on the 18z NAM (pull a forecast sounding in the 3+"/hr rate zone....). Also happens to maximize right in the optimal snow growth zone temperature-wise. That would be quite epic. It is notable that models are still oscillating a bit closer to the coast. Monitor that trend--too close and we have the classic "oops just the poconos" setup. W.r.t. precip types, Ralph is right I think w/95 being a dividing line. As such, I think the 6abc map, and many of the snowfall maps on the models, are a bit generous S of the city. Great dynamics only help if you've got sufficient cold air. Good positioning of the 850 mb low though. FWIW, latest 4km RPM has the dividing line smack dab across Philly and 95--almost to the mile. It does suggest that the corridor will be the locus of the fgen band for at least some period, and that some of that will be in the form of heavy snow. Towards the end of the event, heavy precip rates and less WAA as the low moves NE will likely push the snow line SE. On basis of this being a somewhat classical setup, I'm expecting 4-6 in the city and the 95 corridor, isolated areas of 8" where banding aligns with the best thermal profiles. On basis of the RPM, I think this will be a prototypical "nail biter" for city folks like me, as small deviations right now could really change this forecast and move the axis out to the N&W burbs, or even to C. NJ though I view that as less likely. That's probably the reason for the broad brush 3-6" abc call. Regardless, this doesn't look to be a 10:1 ratio snow..it'll be heavy and wet. If you look at the ratio estimates for this on the models, it's more 1:6,1:7...so even if you buy a more "snowy" solution from these models, you won't see those 10:1 ratio estimates verify.

Cool. Go design a better model then and give us your best accurate forecast for the next one.

Charming discussion. I feel I should chime in here. No forecaster--professional or amateur, would've predicted some of the totals we've seen today with this storm. Often, in complex setups that bust, we can look back and go, "ah, well really the signal was there in the form of {these models/the basic physics/some meteo concept}. None of that applied here. The models were unanimous: lots of snow. Maybe some mixing. Not tons. Not super far N. The physics backed that up--cold air mass in place. This afternoon's afd mentioned that the warm air was actually due to air coming in from the ORIGINAL low, e.g. over Ohio. Frankly none of us were paying attention to that, and neither were the models, or anyone else. But that isn't necessarily a fault. In cases where one model say snowtopia and the other says "oops all sleet!", you can castigate mets who go the weenie route. The thing with Miller B's is, we do have all these axioms...dry slot here, don't trust this, someone's getting shafted. That *isn't* actual meteo. That's how you justify to yourself why you feel cursed. Miller A and B storms are, scientifically, OBJECTIVELY, the Philly area's best chance for sig snow. The analogy of a car engine is correct: for many reasons, to get a good snow here, conditions need to align quite well. And with climate change, as we have seen, those opportunities are dropping. As I said a few days ago, I strongly believe climate change is affecting model performances for these events. If you can't correctly model incoming and outgoing radiant flux, you're going to screw up a lot of your secondary calculations. Weather models depend on, well, certain assumptions about our climate. If those assumptions are now even slightly off, we all know well enough how that translates via the butterfly effect (*cough 180 hour forecasts cough*). In 2009/2010, Miller B storms were what gave us those historic incredible snow totals. In 2016, a miller A hammered us. WE ARE NOT WRONG in expecting major Nor' Easters to produce snow for most of us, and it is NOT bad forecasting if that doesn't pan out. On average, if you assume big snow totals out of a miller B with arctic air in place, you will be right more than wrong. Forecasting is an art not just a science. Figuring out the low position down to the mile at a given hour in advance is very hard. Models do fairly well...within 10-20 miles. The problem here wasn't the coastal low's placement, it was warm air from the original low. Case and point, I, in CC phl, had to scrape 2" of sleet off my car today below the snow. That is about 6" of a 10:1 ratio snow, that we got 2" of instead. That'll do it. Now, here's another thing to realize. Snow is going away long term, for us due to climate change. Waive goodbye. So instead of feeling sad cause you didn't get 2 feet, be happy this isn't 2020 where we couldn't get an inch....heck, it's been 3 years since we had a significant storm that didn't TOTALLY bust (2018). As the planet warms, our local climate does too on average. We aren't gonna see the end of snow any time soon, but over time, average yearly snowfall around here will drop. We've already been seeing it to a degree. Shorter cold periods, 70s heatwaves in December. Less sustained cold. More mixed precip events perhaps (not sure there's a study on that but would be unsurprised if that finding held up). You tell me.... look back on your time in Philly and tell me winter today feels like it did 20, 30, 40 years ago (for those who were around here then). Yeah you can cherry pick a good year here or there, I mean on average. Is it any wonder then, that we bust so often, and miss out so often? We are in a La Nina this year as well. We were not expecting much in terms of snow. We've had 2 fairly-decent storms. We may see a couple more in Feb alone if we are lucky. We're doing quite well, relative to what a La Nina can do for us. I for one, am happy--I had an extra unplanned day off from work, I went for a walk and enjoyed the snow we DID get, and just appreciated the return of a feeling of winter and the happiness I saw on so many people's faces today (at least those that weren't driving). So instead of complaining things didn't work out exactly as planned, STOP. Sit. Breathe. Appreciate that we got some snow, that we have technology that remotely lets us predict the freaking future, and will probably still get a bit more tomorrow. You're (probably) not going to die tomorrow...there will be MORE snow events to freak out over (and be disappointed by). If you truly want to see amazing snow without having to get everything perfect...do what professional chasers do...GO to IT. Figure out where it's gonna snow crazily, book a trip, and go there. And finally, to those who DID get snow, don't be an ahole. Don't rub it in people's faces, don't say "I don't care about so and so region"...do you know how that makes people feel? Think about it a sec will ya? Angry. Sad. Upset. Stop it. Stop throwing out insensitive crap into the universe: it very, very clearly sucks enough these days as it is...so please, practice some freaking decency and kindness to others, and learn some empathy. We are all on this planet together, and most in this forum are quite close, at that. End rant.

Hope isn't TOTALLY lost. Radar shows right now that the winds still have a major easterly component. Not warm, but not cold. As the low tracks up NE, winds will assume a more classical NE flow regime...that should force the line south. Flakes starting to fall again now 3 NW of CC. Edit: now mostly snow.

Well, That's what happens when you encounter a dry slut.