RU848789

This might count as rubbing it in, lol.

Any reports from Philly, proper, yet? Haven't noticed any in this thread. Thanks.

Any snowfall reports from Philly? Heard it's snowing hard, as per the radar, but no idea if it's accumulating (a friend in center city said not on the streets yet, but that's not a surprise).

Looks like you will be right - just hoping, selfishly, that the Edison area at least gets in on some of it - starting to get a nice batch here with light to moderate snow again for the first time in a couple of hours and starting to accumulate at 33F.

Incoming! For 95 corridor in CNJ...

NWS updated discussion sounds like the inverted trough feature will be from SENJ to Philly and up to the Lehigh Valley, although they're not changing snowfall forecasts yet. National Weather Service Mount Holly NJ 639 PM EST Fri Dec 20 2024 .NEAR TERM /THROUGH SATURDAY/... As of 635 PM, an upper air analysis showed a trough axis nearly over our area with strong vorticity advection moving through. This is helping to provide ample forcing for ascent and widespread precipitation across most of the area. It has been drier down in Delmarva but some radar returns continue to develop there. Much of the precipitation is in the form of snow as cooling continues to arrived from the west, although some lingering rain closest to the coast which should mix with and change to some snow at times. Snowfall amounts have been as high as 1 to nearly 2 inches in parts of the Lehigh Valley area so far. There is a weak surface trough from southeast New Jersey northwestward to near Philadelphia then into the Lehigh Valley. It is roughly in this zone where additional snow may become more focused through the overnight. Overall, no significant changes made to the forecast with this update.

Well, let's hope this thing backfills as forecast for the 95 corridor. All we need is 3-5 hours of 1/4-1/2" per hour decent snow at around 32F to get 1-2". Is that so much to ask for lol?

There's a reason he's 5-posted, I guess, lol. When the forecast is for about 1" and the uncertainty on that forecast is probably about +/-1", then one should expect 0-2", so 1/2" would be well within expectations. Funny how nobody says boo when there's a rain forecast for 0.1" and one only gets 0.05" - nobody freakin' notices.

just starting to accumulate a little bit on the colder surfaces here (on the car and the deck chairs, but not the deck yet). With the temp down to 33F and at least steady light snow, I think we'll start accumulating on all but paved surfaces soon.

Never measure on paved surfaces as they often retain too much heat and have some melting. That's why NOAA recommends a white snowboard (to minimize board heatup and melting from insolation) placed on the ground, away from obstructions, but if you don't have that, any colder surface will do (cartop, deck, or even grass, although grass can inflate amounts especially if the snow is fluffy). And one isn't supposed to measure more than 4X per 24 hours, but one should, if possible, measure after a precip change from snow to rain, before compaction/melting (also sleet counts, but again, clearing the board after a change from snow to sleet is ok and the two amounts are added; freezing rain should not be counted). https://theconversation.com/how-is-snowfall-measured-a-meteorologist-explains-how-volunteers-tally-up-winter-storms-175628

NWS updated their snowfall map for the region, extending the 1-2" swath through all of CNJ and NENJ and into NYC, with 2-3" still forecast along/N of 78 (and NW of 287), as the interaction between the clipper from the west and the bombing low well off the DelMarVa is expected to give most of us (except probably NYC eastward) a little bit more precip from this evening through about sunrise, with most of that being snow as temps drop to around 32F for folks along/near 95 by late evening, allowing accumulations, probably even on untreated roads in most locations. And Lee Goldberg also expanded his 1-3" swath to include all of CNJ (mostly 1-2" really), except areas east of the Parkway in Monmouth/Ocean and east of the NJTPK from about Carteret to the GWB, where he has about 1" or so and less for NYC/LI (due to less precip). Not a major snowstorm, but people should certainly be careful on the roads tonight and tomorrow morning, should we get forecasted snowfall amounts. Stiil snowing mostly lightly here with no more accumulation (maybe 0.1" so far), as temps are still 34F, but the sun is setting, so temps should drop towards 32F for the 95 corridor by 9-11 pm, allowing any snow to fall to accumulate after that, whereas accumulation will be more intensity dependent from now until then (and with light intensity, probably not much accumulation along/near 95 and SE of there until mid/late-evening). Would love to get at least 1" just because and an overperforming 2" would be amazing and possibly enough to last through Christmas Eve given how cold it will be until then.

Had occasional very light snow/rain mix from about 10 am to 2 pm with no accumulation at 36-37F, but we've had more light-to-moderate snow since then and temps are down to 34F and we're getting some stickage on cars/grass and I was even able to make a snowball, lol. Maybe 1/8" so far. I'm assuming this will continue without much accumulation until at least early evening when temps drop a bit more, plus there won't be any indirect sunlight impact (much less on the shortest day of the year, but not zero, especially with temps above 32F and lighter intensity). Sticking with my 1.25" snowfall guesstimate for the event.

Doubt very much that NYC gets shut out... less, maybe than other locations but not shut out.

We have almost the exact opposite of what we had ~24 hours ago with regard to the NBM, as it's showing <1" for just about all of CNJ/NENJ/NYC/LI, while every major global/CAM model so far (CMC, GFS, HRRR, NAM, RDPS, ICON and HRDPS) is showing 1-2" with 3" spots for just about everyone N of 276/195 in PA/NJ/NY. Last night we had much more snow on the NBM than shown on most of the major models. Going to be interesting to see what the NWS and others do with this info, especially if the Euro/UK are similar - my guess is the NWS will expand their 1-2" forecasts down to the 95 corridor in NJ/NY - we'll know soon.

Why are you only comparing through 4 am, when the snow isn't over until maybe 10 am or so? 18Z NAM is still less, but not as significantly so.

Euro looks nice and News12 is calling for 1-2" for most of cnj/nenj/NYC and 2-4" N and W of 287 (N of 78).

Surprised nobody mentioned the AFD from Mt. Holly discussing the possibility of an overperforming inverted trough... For now, the best chance of observing accumulating snow will be across the Lehigh Valley, northern New Jersey and in the Poconos where temperatures will be cooler through the duration of the event. Current forecast snow totals in these areas are for between 1-2", locally up to 3". Light accumulations of a dusting up to 1" are possible across the remainder of New Jersey, Pennsylvania and northern Delaware as rain transitions to snow on Friday night as temperatures cool below/near freezing. It should be noted though that these type of inverted trough setups are notoriously difficult to forecast as they can sometimes have localized heavier precipitation amounts. If this occurs, some areas could "over perform" and see snowfall amounts as high as 4 or 5 inches. Best chances for this would be central into NW NJ, NE PA.

@wdrag- for this event, the NBM has consistently shown higher snowfall amounts than all of the major models that most people look at regularly at places like Pivotal and TT (i.e., the Euro, GFS, CMC, UK, NAM, RDPS, etc.) and a decent amount more than the NWS is predicting. I assume this means that the rest of the NBM models (there are many more as per the link below) are showing a decent amount more snowfall than the more commonly used models. I've also always wondered if the NBM model obtains inputs from other models earlier than the public does, since the NBM output is available well before most of the model outputs are available. Any insights on this (or from other folks who might know)? Thanks. https://www.weather.gov/news/200318-nbm32#:~:text=The National Weather Service (NWS,their analysis of the data.

The UK forecasts are out to 168 hours at 0/12Z (was 144 hours), but are only out to 66 hours for 6/18Z, which is better than no 6/18Z forecasts.

Sorry, can't imagine picking Peddlers Village over NYC, especially around the holidays, when NYC is so vibrant and full of beauty (and yes, crowded, but it's crowded because it's worth visiting - plenty of places off the beaten track to visit).

Squall was fun, if short-lived. It put down another 1/8" of snow, so we're up to 1/4" for the winter after last night's 1/8", lol. Threw my first snowball of the season. Another 240 of these and we'll get to ~30" of snow for the winter...

Interesting, given the hype about the AI forecasting from Google, which they just published in Nature yesterday. The performance looks impressive, but I'm certainly not using it to make forecasts and you obviously have evaluated it directly. I wonder what the difference is between what they've published and the "real world" performance. https://arstechnica.com/science/2024/12/googles-deepmind-tackles-weather-forecasting-with-great-performance/ https://www.nature.com/articles/s41586-024-08252-9

We have a legitimate light dusting on cartops and grass now - maybe a whole 1/8"!!

Have the slightest of dustings on a few cold spots; perhaps they'll close the schools, lol (for years I gave the Metuchen schools superintendent detailed weather info they used to help make such decisions).

Can you comment on whether the ECMWF AI model one sees in the model sites, like Pivotal (ECMWF-AIFS, for AI-enhanced deterministic global forecast) is the Google DeepMind GraphCast model referred to in the article below about AI and weather forecasting? The quote in one of the embedded tweets in the link below says, "The Google DeepMind GraphCast model is available on the ECMWF platform. It's open-source and can predict weather conditions 10 days in advance with better accuracy than current methods." If so, certainly the article below is at odds with your commentary on their accuracy. https://www.weforum.org/stories/2023/12/ai-weather-forecasting-climate-crisis/