RU848789

Thought folks would be interested in this; link and excerpt below. https://www.noaa.gov/news-release/us-supercomputers-for-weather-and-climate-forecasts-get-major-bump Enhanced computing and storage capacity will allow NOAA to deploy higher-resolution models to better capture small-scale features like severe thunderstorms, more realistic model physics to better capture the formation of clouds and precipitation, and a larger number of individual model simulations to better quantify model certainty. The end result is even better forecasts and warnings to support public safety and the national economy. The new supercomputers will enable an upgrade to the U.S. Global Forecast System (GFS) this fall and the launch of a new hurricane forecast model called the Hurricane Analysis and Forecast System (HAFS), slated to be in operation for the 2023 hurricane season pending tests and evaluation.

I'm amazed nobody is talking about potential significant snowfall for the interior NE (Poconos, Catskills and interior NY/New England and possibly even far NWNJ and the Hudson Valley) on Monday night into Tuesday - and what might it take for some snow to reach all the way down to the 95 corridor...

Thought Mt. Holly's AFD was excellent. Going to be a wild day for you folks. Normally I'd be observing and posting non-stop, but it's time for a round of disc golf down here in Vero Beach (high near 80F today), then a trip to the casino to play poker with my dad. Will seriously miss not being there for this one. Enjoy, but stay safe! Area Forecast Discussion National Weather Service Mount Holly NJ 613 AM EST Sat Mar 12 2022 .SYNOPSIS... A strong low pressure system will affect the area today, bringing rain then snow, before strong northwest flow develops later today through Sunday. High pressure builds across the southeast states on Sunday, then offshore Sunday night. A weak frontal boundary is forecast to move across the area on Tuesday, before a coastal system passes near or south of the region late Wednesday into Thursday. && .NEAR TERM /THROUGH TONIGHT/... ...WINTER STORM TO AFFECT THE REGION TODAY... Steady precipitation is overspreading the region this morning as strengthening low pressure begins its trek up the East Coast. Widespread low clouds and some fog are also in place thanks to light southeasterly flow. Precipitation is falling as mainly rain for now, though surface observations indicate the approaching cold front has already moved into the Poconos and will continue to progress southeast, with rapid temperature drops and rain changing to snow occurring behind the front. The quick moving low to our southwest will continue to strengthen as it passes over or just east of the region today. Its intensification will be supported by a vigorous mid- level trough beginning to pivot to a more neutral orientation, as well as extremely strong upper jet dynamics which will easily allow the developing low to achieve bomb cyclone criteria by tonight. Regarding the local forecast, the main change overnight, while not a huge change, was a continuation of the trends from yesterday. The track of the low continues to push a little further east, resulting in a faster transition to snow for eastern Pennsylvania and northern New Jersey. This has resulted in higher snow totals nudging a little further southeast. With the eastward trend, QPF has decreased somewhat, especially to the northwest. As a result, snow totals in the Poconos did not increase, and the Lehigh Valley was also little changed. However, they did increase a little more noticeably over southeast PA and north-central NJ. The Winter Storm Warning was extended a little further southeast in PA, and Winter Weather Advisories were extended east of the Delaware River in southern New Jersey, and to Kent County, MD. Considered Warnings for Morris and Hunterdon NJ as well. Will hold off there for now but monitor trends for possible upgrade later. This will be an impactful event. Rain will steadily change to snow from northwest to southeast from soon after daybreak through early this afternoon. Snowfall rates around and locally above 1 inch per hour are likely in the warned area, and could briefly occur in the Advisory area also. This is supported by NBM and HREF 1 hr snow probabilities and strong fgen forcing which will be present. As winds increase (more on this below), blizzard-like conditions will occur for a time late this morning and early this afternoon over much of eastern Pennsylvania and northern New Jersey. Even along the I-95 corridor, this could be a rather impactful event even though snow totals will not be as high. A couple hours of snowfall rates of 0.5 to 1 inch per hour and gusty winds with blizzard-like conditions are likely for that corridor, including Philadelphia. Furthermore, this looks like a classic setup for a flash freeze, with temperatures plummeting below freezing while precipitation is still ongoing. Snowfall rates will taper off by mid afternoon, but light snow will continue and wet surfaces will continue to freeze as temperatures fall further, with flash freeze impacts extending potentially all the way to the coast. In terms of the wind, there may be a couple of main bursts. The first will be this afternoon and early this evening with the initial wind shift to northwest, subsequent pressure rises, and changing of precipitation to snow. This looks like a good bet to bring 40 to 45 mph gusts, locally higher, to much of the region during the afternoon and early evening. These winds could lead to areas of blowing snow and contribute to continued reduced visibilities well into the afternoon even as snowfall rates diminish.

Euro is now an actual snowstorm for the 95 corridor. Just arrived in FL to visit family, so I'll be pissed if I miss a good snowstorm, lol...

One thing to keep in mind with accumulations and melting, which we talk about every March, is that it's all about rates, where accumulation = snowfall rate - melting rate. And once one has a good enough snowfall rate to exceed the melting rate (which is obviously lower on grass than pavement) and accumulation begins, that snow on the ground is now at 32F, so the melting rate for subsequent snow falling on 32F snow goes down significantly, i.e., it's now only a function of melting from above 32F air temps and the impact of the indirect sunlight (where the melting rate due to the warm surface is no longer a factor). And if the snowfall rate is high enough it can overcome the melting rate even on pavement (the melting rate is probably around 1/2" per hour on pavement).

EE rule anyone? That's a lot of snow from pretty good models to completely ignore, although snow depth is less for each (as is Kuchera, given likely above 32F temps somewhere in the column, at least near/along 95). At the very least would be nice to get a few inches on the grass and have some snow during daylight hours to watch.

Along and near 95, like here in Metuchen, we were fortunate temps went above 32F from about 7-10 am (33-34F), allowing melting of the ice on paved surfaces (aided by the indirect sun), so my driveway/sidewalk and street in front of my house are now just wet, but temps have dropped back to 31-32F in the area and not much of the ice on the trees/cars melted, as per the pics. By my eyeball it looks like about 0.15-0.20" of ice accretion on branches (which probably was 1/4" at its worst). We had that on the paved surfaces this morning until at least 6 am when I fell asleep. Here are a couple of pics: a bush from my front yard showing the ice accretion and the view of the pond and trees across the street. Freezing rain is so dangerous, but you have to admit it's exquisitely beautiful to look at.

We've had freezing rain for the last few hours, but the precip has just let up quite a bit as a dry slot has hit most of CNJ/SNJ. Just looked closely at some small branches and I'd estimate between 0.10 and 0.15" of ice accretion. The freezing rain and the 1/4" or so of sleet that fell earlier have combined to make an icy/slushy mess on all surfaces. My driveway is extremely slippery as is the road in front of my house (very lightly traveled overnight) - watching some TV coverage and cams, the more heavily traveled major roads in the 95 corridorappear to be mostly wet but reports are that NW of here parts of roads like 78 and 287 are icier. It's still 31F here, but temps just SE of here in Old Bridge and Keyport are 33F so warmer air is finally getting down to the surface. I'd expect the 95 corridor to get above 32F by ~7 am, but it will take til mid-morning a bit NW of here. Time for some sleep...

Back to mostly freezing rain at 31F with a few sleet pellets mixed in. Wondering if that's it for the sleet or not here. Already have probably 0.05" of ice accretion on trees - easiest place to estimate that, since the sleet didn't accumulate on the branches. Very slick out right now.

It's pouring sleet out there right now - we got 1/4" of sleet in the last 30 minutes, which is 1.5" of snow equivalent per hour, roughly. Everything is covered and roads are very slick. Glad we're getting sleet and hopefully it'll be for awhile. Interestingly, the dual pol looks like the sleet shouldn't be falling here, but it is. 31F still. Fortunately, few people have to travel between now and 5-6 am, when I think we'll be above 32F along 95, allowing some melting to occur, although there will still likely be some slushy areas on the roads if temps don't go above 32F until 5-6 am (not everything melts magically at 33-34F, which is where it'll be through 8-9 am). Anywhere it's not above 32F by 7 am is going to be in for a real mess tomorrow morning, assuming we get several hours of at least moderate sleet and then freezing rain.

I've always thought the dual pol radar was the best one to differentiate sleet from other precip types I assume in the pic below that the yellows are the highly reflected signals from the ice pellets, while the "clear red" (south of 80 in NJ and extending W of Trenton in PA for a bit) is rain or freezing rain. I'm assuming there is no radar that can actually "detect" freezing rain (since rain and freezing rain are identical while falling) and that radars that show ZR are using some built in algorithm that knows the depth of the <32F layer at/near the surface. Is there a good "radar" that shows where the ZR is or should I just look to see where it's below 32F?

We're now getting moderate to heavy sleet here and it's down to 31F. Already a light accumulation on all surfaces, with my driveway/sidewalk and street in front of the house starting to get slick. No idea if we're going to get more sleet or ZR the next few hours, but it looks like it's going to get pretty dicey out there.

TWC is actually calling for 0.1-0.25" of ZR for most of the 95 corridor and 1/4-3/4" of ZR not far NW of 95 in eastern PA (mostly north of 276) and in NJ N of 202 - that may be overstated, but there are several models that are showing that right now, as others have posted - they typically don't overdo it on their forecasts (of course they hype what they think is going to happen, but they don't overdo what is going to happen) and I watch them pretty closely. That could be a major nightmare for overnight travel and could even lead to power outages. Hopefully, temps get above 32F anywhere near 95 by 5-6 am, limiting impact to just the overnight hours before rush hour, but the rush hour 10+ miles NW of 95 and especially N of 276 in PA and N of 202 in NJ/ will likely be impacted significantly with temps not going above 32F until mid morning for many.We have a mix of sleet and freezing rain here in Metuchen that just started getting heavier and we already have some ice on cars and trees, but not on paved surfaces yet, but that will likely occur soon with temps at 31-32F. Will be an interesting night that many won't see, lol.

Thanks!!

With temps below 32F before the event starts, for most (at least north of the Raritan/202), any snow/sleet that fall should accumulate, especially at night. Also, from an impact perspective, 1" of sleet has the same frozen mass as 3" of snow, meaning it will be just as hard to drive in (apart from not having visibility issues) and remove, so I would expect significant travel impacts for anywhere that gets at least 1" of sleet (and then maybe up to 0.1" of freezing rain) - and with temps for most of NYC metro not getting above 32F until 7-9 am, the rush hour could be impacted significantly.

Nope, I'll take a bit of snow, some sleet and a little ZR (which is much less impactful on top of snow/sleet) over rain any day...

For what it's worth, Lee Goldberg was just on and showing a futurecast that looked a lot like the GFS/NAM, i.e., a bit of snow (an inch or two for NYC), then a fair amount of sleet, then maybe a bit of ZR and then rain, but not rain until 8-9 am, which would mean a real mess on even NYC streets with temps around 32F and 1-2" of snow and 2-3" of sleet (which is 6-9" of snow equivalent) for 7-11" of snow equivalent, which makes sense as those two models are showing nearly 1" of LE by 7 am before any rain. I don't think anyone is thinking this storm will be as impactful as the GFS/NAM are showing right now for the immediate NYC/NENJ/LI area (and maybe even down into CNJ north of the Raritan/202, which would include me). Those Tidbits maps show a ton of sleet. And the CMC got "snowier" vs. 12Z, according to the Pivotal snow depth map, which I believe is mostly sleet and which I don't believe is at 3:1 ratios (maybe 5:1, since it's probably some snow and sleet); Tidbits doesn't show sleet as snow on the CMC. Hey @MGorse- you were very helpful answering my questions about how the NWS does take into account snow/liquid ratios in their snowfall forecasts a few weeks ago (as per internal calcs, not Kuchera), so thought I'd throw out another question. Does the NWS ever put out sleet accumulation forecasts or are they just folded into the snowfall forecasts at maybe 3:1 sleet:liquid ratios? I've never seen any, but maybe I've missed it. IMO, sleet is greatly underestimated by most with regard to impact, as 3" of sleet is roughly the same frozen mass as 10" of snow, both of which have about the same impact on driving (apart from visibility impacts) and snow removal - so it would be nice to have sleet maps or somehow factored in better in the snow maps. Thanks, in advance, for any insights.

Don't think I've ever missed any snow at any time of the day or night in at least 35 years, lol.

Euro jogs south a bit with the snow, but doesn't show much sleet (snow depth actually shows less than snowfall, which makes no sense).

Keep in mind (something I discuss in any setup where there could be sleet) there's quite a potential sleet signature, as per the GFS, especially, which is showing >6"+ of "10:1 ratio snow" most of which is really likely to be 3:1 ratio sleet, verbatim, looking at the Tidbits snowfall map. The Tidbits map counts all of the sleet as 10:1 snow, while the Tidbits and Pivotal snow depth maps seem like they are doing some combo of 10:1 snow and maybe 3-5:1 sleet, depending on location. It's impossible to tell exactly, which is why I often prefer the Tidbits snow/sleet map, all at 10:1, so I at least know one important thing and that is the mass of frozen precip (not including freezing rain) - as mass is a very important emergency planning number, as snow removal and driving (apart from visibility) impacts are most closely related to frozen mass, not depth. The NAM shows similar outcomes for the model outputs fro Pivotal and TT with regard to sleet/snow. I wish they would publish separate sleet maps (including the assumed ratio).

Don't think I posted in this thread earlier, but after thinking the snow was over around 5 pm with 3.25" OTG, it just kept snowing on and off, lightly, through much of the evening and we got another 1/4" of snow, for a total of 3.5" and 3.0-3.6" amounts were recorded very near to me (Parlin, Hopelawn, Carteret, South Plainfield, etc. (and most of these were from around 4-5 pm, before the last 1/4" fell). Nice storm, reasonably well forecast by the NWS with 1-3" amounts for most of SEPA/SNJ (S of 276/195) and 2-4" amounts for most of PA/NJ N of that line up to 78 (except only 1-2" at the coast) and 3-6" amounts for NWNJ and the Lehigh Valley (which were definitely well under-forecast). NYC/NENJ got 2-3" for the most part and LI got 3-5" (also under-forecast). 3.5" brings our seasonal total up to 18.75". NWS map of reports is below, but not a final map yet, as there are many incomplete reports in there and in the PNS lists. https://www.weather.gov/source/crh/snowmap.html?zoom=8&lat=39.58&lon=-74.98&hr=24

Well, it just kept snowing on and off, lightly, through much of the evening and we got another 1/4" of snow, for a total of 3.5" and 3.0-3.6" amounts were recorded very near to me (Parlin, Hopelawn, Carteret, South Plainfield, etc. (and most of these were from around 4-5 pm, before the last 1/4" fell). Nice storm, reasonably well forecast by the NWS with 1-3" amounts for most of SEPA/SNJ (S of 276/195) and 2-4" amounts for most of PA/NJ N of that line up to 78 (except only 1-2" at the coast) and 3-6" amounts for NWNJ and the Lehigh Valley (which were definitely well under-forecast). NYC/NENJ got 2-3" for the most part and LI got 3-5" (also under-forecast). 3.5" brings our seasonal total up to 18.75". NWS map of reports is below, but not a final map yet, as there are many incomplete reports in there and in the PNS lists. https://www.weather.gov/source/crh/snowmap.html?zoom=8&lat=39.58&lon=-74.98&hr=24

Not sure if you saw my recent post on Center City - haven't seen any reports from there, but 1-3" reports from Philly outside of CC - could see the UHI effect leading to CC being on the low side. Any intel?

Any reports from Center City Philly? Saw the outer parts of Philly got 1-3", but the airport only had 0.4", so wondering if that was just a measurement issue or was there really less in the most urban part of Philly. TIA. ...Philadelphia County... Chestnut Hill 3.2 in 0345 PM 02/13 Public Manayunk 2.8 in 0430 PM 02/13 Public Shawmont 2.0 in 1140 AM 02/13 Public Fox Chase 1.3 in 0800 AM 02/13 Trained Spotter Philadelphia International 0.4 in 0725 PM 02/13 ASOS

Always prefer night time snow, so there's much less chance of melting and you can see the snow all night if you just don't waste time sleeping. Plus, I really enjoy the late night Jeb-walks when there's not another soul in the world to disturb the perfect peace of a silent snowfall.