RCNYILWX

As others have mentioned in January thread, tonight looks good for a solid fairly short- lived burst of snow. Nice mid-level lapse rate (>7C/km) plume advecting northward over the mini trowal across northeast and central IL and northwest Indiana. One of these similar setups last winter produced a localized swath of 3-4". I think 1-2" amounts will be common for all but the northern tier, with spots of 2-3". Can't rule out a very localized 3"+ given the nature of these potent little waves with good lapse rates.

Enjoy your 1-3"

If the ECMWF weeklies are on the right track, you can toss that CFS January prog as far as you can throw it. Here's a loop of the weeklies put together by a frequent poster on the New England sub: Because there were very valid fears about a warm outcome this winter and we see already how mild December was, the increasingly likely development of major high latitude blocking in the Arctic and Atlantic can only be a good thing. We take and hope more of the subforum can benefit this month and likely beyond. Can probably also include this in the medium-long range thread. PS: Happy New Year to all! Here's to a snowy next couple months and eventually better things to come in 2021 than what 2020 gave us.

Link to a loop of the ECMWF weeklies run last night for the 00z/28 cycle: https://33andrain.s3.amazonaws.com/monthly_2020_12/ecmwf-weeklies-avg-nhemi-z500_anom_7day-1609113600-1609718400-1613088000-20.gif.64969e182ab9478fa5381e7fe5f284d5.gif Not sure if it'll work. Tried to post the .gif but file size is too big. In sum, the ++EPO Pac puke dominated start to January goes over to an Atlantic and Arctic blocking dominated pattern. The latter portions of recent ensemble runs also going to that sort of look. Been a lot of discussion on SSW likelihood into January. Certainly don't want to hype it like it often gets, but long range experts are saying there's good precursors going on near Siberia to favor the occurrence. If so, the tendency for -AO/-NAO that's been there could further deepen and point toward a colder outcome than expected from mid January or thereabouts and probably into Feb. If a major anomalous blocking episode develops, they tend to stick around for quite a while. For most recent met winters that had deep Arctic and Atlantic blocking in the heart of the winter, have to go all the way back to 2009-10 and 2010-11. The 09-10 block lasted all the way through Feb and into March, but the 10-11 block collapsed in early Feb (and probably helped those of us who cashed in on GHD I). After a mild start to January, things "could* turn more interesting if we get cooperation from the Pacific. We'll see how things play out as we get closer to that period. Sent from my SM-G965U using Tapatalk

That pattern could produce snow events because of the assistance of the strong -NAO to modulate the +EPO some. It's certainly not a cold pattern. I'm not on the optimism train, just saying that's not a lock to be snowless like this month has been. The 850 mb positive anomalies are not obscene and the mean 850 mb 0C line is near or south of I-70. If we get a lower amplitude wave, could snow here with that. Sent from my SM-G965U using Tapatalk

Even though it was warmer than normal, January 2012 happened to be the best month of that winter, two decent storms and the only AN snow month of the cool season. The second event in January 2012 had nice high ratio fluff with the longest duration of 1/4 mile visibility in snow at ORD and MDW since GHD I and caused nightmare travel on a Friday afternoon commute. Sent from my SM-G965U using Tapatalk

Not at the office so I'm not sure what went on with that. Seems like there's another chance to get on the board tonight if any of the occasional more robust snow showers move over ORD. This holiday mood dust is better than nothing. Did a lights tour around Naperville and the snow falling made for a nice vibe. Sent from my SM-G965U using Tapatalk

Both winter 2009-10 and 2010-11 had deeply -NAOs, 09-10 pretty much wire to wire, and were good winters for Chicago. The blocking in 2011 eroded in time for GHD I. That's not a statement about how things may go here the next few weeks, but just a note to point out a -NAO can be good here. With respect to moving forward, the ensembles also show a +EPO look with the big NAO block (backed up by the forecast teleconnection indices), so that could help prevent it from being more torchy and *maybe* assist in keeping some systems farther south. The deep blocking may come too late to help us next week though.

Certainly could, as the passage of the vort will be accompanied by a reinforcing surge of cold advection. At least according to the NAM depiction, with the lake effect + synoptic enhancement could see squally type stuff swing out your way during the day on Friday. Sent from my SM-G965U using Tapatalk

I had noticed the 12z RGEM brought in some light (around 1") accums to parts of northern IL late Thursday night into Friday morning. The models have been very consistent in a strong 700 mb vort wrapping around the stacked upper low, but main question has appeared to be available moisture. Tonight's 00z NAM showing some light QPF with this feature, so things might be trending toward getting a DAB+ down for Christmas morning. Sent from my SM-G965U using Tapatalk

Glass half empty view... It just doesn't want to snow here and we're a lock for BN snowfall. This week is very frustrating. Aside from a few model runs that drew everyone in, was never really that excited about big snow for the Christmas Eve threat, just as something thread the needle that could work out if everything came together right. Figured that we could meh our way to an inch or two but that's seemingly impossible now. Even the clipper warm advection wing this morning was a total fail. Glass half full view... Still have plenty of time left and that example of 1998-99 and a few other examples on Hoosier's list. 2012-13 was an interesting one too, because we had several near misses that winter that could've resulted in a much different outcome. The northern tier counties actually ended up rallying for a well AN snowfall winter. Another example not on Hoosier's list: 2014-15. November was cold and had some snow but only a T in December, tied with 2 other winters for least snowy December. Seemed like getting to AN that year was less likely but of course GHD II happened. Ya never know. Sent from my SM-G965U using Tapatalk

IDK, I'm not trying to be overly optimistic, but I don't think the most recent Euro weeklies and GEFS extended (I don't really look at the CFS and it's probably getting discontinued anyway at some point) look terrible for January. It appears the EPO will average positive but it doesn't look to be due to a black hole over Alaska but northeastern Pacific and northwestern North America troughing that's pretty common in La Nina's. The -NAO signal is still there to mute heights some in the east. If there's enough dateline ridging (-WPO) and a huge vortex doesn't set up over AK, that typically provides good cold air discharge that can bleed from western and central Canada into the northern Plains and northern Lakes. I see there being opportunities and probably averaging near to above normal temps but potential for some decent cold shots assuming cold does build into the Plains. Don't get me wrong, it's not screaming great pattern or anything, but it looks more serviceable than the dumpster fire that has been December, except for a few lucky spots.

Those coarse resolution CFS maps don't make any sense. Even if you account for background climate signals, there's no mid and upper pattern configuration that would torch the entire continent. If Alaska is torching that extreme, then there's gonna be a trough over at least the eastern half of North America. If a good chunk of the CONUS is torching, Alaska will be cold due to ++EPO from the TPV parking nearby, like in 2011-12.

Need this post on the potential event thread. Sent from my SM-G965U using Tapatalk

Added more stronger SLP members farther south than 18z EPS so roughly 2 clusters within that increasingly large spread. The northern cluster is still favored slightly more, probably tied to the key question of the northern stream short-wave. Due to the difficulty of getting a proper phase like depicted on the 00z Euro and some of the EPS members, think it's a lower probability outcome but still worth tracking because it's all we got. Sent from my SM-G965U using Tapatalk

It remains a thread the needle setup. It's the old need a phase to work out sort of deal, which as we all know went great last winter. That said, the last two runs have had important changes toward increasing potential for a solid event. Most importantly, the northern stream wave is slower and not as strong, which allows the southern stream wave to come up and eventually phase in. 00z EPS is rolling out, so we'll see shortly how much ensemble member support the operational has. Sent from my SM-G965U using Tapatalk

Euro showing the setup we need for Wednesday night into Thursday to work out. Long way to go but nice to see it on this run. Sent from my SM-G965U using Tapatalk

The IT side of the agency is a running joke. We always talk about what we should have but don't. When we got AWIPS2 5 years ago or whatever it was, it was okay for 2010. Anyone seen the Sportsmax skit from SNL? 'I have 500 sworn affidavits that our IT is the best in the world!' lol Sent from my SM-G965U using Tapatalk

The NWS way. And they didn't even put correlation coefficient on there, only the most useful dual pol product. Can't wait until the next new page comes out in 15 years. Sent from my SM-G965U using Tapatalk

Just one run but the 00z GFS is interesting for December 23rd. Shades of January 29, 2008 with a sharp Arctic front and rain to 1-3" of snow, wind, and a flash freeze. Would sign up for that. Sent from my SM-G965U using Tapatalk

Chicago hasn't had a 6"+ calendar day snowfall since 2/9/18. The last 6"+ snowstorm was 11/26-27/18. Was thinking about that in context of how NYC didn't get as much as some of the earlier model progs, but Central Park still got 10.5", which was their largest December storm since Boxing Day 2010. The last double digit snowfall at ORD was 11/20-21/15 and the last double digit snowfall during met winter was GHD II. Obviously major events are a lot less common out here than the east coast but we're seriously overdue. December has become a feast or famine month locally, mostly famine since 2010, with only 2010, 2013, and 2016 featuring above normal snow. The prior decade on the other hand had some very big Decembers (with also a few lean years), none more so than 2000. We won't be able to finalize what the December normal will be for the '90-'20 climate normal period until this month ends but prelim data is the December average/normal will drop to 7.5" from 8.2".

How was 95-96 in SE MI? That's the only recent low snowfall Nina that was colder than normal here. Even though Nina's don't have the reputation of big east coast winters, 95-96 is snowiest all time for NYC and 10-11 was on track to threaten that had it not stopped snowing in February. The ensembles continue with a not terrible look to close out 2020. Not cold, but not a blowtorch, and near average heading into the coldest time of the winter isn't a bad thing for snow prospects. Sent from my SM-G965U using Tapatalk

It's not the big storm we all want, but the Euro showing a decent Pac hybrid clipper on the 22nd into the 23rd and then a follow up weaker wave into the morning of the 24th not far from here keeps some hope alive of getting snow cover down for Christmas. The ensembles also have a decent look toward the end of the run with a -EPO, -PNA, -NAO, -AO. May make for an active and not too mild stretch into January if that comes to fruition. Sent from my SM-G965U using Tapatalk

Not gonna pretend that I'm optimistic for next week. It looks as usual too progressive on the operational modeling in that timeframe. The trend on the EPS last 2 runs to become much more northern stream dominant, which was the more likely outcome anyway, really diminishes the chances for anything to work out for us out here. All I can say is that it's far enough out for changes to occur from the current look. The cold looks like it'll be legit not very modified Arctic air, so all we can do at this point is hope that somehow we can get some snow down for what looks like it could be a very cold Christmas period. CAD for Christmas would certainly be a nice cherry on top of 2020 lol.

Plot twist, Alek's backyard as the snow capital of the Chicago metro. Edit: In all seriousness though, the LES parameters aren't terrible tomorrow from a thermodynamics perspective and duration as well. When I looked yesterday, lake induced ELs were peaking on the forecast soundings at 6k-7k feet, which is a bit better than marginal. The problem is the possibility as partial ice loss as we lose saturation in a portion of the DGZ. Overall DGZ saturation won't be great and lift peaks below it, so flake size should be pixies. Hoping the FZDZ monster is avoided.