RCNYILWX

GFS performed best with the current setup, way north with the primary and better east for secondary, but it's been spotty at best otherwise (by far the worst for the big dog in the east). I'd say overall the modeling has been poor, it seems to struggle in fast flow patterns. Hopefully with the big time -NAO signal coming up that can help slow things down and improve the modeling. Sent from my SM-G965U using Tapatalk

Not gonna get sucked back in yet, but the 00z GEM came way back south on the 30th-31st, bringing warning level snows into northern IL, including QCA and much of the Chicago metro (which right there probably means it's wrong [emoji38]) except for the far south. We'll see if the UKMET and ECMWF shift at all tonight toward a more favorable evolution, like what the GEM depicted.

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

Aside from the derecho, which I say thankfully wasn't bad at all where l live, definitely a more boring year weather wise. Noteworthy events in the LOT CWA in chronological order: January 10-11 significant lakeshore flooding. The winter side of that system was a big old bust, but the lakeshore flood certainly wasn't, as it was the most significant episode since Halloween 2014 and perhaps since the February 1987 event. - April 7th wind blown sig severe hail in far northern Illinois, some up to 3" in diameter, which is really impressive for an April event. The event was also noteworthy for the SPC handling it quite poorly in the outlooks (removal of general thunder in the day 2 update from some of the areas that had sig severe hail yikes), while it was a pretty synoptically evident good early season severe setup for days. - May 14th and 17th flooding events in the metro. The 17th was the most widespread flash flooding in the metro I think since the April 2013 flood and locally the most sig flooding I had seen where I live in Naperville. We issued our first (and warranted) considerable tag FFW on the 17th. The footage of the Chicago River flooding in the South Loop in particular was pretty nuts. - June 9th Cristobal remnants, more for the novelty of that setup. - June 26th severe event, with some sig severe wind reports. It was actually a pretty respectably widespread event by recent standards and it and April 7th are the most notable severe episodes of the year aside from August 10th. - June 27th flooding. A lot less fanfare than the May flooding because the rural southeast CWA was hardest hit, with actual observed rainfall of over 8" in southern Newton County and radar estimates up to 10". Had this rain occurred over the metro, we would've had a high end flash flood event. It was also my first issuance of a considerable tag FFW. - August 10th derecho and QLCS tornado outbreak, with the strongest tornado in the Chicago city limits since 1976. - Persistent summer warmth, including Chicago setting its warmest summer on record. It loses significance for me because we believe the ORD ASOS site has been affected by local construction to skew temps warmer there, including August being first summer month in our entire dataset in which ORD finished warmer than MDW. Summer 2012 stands out as much more noteworthy and memorable than summer 2020. - November 3-10 warm wave. Up there with mid to late February 2017 as the most impressive stretch of out of season warmth in recent history aside from Morch 2012.

The GFS hasn't caved yet, but I would be surprised if it ends up being more correct on the setup. It's on its own with the early development of a deep surface low way up in the northern Plains from a completely different handling of the northeast Pac wave. Edit: Unfortunately, the 12z GEFS doesn't tell us much because it appears that ensemble remains too non-dispersive with the operational. Meanwhile, the GEM is pretty similar to its previous runs, just on the deeper more phased side of the spectrum, so in that sense would not be good for the LOT CWA but a good event in MN, northern IA and WI. The NAM at the end of the run looked interesting and pointed toward a phased solution, though caution advised in trying to extrapolate out from the end of NAM runs. Either way, it's certainly more in the Euro and GEM camp.

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.

I think there's a decent enough chance at this range to get some modest accums but certainly lean against the fun phased outcome from the 00z Euro two nights ago. Overall there's been a slight uptick in ensemble probabilities of light (1"+) accums. With the cold air mass coming in for Christmas, will take what we can get for the holiday mood and to get on the board if tomorrow morning doesn't produce measurable at ORD. Edit: Re. IWX's tweet, a little surprised at the 'significant rain and snow' wording because that would require the phased solution. Otherwise, best chance for a significant precip event looks to be in the eastern Lakes and points east, probably east of their CWA. Edit 2: Just saw 06z Euro, and it looked potentially more interesting extrapolating out from hour 90 than the 00z run ended up being. On the Euro ensemble though, currently very little member support for a heavy snow swath in the western and central sub, though a rough estimate is about half of members have light to moderate snow swaths nearby.

The GEM was much more 00z Euro-like but also emphasizes the thread the needle nature of the setup. The southern wave goes neutral to negative tilt on its own and the system takes off but cuts too far northwest, followed by full phasing of northern and southern waves. From a big picture perspective, it's a step in the right direction. Edit: The 12z GEFS was also another step in the right direction.

FWIW, the NAM wiped the floor with the current GFS from 84 hours out to verification on the east coast storm. Should keep an eye on how the parallel GFS is handling things because it performed much better than the operational with that system. Sent from my SM-G965U using Tapatalk

06z GEFS was a step in the right direction, pretty easy to see just by looking at height anomaly run to run comparison with the 00z. Sent from my SM-G965U using Tapatalk

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

Re. Euro op, the 00z run wasn't a huge difference from the 12z run conceptually, just shifted farther south with the surface low. Key thing is the wave rounding the trough being allowed to come up and have a chance to phase in with the northern wave. Member spread increased between the 00z and the 06z EPS, so we might be reshuffling the deck, and need to see the clustering lean more toward the southern solutions on the 12z run and the other ensemble systems as well moving forward. As is seemingly always the case, we have pieces of energy coming from two data sparse regions plus the reliance on a phase to play out in a way that results in a favorable outcome for our area. With the very mild air mass out ahead of the possible system and owing to this strong positive mid-level height anomalies to the east, we also can't rule out a farther northwest rainer cutter. I think chances of a decent event somewhere in the sub have increased a bit, but still need a lot to happen just right for the Chicago metro snow hole.

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