RCNYILWX

Feeling increasingly confident we'll need to issue our first SQW for this. It's won't be a squall technically to state the obvious but it will behave like one. Maybe we can consider pulling trigger on extending WWA for greater awareness and then target SQWs for the actual event. I'll mention this to my mid partner. Sent from my SM-G965U using Tapatalk

Top 5 most interesting event of the winter if it pans out lol Sent from my SM-G965U using Tapatalk

While tomorrow won't be the warning criteria event that everyone is craving in northern IL, it could be interesting for a few hours. Very steep lapse rates above 600 mb, possibly some small MUCAPE, and transient strong f-gen may yield convective snow rates in the quick moving WAA shield. Wouldn't be completely surprised if TSSN happened somewhere. The 12z CAMs all hint at this, but most notably the 12z HRRR, which has a wall of 40+ dBZ reflectivity. Duration will the biggest limiting factor, as these potential heavy rates may only last an hour or two, maybe a bit longer far north. I'm not saying tomorrow will, but sometimes these setups can overperform locally if you really max out the heavy rates for that 2-3 hour window. One such recent setup that comes to mind is February 17, 2018 (2-3", locally 4" in 3-4 hours with marginal surface temps). Throw in the gusty south winds and conditions could be legit for a couple hours, with a bonus that if it happens it'll be during the daytime. If something like the 12z HRRR pans out, might be worthy of snow squall warning consideration.

I think the NAM continues to struggle with dry air it thinks will be there and probably won't be and therefore saturates later and limits the duration of the snow. Still gonna be a quick hitter but losing a few hours in the morning matters. That said, the UKMET shifted north a bit though still has about 0.2" liquid equivalent over northern Illinois so pretty much in line with consensus. Sent from my SM-G965U using Tapatalk

Snow Squall Warnings have a wind criteria as well so this morning's situation didn't really fit that. The lake effect the past few days had pretty low predictability. Probably in an ideal world a WWA would have been issued in advance but having been on the shift last night I can say there wasn't enough confidence for that. And then once it's happening, there's not much that can be done. We did issue a SPS and hit it in a graphical nowcast.

Bust low or high? Overnight trends were good for you to nail your call and possibly bust a bit low. Sent from my SM-G965U using Tapatalk

Sometimes the WAA wing in these setups can produce a short period of nice rates. Sent from my SM-G965U using Tapatalk

I looked at that in more depth this evening. Not sure how reliable the new GFS is for LE and lake effect is very fickle anyway, but what the 00z run showed is quite impressive for Chicago and eventually Lake IN. Strong low level omega with a crosshair through the DGZ and strong low level convergence. Also good thermodynamics with 850 to lake delta Ts around 14-15C, equilibrium levels (lake induced inversion heights) climbing to almost 9kft, and 200-300 j/kg of lake induced CAPE. Those sort of parameters if they were to materialize would support moderate to heavy snow Thursday evening and overnight and headline worthy on its own. While some of the globals have been keying on that timeframe, the NAMs are not as excited yet, as they bring in drier air quicker and much faster to lose the low level wind convergence. The upper trough takes its sweet time to finally cross the area, so that's a favorable factor as things stand now, having large scale lift in addition to the lake induced lift.

Agree that 4" still in reach for you. You may get into the evening banding and signal for lake effect/lake enhancement still looks pretty good. Our dayshift didn't make huge changes to the previous forecast considering the uncertainty and also WPC went pretty bullish. For our graphic for the storm, it's tough, with several models except 18z GFS and 21z RAP showing a sharp cutoff on north edge of evening f-gen band, opted to focus on that and then mention the additional 1-3 psbl the rest of Thursday. I still think 2-4" is attainable here in the southwest suburbs to the Chicago shore but we'll probably be riding the edge. Sent from my SM-G965U using Tapatalk

17:1 is likely too high as an average but 10:1 is too low, probably near or slightly above climo average is the way to go. So let's say an average of 13 or 14 to 1. Sent from my SM-G965U using Tapatalk

The Euro was consistently one of the best solutions for the Chicago metro until the 12z run. It was the GFS and NAM that were well southeast until yesterday and last night and now the 12z runs are the most amped. How the models turn lol. Sent from my SM-G965U using Tapatalk

Here's the event total Kuchera, with some lake effect/enhancement on back side of low pressure Thursday night into early Friday added in. Definitely not what we wanted to see today but hopefully it doesn't trend any worse.

Unfortunately, wouldn't say confidence in the outcome has increased today for the LOT CWA. While the NAM and GFS were good, and 3km NAM was decent, other models backed off/shifted southeast with snow swath, most notably UKMET and GEFS. Hopefully the 12z Euro doesn't follow the trends of the other guidance since it's overall been most consistent with this set-up.

Ladies and gentlemen...the GFS

Definitely an interesting evolution on that run of the Euro. Main trough hanging back is to our benefit here as it goes negative tilt and closes off but much colder aloft by then. So well developed deformation axis snows happen Thursday afternoon and night into Friday displaced well west of what becomes main surface low. An initial strong surface low with good track Wednesday night into southern IN has less cold sector precip than you'd think just by looking at MSLP prog, because of trough hanging back, so you're just in broad southwest mid and upper flow at that point. The secondary low then tracks over TN valley gets captured by the closing off ULL and bombs to low 970s over Lake Huron late Thursday night. Hopefully this general idea has some support from the 00z Euro ensemble. Still so far out but the good news is that the better performing models (Euro and UKMET) have a good event with this set-up in the 00z cycle. It's such a complex pattern to nail with once again tons of convection likely in the warm sector like Jan 10-11 so it's gonna take time to sort this all out.

Certainly too far out still to feel comfortable but I like that the EPS hasn't lost the general look it's shown over the past several days, which continued with the 00z run tonight. The EPS has definitely performed the best out of the ensembles this winter, so that alone gives a reason for cautious optimism. We're going to have well above normal temperatures for DJF no matter what but the bottom line is getting a good region wide event and hopefully more than 1 to help salvage the season. We can do that if the pattern look that's been shown doesn't trend substantially worse and things break right on the evolution of individual synoptic waves. Sent from my SM-G965U using Tapatalk

ECMWF ensemble took a small step back with 00z run last night but today's 12z run went back to a nice west based -EPO with southeast ridging setting up that gradient pattern you mentioned. The run total mean and member snowfall outputs from both EPS and GEFS are really impressive (and something we haven't seen since last winter) and strongly suggestive of the active wintry pattern that could set up starting with whatever happens Tuesday onward through mid February. Definitely shades of Feb 2019 in the medium to long range on the ensembles. If we can keep the storm track a bit more muted than last year, then more of us could cash in than last year when it was mostly IA, WI, MN and northern MI that were hammered, while we dealt with mixing issues and several icing events in northern IL, IN and southern MI. Need to see that -EPO lock in as we get closer to feel more confident moving forward. Saw on another board that OHweather's company is going with AN snowfall for Feb for the upper Midwest and Great Lakes, so hopefully he chimes in here.

The upside with this setup is probably something like the I-70 event in December, shifted north. A nice pool of near or over 200% of normal pwats on the ensemble means and tight baroclinic zone could lead to a nice event somewhere. With the mild antecedent 850 mb temps, within LOT CWA will likely once again be rain/snow battleground assuming a decent system materializes. There may even be an ice to sleet risk zone as boundary layer cooling could bleed in prior to sufficient cooling aloft for snow as primary p-type. Sent from my SM-G965U using Tapatalk

Agree on the active look. The MJO trends indicate a likelihood of a -PNA and southeast ridging, also supported by the ens mean height anomalies. So hopefully we can get the -EPO that has been advertised in the medium-long range to keep the northern half or so of the sub on the good side of the thermal gradient. If it becomes yet another phantom -EPO, the background pattern would argue for a warmer risk, but still active and maybe enough cold air depending on storm track for parts of the northwestern sub to benefit. One thing is for sure, the AO and NAO will remain raging positive for the foreseeable future.

Also, all trolling aside, the GFS is and has been a disaster for this event. Most runs through at least yesterday had no snow anywhere with round 2 and 3, but yet it's already been a nice event for parts of the western sub. Regardless of what happened over the Chicago area, argument that the GFS would be wrong applied toward it having an unrealistic huge area of >0C at 925 mb, which clearly has been wrong. Sent from my SM-G965U using Tapatalk

12z EPS and GEFS snowfall mean

Tth bro...EPS >>> SREF Sent from my SM-G965U using Tapatalk

Yep quoted because figured you were thinking that same thing Sent from my SM-G965U using Tapatalk

January 2nd 2014 or the event later that month that slammed Cook and then especially northwest Lake County. Sent from my SM-G965U using Tapatalk

925 mb temp watch: 00z RAOB at OAX (Omaha, NE) Observed: -0.9C GFS: +1C ECMWF: 0C Sent from my SM-G965U using Tapatalk