RCNYILWX

Call it 4" here and just started snowing nicely again. Everything plastered, looks great and sledding should be prime for the kids over the next few days. Obviously wish we could've had more, but I'll take it. One of the red flags noted by some of the posters when this event started to change character was the main mid-level vort centers being pretty far north. That helps explain the most persistent mid-level f-gen banding setting up farther north. Fighting dry air at times didn't help either, without that we do a little better. Hopefully the lake enhancement and lake effect performs well the rest of day and tomorrow. Sent from my SM-G965U using Tapatalk

No to a slop fest here, maybe it ends as slop if we dry slot, though those details still too early, as we saw with how current event totally changed evolution from a few days before it. The non-GFS guidance is cold enough aloft for most of it. It's another beggars can't be choosers event lol. Without the Hudson Bay block, not a chance we'd get snow with that antecedent setup. Sent from my SM-G965U using Tapatalk

Ripping here in southeast Naperville. Huge flakes and legit +SN under this band. Calling it 2.9" now but we're stacking quickly. Just got home from the office, it was freezing drizzle/mist and snow grains when I left there, and the band suddenly blew up near Bolingbrook.

Filling in better now and maybe lake enhancement starting to kick in. Sent from my SM-G965U using Tapatalk

For everyone with RadarScope in LOT CWA, use tORD or tMDW Long Range Z while KLOT is down. Sent from my SM-G965U using Tapatalk

I think the convective bands lifting up from central IL should help with the snow rates from near here (LOT) and north once they get in. Starting with evening updates here. Edit: looking at SPC mesoanalysis, there's a relative minima in max 2-6km AGL lapse rates (6.5C/km) over NE IL with steeper lapse rates southwest of that (7.5 C/km) so we could be seeing the response to those lapse rates getting advected northeastward.

Did you check out your P&C? Our dayshift went big for Cook. Sent from my SM-G965U using Tapatalk

Maybe just give him his own thread to post maps all day? No one gives feedback on his posts anyway so he probably won't know the difference. Sent from my SM-G965U using Tapatalk

I think we need a board intervention. Sent from my SM-G965U using Tapatalk

The 12z GFS really likes the IL side LES and also gives@Hoosier some love. GFS v16 not quite as generous but still quite solid 3 day totals. Ratios should be pretty good in the LES phase. Sent from my SM-G965U using Tapatalk

I was at the office late last night and there wasn't a ton of time to refine the pure lake effect part of the forecast, though the forecaster handling it liked the setup. I see it as being distinctly possible with travel impacts into Wednesday. We'll see what the dayshift thinks today and I'll get to take a look at it this evening too. If there's long enough residence time, convergence and parameters look sufficient to get 2-3"+ totals, which is probably the bar we'd use vs SPS. Sent from my SM-G965U using Tapatalk

I'd be up for changing the name of the Medium Long Range thread to Spartman's Model Hub. Sent from my SM-G965U using Tapatalk

1-3/2-4 additional probably reasonable and anything more than that on the Illinois side of the lake is gravy. Sent from my SM-G965U using Tapatalk

Euro ticked back up for the main swath in northern IL as well vs. 18z run. Sent from my SM-G965U using Tapatalk

GEFS still nice for northern IL, so we have that going for us. I think the best way to look at this event now is one of managing expectations. A few days ago, it looked like it could be something special. Now it trended away from that but it still should be the single largest snow event for many of us in the metro in a while. Also the winds look like they will perform. The lake assist should be nice for parts of Lake and Cook County and LES should continue beyond the synoptic snow Tuesday night into Wednesday. So taking it for what it is, it won't be a bad event. Sent from my SM-G965U using Tapatalk

That dry air at 500 mb can clearly be seen moving into southwest TX on mid-level W/V imagery. Looking at the various soundings, it certainly can be a negating factor to ratios tomorrow evening as you point out. If you look at some of the 00z soundings from the southwest like El Paso, Midland, Del Rio, and Albuquerque, also being advected northeastward with the dry layer at 500 mb will be very steep mid and upper level lapse rates, which can be seen on local forecast soundings tomorrow evening (lapse rates of 7.5 to 9C/km, depending on which model you look at. The possibility of upright or slantwise convection as the snow arrives tomorrow evening is a wild card in terms of the rates we'll get. If convection occurs, it's difficult to predict how the profile will be modified. If the dry air wins out, that will certainly be very detrimental to snow ratios and amounts tomorrow evening. On the other hand, I'm not sure we can safely assume that in the presence of such steep lapse rates that convection won't enable re-saturation up there and help produce heavier rates. Something to watch.

Agree without looking too deeply into it yet (which I'll be doing tonight) wherever the LES has longest residence time could even see up to 2-4", possibly 3-5" on the high end. Sent from my SM-G965U using Tapatalk

The LES signal on Wednesday is pretty solid. Wherever the banding sets up could need an advisory. It checks the boxes: Good convergence Decent lake induced thermos Synoptic ascent with 500 mb wave overhead

Excellent point. As an agency we're also moving away from always trying to strictly adhere to criteria for headlines and leaning toward impact based headlines. The people don't know why we have certain criteria. If we get close to forecast snowfall in this event, plus the wind, that will feel like a warning event. We'll see what they do but my gut is they go WSW. Sent from my SM-G965U using Tapatalk

Here's the Pivotal Wx Kuchera output for the 12z Euro Sent from my SM-G965U using Tapatalk

Our criteria for WSW verification is 6"/12 hours and 8"/24 hours. That might be tough to accomplish verification wise, or maybe the pendulum does swing back guidance wise. Either way, I think there's enough evidence to largely stay the course with amounts. Our primary QPF input is WPC and they apply time lagging to their QPF. I also think they mostly stay the course in light of the GEFS and prior runs of the EPS justifying that. Hopefully the new EPS doesn't cut back much. Regarding what headline we issue today, we've noticed that issuing an advisory after having issued a watch can be found confusing to the public. I'm not part of the decision making process on the headline, but my speculation is that our intent is to issue a warning even if we don't technically meet WSW criteria. I'm very confident DVN will issue a WSW. When you throw in the wind impacts on top of having the largest snowfall for most of the metro since 2018 or 2019, that should support going with a WSW.

I'm sure it would be for the Monday-Tuesday period for the event. Any additional snow could be counted as a 4-day total but I think the 2-day total would be what we use for PNS and LSRs. Sent from my SM-G965U using Tapatalk

Astounding when you consider that it wasn't as bad as it could have been out this way. Had it maintained the massive descending RIJ driven blowdown structure across northern Illinois instead of transitioning to prolific QLCS mesovortex tornado producer, there's no telling how much higher the damage number would've gotten. Sent from my SM-G965U using Tapatalk

This quote from TSSN12's sig via baro from GHD I. Such perfection, it's amazing how much more rare it is to get everything to come together like that at our latitude and longitude. It's just about time for my annual tradition of reading Gino Izzi's AFDs going into that event. Sent from my SM-G965U using Tapatalk

I think maybe some equipment issues? Such bad timing for these RAOB outages. Hopefully not a problem for the all important 12z runs tomorrow. Sent from my SM-G965U using Tapatalk