RCNYILWX

It's looking decent on Tuesday. When I get to the office, will dig in more on BUFKIT. 850 mb temps still look on the marginal side for the bulk of Monday night from a thermodynamics perspective, but there's going to be good speed convergence and there's little shear. 850 mb temps on Tuesday cool to or just below -10C, which considering the well above normal lake sfc temps, seems like that would get it done with still supportive wind field. Sent from my SM-G965U using Tapatalk

12z UKMET in line with the consensus and not too much dampening into northern Illinois. Surface low track came in a bit farther south, which isn't a bad thing because 00z run was more concerning for mixing up to here for a time. Sent from my SM-G965U using Tapatalk

I could go either way, there's enough supporting evidence to issue today but sometimes it's not the worst to wait. My guess is DVN issues today. So it would be up to our forecasters whether to hoist a watch too because MKX would have too much uncertainty.

I could see waiting until tomorrow morning for the watch. Sent from my SM-G965U using Tapatalk

And the NAM is finally getting a clue. Sent from my SM-G965U using Tapatalk

I didn't want to be the first one to say it and I thought exactly the same thing when I saw where the max sleet amount is modeled lol. Glad I was able to get some sleet added into the forecast today. If that Euro output comes close to verifying that's a pretty significant amount of sleet. Sent from my SM-G965U using Tapatalk

The 00z Euro was the first run to hit the sleet threat harder. I was wondering if any of the models would pick up on this. It makes sense that there would be a sleet zone in between the snow and freezing rain zones, usually don't transition directly from freezing rain to snow in a system of this type. Sent from my SM-G965U using Tapatalk

Does anyone have any idea why WeatherBell's Kuchera output seemingly always bumps up totals to an unrealistic degree even in near freezing setups? Looking at the Pivotal Weather vs WxBell for 00z Euro it's a very noticeable difference that doesn't make sense since Kuchera is based off of MaxT from sfc to 500 mb. The WxBell Kuchera can rarely work out like with the clipper snow squall a few nights ago but otherwise always seems overdone. Sent from my SM-G965U using Tapatalk

That Ukie depiction of a 997 mb low just east of KC at hour 72 to 1000 mb near Cincy at hour 78 seems a bit far fetched even if you account for the good probability of the system occluding and weakening eastward. The UK has been very unstable leading up to this system so its hard to put a ton of stock into it for the forecast, even though (weenie goggles on) it is a nice run for the outcome we're hoping for. However, if we take the 00z Tuesday position off to the east of KC as a perfect prog, it becomes clear that the occlusion process aided by the confluence and shearing of the wave saves us from mixing or a rainer. That surface low position has me concerned anyway if it gets more guidance support for mixing getting farther north than the model depicts explicitly. Sent from my SM-G965U using Tapatalk

Yes, what I'm trying to convey below your post, but you in so many less words lol. Putting trust in the ECMWF because it's been the most consistent doesn't guarantee anything to the eventual outcome, but I think it being more stable and well within its ensemble envelope is useful confidence building information for the forecast process. Sent from my SM-G965U using Tapatalk

Very valid points you make aside, I'm struggling to come around to the idea that the precip shield of a well developed mid latitude cyclone is going to be that bullied by confluence from the north when the system had already established an expansive moderate to heavy precip shield. I think that it would be a more gradual process. An event that comes to my mind from growing up in NY is the Feb 5-6 2010 mid atlantic "snowmageddon" blizzard. That was probably the strongest west based -NAO on record amidst a record prolonged -AO. The confluence over the NYC metro was true buzzsaw stuff on the north edge. But yet the system itself didn't get shredded apart, it just led to one of the most extreme north side gradients you'll ever see (~30" in PHL and T at KNYC). As a snowlover, it was a nightmare scenario. But I think I go back to it because I want to believe a model like the GEM is depicting too rapid of destructive interference on the system. Itll happen eventually but I'd think longitude of my area has more wiggle room than points east. It's like a hurricane making landfall, it loses its heat source and eventually the whole system winds down but the precip doesn't fall apart immediately. If we're talking unimpeded Gulf trajectories, a well developed trowal and intense low and mid level f-gen into Iowa at our latitude, is the precip shield all of a sudden gonna dance southeast because of confluence? I'll end my rambling but that's my thought process on this. I buy the weakening eastward of the synoptic system because it makes sense but not such a rapid modulation of the precip swath. Sent from my SM-G965U using Tapatalk

I don't think even this version of the GFS has a great handle on boundary layer processes. My conceptual model is that unless the surface low tracks into our CWA, the strengthening northeast flow from lower dewpoint air to the east and northeast plus evaporative cooling as precip starts is going to make it tough to warm effectively. If anything, the later precip start could allow for maybe slightly more BL warming than if precip were starting earlier, but on the other hand, gonna be socked in with lowering and thickening overcast. The GFS is hard to trust in properly handling evaporative cooling in the boundary layer. Sent from my SM-G965U using Tapatalk

I think it's a bit of a wait and see until we have an even better idea on exact surface low track and can see signs of where things are pointing toward regarding position and magnitude of warm nose aloft. Sent from my SM-G965U using Tapatalk

Re. mixing issues near the lake, even though the lake is very mild for late Jan, I think it's probably still cold enough to preclude something like what happened in the November 2015 and 2018 events. If anything, assuming mixing line stays south, could see ratios being held lower along lake and just inland earlier on in the event due to the strong northeast flow. All the above said, if a 18z GFS and ECMWF (operational and ensemble) type solution verifies, or north of that, mixing south of I-80 is a lock and possibly up to or a bit north of I-80 for a time on Monday before cold air comes in on the backside. I do think the block will be our friend in helping avoid a much farther north mixing line. Sent from my SM-G965U using Tapatalk

Getting close to 100% for a top news story barring a horrible crapping the bed of this setup, since we do event pages even for light to moderate events. Chances for a historic event we'll be talking about years from now and be updating for anniversaries, let's say 10% right now. I don't want to rule it out, because at this lead time from GHD II, I can't recall anyone thinking historic amounts were in the offing, and we'll certainly have the moisture in place if it all works out right. For us starving Chicagoland snow enthusiasts, even getting it to perform to something like the EPS and GEFS ensemble means will be a feat in and of itself and I think it will be a fondly remembered event even if it's not historic. Edit: And speaking of the GHD I page, we're hoping to be able to update it to our current tabbed interface and add some new images such as a recreation of the snow amounts using our current graphics generation software for the 10 year anniversary. If anyone has suggestions for additions to that page, let me know in a PM or in the new past snowstorms thread.

Good evening y'all, just got back from the office a bit ago. Fun shift. Would be happy to answer any LOT specific questions if anyone has any. Regarding who's working in the lead up, I'll be back on evenings with Ratzer tomorrow through Monday and I expect I'll probably be doing evening update AFDs. Our midnight crew is the same as last night (Carlaw and Kluber) and it'll be them through the event. Dayshifts will be MTF and Petr. We should be in good hands. Glad that we stayed the course with the most consistent guidance in terms of our forecast lean and messaging in light of guidance trends already for 18z cycle. Here's to a good 00z cycle. Sent from my SM-G965U using Tapatalk

Everyone freaking out can put down the paper bags. Sent from my SM-G965U using Tapatalk

Without access to ensemble data from the UK, we don't know where the operational falls within the spread of its own ensemble system. The only more consistent forecast system has been the ECMWF/EPS. That said, while GFS operational has been very inconsistent, the overall suite has trended north the past several cycles, especially on the 12z GEFS. The UKMET is concerning in that it's a possible scenario that can't yet be ruled out. The 12z ECMWF/EPS are the big key to this. If there aren't big changes from the 06z, I'd consider the UK a lower probability southern outlier like the NAM. Edit: And I'd like to restate from yesterday, given antecedent pattern for this event, including initially pretty marginal thermals, I feel confident in saying we wouldnt even be in the game in most of northern IL without the NAO block. Maybe a more east based block could modulate enough and still keep us in the snow threat zone, but with a positive NAO, I don't see how Alek wouldn't be posting the Eurythmics video.

Absolutely. Pattern recognition and textbook meteorology >> raw model output in this case Sent from my SM-G965U using Tapatalk

Total toss on the verbatim depiction of the heavy qpf/snow swath on the GFS. That's a great surface and 700 mb low track for the metro. Sent from my SM-G965U using Tapatalk

Yep, if anyone has been following the under the hood analysis, the northern burbs are definitely not out of the game. Key thing to watch on the globals today is the track of the 700 mb low. Often times when mesoscale banding sets up, there can be one pretty well displaced to the northwest of the h7 low track.@weathafella can attest to this "mid-level magic" from east coast systems. Sent from my SM-G965U using Tapatalk

There's the suicidebooth.gif run from the NAM. Knowing how it struggles when the key features are mostly outside its domain space, definitely too early to put stock into it. Sent from my SM-G965U using Tapatalk

Really nice 700 mb low track on the UKMET for much of the Chicago metro to get in on the 700 mb deformation axis snows. Sent from my SM-G965U using Tapatalk

Agree, it's generally a mess. 700 mb streamlines and RH would indicate respectable banding up into WI and it crushes precip shield to mainly I-80 and south. This is where the human input into the forecast remains important, to be able to pick out these biases/flaws in the models and look deeper into the meteorology with respect to other mass fields that aren't as fickle as QPF, which seems to especially be the case with the GFS. Unfortunate part for this event too is that the GFS v16 hasn't been running since last night or something. Sent from my SM-G965U using Tapatalk

This run of the UK was several hours slower. Similar latitude at 18z Monday, but while 12z run was north of EVV at that time, the 00z run is just southwest of STL. There's been a decided slowing trend on the 00z guidance thus far. Sent from my SM-G965U using Tapatalk