RCNYILWX

Nice, I informed you that your snow measuring methodology is incorrect and then get called an asswipe. Makes your complaints about etiquette in here ring hollow. There isn't a different way to report your snow total. You could have your own thoughts on it, but there's no way around the fact that snow is reported to the nearest tenth of an inch and has been that way since records have been reliably kept by the NWS.

It's to the nearest tenth of an inch. That's the correct way, period. Sent from my SM-G998U using Tapatalk

2" here. Our forecast was overdone in the south and southwest burbs, but solid for the rest. We had that 3-5" swath well forecast. Overall, the event wasn't far from expectations. Glad the DKB to north burbs area had a decent snow. Sent from my SM-G998U using Tapatalk

would surpass yesterday morning's hail as the event of the winter for the NW burbs Sent from my SM-G998U using Tapatalk

Looking like a nice fluffy 2-4/3-5 type deal with some lake enhancement. Getting to that time of year when getting heavier rates matter more toward pavement accums during the day, so the bulk of the snow falling after dark means no issues there. Not really buying that heavier snow swath south idea like GFS is holding onto. Euro has a stout mid-level wave pivoting through while we're in the left exit region of the departing upper jet. That plus deep DGZ should mean 15-20:1 ratios are attainable as long as the strongest lift is well aligned with the DGZ.

4" here in southeast Naperville. Assuming 2-3" of that fell during the death band. That was the heaviest snow here in quite some time. Probably heaviest locally since the death band on February 9, 2018. For the metro, heaviest snow rate since Feb 15, 2021 in Chicago. Since expectations for this event had gone way down, feels like a win. And cool to finally have a La Nina like pattern here for a bit. Sent from my SM-G998U using Tapatalk

Pouring snow here under this band. Pretty awesome. Woke up just in time from post midnight shifts nap. Sent from my SM-G998U using Tapatalk

If you've been following the CAM runs since they've gotten into range, they're modeling extensive warm sector convection which they explicitly forecast (hence Convection Allowing Models). The operational models and ensemble members parameterize convection, which is simulating the combined effects of convective clouds that might exist based off other elements being explicitly modeled. One of the pitfalls of higher resolution operational models and ensemble members is that the convective effects applied to many more grid points can result in a high resolution garbage in, high resolution garbage out phenomena. We had an internal call with WPC last night and a forecaster from one of the offices on the call made the point that it's possible the GFS and NAM were being affected by convective feedback. The thing about handling convection is that it's hard to be confident if the mass fields will be impacted in a negative way, if models are over deepening a key short wave due to simulated convection, or if some guidance members are overemphasizing negative effects. There's plenty of examples of the all of the above occurring with mid latitude cyclones modeled to have a large convective footprint in the warm sector. I've been thinking about that point made last night and wondering if it helps explain the lingering high uncertainty in the guidance. Even the CAM solutions are struggling, given the large difference between the members of the 00z HREF. My thinking is that since there's reasonable agreement in a sub 1000 mb low tracking north of the Ohio River, this has historically been a good track for sig snow into Chicago metro. So while I certainly can't ignore the possibility warning snows miss us south or that the whole system is weaker due to destructive interference from convection, holding with the thinking that the central (including western burbs) and south metro and points south do well. This is based off pattern recognition, favorable jet dynamics (left exit and right entrance of jet to our north) to allow for more expansive precip shield than some of the stingier guidance on north end, and the antecedent strong downstream ridging (possibly enhanced by latent heat release). I believe that some of the above factors (minus sfc low track), while unfortunately not overcoming the dry air for the far north and northwest metro and points west for GHD III, enabled the big dog type totals to get up to the I-55 corridor and solid warning snows decently north of that. Sent from my SM-G998U using Tapatalk

Hopefully see more amped members on 00z GEPS. Wish there was access to the UKMET ens. I'm aware of only 1 pay site that offers those, which I believe is True Weather. Sent from my SM-G998U using Tapatalk

NAM looked like it would be a hit here, just not as amped as 18z GFS and also a bit slower. Important cycle for the varsity models tonight. Sent from my SM-G998U using Tapatalk

Definitely wasn't expecting solid dendrites that far north. Don't recall seeing any forecast soundings for your area and north that didn't have the omega above the DGZ. Sent from my SM-G998U using Tapatalk

The setup is sensitive (as they all are really) to the various key pieces. Most notably from a big picture perspective being: whether northern stream (PV) is more or less suppressive, the strength and tilt of the main wave, magnitude of positive height anomalies (ridging) over us and downstream, and how much jet streak phasing/coupling occurs. All of these pieces favored a hair farther south secondary surface low track than 06z, but plenty deep enough for the heavy snow swath. Sent from my SM-G998U using Tapatalk

Nothing says jaded snow enthusiasts like no posts on this thread for an hour when the NAM has run and looks like the 06z GFS at the end haha. FWIW, the 06z ECMWF operational, while not quite headed toward a 06z GFS type solution if extrapolated out, was an improvement from the 00z run with respect to the Hudson Bay PV lobe being farther north and less suppressive. Also upper jet configuration in that run suggests coupled jet streak would be probable and increase chances of a deeper secondary surface low. On the 06z EPS, noted a similar signal that the members with the 6"+ snow swaths were the deeper solutions. It makes sense, but it's also appearing that unlike GHD III, this event would be less likely to produce big amounts farther south if a farther southeast and weaker secondary low pans out.

As noted earlier, very large spread still on the GEFS, with many members northwest of the operational and the mean. Compared to the 18z GEFS, solid cluster of member lows west/northwest of the mean Wednesday night into Thursday. The 00z ECMWF (EPS) ensemble also definitely left the door open for the main wave and associated secondary low pressure to track farther northwest. Comparing to the 18z EPS, similarly to the 00z GEFS, the 00Z EPS has a solid clustering of member lows northwest of the ensemble mean Wednesday night into Thursday. Along the lines of my post yesterday, a distinct majority of the GEFS and EPS members with 6"+ snow swaths are tied to the deeper solutions. And sure enough, the 06z GFS came in way deeper and farther northwest with the secondary low. Given the trend on the 00z suite and continued on the 06z GFS/GEFS, I wouldn't at all hang it up yet in eastern Iowa, NW IL, northern Chicago burbs and southern WI. Plenty of time to go on this one with multiple moving parts.

*Longer post with some explanation of ensemble analysis for this event* Things to consider regarding sensitivity of the setup to key features: - Obvious one being strength of southern stream/main short-wave, also entailing whether wave is negative, neutral, or positively tilted. Most recent ECMWF and GFS solutions favor neutral to negative tilt in southwest trending to neutral to pos tilt in Midwest. - If there is phasing with the northern stream or at least constructive interference/interaction between northern stream and main wave. - Strength of downstream positive height anomalies. One of the things you've probably seen referenced in LOT AFDs over the past year is ensemble cluster analysis. WPC has an experimental page for this: https://origin.wpc.ncep.noaa.gov/hmt/wk2/day_3_7/view.php?type=day_5_&field=cluster_qpf&reg=_central&regstr=CENTRAL (linked to day 5/24h period ending valid 00z Friday) Abbreviations to note on the attached images: C: Canadian ensemble members E: ECMWF/EPS members G: GEFS members T: I believe UKMET members but not 100% sure I'll focus first on clusters 2 and 3, which are wetter farther northwest Wednesday night and Thursday, our time frame of interest. Cluster 2 has the highest % of GEFS members at 37%. Cluster 3 has the highest % of EPS members at 36%. The drier clusters farther NW, 1 and 4, have the highest % of Canadian members, but note that cluster 1 has a noteworthy minority of GEFS, EPS, and T (UKMET?) members. You can then see the ensemble cluster mean 500 mb height anomalies vs the multi-model ensemble (MME) and the 500 mb height differences between the clusters and the MME. My interpretation of h5 w.r.t the cluster precip difference vs the MME is that the favorable clusters either have stronger downstream positive height anomalies (cluster 3) or better northern stream interaction (cluster 2) with the main wave via phasing or constructive interference. This is kind of an obvious point, but in light of the 06z GEFS and EPS, what I'm seeing is that: Of the members with heavy (6"+) snow swaths, a distinct majority of these are farther northwest with the swath. There are only a few that are solidly farther southeast/ie. congrats IND. My take from the above is that the more likely way to get a heavy snow swath out of this is represented by ensemble cluster 2 or 3, or a combination of those. I'm not sold that there will be a warning worthy snow swath in a flatter/more progressive/farther southeast scenario, which is essentially what most recent GEM runs have shown. A flatter solution will have much narrower deformation area cold sector precip and will contend with being undercut by encroaching dry Arctic air mass from the NW. As far as which scenario I'm currently leaning toward at this point, I'd say *slightly* toward a decent (warning worthy) event within the LOT CWA and parts of surrounding CWAs, given the EPS and GEFS lean toward this. I'm certainly worried about the GEM like solution however. We'll see here shortly if the various clusters diverge much with the 12z cycle today.

Unfortunately the southern stream wave is in strong agreement to get squashed far enough south to preclude much in way of additional snow sans lake effect (see my post above), but with decent synoptic lift maybe low quality seeder feeder in your area. Guidance continues to focus the convergence axis onto the IL side after brief period this evening over Lake County IN.

Yeah, feel pretty confident the HRRR is overdoing things again.

Doesn't look nearly as favorable as last week's event due to much lower inversion heights and less instability, but the convergence is quite good and persistent and good agreement that it'll be nearly stationary for a while tomorrow into tomorrow evening. Part of the event looks to be seeder feeder due to synoptic lift (upper jet forced) upstairs with DGZ saturated, and then low level lake induced lift, with DGZ partially saturated (up to about -15C) down there. Tomorrow evening we'll lose seeder feeder with a transition to low level saturation only and still up to about -15C. Thinking is this all shouldn't result in an intense single band for most of the time but a focused area of snow showers with embedded heavier snow showers. Potential exists for a band to get going tomorrow evening. Due to lake induced portion of the sounding not being fully saturated up to -18C (top of DGZ), expectation is smaller, lower quality snowflakes that should keep rates in check, but good convergence could result in heavier snow showers producing solid rates and sub 1SM visibility (small flakes tend to reduce visibility as or more effectively than quality dendrites). We'll probably have Lake County in an advisory with the evening update. In the update to convert central and south Cook over to an advisory, mentioned accumulation of 1-4".

If anyone from LOT CWA has reports from their area that you'd like to go out as LSRs, reply to my post here. Include estimated time you measured. Thanks. Edit: I had a storm total in Naper Carriage Hill of 7.8" on DuPage side (I back up to 87th St), but then a neighborhood friend just south of the county line in Will reported 8.5", so seems like anywhere from 7.5" to 8.5" in my general area. Good storm.

6.1" here as of 930 am. The rates when I woke up at a bit after 8am were really impressive, some of the heaviest since I've been living in the Naper Carriage Hill subdivision (since May 2015). We've since eased back to -SN/borderline SN with a slight recent uptick. Had told neighborhood friends expecting 6-8" locally, so should fall right in that range. My top end/90th percentile range was 10-12" which would've required that band to be a lot more slow moving. Nice event.

Looks like the banding push extending back to far southeast IA is and should fill in places currently just northwest of the heavier band over the metro. Tilt 2 on KLOT almost completely filled in. Sent from my SM-G998U using Tapatalk

Pouring snow here now, heaviest rates imby since Jan 30, 2021. Sent from my SM-G998U using Tapatalk

Broke the seal here in southeast Naperville a few blocks north of WillCo border. Sent from my SM-G998U using Tapatalk

My general perception is that more often than not dry air effects are overdone rather than underdone. Tonight-tomorrow will have the additional effect of f-gen sharpening up precip gradient, so I buy the sharp cutoff somewhere over northern IL (hopefully north of most forecasts for places up north that legit need the precip anyway). Later tomorrow night and Thursday won't be a heavily banded setup up farther north, so I would tend to think the dry air effect would be overdone on a day like that, unless everything is squashed south, which is possible. Last February 14-16 was a great example of favorable jet positioning aiding in a precip shield much farther north and west than earlier forecasts. Link to SPC mesoanalysis archive: https://www.spc.noaa.gov/exper/ma_archive/action5.php?BASICPARAM=300mb.gif&STARTYEAR=2021&STARTMONTH=02&STARTDAY=15&STARTTIME=22&INC=-6 Textbook right entrance region of an anti-cyclonically curved upper jet streak. In addition to the strength of the mid-level wave, this magnitude of large scale ascent played a big role in both the expanded precip shield and the intensity of the lake effect into NE IL and far NW IN.

No prob! Glad to help with analysis on here. I'm back 3pm-11pm tomorrow so for evening update AFD and any headline changes (if needed) would be me or MTF. Sent from my SM-G998U using Tapatalk