RCNYILWX

Certainly too early to feel confident in it given uncertainty in the MJO realm, but nice look (500 mb height anomalies and 850 mb temp anomalies) on the 12z EPS in early Feb. GEFS was decent too, but would be cool to get something like the EPS evolution to play out in the extended. Anything to shake things up from the extended CAD doldrums. At least next week will be warmer here. Should still be a decent pattern (clippers and periods of LES) for the northern Lakes though.

Yep, should be a band that breaks through the dry air earlier in the day, most likely across far northern IL into southern WI, then the rest of the area with a period of snow late in the day through the evening. Sent from my Pixel 9 Pro using Tapatalk

Agree, really impressive airmass. The most intense cold with no snowpack in quite some time. For Chicago, have to go back to Feb 4-5, 2007 for a comparable event. Rockford had snow otg in that stretch, so it's been even longer there. Would've been interesting to see how close this got to the end of January 2019 with a solid snowpack in place. Edit: Rockford, at -11, at least tied 1/17/1954 for the coldest temp without snow cover since 1951.

It should be labeled more clearly what the sample point ranges indicate. At my office, we've chosen to stick with the standard color curve ranges. Sent from my Pixel 9 Pro using Tapatalk

That's the 25th to 75th percentile ranges for those locations from the NBM distribution and including the NWS deterministic forecast. I really don't like that we're doing this, because as you and others noted, our forecast is still there represented by the standard color scales. It's a misnomer to call those maps with the 25th-75th percentile sample point ranges plotted "official NWS forecast". Sent from my Pixel 9 Pro using Tapatalk

ORD lost its snow depth for the 00z ob. Either way, wasn't going to last through tomorrow. Sent from my Pixel 9 Pro using Tapatalk

Felt like it was good context to have vs. the 1996 event, plus the T snow depth in those older dates may have been close to an inch based on the daily data.

With officially 0 SD, it's only happened twice: 2/2/1996 (-5/-16) 2/3/1996 (-5/-19) I believe that -19 is the record low with no snow cover. With a T snow depth, it's happened 4 times: 2/23/1889 (-2/-11) 1/5/1912 (-5/-10) 1/6/1912 (-1/-11) 1/7/1942 (-4/-13) There's been 47 days total with sub-zero highs in the entire period of record. Sent from my Pixel 9 Pro using Tapatalk

Very good question - I will look that up. Sent from my Pixel 9 Pro using Tapatalk

You got it, impressive! I had forgotten that one. Sent from my Pixel 9 Pro using Tapatalk

Chicago posters, without looking it up, when was the most recent sub-zero low at ORD with 0 snow depth? Sent from my Pixel 9 Pro using Tapatalk

https://rapidrefresh.noaa.gov/ https://journals.ametsoc.org/view/journals/mwre/144/4/mwr-d-15-0242.1.xml The RAP is 13 km resolution, vs. 9km for the ECMWF, and 12km for the GFS and NAM, of the most commonly cited non-CAM guidance. The GDPS (GGEM) is run at 15km resolution and the RDPS (RGEM) is run at 10 km resolution. Finally, the UKMET is at 10 km resolution. What makes the extended RAP runs more prone to errors is that it's a hot start, hourly updating model with radar reflectivity as part of its data assimilation. This is just like the HRRR (which is initialized with RAP data) is more prone to errors in extended ranges. Think of the outer ranges of the RAP like days out on the ECMWF and GFS and beyond 24-36 hours out on the NAM. The RAP/HRRR can be right beyond 12 hours out, but in general they're more likely to be reliable within 12 hours, and even more so within 6 hours.

Should never have been issued so early, in hindsight.

I know you know that's overdone, but re. the LES, def a signal there for some accums, orientation and residence time of convergence TBD. Main limiting factor is lower inversion heights (around 850 mb), which would reduce flake size and snow ratios. Also the instability and lake to 850 delta Ts are on the modest side. The Canadians have higher inversion heights than the other guidance but not so much higher to explain the difference in QPF/snow amounts.

That plus the confluence from the upper low/PV lobe over eastern Canada and the northeast forced south by the NAO block.