RCNYILWX

Getting -SN with decent flake size from what appears to be the far southwest fringe of the LES band here near the DuPage Will border, southeast Naperville. Sent from my SM-G965U using Tapatalk

The Kuchera ratio is a linear equation based off the maximum temperature from the surface to 500 mb. So necessarily when it's very cold, the ratios it gives are high with no regard for the snow growth processes (DGZ depth, lift through DGZ and whether it's we'll aligned with DGZ, and how well saturated the DGZ is). That's the flaw of the method, since there's plenty of occurrences of low ratio pixie dust type snow in very cold temps. The Cobb ratio is based off those snow growth processes. Edit:@madwx beat me to it

If anyone from the LOT CWA is interested, you can PM me your snow reports through the event. It would probably be easier to keep up that way. I know everyone on here is pretty diligent at measuring, so it would help to have some solid reports. Also, believe it or not we don't get a ton of reports from the city, so in particular for this event with the LES, it would be greatly appreciated. Sent from my SM-G965U using Tapatalk

My friend lives up in North Center/Roscoe Village area and he said already 2-3" down, I'm guessing which includes non LES into this morning. Sent from my SM-G965U using Tapatalk

A record that will be tied tomorrow at ORD is consecutive days with measurable snow, set in Feb 2018. Today makes the 8th consecutive day and tomorrow will make 9. If Wednesday can manage to get measurable snow, a new record will be set. It's too bad there was no measurable snow on Feb 7th, because otherwise would've blown by the 2018 record. The record for days with measurable snow in February is 15, set in 1962. So far this month there's been 11 days with measurable snow at ORD, so there's a good chance to at least tie that record. Sent from my SM-G965U using Tapatalk

The 6+ line inching toward your backyard Sent from my SM-G965U using Tapatalk

The look of the LES already into northeast Lake IN seems to bode well for IL side lake effect/enhancement. Your area looks prime. Sent from my SM-G965U using Tapatalk

Even though the sfc low track is still well southeast of us, the position of the surface high and the surface low being farther northwest than earlier runs brings the low level convergence axis farther west/northwest. The thermodynamics were always favorable to get good lake enhancement/effect but getting the synoptic farther northwest only helps with totals for locations in line for lake enhancement. Sent from my SM-G965U using Tapatalk

The WRF-ARW is an ORD destroyer and gives[mention=14]Hoosier[/mention] some love. There's enough of a signal across the high res models and some of the ops I think to buy into a corridor of potentially well over 12" totals from synoptic+lake enhancement.

My response to your WxBell Kuchera issue response lol: Oh yeah agree, maybe they liked the publicity with those going viral on Twitter? Was probably a begrudging change made more urgent because Pivotal came out with Kuchera maps for the Euro. Sent from my SM-G965U using Tapatalk

The new and improved Kuchera output from WxBell.

Finally, took a while. I think one of our forecasters had emailed them as well about that issue. We have a pro account for the whole office with them. Sent from my SM-G965U using Tapatalk

Maybe WxBell finally fixed their Kuchera algorithm randomly on a Sunday? Sent from my SM-G965U using Tapatalk

Ensemble mean QPF for 18z GEFS, a tick up from 12z. 0.5"+ LE for downtown Chicago is impressive for an ensemble mean. And IND is looking money, as well as Detroit area. Sent from my SM-G965U using Tapatalk

Re. those regional maps, there's latency issues on NDFD, so if one office published their grids later than the data grab time for that particular map, it'll use the previous update. Would wait until about 4pm CST and 5pm EST to be sure those are the latest maps from each office. Sent from my SM-G965U using Tapatalk

Okay I'm gonna do a little bit of armchair meteorology here. This is while acknowledging such a big change from one forecast package to the next is a big deal and we try not to have too much of a windshield wiper effect in our products. That all said, I'm surprised DuPage and all of Will County were not included in the warning, as well as Livingston. For all three, there's valid meteorological and impact reasons why they should have been included. In addition, the hazard map looks cleaner with them in. DuPage County, to be even a bit more specific, the eastern half of the county or so typically does well in northeast flow lake effect/enhancement. Also ORD actually partially goes into far northeast DuPage. If we're saying that northern and central Cook can expect 8-12" and locally higher, you can be sure those warning type impacts won't stop at the county line, barring a major subsequent shift back southeast. From my experience, parts of northern Will also do well in northeast flow LE. Finally, there's multi-model support for 6+ amounts in southeast half of Livingston. Sent from my SM-G965U using Tapatalk

The NAM giveth and taketh lol Part of what makes it tough is it's hard to pin down when that model is not going to be unstable for this area. Running with roughly what ensemble means show and added detail for lake enhancement probably the way to go for QPF and snow amounts. Figure a 15-20:1 ratio on average and greater than that for lake enhancement.

The 18z HRRR is legit save worthy for downtown Chicago. And also very solid for the metro. Which represents a bump from the 12z run. Sent from my SM-G965U using Tapatalk

That's not really an accurate statement. There's multi model support for higher than 1-2" amounts, especially for eastern half of the county. 1-3" looks reasonable for RFD. Sent from my SM-G965U using Tapatalk

Always fun to take the time to post on here along with [mention=1610]purduewx80[/mention] and any other NWS mets that post here and on other subs, and see others saying they'd have no problem defunding the NWS.

The 06z EPS as you'd expect also notably bumped NW vs 00z run, which itself was a noteworthy jump from the 18z run. Can a trend gif be created on WxBell? Sent from my SM-G965U using Tapatalk

I think ultimately it shouldn't have been too surprising that this could come back northwest when you have a strong short-wave ejecting out of the southern Plains and already good eastern ridging out ahead. The TPV lobe exiting east quicker and the short-wave coming in even stronger and negatively tilted looks like it's sealing the deal.

You have wiggle room because of the excellent antecedent air mass. Never want to say never in weather but I think your area will be okay. Ohio is more of an issue with east and southward extent.

Yes, see new NAM rolling out haha Edit: Warning amounts for much of the metro through 09z Tuesday and still snowing.

From my coworker at LOT on shift today: "Yeah, this really got interesting. 0.5" QPF contour comes into our CWA now, already chatting with neighbors we'll have to increase totals perhaps by a factor of 2. Also, NBM gives Chicago a foot of LES. If the NBM is doing that, we're in trouble. Could envision having to issue a warning for a good chunk of the area."