RCNYILWX

Incorrect on the cloud cover. It was clear everywhere until basically sunrise. And I wouldn't say the cold underperformed. We were slightly too cold at RPJ, we had ORD at -1 to -2, and we never had RFD tagging 10 below. We went below MOS guidance. The Euro was overdone with the coverage of teens below zero (and the GEMs are always overdone), but getting 7 sites to -10F or colder in our late AM updated RTP is not really underperforming imo. https://forecast.weather.gov/product.php?issuedby=LOT&product=RTP&site=lot Sent from my SM-G998U using Tapatalk

The best that can be said is that the ensembles currently have an active non-torch look out towards mid month. But we know how that goes, plus it'll be mainly doldrums until then. It's unfortunate that there wasn't a more widespread warning criteria snowfall event in this recent more active stretch. And that the short-wave for what might have been the semi-annual end of January to GHD period storm got buried in the southwest.

If the winter out here is getting F or F- grades, what does this winter in NYC get? Expelled?

Was freezing rain here (DuPage/Will border) for a bit now back to mainly snow with some freezing rain mixed in. Gonna be a fun drive to the office tonight. Sent from my SM-G998U using Tapatalk

I think the models also were too slow to saturate with southward extent. The fact that the lead band already is 25-30+ dBZ down in ILX CWA could very well be a sign of things setting up a bit south later on. But even if the band is progressive, should be a nice burst of snow moving through later this morning into early to mid afternoon. Definitely liking this evening too if the main band sets up northern tier and north during the afternoon. And finally, the NAM indeed was out to lunch haha. I'd still hedge a bit south of where the HRRR is putting the zone of freezing rain this evening. Expecting the advisory to be expanded south with the mid-late morning update and also the day shift will assess whether any part of northern Illinois in the WWA needs to be upgraded to a WSW.

Thinking we will. Did increase things last night some. Sent from my SM-G998U using Tapatalk

The NAM remains very different from the other non CAM guidance at 850 mb, with a 1410 m 850 mb low, while other guidance is much weaker with 1440 850 mb heights. This induces stronger 850 mb winds and brings the 850 mb 0 line much farther north. I definitely don't buy the stronger surface trough and the front getting north of Chicago tomorrow night, which is also related to being stronger aloft. There are times when the NAM is onto something with warm noses and freezing rain threats farther north, but this looks like the model struggling and being too amped with mass fields and gradually correcting. Might be a nugget of truth with the warm nose farther north than some of the globals show, though still think mainly south of I-80 for mixed ptypes.

Still well too strong with the surface trough tomorrow night. It'll figure things out with the 06z run or 12z tomorrow I guess. Sent from my SM-G998U using Tapatalk

Some (rambling) thoughts before I go to sleep: While the 6"+ snow potential has clearly shifted north, I continue to believe that the NAM and CAMs are too aggressively far north in their depictions of accumulating snow. For me, the NAM remains a toss with it still spinning up a meaningfully stronger weak surface low reflection and being way farther north with the stationary front. For it to show this, means it's also stronger aloft. The NAM can do better with warm advection setups, but if it's too strong with the system and low level mass response, the magnitude of 850 mb winds and warm advection will also be too strong to an extent, and affect placement of mesoscale banding. Even though the ECMWF shifted north with the heaviest banding, if you still want snow in northern Illinois, important to note that the ECMWF and its ensembles have 9 km resolution, so it's not like you can toss it for being a too smoothed out global model. The near 0.2" QPF gets down to around I-88, so with higher than 10:1 ratios, still can put you in 3+ range. Tomorrow evening into the overnight, as cold advection starts to increase, large scale forcing will also increase (modest mid level support and upper jet right entrance region), expecting light to moderate snow north of I-80, with a threat for freezing rain south. Wouldn't be surprised if the backside snow lingers all the way into Sunday morning. If you're looking for sources of error - check out the non-NAM and RAP/HRRR depiction of 850 mb fgen tomorrow - still over northern IL. It appears the sweet spot for the fgen response may be in 850-700 mb layer, though the models can certainly err in the placement of response to an fgen circulation. Sometimes low level response can be more dominant, or you can get dual banding. Mesoscale snow band forecasting is essentially forecasting convection, so it's more challenging and uncertain than already tough winter weather forecasting. The GEMs (and 2.5 km HRDPS) continue to be stubbornly steadfast in their more southerly solutions and the GFS has trended north since yesterday, but still gets 1/4"+ liquid equivalent down to the I-80 corridor (slight improvement from 06z). I certainly wouldn't discount pessimism about getting the higher end amounts down into the heart of the metro, but gut feeling is decent accums (~2-4") get down to a bit south of I-88, and the northern tier is still in play to get into the heavier banding. Just not ready to buy into the CAM idea of little/no snow south of the WI state line. Also not ready to buy into the Canucks scoring a total coup on this, though it sure would be nice [emoji3]

If the other guidance stays relatively similar, it shows how unreliable the NAM is. I can recall it doing exactly this sort of thing in similar setups at around this range that went on to produce solid accumulating snow in the area. Having this sort of jump muddies the water forecast wise. Re. the HRRR, it probably shouldn't be used for winter forecasting beyond 24 hours, and 24 hours out is still a stretch. The HRRR is most useful for near term trends, within about 12 hours, maybe as much as 18 hours.

Ah didn't realize you volunteered at LOT. That was way back in the early days of the office. Paul Merzlock retired in 2011, just under a year after I got here. His last day was June 30, 2011. The Lake Michigan supercell happened that evening and the continued thunderstorm activity over the southern tip of the lake busted a Heat Advisory on July 1, 2011. Ratzer is still at the office and wrote this evening's AFD update. Sent from my SM-G998U using Tapatalk

February 8-9, 2018 begs to differ on them never panning out for Chicago. Also December 31-January 1, 2014. And December 10-11, 2016. It's the nature of fairly narrow snow bands to miss sometimes. I don't think from experience here that we do worse than elsewhere with these fgen banding events.

First off, and I'll say this respectfully, try not to stress about weather related things that you can't control. Variability is the hallmark of our winter weather here, regardless of background climate warming context. You're pining for a winter climate that does not exist at this latitude west of the lake. Now, regarding the measurement, why shouldn't the depth have compacted to 2" by 6pm today? It was a relatively wet snow and the temperature reached the mid 30s. Saying the measurement seems inflated because essentially you're annoyed that we didn't hold onto the max depth is...not a great argument about the measurement being inflated. A 6 hour board clearing method will often come in higher than measurements of volunteer observers who we can't require to do 6 hour board clearing snow obs, but it does a better job capturing snow that does occur. It also accounts for some compaction. The 6 hour board clearing method has been used for decades at official climate sites and I don't anticipate that changing. If you want people to respect the posts you make more, rant less about things out of your control, post more about the forecast, ask questions about certain setups if you have any, and enjoy the weather you prefer when we do get it.

Felt like this event exceeded our low expectations for northern Illinois. Some positive vibes as we kick off this active stretch. The higher ratios early this morning were interesting, because the snow definitely didn't feel light and fluffy when shoveling this morning. It also wasn't true cement though. We had strong omega well aligned with the DGZ, and steep lapse rates above the DGZ during the heaviest snowfall rates. The lift was associated with an upper jet streak and a mid-level fgen circulation. At onset last night, flake size was small, as the strongest lift was above the DGZ. A couple hours later, we had good alignment, and flake size improved, supporting the at or above climo ratios, despite surface temperatures hovering near freezing. This was yet another example of the challenge of snow ratio forecasting. Even if you have somewhat marginal temps, the sounding will often be a bigger driver of the ratios (Saturday night-Sunday was another example of higher than expected ratios). The Cobb output can help in these setups, vs. the Kuchera actually being too low. 10:1 maps appeared they did well enough for this event since they were higher than the Kuchera ratios. Of course once temps warmed and rates diminished late this morning and this afternoon, we've had essentially white rain, so the effective ratios are well below the Kuchera.

3" here in southeast/south central Naperville near the DuPage-Will Co. border. Picturesque paste. Edit: Checked a few other spots in the back yard and it might be more like 3.4".

Yep have been noting that on other guidance too. The Euro as you noted had kind of lost that look for a few cycles. It's going to snow over a large area due to that northern stream influence vs. the classic sharp cutoff northwest. Pretty interesting forecast in that the heaviest banding will be tucked in atypically close to the surface low while the lighter accumulating snows will expand well north and west. Also tricky from a headline perspective because I think the snow falling Wednesday beyond mid-late morning will be pretty low impact due to the temps at or above freezing. I think we're probably starting out with an advisory for the I-80 and south counties and then the day shift can make adjustments northward if needed. Some of the metro counties and into Chicago are a tougher call. The initial snow could come down at a decent clip, so if confidence grows in impacts to the commute, we may need an advisory for at least up to central Cook zone and probably DuPage. Sent from my SM-G998U using Tapatalk

The 18z Euro bumped north very slightly, but not in a meaningful way, and remains very different from the NCEP guidance. In fact, since temperatures will be around to even above freezing, could make a case using the Euro as a perfect prog that we wouldn't need an advisory for most of our counties. The places that have the snow start earlier tomorrow night are probably gonna have enough impacts Wednesday morning to justify an advisory though. While the latest ECMWF is generally a bit lower QPF wise farther north than the foreign guidance, it's probably not a meaningful difference. It's the NCEP guidance that stands out, particularly the NAMs. The GFS is not very different farther north, but it is farther north with the heavier banding across central IL and Indiana than the other globals. Sent from my SM-G998U using Tapatalk

I think another issue with this system is it's very compact. That sfc low track is normally good for much of the Chicago metro, but the 850 mb and 700 mb lows are tucked in closer to the surface low than typically occurs. Sent from my SM-G998U using Tapatalk

The 18z EPS only showed a slight downtick from 12z in its 10:1 mean snowfall output and that op run is not significantly different from the previous few runs aside from the lower QPF. Surface low track is almost identical to the 06z run. Concern shouldn't be based off that one run. Even though late January isn't sun angle season, our bigger issue is the lack of cold air going into the event plus temps near to even above freezing during the snow. This will limit accumulations unless the higher rates can get farther north. So we need to see support for better banding and higher QPF resulting from that farther north. Otherwise, the 1-3"/2-4" range from Gino's AFD is probably the ceiling in the metro (on colder surfaces).

Had forgotten to respond to @Hoosier a few nights ago about snow expectations for this mini event. I felt despite the guidance poorly handling things amidst a general downtick in QPF and snow that a corridor of 1-2" still looked good in northern IL and at the time favored north vs. south. Honestly had lost some confidence in the forecast and felt that localized 3" amounts were probably not happening anymore, but sure enough we had some 2"+ reports out in the northwest CWA and it looks like ORD will have over 1" for this event since they had 0.9" at 12z. RFD already had 1.3" so they should end up over 1.5" and may make a run to near 2". Also, it appeared at the time that some areas would have a dusting/coating at most, which looks to have been the case from the south suburbs and south and northwest Indiana. Tough forecast since the guidance struggled handling this one - the GEM and RGEM and HRDPS seemed to do probably best overall. Sent from my SM-G998U using Tapatalk

The track of the 00z run would probably result in better snow farther north than the verbatim output. Sent from my SM-G998U using Tapatalk

Because the GFS is more of an outlier now, I'm currently leaning toward the foreign guidance to be more likely on the right track. The warning type event is less likely, but that may not mean a whiff (maybe ALEK was onto something haha). Sent from my SM-G998U using Tapatalk

Still have to wait on the Euro for our final 12z operational data point, but did want to note that the foreign models (12z GEM and UKMET and 00z Euro) have a more expansive precip shield with light to moderate snow accums farther north. The GFS has the sharp NW cutoff that's seemingly more common in these setups. This is despite relatively similar surface low tracks and mid and upper level depictions. There's probably another physical reason beyond this, but simplest way to see the difference is that foreign models have much higher 850 mb RH farther north than the GFS. Sent from my SM-G998U using Tapatalk

That run was hurt by the h5 low digging a bit farther southwest, but even more so, comparing to 12z, positive tilt of the parent wave valid Tuesday night-early Wednesday vs neutral to negative tilt on the 12z run. The farther south h5 low path hopefully ticks back some on the next model cycles, though might very well be a meaningful data point, while the other element is much more uncertain. Any farther south with the parent wave definitely will make it tougher to get a far enough north surface low track because then you'd need to be more reliant on wave going full negative tilt. The 00z operational runs showed the caution flags in this setup - I think we'll have a decent idea by Sunday on which way things are leaning.

The GFS was a fast outlier with our main wave going back to the model runs 24-36 hours ago - it's now closer to the consensus, with main issue being how far south it digs the wave. Something to watch vs. getting overly concerned at this point. With the latest GEFS showing the spectrum of plausible outcomes better than it seems to do usually, the Euro suite should be a little more helpful given the sheer number of members, plus the better overall performing op model. RAOB sampling wise, should get partial sampling 00z Sunday and close to full 12z Sunday. The satellite derived stuff is so much better now, plus any over Pacific aircraft data can help, so this might be a more stable forecast (big picture) than some of our events.