RCNYILWX

And then the Euro completely backed off lol Sent from my SM-G965U using Tapatalk

I know 11/25-26/18 is not as good a comparison because the air mass was also too warm aloft initially but it was another case of full fetch down the lake making it tough to get much accums downtown. All of the snow lakeside fell on the morning of the 26th when low level flow turned northwesterly and cold advection intensified. For Monday I'm not sold yet it's going to be a big deal lakeside for IL. In addition to the low level flow being a full fetch down the still mild lake (could see northerly Island being locked at 33 to even 34 while flow is onshore), the Euro and the NAM are a bit slower with the CAA so 850 mb temps 12z Monday are only about -8 to -9, yielding delta T with Chicago shore water temp of about 15-16 C. Equilibrium levels less than 6kft prior to 12z only get up to just shy of 7kft by 15z, which is pretty marginal. Gonna need the low level convergence to hold back longer over the southwest part of the lake like the 12z Canadian to allow the cold air to deepen and improve parameters as well as cool the boundary layer sufficiently. The 18z GFS is quicker with the CAA but it also is much quicker with flow turning to NNW and favoring Indiana. Even for inland of the lake in IL, the NAM and ECMWF being marginal with thermodynamics during most favored timing of convergent boundary layer flow casts some doubt on how much lake enhancement there will be. Sent from my SM-G965U using Tapatalk

Could see there being a narrow band of 2-4/3-5 for the late Tuesday night-Wednesday morning round. Sent from my SM-G965U using Tapatalk

We were very open to issuing a wind advisory for southern CWA but ILX, IND and IWX still preferred to hold off. Given the run to run consistency of the HRRR for a corridor of 40-50+kt gusts tonight, I was surprised the neighbors didn't want to issue an advisory. Could very well have high wind warning type impacts if the HRRR comes to fruition. 18z RAP has a large area of 50+ kt winds at 925 mb spreading across central IL and IN. Forecast soundings suggest that there will be sufficient mixing to tap into the high winds aloft, with cold advection and very strong pressure rises immediately following the surface low. Sent from my SM-G965U using Tapatalk

Can easily see the tropical connection on the pwat plume on the 12z Euro. Intense 850 mb LLJ in the warm conveyor. Impressive rain event locally modeled by the 12z Euro. Would imagine with the magnitude of the WAA and near record high pwats that embedded thunderstorms could occur due to slantwise instability in the comma head. Sent from my SM-G965U using Tapatalk

Very reminiscent of January 30th failing to set a new monthly record low max for January by 15-20 minutes. Sent from my SM-G965U using Tapatalk

Based off what just happened at PWK on 5 min obs, appears more likely than not that ORD will fail to set the record. PWK went from ~81 at 12:05 am to ~70 at 12:10 am. Edit: ORD officially failed to set the new monthly record.

I buy upper 70s but not sure about low 80s dew point there right now and 80 at Morris. Surrounding sites have 77-78 dew points. Sent from my SM-G965U using Tapatalk

For Cook County, watch/warning criteria is: 1 day of 110+ HI 2 days of 105+ HI 3 days of 100+ HI For the rest of the LOT CWA: 2-3 days of max HI 110+ and min of 75+ 4 days of 105+ HI Sent from my SM-G965U using Tapatalk

I was the one issuing the warnings and things started lighting up further west with areas west of Momence also showing up as exceeding flash flood guidance by a decent amount. It was an in part forecasted warning and part of it didn't work out. Considering how things had been going to your east and over the far south burbs with continuous training convection, was concerned it would be similar there. Also by then I had been on radar since before 5pm, so it had been a very long night and I was erring on the side of caution partially. I do tend to be more conservative with FFWs normally because I'm very aware/cognizant of the likelihood of waking people up for a marginal warning.

It's an error on the page with 2012 not being listed. 1988 was accidentally listed as being #1 and #2 in the rankings. 2012 should be there in #2 tied with 1955. I let the office know, so hopefully they fix it today. Sent from my SM-G965U using Tapatalk

PWK is probably running warm. Part of the issue is that the tolerance interval is at least 3 degrees if I'm not mistaken, so even though it stands out to those of us that follow this stuff every day, it hasn't risen to the level of getting a trouble ticket requiring maintenance. Also, hate to say it but it's not been a priority with how active it's been. I'll mention it to the electronics techs next week if it continues to run warm. Sent from my SM-G965U using Tapatalk

This May was far more impressive in areal expanse of extreme rain amounts. Last year's short lived May record for ORD I jokingly call a fake record because it was pretty localized, with the high totals focused over the northern metro. ORD happened to jackpot a few events. If I counted correctly only 13 measurable rain days in May 2018 compared to the ridiculous 21 days of measurable this year (23 of T or highe). Just as a reference for the localized high totals last May, through May 31st, LOT was over 2" below normal for March 1-May 31 period. This year we had ~10" more at the office in the same stretch.

Doesn't seem like the smoke should dampen insolation and thus instability too much. Even with pretty thick smoke yesterday we got to low-locally mid 80s highs without a problem. Sent from my SM-G965U using Tapatalk

IMO using the baseline of the issued Enhanced Risk, placement should either be shifted north into northern IL or expanded from current area to include northwest 2/3 of LOT CWA. Based off path of well defined shortwave tracking across the area around mid afternoon, strongest mid-level winds and deep layer wind shear will be across northern IL and southern WI. There will be more than enough instability area wide and very steep lapse rates, considering that we already had pretty stout elevated hailers this morning over northern IL and southern WI. Looks like a solid early summer severe day, with large to isold sig hail with initial discrete/semi discrete storms likely trending to more of a damaging wind risk if things as expected congeal/grow upscale. Doesn't look like much of a tornado threat with weak low level winds, little/no directional shear, and soundings showing well mixed low levels. Would likely need outflow boundary interaction for any brief tor threat, or possibly in proximity to the weak surface low moving over southern WI. Sent from my SM-G965U using Tapatalk

This is shaping up to be a concerning day for the metro. The convection out there this morning doesn't seem like it'll keep the warm front well south. Latest guidance gets the warm front to or north of the I-88 corridor later. Aside from the immediate lakeshore possibly being helped by onshore winds, Rockford area to interior parts of metro to northwest Indiana could be under the gun. In addition to the strong directional shear/SRH maximized near the front, as has been noted, very high levels of 0-3km CAPE are being progged in forecast soundings with values of 100-200+ j/kg (50+ is typically favorable for tornadoes). Bunkers right moving storm motion vectors are out of the west-northwest, which would parallel the west northwest to east-southeast oriented warm front and maximize ingestion of streamwise vorticity. Observational trends to say the least are very important over the next few to several hours, chiefly all important position of the warm front. Wouldn't be surprised if SPC needs to add a MDT in one of the updates.

I expect to be called into work tomorrow. Sent from my SM-G965U using Tapatalk

Since Broyles did the 01z update this evening, it'll be him. He also did the previous 06z Day 1 outlook. Sent from my SM-G965U using Tapatalk

Pretty heavy rate of fall here in southeast Naperville. Had a brief period of very large flakes that since dropped a bit. Grass and mulch have whitened up a bit and slush on tabletops and some car tops. Melting on contact on paved surfaces thus far. Sent from my SM-G965U using Tapatalk

Most interesting somewhat comparable time period I could find when putting together stats for the office was late April 1910. There were 5 consecutive days with measurable snow from the 22nd to the 26th including 2 days with 2"+. Then 2 days after the streak ended, April 28th had a high of 76, followed by a high of 86 on the 29th. In addition, prior to that latest on record stretch of 5 consecutive days of measurable snow, there was a high of 80+ earlier that season, on March 27th (81 deg). Sent from my SM-G965U using Tapatalk

I have not posted in a while, especially since going back to work in early March after paternity leave for birth of my 2nd child, but I've been lurking. Worked leading up to the event and saw that a few of my AFDs were pasted here. Several posters criticized my office's (LOT) handling of the event, and admittedly, when amounts are that much higher than we were forecasting, some criticism is warranted. Wanted to make a few points from my perspective as an explanation but certainly not an excuse for what wasn't a good forecast. Apologies if this is a bit meandering and a lot long. We were well aware of the models that showed the heavier amounts; climo and time of day definitely played a role in not really fully buying into the extreme amounts. At the same time we were also well aware of the potential ingredients it had going for it toward producing heavy snowfall rates, many of which I included in my AFDs so I won't list them here. I saw the points made about snowfall rates and run angle w.r.t. road impacts and the point is well taken that extreme rates can and will overcome the hostile sun angle this time of year. On the day before the event, I wasn't doubting that there would be heavy snow, mentioned it and the TSSN potential. The main questions in my mind were exactly how heavy it would be, how long/persistent the heavy rates would last and how narrow the area affected by heavier rates would be. These are important because I think the sun angle is still part of the equation. Once the rates eased on Sunday, the accums basically stopped until toward and after sunset, which showed the how important it was to get that very persistent death band with 30-45+ dbz echoes to get the sig accums, accums on roads and magnitude of travel impacts that occurred. Ultimately I think it's hard to fully buy into the idea that we could be staring at a historic event, despite there being support from the Euro/NAM12, SREF and RAP/HRRR, when the bulk of the snow qpf would occur during daylight hours. I believe it's a natural thing for a forecaster to gravitate toward the idea that some failure modes would help keep things relatively in check, given how rare heavy snow events are at our latitude in mid April. This appeared to be the case not just at my office but also at surrounding offices in the lead up to the event. I do believe that if the heaviest rates were forecast to be at night, we would've been more bullish with our amounts. I personally am leery of events that are very dependent upon dynamic cooling, an issue any time of year but especially in April because so much needs to go right. One of my most memorable busted forecasts was Christmas Eve 2014, a relatively similar setup modeled to what occurred on Sunday. I had made mention in one of my AFDs of the potential for widespread intense warm sector convection to *possibly* mess with cold sector dynamics, with that 2014 event in mind, something that obviously didn't come to pass this time. With all of the above being said, I definitely was quite concerned for the potential for heavy snow rates Sunday AM-early PM, and hit my Saturday afternoon AFD and graphic much harder than the Friday PM ones and had a pretty good idea of what would end up being the hardest hit swath. In hindsight, I wish I issued a WWA instead of only a SPS with that Sat. PM forecast package considering what played out even though my amounts would've been too low. I was open to the idea, but DVN/MKX/ILX were not leaning that way, so ultimately felt I was lacking confidence to do one. I can't speak for the other forecasters at my office that worked the event, but I can assure you we all worked hard like we always do, but end result wasn't good. As to the slower response to issuing the headline on Sunday, I'd like to say I'd have been a bit quicker to do so given radar and report trends and that DVN and ILX had issued, and that it is a valid point of criticism. However, it's never an easy thing to be in the driver's seat at a NWS WFO with those decisions to be made. From asking someone who was there, I think it came down to exactly how persistent that extremely intense would be and how roads would respond, and how widespread impacts would get and wait more for trends to unfold. How it exactly transpired made it seem like we were ignoring the obvious but again I can assure everyone that it's not something that was taken lightly. We will certainly have this as important case to learn from moving forward, and I know I'll never forget it. Sorry again for this being long, but if you have any other questions, I'd be happy to at least attempt to answer.

Obviously tons of spread on that weekend system. 12z Euro ensemble leaned toward warmer OP a bit. FWIW Euro op did bring the Thursday night-Friday snows north vs previous few runs but still a miss locally. Also FWIW, GEFS mean for the first round in northern IL/northwest IN is about 2-4", a few members with decent hits locally or close by. Best that can be said at this point is that there will probably be a decent system in the region (could be a miss locally) Thursday-Friday with a stronger system over the weekend a good bet to bring precip here but everything else TBD. Hope for the best so that this cold start to the month doesn't go to waste and then hopefully onto a more spring like pattern. Sent from my SM-G965U using Tapatalk

I'm sorry to keep harping on it, but the map posted on the main Feb thread shows your standards are pretty high. 125-150% of normal snowfall since January 1st is objectively not terrible. December 1st to early January objectively was terrible. Of course it's been better north and west of us this month and we've missed some fun. But it's been very active since mid January and we had a very good stretch of snow from the January 12th system through Feb 1 and close to normal snow this month. Plus one of the most significant ice storms downtown in years (decades?) on Feb 12th.

I have my eye on Tuesday-Tuesday night for fronto snow. GFS has been consistently more north, favoring WI, but 12z GEM was nice for northern IL. Sent from my SM-G965U using Tapatalk

18z NAMs came in way south/east, with surface low tracking over Chicago area. 3km is even farther south than 12km. Both show a rain/thunder to heavy snow and wind scenario for northern Illinois. Only run that's shown this so we'll see if it's a one off. Would certainly fit the idea of the low coming in farther south. Sent from my SM-G965U using Tapatalk