RCNYILWX

Edit: I put this in the Medium LR thread now, but left it here too. Need a banter thread. Surprised no one posted about the 12z GFS - actual potential in not clown range. But in all seriousness, the 12z GEFS does have an intriguing look later next week, which would fit in the window Joe alluded to on the Medium LR thread. Beyond that, we'll see if things go to a favorable pattern for decent clippers/Pac hybrids. Overnight ENS pointed in that direction. Attached is the composite mean 500 mb heights for December 2010. That had a bigger system (the Metrodome roof crusher) on the 11th-12th then trended to a good clipper pattern through the holidays. It was a Niña with a high end NAO block. We'll see if we have a relatively similar progression this month. The NAO block should have staying power given the forecast magnitude, so if snow can be put down it'll likely stick around. Sent from my SM-G998U using Tapatalk

A few things are becoming clear for December. Not going to be persistently mild, which is already a change from the last several Decembers. Snow chances are more nebulous, at least through the next 7-10 days. It's clear that the models are struggling with the very progressive and northern stream dominant pattern we're in now. I actually think the retrograding NAO block has some potential to help in that regard. There's some chance for corridors of light-moderate accums in portions of the sub next week but don't expect the models to handle them with solid lead time. Last night's EPS was a step back in the right direction in the day 10-15. Following a brief pseudo +PNA Rockies ridge which may still offer some Pac clipper hybrid type threats, the block connects with the EPO domain block and a signal for lower heights (-PNA) on the west coast toward the end of the run, with neutral heights elsewhere. So basically the connected blocks would allow for a more zonal pattern and not one crushed by the northern stream, plus having sufficiently cold air available due to -EPO/-NAO. Not going to say I'm confident yet in decent event(s) materializing toward and beyond December 10th, but could do worse than the look of the 00z EPS last night. It's a misnomer to think that a big -NAO has to be bad out here. It helped deliver late Jan-Feb 2021. February-March 2013 was another solid stretch of winter weather with a prolonged -NAO. December 2010 was a solid winter month for many with a huge -NAO (Jan was drier and favored EC then the -EPO and -PNA delivered you know what in early Feb 2011. 2009-10 was a very good winter in a moderate El Niño no less with a historically strong NAO block. There's obviously counter examples that mostly benefitted the east coast, such as March 2018, though that did have the late March event for parts of IA and IL. The thing most of us, especially with westward extent, don't want is a big +PNA, which with a -EPO and -NAO would be CAD hell. If you like snow, it not being mild is part of the equation, so we should have that for a good chunk of the month, which we haven't had since 2016 and 2017. Could many of us get skunked? Sure. If I were to bet I'd probably go around normal for ORD (7.7"), which a. shouldn't be that high a bar to clear and b. ORD hasn't had AN December snow since December 2016 and before that previous AN snowfall Decembers were 2013 and 2010. Yikes.

Best in NW IN within the past 10 years was on January 21, 2014 when Griffith area had 20-24" of snow with estimated rates up to 4"/hour. That was the most recent truly high end purely LES event in the LOT CWA. Sent from my SM-G998U using Tapatalk

Will be making the annual return to more frequent posting soon. Been a crazy 6 months personally (house stuff). Encouraged by the generally persistent ridging up near Alaska shown on the ENS data. No black hole PV in that area is a good sign for the season. Warm Novembers in La Niñas since 1950 that were driven by a strong positive +EPO were more prone to featuring a predominantly ++EPO and AN to well AN temps in DJF. Even if this month ends up AN due to the very warm start, it will have been driven by a strong-PNA and southeast ridging to start the month. The decent northeast Pacific pattern progged in the ensembles backing up what the seasonal/weekly models showed for November at h5 leaves me feeling more glass half full rather than glass half empty.

I went 95 MDW, 94 RFD, and 93 ORD. Your call is definitely reasonable. The two degree difference between MDW and ORD seems about right. Today they were more uniform because the lake breeze went through MDW slightly earlier than ORD. Sent from my SM-G998U using Tapatalk

I don't share the optimism for appreciable short term dryness/drought relief rainfall this weekend in the Chicago metro. The Saturday morning potential is from a likely rapidly decaying MCS due to outrunning the instability axis. While the 12z ECMWF, Canadian, and UKMET have optimistic outputs for the Saturday evening/night threat, the timing seems rather late and western and southwest/southern CWA appear more favored for any decent totals. Of the two periods, Saturday evening/night has the highest but still low chance for widespread appreciable drought relief. Sent from my SM-G998U using Tapatalk

I've been having a friendly back and forth with Gino (who bumped ORD and RFD to 100 with evening update yesterday) re. whether ORD would hit 100 today. I've been going with 99 since earlier this morning and feel decent with that call but 100 is definitely still in play. Personally rooting for it to happen because 100 has become one of the unicorn temperature extremes in my time here (almost 12 years now), with it not happening since the legendary 2012 summer. Here's what I had as of like 8 or 9am today: MDW: 101 ORD: 99 RFD: 99 Sent from my SM-G998U using Tapatalk

While the ECMWF/EPS combo certainly tends to verify better in the medium-long range, still too far out to be completely confident in what the last few full runs (00z last night and 12z today) have been showing. That said, the Euro really does mute the heat and humidity locally for several days after Tuesday. I'm bearish on even the guidance with more extended heat and humidity being supportive of meaningful severe threats locally, so imo after the mostly miserable past 5-6 weeks, bring on what the Euro is showing Wednesday-Friday next week. The far northwest parts of the sub could get some action closer to the better mid-level flow and upper support and a less dry and capped column. Sent from my SM-G998U using Tapatalk

I envision this being similar to 2018 but the flip to summer set back deeper into May because the SPV disruption happened in March this year vs February in 2018. Sent from my SM-G998U using Tapatalk

Piggybacking on Joe's post above, the teleconnection forecasts are legit the stuff of nightmares for this time of year, unless you like extended winter. Both the EPS and GEFS indicate deeply negative AO, NAO, and EPO. The EPS, to make matters worse, has the PNA trending to weakly positive later in the run. The 18z GEFS was marginally better for keeping the pattern more active with a weak negative PNA. Meanwhile, the control runs, on the other hand showed opposite PNA trends to the ensemble means, so it does appear there's uncertainty in that regard. At best, we're looking at a continuation of the below normal temps with regular bouts of precip and maybe a thread the needle severe threat or two. At worst, we'd enter into CAD in early May with little/no threat for thunderstorms, let alone severe weather. Given the consistency of the ensemble mean height anomaly forecasts with the teleconnections, main takeaway is to continue to hold off on doing much planting until Mother's Day and beyond. Sent from my SM-G998U using Tapatalk

Toss the GFS. I'd be really surprised if it's not doing the same over-deepening and earlier closing off of short-wave troughs that it exhibited leading up to the February winter storms. The much quicker and thus earlier occlusion process has been resulting in the much faster frontal timing and a much lower ceiling threat on Wednesday. The 18z run did show some baby steps toward the consensus later frontal timing on Wednesday, with the front not coming through Chicago until 00z now. Problem with the NAM at this range as well is that the wave is not coming ashore until tomorrow morning and thus off its domain currently. The gap is filled in with an interpolation from GFS domain. So it shouldn't be too surprising that the NAM also has a faster frontal timing than the foreign guidance. It's times like this (barring an unexpected GFS "win") when the GFS and many GEFS members being bad is that it unnecessarily adds uncertainty to a forecast on big picture items that wouldn't be there if we weren't using the GFS. Edit: Regarding chaseability locally on Wednesday, there's the morning/mid day southern wave that may cause destabilization issues depending on how quick it is to get out. On the other hand, just for reference, April 9, 2015 also had extensive earlier convection. There's definitely questions on storm mode even with the later frontal timing. The magnitude of forcing, less than ideal shear vector orientation to the cold front, and the rapid fwd propagation of the front may spell fairly quick transition to QLCS east of the MS River.

If I'm not mistaken, the western half of LOT being in the day 5 outlook for Wednesday is the first time any part of LOT has been in a day 4-8 outlook in April since April 9, 2015. Seems fitting that the day 5 inclusion would come on the 7 year anniversary of Rochelle-Fairdale. With the exception of the GFS being a fast outlier still on Wednesday, the ECMWF depiction, supported by the GEM and UKMET, certainly warrants the large 15% area all the way up to the upper MS Valley on the day 5. The deep layer bulk shear magnitude and low level wind profile are supportive of supercells and tornadoes, but shear vector orientation is too close to parallel to the cold front due to the meridional mid and upper flow. That plus the strength of the synoptic forcing Wednesday evening may yield initial supercells and tornado threat west of the MS River transitioning to a squall line (with QLCS tornado threat) with eastward extent. I think the day 5 outlook depiction is reasonable, as the timing on the non GFS consensus is a bit late for the eastern half of LOT. It's not a slam dunk severe weather outbreak, but it's a solid setup for this region by recent April standards. Certainly still time for changes for better, or for worse. The potential warm front setup on Tuesday looks a little less favorable than my initial post, with later arriving moisture and decreasing forcing with southward extent, making breaking the cap more uncertain. If any storm can go Tuesday evening, would still have a tornado threat. Otherwise, most of the convection Tuesday PM will likely be elevated north of the warm front, with the steep mid-level lapse rates potentially supporting a severe hail threat if large enough MUCAPE materializes given favorable deep layer shear.

Bumping the short range severe thread for early-mid next week. Particularly Tuesday-Wednesday, not quite short range, but not really medium-long range either. Anyway, on the 00z operational runs (the extent of my model analysis), both the Euro and GEM featured an intriguing I-80ish warm front scenario on Tuesday afternoon-evening in IA, IL and IN, with well into 60s and 70s surface temps, low-mid 60s Td near and south of the front. (ECMWF actually indicates front near/north of I-88 valid 18z Tuesday but then reinforced south to traditional I-80 and south during peak heating). Meanwhile, the UKMET holds a rather volatile looking setup back to Wednesday afternoon and evening. On everyone's favorite GFS, the timing was out of whack, but large scale pieces pattern wise are there for severe weather potential. Importantly to the setup, a reservoir of very steep 7.0 to 8C/km (or higher on some guidance) 700-500 mb lapse rates are currently favored to be advected northeastward and in place for the warm frontal zone/warm sector. This suggests that modeled 2000-2500+ J/kg ML/SB CAPE forecasts are not outlandish. Lots of questions still on evolution of the trough ejecting out of the west and the track, strength, and timing of the main surface low that emerges out of this. For this reason, Wednesday certainly has potential, but is very contingent upon multiple favorable factors coming together. Tuesday on the other hand has had recent support from the ECMWF and GEM for the warm frontal zone (possibly weak secondary low for a time) to be draped across roughly the I-80 corridor at peak heating paired with solid southerly surface flow south of the front, a decent LLJ, and brisk west-southwest mid-level (500 mb) flow of 40-60 kt, for roughly 35-55 kt of deep layer bulk shear, favorable for supercells. One of the key elements of uncertainty on Tuesday is sufficient forcing for ascent, as modest height rises are progged, so subtle vort lobes from 700 to 500 mb may be needed, though the capping doesn't appear too prohibitive. Finally, getting just enough lift isn't a bad thing when it comes to potential warm front setups for chasing/spotting interests, to keep activity discrete. It'll be interesting to see if this possible Tuesday PM scenario holds as we get closer. While a substantial severe weather episode is far from a high confidence proposition at this lead time, would be surprised if there's no instances of severe weather in the western half of the subforum between Monday night and Wednesday PM. At the least, the EML points toward threat for elevated hailers north of the surface front.

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