RCNYILWX

Euro ensemble still with a reasonably solid look around that time and even some individual member support. Risk there is the ridging out ahead, and any system favoring far north/northwest sub. However, the smoothed out ensemble mean isn't going to do a good job picking up the influence of the -NAO and its tendency to limit how far north/west systems can track. This is despite the ensemble mean showing a strong signal of a -NAO and the teleconnection chart from the 12z run backing that up. @Hoosier are we allowed to post images from WeatherBell on here? I could post some visuals to illustrate better if I can. Sent from my SM-G965U using Tapatalk

In grasping at straws mode, but just looked at the 12z EPS, and heading into Christmas Eve and Day it does have a pretty interesting look, with a frigid cold trough dumping into the Plains and ridging out ahead into the east though still with a -NAO signal. Surface pressure anomaly even hints at a surface trough over the southern Plains lifting into the lakes and an expansive high over the northern and central Plains. A few of the individual members as expected from the above hint at some potential in the region during that timeframe. 00z run wasn't too different so we'll see if any continuity develops in that timeframe. Also GEFS not crazy far off but not as potentially interesting as the EPS. While we could do a lot worse than that modeled pattern, need to get it within 10 days. The hope is that *if* a system does develop in that timeframe, the -NAO could help prevent warm cutter. Sent from my SM-G965U using Tapatalk

Even though modelers will tell you the RAOB data doesn't affect performance much, it's not what we're seeing anecdotally with a lot of these systems. It seems like with every system in recent winters, drastic changes and or variability occur prior to main wave or one of the primary waves coming ashore from the Pacific, followed by a relative stabilizing once there's full RAOB sampling. Sent from my SM-G965U using Tapatalk

If you're in northern DVN to northwest 1/3 or so of LOT to MKX, have to like where you sit at this point. For points south, if weaker and southeast trend from last winter resumes, not sure that really helps because the strong dynamics are an important factor in getting the potential 6"+ accums.

Here's the snow depth output, which might be more realistic in this setup with ratios likely to be sub 10:1 for much of the event. Sent from my SM-G965U using Tapatalk

Not too surprised to see how things have trended for the Chicago area. Going to have to see significant changes tonight and tomorrow to have hope of getting decent snows into the heart of the metro and south metro. At this point, far north and northwest metro clearly has best shot. Sent from my SM-G965U using Tapatalk

Also shows marginal temps overall. Surface 0 line is way up in northwest IL valid 12z Saturday. Gonna need heavy rates to consistently overcome the boundary layer issues. Sent from my SM-G965U using Tapatalk

In that setup, your backyard would be screwed until winds flip northwesterly Saturday evening. Lake is still quite mild. Sent from my SM-G965U using Tapatalk

Some initial thoughts on weekend system... When I posted a few days ago, wasn't too optimistic because of the bad antecedent air mass and rain prior to any snow. What happened in the past obviously doesn't determine what happens in a different event in the future. But, the fact that good rain to snow scenarios are rare suggests that lots of things need to work out at this latitude, so to be skeptical in this range. Give a nod to Euro for decent run to run consistency past couple days. But since it's the only model that's been showing this on the operational, want to see some multi-model support before getting more excited. While the EPS members trended better up until 06z run this morning, what I've noticed in the ensembles overall (including 12z GEFS) is that a majority the members with a solid hit favor areas north and northwest of here. The 12z UKMET looks like many of these ensemble members. It's gonna be a big time thread the needle to get a strong enough system to get good totals without it being biased farther northwest in the key synoptic features. Also wanted to note to use caution in getting too excited by the 10:1 and Kuchera maps from the Euro. As modeled on recent runs, temps don't fall solidly below freezing until the end of the event, along with good cold advection aloft (850 mb) not arriving til Sunday morning. These are all reasons to lean lower than 10:1 for ratios. I'd suggest looking at the snow depth output from WxBell or weathermodels.com as a good first guess and then can assess reasons why you'd get ratios to 10:1 or higher in spots.

First post a long time. Have nothing really optimistic to add to what's been written recently for the next few weeks. Barring no major changes for the weekend system (I'm not currently liking that period to work out), going to have to hope there's something snow wise in the cooler interlude behind that. Interestingly enough, both the GEFS and EPS have a -NAO look for most of their recent runs. Problem is they both develop a ++EPO toward the end of the run, which would torch the CONUS even in the presence of a -NAO. Would in all likelihood mean another warm Christmas period if that look pans out. Concur that January is probably best chance for a decent snow pattern for a time. For what they're worth, weeklies kind of point that way as well. In our local winter outlook (NWS LOT), we leaned warmer (actually got a nastygram from CPC for going against their temperature outlook 2 winters ago so we didn't explicitly say warmer than normal), and AN precip, which has strongest signal in Ninas. Since December is leaning dry, we should get most of our winter precip in J-F. Snow wise, think somehow we'll end up within range of normal. Last year was crappy as we all know and it eeked out just slightly below normal, though did have a head start from late Oct-Nov events. We're overdue for an area wide higher end warning event, so hoping we get 1 or 2 systems to track favorably. Figure if we do get into a more classic Niña pattern, we can manage to get one to work out ala 1999. Sent from my SM-G965U using Tapatalk

I think you might be right on that, someone can correct me if I'm wrong though. Sent from my SM-G965U using Tapatalk

Lurker on this thread from the Chicago NWS office. I'm originally from NYC, so interest in weather started with noreasters, especially Blizzard of 96. Anyway, have noticed a lot of discussion on WxBell snow map algorithms. Last winter out here we found that for the Euro the modeled snow depth algorithm often did a better job than the clown maps. Curious if any of the other mets on here have noticed similar. For all those getting a pasting from this storm, enjoy! Sent from my SM-G965U using Tapatalk

Liking the ARW tomorrow night and Euro continues to be locked in. If we had northwest flow aloft, would've been better for faster propagation and maintaining severe farther south. That said, temps well above 80 deep into evening with 70s Td, and breezy southerly winds should yield at most a shallow stable layer. Expecting the outflow and 850-300 mb thicknesses pointing southeast ahead of the MCS to do the trick in keeping it decently strong farther south than you'd normally expect given less than ideal 500 mb flow and time of night. As Alek has been mentioning, in support of this idea is strong low level jet pulling from a very steep lapse rate plume, and large (>2k j/kg) MUCAPE reservoir. Best chance for severe winds in LOT CWA looking like northern tier but could see severe threat extending south toward I-80. The faster movement the better to maintain intensity farther south. Edit: spoke to SPC day 2 update forecaster and it sounds like he's gonna pull the risk areas farther south, with slight possibly down near or slightly across WI/IL state line.

It's still running on the ESRL page. Obviously not nearly as good an interface as COD. https://rapidrefresh.noaa.gov/hrrr/HRRR/Welcome.cgi?dsKey=hrrr_jet Sent from my SM-G965U using Tapatalk

We fixed it. 82 is what we came up with, which is much more reasonable. I believe that was with the help of the observer doing a manual observation. The ASOS had a power surge that likely resulted in the problems. We also noticed that the low temperature in the afternoon CLI was incorrect, erroneous 54 degree reading at 10 something AM CDT. Sent from my SM-G965U using Tapatalk

Any flooding you know of there? Sent from my SM-G965U using Tapatalk

Just put out an infographic on our website and social media. Even though Chicago and Rockford didn't overperform, it was still the coldest May morning since 5/3/04 at ORD and coldest since 5/4/05 at RFD. I did a quick query for the Rensselaer COOP site which bottomed out at 24. There's 9 missing years but most years do have data going back to 1902. The low there is by far the coldest in their records in the month of May. The latest reading of 24 degrees or colder is April 25th. Sent from my SM-G965U using Tapatalk

Regarding this potential event and 4/14/19, I think that these are two different scenarios, though it's a fair point about the temperatures leading in. Aside from the NAM likely being overamped with a much stronger synoptic forcing and low level response (closed 850 mb low, 50+ kt southwesterlies at 850 mb, even tighter thermal gradient and f-gen response), the other guidance seems to be pointing toward this being driven heavily by narrower mesoscale banding. 4/14/19 was a stout synoptic system with a strong deformation axis with embedded f-gen circulation. I certainly think there will be road impacts with this event given the favorable timing and obviously as last year showed heavy enough rates overwhelm even April sun. But paradoxically, temps in this case will have to be driven downward solely by evaporative cooling, as well above freezing starting point won't be aided by radiational cooling since clouds will have been increasing by then. The guidance is showing dew points ending up around 31-33, so I do think it's plausible many areas outside the heaviest banding end up staying above freezing, while locations within heaviest banding are driven down to 31-32. Euro may be overzealous in keeping even places within heaviest banding above 32F, though I can't completely discount it because it tends to perform quite well overall with 2m temps. In this event, I'm not sure yet that more than a narrow area and a good deal narrower than 4/14/19 gets the very heavy rates for reasons I mentioned earlier. I'm curious to see how roads behave since in the March 22-23 event, it was surprising how little impact the 3-6" amounts had overall.

Having looked at things a little bit, some thoughts: The model guidance is overall in good agreement conceptually that there will be a fairly narrow band of higher QPF and snow. This will be driven at the mesoscale by response to a strong f-gen circulation amidst high moisture for a snow event (PWATs up to 3/4"). It's too far out to be a lock still and we know how things went at this time range during the winter. However, we can be reasonably confident that the above scenario will play out in some fashion. That said, while models are good at indicating f-gen response, actual placement can vary substantially at go time. Temperatures, while chilly for April, will warm to 45 to 50 Thursday PM. With late August equivalent sun, road and near surface soil temps will be quite warm going into the evening. Evaporative cooling will quickly cool air temps, but it's possible they only get down to freezing, or even stay above freezing, as shown on 00z Euro. Ground and especially road temps will lag. This will cut into accumulation efficiency and the ratios despite the otherwise very favorable timing to get sig. accums in a late season event. Going back to the placement of strongest mesoscale forcing from the f-gen, another thing we know is that in intense mesoscale banded setups, there is subsidence outside that band. Considering the marginal surface temps and antecedent warm ground temps, accumulations could struggle outside the heaviest banding. Inside that banding, rates could be 1-2"+/hr. But even there, road impacts might be mitigated some like the March 22-23 event. The snowfall gradient *may* end up tighter than modeled due to the above factors. At this time, there is a decent shot at wet snow accums of 6"+ within the heaviest banding. However, regarding headlines, unless we become confident in amounts well over 6", we might be able to get by with an advisory given overnight timing, less cars on road due to covid and possibility that marginal surface and road temps mitigate road accums and impacts. As an example, the 00z Euro increased QPF amounts vs 18z run but actually only has narrow areas of 6"+ within LOT and DVN CWAs due to the marginal 2m temps and low ratios.

April 2, 2016 redux. Sent from my SM-G965U using Tapatalk

The thinking for our area is that the biggest concern is the strong capping that could potentially hold. However, the conditional threat is rather high given how steep the lapse rates are along with more than sufficient bulk shear. We routinely get marginal or even slight risks in this sort of scenario where strong EML capping is a concern. And then to go farther and remove the general thunder when that's always broad brushed while several models not just the Euro show CI in the area it was removed from is an even bigger head scratcher. The Euro has had essentially the same scenario for 4 days in a row, which doesn't necessarily mean it's right, but it hasn't diverged as it's gotten closer to the event. Considering that the Euro typically does quite well with temperatures, dew points and thus instability in this area, I'm not sure why it was completely discounted by Goss. What makes it tough is that the outlook text doesn't even explain why the change was made, plus the fact that within marginal or slight risk categories the SPC never collaborates proactively with the WFOs. We have to chat them to get feedback about how the outlook may look. Sent from my SM-G965U using Tapatalk

I'm completely baffled by that outlook. The ECMWF has had CI over northwest/north central IL every run since at least Friday. And SPC took general thunder out from that area. It makes no sense. Sent from my SM-G965U using Tapatalk

Liking Tuesday for a potential NW flow severe event somewhere in N/C IL. Wind/shear profiles provisionally would favor supercells and models in good agreement on strong EML with plume of very steep lapse rates overhead (near or above 8C/km 700-500 mb). 12z ECMWF verbatim would support a potentially sig hail threat. Boundary layer moisture and thus LCL heights are somewhat questionable for for tor threat. There's been variance on warm frontal progress, though 12z op runs favored area getting solidly into warm sector ahead of cold front. Warm front getting hung up some would probably elevate tor potential. Sent from my SM-G965U using Tapatalk

I can confirm that IND has a positive COVID case. IWX is providing service back-up through the weekend. So far so good here. Hopefully it stays that way. The way the agency is limiting our potential for exposure is by limiting people in the office to 2 people as much as possible, with main exception to that being severe weather. Everyone else is teleworking and we've developed remote capabilities so teleworkers can help the ops staff as needed. Last Saturday, we had someone doing mesoanalysis remotely. Edit: just got word it wasn't a positive case but someone who is a high risk of testing positive because of exposure to a positive COVID case. That forecaster is on quarantine and those who were in contact with the forecaster are self quarantining. They are planning to open back up tomorrow.

Moderate risk coming for eastern DVN, western LOT and northwest ILX CWA with day 2 outlook. Sent from my SM-G965U using Tapatalk