RCNYILWX

January 2nd 2014 or the event later that month that slammed Cook and then especially northwest Lake County. Sent from my SM-G965U using Tapatalk

925 mb temp watch: 00z RAOB at OAX (Omaha, NE) Observed: -0.9C GFS: +1C ECMWF: 0C Sent from my SM-G965U using Tapatalk

For the benefit of the board, a visual of our grand total snowfall forecast tonight-Sat AM snowfall from the LOT dayshift (MTF through 12z Thursday portion and myself the rest of the event). This ended up falling out pretty close to the internal graphics WPC shares with the WFOs for collaboration purposes and I think looks pretty reasonable based on all the available data. We've been breaking the forecast into two separate "events" in graphics and only going with the first part on the probablistic snowfall page. That's because we feel that putting out the grand total snowfall forecast in a public facing graphic on the web and especially social media would make the event seem more impactful than it will likely end up being. Plus, as has been discussed, the net snowfall will end up some percentage lower than this grand total when accounting for melting and compaction. Will post additional thoughts later.

Honestly don't know what's going on at this point, why I said hopefully they do a case study and can attempt to address the issue if it ends up being wrong as seems likely. I wish I could give a better explanation. The divergence crops up on Thursday morning and then it's a strong outlier until Friday night. I think one of the best timestamps to compare is 12z Friday. One of these things is not like the other (00z GFS, 00z NAM, 00Z GGEM, 12Z ECMWF, 00z GEFS ptype as proxy).

100% agree. I was looking more closely at the various model depictions and the GFS doesn't make much physical sense. Particularly Thursday night into Friday, there's barely any thermal gradient with a developing and strengthening 925 mb low and it keeps doing this run after run. Regardless of ultimately how things turn out, the 00z NAM depiction makes sense as a direct point of comparison. It has the warmer air on the east and southeast side of the low wrapping back into the colder air on the north and northwest side of the low. The GFS has most of the 925 mb low uniformly from 0 to +1C until Friday evening, like it's wrapping that air in and locking it in place. If the GFS ends up wrong as we expect, would hope the modelers at NCEP will investigate what went wrong. Based on WPC's internal collaboration graphics this afternoon, they completely tossed the operational GFS thermal profiles as well. Sent from my SM-G965U using Tapatalk

Agree that better dynamics could be at play later on in the event. Also it's late January and not late March or April, that helps. I was thinking about the daytime vs nighttime issue and even though it's not worry about sun angle season yet, would think with such marginal BL temps, daytime might hurt if rates are too low vs same conditions at night. Sent from my SM-G965U using Tapatalk

If anyone is looking closely at point and click or hourly weather graphs for this event we do have a fair amount of rain and snow mention during the day on Friday because of surface temps being as marginal as they are. Would think that at periods of lower precip rates that we could mix or flip to rain, or falling snow would not accumulate and essentially function as white rain. Sent from my SM-G965U using Tapatalk

Exact details of the setup are certainly still subject to change, especially farther out in time, but I have a hard time believing all the other models and ensembles are wrong on 925 mb temps. Sent from my SM-G965U using Tapatalk

I think we can safely toss the operational GFS 925 mb temps. That doesn't detract from the concern about how marginal the surface temperatures are for accumulation efficiency. Ratios would also be below 10:1 much of the time, so accumulated liquid precip as snow at an average 8:1 ratio might be the way to go. Not sure why the Kuchera map on WxBell has higher snow amounts than 10:1, since Kuchera method is supposed to account for more marginal setups to give lower than 10:1 ratios. The 12z Euro favored time windows for the LOT CWA/Chicago metro would be later Wednesday night into Thursday morning, Thursday night into Friday morning and then later Friday afternoon-Friday night. There would likely be lulls in between these windows. Sent from my SM-G965U using Tapatalk

Looking at ptype progs from individual members, such as on COD, the ensembles are still nothing like the operational. Sent from my SM-G965U using Tapatalk

The GFS stubbornly keeping 925 between 0 and +1C is really what it comes down to. The other models aren't doing that. On the midnight shift last night, the forecasters considered the GFS thermal profiles to be an outlier. That said, the combination of weak and disjointed forcing and marginal BL conditions means that accumulations tomorrow night through much of Thursday night will likely be inefficient (lots of white rain). Would look to Friday and Friday night as the upper low gets closer while slowly deepening and the system develops better deformation precip for a bulk of the snow accumulation, wherever that max axis ends up. Sent from my SM-G965U using Tapatalk

I find it interesting that the GEFS has consistently been hitting this harder than the operational GFS. Perhaps different physics packages helps explain, but also, in an inherently complex and odd setup like this, the higher vertical resolution of the op vs the ensembles might be of detriment. The lower vertical resolution of the ensemble can help smooth out features as opposed to what at times can be garbage in garbage out with the operational models. We haven't really seen this behavior with the ECMWF suite for this potential event but it can be an issue at times. My inclination now would be to lean toward the GEFS and ECMWF suite since those have been more consistent. Outer ranges of NAM have pointed more toward the latter. As things stand right now, this doesn't look like an exciting event (aside from a interesting analog mentioned in previous posts), but with such a long duration, could add up to respectable totals on colder surfaces if things break right. In a mild hemispheric pattern, I'd take that as a win. Since I like to think of local events that may have some similarities, off the top of my head came up with January 14-15, 2018. That was a long duration 3-6" snow due to a slow moving ULL, though it was much colder aloft. Parts of DeKalb, Kane, and DuPage had a jackpot zone of 6-7". https://www.weather.gov/lot/2018Jan15_snowfall Sent from my SM-G965U using Tapatalk

Would suggest posting Midwest view Sent from my SM-G965U using Tapatalk

GEFS did once again. Ride the ensembles. Sent from my SM-G965U using Tapatalk

WWA for Porter County. Still a good amount of uncertainty close in, as latest HRRR is earlier to focus the convergence into Lake County, and actually has slightly higher amounts in eastern Lake than within Porter County. It then goes onto scrape the Cook County shore with the band. NAMnest on other hand primarily focuses on Porter County much of the time and never gets the heart of the banding over Lake County and misses Cook County altogether. Sent from my SM-G965U using Tapatalk

Need a halfway decent lake effect event. Even in the worst winters, usually get at least one. As an example, 2011-2012 had a short but intense LES event for NW IN in Feb, for which we issued a Blizzard Warning. 10" of snow in spots in 4-6 hours with 40-50 mph wind gusts. Sent from my SM-G965U using Tapatalk

Great, informative post. Have learned a lot about long range forecasting from reading your posts over the years. Sent from my SM-G965U using Tapatalk

Check Don S's stats on strong MJO waves in the warm phases. Almost every historical case (7 of 8) since 1950 I believe of p4 wave at or above this year's amplitude progressed into phase 7 and 8. Most cases featured the wave being at least at an amplitude of 1 on the RMM plots for at least 14 days, which implies that the ECMWF ensemble should correct toward bringing the wave into phases 7 and 8 and potentially 1 and 2. CFS has gone to this idea. Also, phase 7 composites for January are colder for the east than the trimonthly composites on the CPC website. This doesn't mean anything for snow chances down the road, just that pattern should be going to more persistently colder. Sent from my SM-G965U using Tapatalk

I think that, however much one wants to ascribe CC to things, the reality of the winter climate on the west side of the lake at this latitude (Chicago area and west) is one of volatility. These forums became really popular back in the late 2000s and early 2010s. 07-08 through 10-11 happened to be the best 4 year stretch for winter enthusiasts in this area since the late 1970s. Since that stretch, it's been much more mixed. The highs of the highs (13-14 and GHD II) and the lows of the lows (11-12 and 16-17) and a lot in between. Last year was extremely cold and active just west and north of here through Feb after a break in December-early January and we had a good stretch of winter from mid January through beginning of Feb. 17-18 had fairly lengthy doldrums but also had a memorable stretch of 9 straight days of measurable snow and the bitter cold of late December-early January. This really isn't unusual for our winter climo. Think back prior to the 4 year run, the 00s were not great until then. 00-01 had one great month, 01-02 was one of the worst winters until March 02 (which still sucks when you think about it), 02-03 was only good east and southeast of here and 03-04 was also not good here. 04-05 had one good month in January and 05-06 was torchy with only 26" at ORD. The 90s also were very mixed, with the best event of the decade being of course the 99 blizzard. The 80s were mixed for snow as well, 81-82 the big snow season of a decade otherwise known more for its extreme cold shots. So I understand why there's a lot of complaints about this winter, it hasn't been good for winter interests after the early start. If it doesn't turn around in the snow department, then it would rightfully deserve a low grade, but it wouldn't be unusual in the context of winter climatology. Stringing together good stretches and getting things to break our way with storm tracks or not is what separates the good from the mediocre winters and often one or two events separate good/mediocre from bad. It's the winters like 13-14 and the late 70s are the exception to the rule and are once a decade or every couple decades type phenomena. Having 4 consecutive good winters like 07-08 through 10-11 is also rare on the climo spectrum, but a lot of us are constantly hoping for a stretch like that.

00z EPS (ECMWF ensemble) has continued theme of last few days of going to a very cold pattern look out in the day 10-15. MJO is at a very high amplitude phase 4 crossing into 5, warm phases for the winter explaining the very pronounced east/southeast ridge currently. According to information posted on other subs by Don S, this progression has historically supported the MJO wave keeping enough amplitude to progress into the colder phases. Assuming this holds, the idea of a sustained colder pattern unfolding later in January and beyond holds merit. The GEFS has also basically gone over to the EPS idea out in the extended. I still think our best chance for a more significant spread the wealth type of event would be prior to the pattern going in the direction of the EPS, if it's on the right track. Thereafter, the exact position and orientation of mean western and Alaskan ridging and downstream trough over will determine whether we go to a very cold and dry clipper type pattern (ex. Feb 2015 after GHD II) or a more active but just as cold pattern (ex. January-February 2014). Sent from my SM-G965U using Tapatalk

Alek to Geos bullseye in IL. Lock it in. Sent from my SM-G965U using Tapatalk

The 00z EPS, in a big change in recent days, went to a broad west coast ridging and Alaska ridging out in day 10-15. PNA trended back to neutral on the teleconnection charts. So the hope there would be to not have an amplified western PNA ridge. If that sort of look verified as shown on the EPS it might be an active clipper/hybrid pattern versus the true dreaded CAD when the PNA ridging becomes more amplified and east based. Also that sort of pattern would be good for the lake effect belts. I've read some LR gurus wondering if EPS is rushing pattern change some, but it's done pretty well thus far this season. Edit: As posted above, that look would more likely favor the east coast for larger synoptic systems but still no signs of a -NAO. Sent from my SM-G965U using Tapatalk

The tight baroclinic zone over the region indicates potential for strong low and mid level f-gen and associated banding. Don't need a wrapped up system to get good precip amounts in cold sector with that as the mid December event along I-70 corridor showed, along with some of the events in recent winters (Feb 8-9 2018 comes to mind up here). Also, there's good agreement in strong upper jet divergence for large scale ascent. There's lots of ways this could go and it could certainly be a minimal event, but also counter reasons why it could work out. Sent from my SM-G965U using Tapatalk

Although it's not registering as a -EPO on the teleconnection charts because of the strong negative height anomalies along the Pac NW coast, the mid week ridge spike over Alaska due to a deep ULL over the Bering Sea functions as a temporary -EPO to dislodge that very cold air and send it southeastward. Then it looks like another ridge spike over Alaska Friday into Saturday that's trended stronger on the EPS vs yesterday.

That's actually incorrect. Look at the GEFS and EPS ensemble mean 2m temps over the northern Plains and northern Lakes next Friday and Saturday. There's pretty high confidence in a cold surface high being draped north of us based off MSLP anomalies in both ensembles.