RCNYILWX

I looked back at the recent weak low-moderate Ninos, and it shouldn't be surprising to get a prolonged mild/low snow stretch. A crappy December is common in these events, and I wish we had stuck to our guns from original outlook with statement about December potentially being mildest of the winter. You have to go back to 76-77 and 77-78 for wall to wall weak El Nino winters. 14-15 only had a T of snow and was +4.2 at ORD in December. First half of January was cold and fairly snowy but then it was mostly mild and it took until after GHDII for the extreme cold pattern to lock in. 04-05 had 27.8" of snow at ORD in January but very little in December and Feb. 02-03 had a long stretch of predominantly above normal from 12/10 to 1/9. If the expected pattern flip this January does indeed get delayed til 2nd half of January, wonder if progression of this season will be more like 06-07. That had 5.8" at ORD on 12/1 and then no snow the rest of December. Only had 3.5" between 12/1 and 2/6/07, with February at -9.8 and 20.3" of snow. 94-95 was probably the worst recent low moderate Nino for the sub as a whole for snow, but it wasnt warm in Jan (+0.2) and Feb (-1.3) after a very mild Dec (+7 at ORD). Perhaps the outlooks can do a better job of conveying to not be surprised with a long stretch of mild/low snow. Just in general, outside the lake belts at around this latitude, only the rarest winters (ie. 76-78, 13-14) have had wire to wire winter. I'd be surprised if we don't at least get into a fairly long noteworthy period of cold at some point this winter, with snow still a wild card. Sent from my SM-G965U using Tapatalk

Caution is advised with the RMM plots right now due to a westerly wind burst causing interference and "masking" the likely true MJO propagation into colder phases with time. Also, expect significant run to run variability/volatility due to everything going on with forcing from the tropics. Good thread by Michael Ventrice here: https://mobile.twitter.com/MJVentrice/status/1078661726906789888 Excellent post here about it: https://www.33andrain.com/topic/1520-eastern-us-dec-2018-consolidated-discussion-obs/?do=findComment&comment=113432 Sent from my SM-G965U using Tapatalk

Much better developed cold sector due to the phasing but cuts much farther northwest for the same reason, as Stebo mentioned. The wishful thinking part of me will hold out hope for a happy medium between phasing and southern stream system having far enough east longitude when phasing occurs to allow for changeover to snow here in the Chicago area. Similar to a few nights ago, some 12z European ensemble members had this sort of idea. Sent from my SM-G965U using Tapatalk

The lack of any lightning this evening in IL was likely caused by a strong inversion around/just above H7. Freezing levels were low as you'd expect in late December on DVN and ILX soundings at around 6kft but with that inversion, very small MUCAPE and only about 3kft from freezing level to the cap. Sent from my SM-G965U using Tapatalk

Can see what you're saying, just taking 00z operational Euro as example. Southern stream wave coming up out of western Gulf region looks pretty juiced and there will be northern stream energy diving in across the northern Plains. Phase is narrowly missed, which would have served to deepen the surface low, pull in much colder air quicker and markedly expand cold sector precip. As it stands on 00z Euro op, system is mostly southern stream driven and thus warmer and gets only so far north and then sheared out eastward. There are a few 00z EPS and GEFS members that show the phase occurring and spin up a deep surface low with well developed cold sector precip. Wouldn't put high odds on it occurring right now, but worth watching for a few days. Sent from my SM-G965U using Tapatalk

Merry Christmas everyone. Hope the Christmas gift is for actual winter in January and accumulating snow for all the winter lovers in the sub. While the expected return of a colder pattern was certainly rushed in guidance from a few weeks ago, trends still look favorable for bouts of below to well below normal temps in January. Snow outside of the lake belts remains a wild card, but would be surprised if it's another near shut out for many areas. Sent from my SM-G965U using Tapatalk

Outer hours of the NAM caveats apply, but when you're hoping for a Christmas miracle, that 12z run is better than nothing. Sent from my SM-G965U using Tapatalk

Any takers on latest Christmas fantasy hope, this time on 12z Euro? A decent amount of Euro ensemble members show the system, but we're still far enough out that it could be a fake out too. Would like to see several more Euro cycles with the signal and better support on other guidance. Sent from my SM-G965U using Tapatalk

Euro also had the quick hitter on Sat. night-Sunday so was grouping that and Christmas day system in. Not gonna have any real expectations going in and hope things work out here and for others. Sent from my SM-G965U using Tapatalk

Christmas eve-Christmas morning miracle for parts of the western and central sub on 12z GEM and a not disastrous 00z Euro favoring northward extent. Obviously can't put any stock yet in the op runs verbatim but taking into account some recent op and ensemble members there *may* be hope for a clipper/hybrid or 2 to put down light-moderate accums somewhere in the Sat-Tue timeframe (likely favoring northward extent) and brief LES windows. Current signs are then pointing toward a torchy cutter for most except maybe far north and west sub Wed-Fri period. Would be nice if we could get even a bare minimum white Christmas here in northern IL in what's been a crappy month.

Consistent theme that's been showing up in this upcoming stretch starting late in the week through the end of the month is it being active. Will certainly be playing with fire and storm track driven with lack of entrenched cold airmass but there looks to be sufficiently cold air masses lurking to tap into. Could see parts of the sub taking a big chunk out or even removing the December snowfall departures if things break right. Latitude will likely help given the southeast ridging tendency. Sent from my SM-G965U using Tapatalk

The 00z Euro ensemble snowfall mean fwiw was also much more solid than it had been lately. Sent from my SM-G965U using Tapatalk

Gif created by Thundersnow12 Sent from my SM-G965U using Tapatalk

More in response to Jonger's original post lol. I think it's easy to forget we've been basically cold since mid October til now. We were overdue for a mild stretch. On the same token, I dont think anyone thought the late 70s or 2013-14 was walking through that door this year.

And also, not out of the realm some of us get lucky in the upcoming Niña like stretch. 12z FV3 lol: Sent from my SM-G965U using Tapatalk

I'd be really surprised if 2011-12 was walking through that door. In hindsight, the cold December thought was a fake out and this month likely finishing AN shouldn't be surprising in a weak Niño. Not sure how the snow dept will work out but no reason right now to punt the rest of the winter. I think we'll have some periods of exceptional cold at least. Sent from my SM-G965U using Tapatalk

Perhaps some similarities to late December 2012 for a time with the temporary Nina like state coming despite that year being a cold neutral. Wasn't any deep cold around but had 2 major events (12/20-21) and the 26th in an otherwise mild +EPO month. Sent from my SM-G965U using Tapatalk

Great post. I've seen it debated whether a true by the book SSW will occur but that a vortex split is still likely either way with tropospheric effects to come later. Though in recent days have seen increased confidence among strat experts that a true SSW will occur. I think there's a lot of merit to your idea of delayed but not denied with the deep cold. In the interim, I'm seeing on the 12z GEFS some dateline ridging around Christmas, so the hope is that the Niña like state you referenced will have workable cold around the region with western troughing and southeast ridging leading to a decent storm track. The possibly nice thing during then is lack of a big time AK vortex with ridging out by the Aleutians. EPS and GEFS are not too dissimilar earlier on in Christmas week but the 00z EPS reverts to a more strongly +EPO look with AK/GOA vortex more quickly than GEFS. Might be at least a few trackable threats that period before pattern becomes more hostile again? Sent from my SM-G965U using Tapatalk

I'm still learning stratosphere stuff myself, but it *should* be good news for the eastern US. There are cases when the SPV split or displacement evolution favors Eurasia for cold, though from what I've been reading that is not expected to be the case with this. Last February, the vortex split had a major role in the very wintry March and April in the east. Not everyone benefitted from major snows but there were certainly multiple opportunities in the sub. Definitely a wait and see on the pattern for the last week of December. Right now it's kind of an ugly look on the ensemble means. Really hoping for some blocking and there being some cold around so that favorably tracked systems give snow chances for some of us.

The ensembles definitely got worse the last week of December than what they had been showing for quite a while. Possible it's MJO influence which is forecast to be in phase 5 at that time, generally a warm phase for eastern US. OTOH, MJO can muck up long range predictability too. The big talk has been the assault on the stratospheric polar vortex, but perhaps the lag effects of this take us into January. Hopefully there will be some effects of the warming in stratosphere toward the NAO/AO domain being undermodeled w.r.t. there being more blocking and heights being kept lower in the east than shown verbatim on the ensembles. The main message is that the big -EPO that seemed to be highly likely doesn't appear to be coming back in December as things stand right now but with the large swings in LR this week, perhaps things are more uncertain than the normal uncertainty that far out. Pattern could be relatively active so it's possible some of us thread the needle and get some snow out of it. Certainly will need to watch the Thursday-Friday system for location and timing of phasing. Big signal for that system in the h5 anomalies.

My biggest worry out this way is something like 02-03, though for just east and southeast of here that was a good winter. I think the cold won't be hard to come by once the pattern changes. Hopefully it's more like most other weak Ninos with frequent light-moderate snows and we luck into a big event like GHD II. Sent from my SM-G965U using Tapatalk

Impressive flip from ++EPO to -EPO on 06z GEFS next week through Christmas. The good news is the ensembles continue to be consistent with this pattern flip. The bad news is the pattern will be brutal for most for winter interests until then. When the flip occurs, and from reading other long range gurus, have no reason right now to doubt that it will, the hope is that the look shown on the ensembles will equate to chances for some events instead of a big cutter followed by cold and dry.

I'm mildly interested in Wednesday's clipper/hybrid. Pretty stout little wave with it, along with steep mid-level lapse rates. Quickly cooling 850s shown on the models are indicative of the rapid height falls and evaporative cooling given very dry low and mid levels ahead of system. Someone could get a surprise slushy inch or two or three *if* the wave ends up as strong as shown on recent Euro/GFS/NAM op runs. It's somewhat reminiscent to me of the fast moving burst of heavy snow this past Feb 17th. We had a very marginal air mass ahead of it but the steep lapse rates & evaporative cooling more than made up for it. After the possible Wednesday system, late week closed low is a crap shoot and not worth trying to figure specifics yet, also any snow accums will be very thread the needle with it. Thereafter, our mild +EPO pattern should continue until about the 20th or so. At that point, ensembles are indicating the GOAK vortex retrograding to the Aleutians for classic weak Nino position allowing -EPO to build and cold to return. There's also a decent chance of -AO returning with SPV displacement/split possibly further aided by a SSW. There could be a window for some winter fun somewhere in the sub in the runup to Christmas, with the -EPO induced downstream trough possibly dumping cold air mass into the west/Plains and sub forum and then spreading east. Euro ensemble runs have been pretty consistent with this idea toward the end of the runs the past few days and 06z GEFS also hinting at that. Way out there, but worth watching for if we can get a stronger west/southwest system before trough axis maybe shifts farther east after Christmas. The pattern will almost certainly continue to suck in general between now and about the 20th, but I'm cautiously optimistic for the last 10-11 days of the month.

Just for S & Gs, the 00z Euro for late next week storm. [emoji38] Sent from my SM-G965U using Tapatalk

Assuming they cracked 12" for the event, it'll push them into a top 10 snowstorm overall. Sent from my SM-G965U using Tapatalk