RCNYILWX

Yep, guaranteed based on the Aviation AFD that they'll be taking them up. Sent from my SM-G965U using Tapatalk

Nice tidbit here from our 18z TAF Aviation AFD Sent from my SM-G965U using Tapatalk

I'm liking a 2-4" range for the LOT CWA. Sent from my SM-G965U using Tapatalk

While it's possible that the northern tier ends up with somewhat less snow, I doubt anywhere in the CWA gets shut out tomorrow. Sent from my SM-G965U using Tapatalk

Award for most weenie 12z run goes to the WRF-ARW Sent from my SM-G965U using Tapatalk

I think there's upside potential above our official 1-2, locally 3" forecast, for reasons that have been discussed (high SLR, steep lapse rates, low and mid-level f-gen). Now that the HRRR has gotten more realistic, the 06z NAM runs probably represent a reasonable best case scenario for now. Good to hear the Euro bumped QPF on 06z run. Sent from my SM-G965U using Tapatalk

WeatherBell weenie vision still fluffs it up to 1-3", looks like that's still doable as long as we get snow out of this wave and the DGZ is very deep. If the meso models hold with a better event through tomorrow, then can put more stock in them. Sent from my SM-G965U using Tapatalk

Solid event around here today. Unfortunately missed the first round of ++SN but woke up in time for next round, then the backside snow and wind this evening has been solid. Considering much of the modeling had this as a rainer a week ago, no complaints even though I bought into that for a bit (was just trying to jinx it [emoji38]). Regarding headlines for this event, without a true impact based winter storm criteria, we're kind of just left to wing it and decide on a case by case basis. The WSW we issued for the NW CWA was definitely for impacts and largely to match up DVN and MKX (they ended up going with a WWA). As it turned out, and probably not too surprisingly, open areas outside of the warning had some legit winter storm impacts this evening and of course when the heavy snow came through it was briefly extremely low visibility. It's a tough call on these since you'll have a good amount of time with WWA impacts and the more sustained winter storm type impacts. I was also surprised DVN never upgraded any part of their CWA to a BZ.W, as they we're strongly considering one. Not always true but my perception is that they generally prefer to have the same winter headline for their whole CWA, eastern IA posters can confirm. Sent from my SM-G965U using Tapatalk

New Euro and EPS will be key tonight. UKMET not a total dud like other globals with implied 1-3" from just under 1/10" to some spots a bit over 1/10" liquid equivalent across the CWA. Figure ratios of at least 15:1 are attainable with a very deep DGZ and previous NAM runs also had steep mid-upper lapse rates. Even though the 12km NAM backed off on QPF, its simulated reflectivity still looked pretty good. Sent from my SM-G965U using Tapatalk

+SN BLSN, visibility under 1/4 here, can tell because it's tough to see across the park from my backyard and that's no more than 1/8 mile away to houses on other side. Sent from my SM-G965U using Tapatalk

AO and NAO negative through the end of the run, just less negative after day 10 than they'll be through day 10. All in all, not really disagreeing, will probably be last week to 10 days of the month before there's much change. By then, some huge negative departures will have been built up and snow pack should also too, which could also help serve to delay a noteworthy pattern change. Sent from my SM-G965U using Tapatalk

Depends which ensemble you're looking at too, new 12z GEFS looks very cold through beyond d10 and the 06z run only hinted at possible relaxation at the end which takes us almost out to the last week of the month. 00z EPS showed an easing out in the day 10-15 but it too hinting at higher heights near Greenland all the way through day 15. At some point figure this has to end, though the polar blocking has been way more persistent than anyone expected going into this winter, so that probably remains a wildcard. If the past is any guide, the 09-10 block actually lasted into March but by the cold air was gone. I'm not sure how much influence the MJO is having as most phase diagrams have it looping around in 7, with only CFS trying to send it into p8. Sent from my SM-G965U using Tapatalk

In this sort of a pattern, each operational run needs to be treated similarly to an ensemble member. A good way to tell a pattern is active and also prone to less lead time for higher predictability is looping 6-hour QPF or snow on the ens. Starting Saturday there's members that have action every 6-hour block, with certain time periods a bit more favored than others. With multiple lower amplitude short-waves it adds a lot of chaos to the modelling. Sent from my SM-G965U using Tapatalk

Since I think it's meant to be for this thread, the 12z GEM has a really nice event starting Sunday evening and continuing through Monday. Probably would've been better to group together the 7th through 9th because there's a way you can get a longer duration round out of this setup, such as shown by the GEM. The ECMWF runs I cited in medium long range thread had some wave spacing between Sunday and Monday, though it's too soon to tell if we could get one longer event or two shorter events or specifically most favored areas. All we can say is that multiple short-waves that won't be sampled for a couple days lends to lower predictability than last weekend's event. Don't think the threat has really trended downward, gotta take a wait and see approach. The pieces are there for a nice event because of the tight baroclinic zone expected to be in place. Sent from my SM-G965U using Tapatalk

You wrote that before the 12z GEM rolled out haha. Looks really nice for Sunday evening/night through Monday. I think ultimately the later Sunday-Monday period has a decent chance to work out for a solid event. Saturday PM should snow in most of the CWA but needs work to be anything more than a 1-3" type event. Sent from my SM-G965U using Tapatalk

I didn't see any zzzz overnight. The 00z Euro looked really good on Sunday and it had good support from its ensemble and the signal for Monday is still good with GFS/GEFS the most excited. Edit: I see the 06z Euro shifted south on Sunday, but that's not really a big deal in a pattern like this. Could easily come back north, as the guidance is going to struggle with exact positioning of the baroclinic zone and the influence of the PV being to the north.

Expect a good amount of run to run variability on the op runs. 00z GFS is still decent but not nearly to the extent of its previous runs, while GEM is more suppressed and sheared. Meanwhile the 00z UKMET is juiced for the system with QPF up to 0.4 to 0.7 across the LOT CWA. Sent from my SM-G965U using Tapatalk

Aside from the extreme NAO block, the pattern this weekend through next week is the closest looking to 2014 that we've had since 2014. The initial ridge spike dislodges the PV lobe which then gets trapped underneath the block. Whereas in 2014 there were constant reloads of the EPO ridging that brought down PV lobes. Either way, it gets to a fairly similar look in the CONUS, with a strong polar jet directed right into the subforum and a train of Pac hybrid shortwaves. Sent from my SM-G965U using Tapatalk

Looking forward to another fun shift tonight. MTF will be doing the grids and AFD. Certainly an interesting setup to get accumulating snow in the area. In addition to the support for dynamic cooling, it helps that the surface high is not too far off to the east so lingering dry air aloft helps the process. Sent from my SM-G965U using Tapatalk

For those up tracking, we will be ramping up our winter weather messaging for Thursday in collab with WPC. Still concerned for freezing rain within the CWA earlier and now with trends of a lot of the guidance and strong ensemble support with a decided shift southward we're liking idea of accumulating snow, strong winds and blowing snow across northern IL Thursday night. Flash freeze scenario still in play as well since it does look like all areas should briefly rise above freezing. Sent from my SM-G965U using Tapatalk

If I may jump in on the Chicago snow talk stuff, I have no problem with posting historical context about low snow starts or even simply just expressing frustration about a cruddy pattern; after all we're posting on winter threads because most on here want as much snow as possible. I get more peeved at the persistence pattern posts, that it's sucked so it will continue to do so. The pattern is persistent until it changes. We've had plenty of recent examples that what happens in December the rest of winter does not remember. I personally wasn't overly optimistic about this winter, was fairly bearish about it until unexpectedly persistent blocking materialized. I always go back to the mantra all it takes is one, or two, or at our latitude, we get chances. Our middle 50th percentile for seasonal snow in the Chicago area is near 30" to low-mid 40s", so it's much more common to get a bit above normal snow than to dabble with futility. What I did feel confident about in this winter is that we would realize an active stretch where those chances would become possible and that even in the warmest Nina winters, usually get a few opportunities for a favorably tracked southwest type system. Glad that the blocking gave us a chance to get into a stretch where we got two solid systems in a week, as it appeared quite possible it could. Sent from my SM-G965U using Tapatalk

On the range of possible outcomes, certainly an interesting solution to add into the mix. That run has a sharper digging northern s/w able to phase with more southern routed energy and the whole thing quickly goes neutral to negative tilt. I'd place it on the lower probability end of the spectrum to get that well timed phase, though we'll see shortly on the rest of the incoming 12z operational and ensemble cycle if that idea gets any more than minor member support. Sent from my SM-G965U using Tapatalk

See overnight AFD for my thoughts on this one. No longer concerned about a snowpack nuke which is nice. Would certainly prefer a snowpack net gain like NAM/RGEM and last night's GEM solution. Not putting my eggs fully into that basket yet with so much ensemble spread and NAM and RGEM rather far out in their range, but tend to favor the colder outcome which could include light-mod snow accums in parts like above mentioned solutions. Think that even in a change to rain outcome there would be a freezing rain risk in the morning. Probably a decent chance we end up needing an advisory for parts of the area. With sloppy non snow ptypes possible into parts of the area and support for post polar front precip with crashing temps could also see a rare flash freeze type setup materialize. Models like the GFS commonly overdo surface warming when southeast surface winds are pulling from a lower dew point air mass and we have extensive deep snow pack. Also think it's possible previous runs have not been accounting for wet bulbing aloft enough. Sent from my SM-G965U using Tapatalk

Are you right in Kankakee? We could use some quality reports for the event write-up. Definitely noticed a lack of quality reports from down there. Erroneous reports like what you cited affect the NOHRSC analysis that drives the automated snowfall analysis maps. We tried to account for the reports we received in the storm total snow maps we've posted. Sent from my SM-G965U using Tapatalk

So we just spoke to overnight ORD observer and the evening shift did mess up, did not account for snow that fell between 18z and 20z in the 00z report. So actual total in that period was 1.7". 0.3" between 00z and 06z brings the storm total to 10.8". Sent from my SM-G965U using Tapatalk