RCNYILWX

Kuchera totals Sent from my SM-G965U using Tapatalk

That is odd. 00z GEM looks close to what the general guidance consensus has been and nothing like the 00z GFS. If the GEFS (different physics package from op and all) diverges significantly from the operational, may have to chalk up the op to being an outlier if ECMWF is close to previous runs at 00z. Overall, it's hard to ascribe much to one of the models handling a feature differently as being anything but something that can happen in this range. And With the main wave still well out over the Pacific, we'll have to wait and see. But want to see more support for an operational GFS like outcome before getting too concerned by it. Sent from my SM-G965U using Tapatalk

00z GFS is not what you want to see for a good event...except for MN, central and northern WI, the UP and northern Lower MI. Sent from my SM-G965U using Tapatalk

Yep just looked, ticked north slightly, but can tell it also lost some of the beefier members, as the 24 hour mean came down over WI and far northern IL. At this point, can be considered noise level changes. Sent from my SM-G965U using Tapatalk

To go back to this and your original post, I don't think surface low track is that important early on. Barring major changes, with the air mass we'll have in place, evaporative cooling will further knock down temps aloft so that we'll start as snow. But if you're trying to denote the areas favored to stay snow the entire event, then that's fair to start from the IL-WI border. Given latest data, I'd be surprised if most places, except maybe far southern CWA, don't start as snow and easily accumulate. The question becomes how quickly temps warm aloft with stout southerly flow and how much resistance is given by evaporative cooling. That's where the models rarely ever overestimate and often underestimate WAA. But even in this case, a solid front end thump can bring a few to several inches of snow prior to changeover. That's what WPC is favoring in their day 5 outlook, with most of the CWA in 70-90% probs for 0.25"+ liquid equivalent in snow/sleet accums, supported by the GEFS and EPS. In fact, the 12z EPS (haven't looked at 18z yet) had 80+% probs for 24 hour 10:1 snow accums of 3"+ for I-80 and north.

Do you mean rain including freezing rain or just plain rain and snow line? You're ignoring the strength of the departing surface high. My biggest concern is WAA resulting in a quicker flip to an icy mix but I'm not concerned about temps below freezing in the metro until later Friday night, surface low track dependent. The surface low being well southwest of us, with the surface warm front well south and the high slowly shifting east puts us in a good spot to start as snow everywhere with questions on duration. Sent from my SM-G965U using Tapatalk

I don't trust how long into Friday evening the 12z Euro verbatim keeps 850 mb temps Conceptually with a setup close to as depicted would favor 3-6 hours of snow thump then mix/change to sleet then freezing rain and then plain rain, maybe flip back to snow on back side. Looks like a mess for the Friday PM commute as things stand now.

Good to see the Euro come in colder aloft. It looks like the 500 mb wave is less amped than the previous run and eventually the surface low comes out farther south. It's a solid antecedent air mass with the cold dry high pressure influence slower to depart and 850 mb level starts out quite dry and doesn't moisten as much as 12z run. But still odd to see the 850 mb level staying that cold due to evaporative cooling alone with straight southerly flow of 30-40 + kt. The southerly flow aloft is weaker than the 12z run, but still plenty for strong isentropic lift. Sent from my SM-G965U using Tapatalk

Recall that's essentially what the non NAM guidance was showing for Feb 12, 2019 ice event. Sent from my SM-G965U using Tapatalk

Looks like a decent icing setup for a time because of the position of the high pressure off to the east and warm front stays south. Your east southeast wind trajectories are pulling from lower dew point air off to the east which would help with evaporative/wet bulb cooling. I do wonder if with that exact setup shown on GFS the surface warming would occur quicker once wind goes more southeast due to lack of any snow cover over the region. Sent from my SM-G965U using Tapatalk

Even though the GFS is showing it staying snow for a decent amount of time, I don't like that setup to stay snow as long with southerly flow at 850 mb for a while. Would think the thermal profiles would verify warmer than modeled in medium range and it would be more of brief snow to sleet and freezing rain here. The surface may be more conducive to staying colder with the departing Arctic high influence and winds more east southeast. Need changes in the mid-level pattern to feel better about a snowier outcome locally.

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.

Strong ensemble support for that long of a lead time. Both 00z EPS and GEFS ensemble means have a surface low tracking up the Ohio Valley and expansive high pressure off to the north/northwest. Next weekend could be a window for snow for some of us, along with an icing zone in between as you mentioned, in an otherwise fairly hostile pattern. Friday's cold front would temporarily shunt the low level baroclinic zone farther southeast and then the question is what comes of the southwest trough after it ejects. One way to avoid the phasing issues we've been having is to allow the southern stream wave to come up on its own and deepen due to the tight thermal gradient. Just to use the operational runs to illustrate the point, the 00z Euro kept the northern stream wave much farther north, allowing the southern stream wave to come farther north. On the other hand the 00z and 06z GFS brought northern wave much farther south, compressing flow between it and southern wave, which flattens heights and keeps the southern wave moving quicker and farther south. At the very least, some possibility of having more interesting weather to track. Sent from my SM-G965U using Tapatalk

Big news...Pivotal weather now has forecast soundings from the Euro. Sent from my SM-G965U using Tapatalk

Sign me up Sent from my SM-G965U using Tapatalk

Painful miss east Sent from my SM-G965U using Tapatalk

Written by my good friend and one of our lead forecasters at NWS Chicago. Have a happy and healthy 2020 everyone and here's to a fun year of weather. Sent from my SM-G965U using Tapatalk

Cross posting from January thread: Can say with reasonable confidence that January will be active. The big question is how persistently amplified the southeast ridging is and the placement of Aleutian/AK ridging. Getting the ridging farther east into the EPO domain could make for a more than serviceable month for central, western and northern portions of the sub. Farther south and east could certainly be dicey if this weekend and next week's possible window is not cashed in on. The January-February 2019 500 mb composite anomaly below and sensible weather results shows that the general idea being forecast by the longer ranges of the ensembles and Euro weeklies can work out really well for portions of the sub. On the other hand, a too amplified southeast ridge and Aleutian ridging too far west could make for a warm/rainy active month for much of the sub and congrats MSP and north/northwest. I don't think we can say yet for sure that the MJO being forecast to go with amplitude into the warm phases makes it a lock that it'll be a trash pattern even central and west, just that the warm risk is certainly there. If I'm recalling correctly, a good chunk of last January and February was spent in the warmer MJO phases. This shows it can work out for some of us, but did also make for the bad winter farther east and southeast in the sub and points east. Also, I'd much rather have an active month biased warm that at least gives a chance for things to break right for a good event than endless cold and dry. Experience shows us that for a big dog we need at least some southeast ridging. The oscillating going on in later ranges of the EPS shows that we'll be on the edge so we'll have to wait and see which way things are leaning. Finally, with the likelihood of stout low level cold air masses northwest of here and warm press from SE ridge, we'll also have to watch for sig icing events in the battleground zone, similar to last February. Sent from my SM-G965U using Tapatalk

Can say with reasonable confidence that January will be active. The big question is how persistently amplified the southeast ridging is and the placement of Aleutian/AK ridging. Getting the ridging farther east into the EPO domain could make for a more than serviceable month for central, western and northern portions of the sub. Farther south and east could certainly be dicey if this weekend and next week's possible window is not cashed in on. The January-February 2019 500 mb composite anomaly below and sensible weather results shows that the general idea being forecast by the longer ranges of the ensembles and Euro weeklies can work out really well for portions of the sub. On the other hand, a too amplified southeast ridge and Aleutian ridging too far west could make for a warm/rainy active month for much of the sub and congrats MSP and north/northwest. I don't think we can yet for sure that the MJO being forecast to go with amplitude into the warm phases makes it a lock that it'll be a trash pattern even central and west, just that the warm risk is certainly there. If I'm recalling correctly, a good chunk of last January and February was spent in the warmer MJO phases. This shows it can work out for some of us, but did also make for the bad winter farther east and southeast in the sub and points east. Also, I'd much rather have an active month biased warm that at least gives a chance for things to break right for a good event than endless cold and dry. Experience shows us that for a big dog we need at least some southeast ridging. The oscillating going on in later ranges of the EPS shows that we'll be on the edge so we'll have to wait and see which way things are leaning. Finally, with the likelihood of stout low level cold air masses northwest of here and warm press from SE ridge, we'll also have to watch for sig icing events in the battleground zone, similar to last February.

Any event like modeled on the 00z Euro has to be considered low probability this far out. But the good news is that it wasn't a one off. The 12z run yesterday had a system in a similar general area, just less phased and weaker. And there was modest 00z EPS member support for the time range. Can add next week to late Friday-Friday night possible rain to snow scenario for parts of the sub to *things to watch*. Of course the 12z operational GFS has no phasing at all with the northern and southern stream waves in that period.