RCNYILWX

Euro and EPS ticked southeast a bit vs 00z run. We'll see if that starts a trend.

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I'll say 6-8.  Was pretty close to a white out around an hour ago.  I'll get out and measure in a bit. 

What's your location? Will pass your report to my office when you do measure.

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Ukie remains south and colder than the rest of guidance along with the NAMs and the Euro to an extent. Against the GFS, the FV3 and the CMC. I *still* think we see this trend colder/south, but I guess we will have to see. 

The Ukie solution for the surface low makes sense to me. It's not like this is gonna be a negatively tilted wave, it's a sheared/elongated, positively tilted wave embedded in southwest midlevel flow. I still think the warmer models are not adequately accounting for the extent of deep, cold snowpack across the region, which *should* cause a sfc low adjustment southeast closer to edge of low level baroclinic zone.  

 

The NAM12 solutions have been interesting because they are wet bulb cooling the profile to snow despite what is typically a not good surface low track for snow in northeast IL. The 3km NAM is even weaker with the sfc low and looks to be close to all snow here. Perhaps this is a case in which they're handling the lower level thermals and dew points better coming out of a deep cold airmass. I find it hard to believe that we're gonna start the day with dewpoints in the low-mid teens here and push them to above freezing just hours later.

 

This also could be a case even with a farther west low track that the warm front does get hung up because of the snowpack and prolongs icing concerns, plus the idea we could still be icing with temps above 32. Still lots to sort out with this.

 

 

 

 

 

We'll be issuing something for the lake effect this afternoon, leaning advisory at this time. HRRR soundings in the band tonight look very good for IL shore. As has been mentioned already, trend has been to be a bit more progressive along the IL shore and slow it down into NW IN on Sunday. As of now, and obviously subject to change my biggest concern for 6"+ totals is NW IN. NAM and FV3 max out low level convergence and omega near the Lake/Porter border tomorrow morning and appear to favor longer residence time there before the band swings back west tomorrow night.

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Am I wrong to think this trends south due to the fact the system is shearing out as it moves east and that the snow and cold(especially if cold is under estimated) could shunt the baroclinic zone south into Missouri? I think models are cutting the system a bit too hard. 

I've been thinking the same thing and suspect there will be at least some correction colder.

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If you loop tmdw long range reflectivity, can see things filling in down to close to I-80 near JOT latitude now. So that'll stop the northward advance of the snow line that had been occurring.

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SN here in southeast Naperville, already covered my driveway. Thinking somewhere in 4-6" range here, hopefully sneak in over 6". A bit uncomfortably close to where the gradient is setting up, but I think we'll be okay in this area.

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Starting to think a Lake Effect Snow Watch (or at least advisory) should be issued for Lake and Cook counties. Many people I’ve spoken to are completely unaware of any precipitation on Saturday night after the synoptic snows and will be caught completely off guard.

Unfortunately, with the wind field slackening, almost impossible to tell where the low level wind convergence will ultimately set up. The NAM favors long duration IL side, GFS drifts fairly quickly into NW IN, FV3 and GEM kind of split the difference a bit. With that said, from a low level convergence and omega perspective, it looks good to overcome the less than ideal inversion heights. I think 6"+ amounts are a distinct possibility if evolution of convergence allows for a stall scenario.

I'm working today but not sure yet how it will be handled by forecast desk, could see us holding off and midnight shift issuing a watch or advisory, or we go with a low confidence watch. From what I've looked at, I'd consider Cook, Lake IN and Porter for a watch and would feel best but still low confidence about Cook and Lake IN.

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We were rerunning the expected snow graphic and probs this afternoon and wanted to only include the system snow but we're having issues with it including the LES as well. That's why there's a disconnect with the other probabilistic stuff and 10th and 90th percentiles.

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Hi. Models have been very consistent in the sucker hole. IKK just happens to be pretty much locked in it. That’s why I think a Watch for here is kinda silly. It’ll be an advisory at best for the LOT CWA south of I-80. North of there, different story. 

We preferred not to do a watch south but for collaboration purposes went along with it.

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I'm starting to think that there's something going on with the warm sector convection with this system that some of the globals aren't handling that the meso models are.

There's a good reason to be a bit uneasy when the Euro is much more paltry and you'd like to see some even minor positive trends today. On the other hand, we're in the non clown range of the meso models, sampling of the Pac wave has begun, and the meso models aren't backing down. Also, to second what's been said, fgen will absolutely be handled better by the meso models than the globals.

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Was clicking around weather.us and found out that you can view a bunch of the parameters for the individual Euro ensemble members, including at the all important 500 mb level. A nice way to check out what's needed to get to the more amped solution some of us are hoping for is by looking at the h5 evolution of the more amped members.

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A lot of the notorious systems do have more SW-NE components, but not always.  You can certainly get a very big storm on more of a west-east trajectory.  The Feb 2015 storm is an example of that.  The Gulf is wide open in this case, which is obviously very important.  

The system that just hit had pretty high amounts with less moisture moving W to E. I don't see why that would change this go around...

The Euro shows pwats of upward of 1.5" (spots pushing 2"!) in the warm sector available to wrap back into the cold air, with a large area of 0.6"+ in the cold sector. I totally buy the potential for extreme cold sector qpf and snow amounts unless the system ends up a sheared out pos. Orientation W-E vs SW to NE matters less than available moisture.  

With this system, should it come close to what's modeled on Euro or further maxes out will likely have, in addition to antecedent Pac moisture, additional deep layer tropical Pac moisture drawn northward as it matures, which was easily seen on w/v with just this past system and GHDII as recent examples. In addition, once it emerges into the Plains you'll ramp up low level moisture advection from the Gulf.

 

 

 

 

 

Is an op run any better than its ensembles? Or is it the lucky one that gets the spot light? In other words...could any one of the 51 euro emsembles be considered the same as the op? Or any of the 20 gefs?

The ensemble members have the same background model physics but are run at a lower resolution than the OP so the operational model is certainly better in that aspect. The big thing is that the small changes in initial conditions in the ensembles show you the range of possible outcomes and give you a sense of confidence or lack thereof in a certain solution (uncertainty interval). One of the members could certainly end up being close to what verifies, but if there's a ton of spread at a certain lead time that individual member is not really useful.

The EPS itself is considered a very useful ensemble suite because it has 51 members and does a better job than the GEFS in showing that pdf (probability density function) of the projected future state of the atmosphere.

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Glancing at gefs looks like if anything it ticked north.

Yep, a pleasant surprise. An encouraging sign considering that known tendency with ensembles vs. the OP model. Despite what I posted earlier about the GEFS in particular, this is a good reason to lean more heavily toward the ensembles at this range. The op models are not useless, they shouldn't be taken verbatim but they can be instructive on the positives and negatives with a particular setup.  

 

 

 

 

If the ensembles shift south, I think we can safely say the trend is not our friend.

I fully expect the GEFS to shift south because it's well known as being too non-dispersive with the operational GFS. 

Edit: Obviously if the negative trends on 12z runs thus far continue as we get closer, then we get concerned. Just for point of comparison, both GHD events had a few model cycles that drifted south until correcting way north. The synoptic setup has too much potential to give up on it yet.

 

 Edit 2: Never mind on the GEFS

Good sign there.

 

 

 

I like to think of operational model solutions at this lead time as being like individual ensemble members. They fall into the range of possible outcomes like the ensembles themselves. It's a good way to assess what you need to see happen to get the event you want or what could go wrong. We're still at a point where the shifts you see in the model suites may or may not be meaningful to the eventual outcome.

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The 12z GFS has the longest duration single snow event I've ever seen modeled here next week.

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Pretty interesting differences at H5 on the 12z GFS. Higher heights out ahead but low is further south at 500, causing the surface low pressure to be further south.

Not a good run vs very encouraging 00z last night. Good thing there's plenty of time to get the changes we need. GFS did a horrible job handling the h5 wave at closer leads with this past weekend's event, so there's that.

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End of NAM caveats apply but nice look at h5 at 84 hours and surface low a good deal farther west compared to GFS and FV3 at that time.

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All I want is if it phases, no rain here.

I think our latitudes are in good shape, still would be enough confluence from PV to your north to act as a pseudo block from enabling a hard cut. We just want the more SW to NE trajectory you mentioned earlier. This run was a step toward getting that if we can get the further needed improvements.

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Yes, this is actually epitomizing my thought from the other day, the northern stream has sped up such that now another piece of energy is coming down at the right time not to mention the Thursday thing is weaker/quicker allowing for ridging and the southern stream to go more neutrally tilted in the plains.

Yep, really not far at all from the extreme totals being pulled farther north. Southern wave was much improved until final approach toward northern piece, going neutral tilt and closing off at h5 over the Plains. If we can keep that southern wave stronger for longer, it would argue for gaining more latitude before phase. Great trends overall on that run. I expect to see some explosive solutions on the EPS members.

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Yea pretty big run of the FV3. Gotta wait for the Kuchera.
 

Looks particularly good for west side of the lake LE/LES. And a huge run for northern IN-OH, solid for southern lower MI.

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Living E of the Rockies now, please no.

Also looking at how long the cold lasted and the futility of that subsequent severe season, please no.

It appears that the long expected effects from the downwelling of the SSW will be coming, so the sort of output on the weeklies is not unexpected. From what I've read both last March and April were significantly affected by the Feb 2018 SSW.

Can't expect the same sort of behavior this time, but perhaps Feb and part of March and then things break.

 

I guess the hope would be that with everything shifted a month earlier, would give time to get back into a better pattern earlier, as opposed to last March and April both being toast and then quickly flipping to summer in May. I am with you on not wanting this to last deep into spring.

 

 

 

LES setup will certainly feature extreme lake induced instability with 850s plunging to -20C or colder over the lake by early Sunday. Forecast soundings indicate inversion heights between 850 and 700 mb lifting to closer to 700 mb during Sunday as cold air mass deepens. The inversion height is probably on the low side but when you consider that the DGZ is so low in such a cold air mass, it may be less of an issue than you'd otherwise think.

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