March 3-4 Potential Winter Storm

[Baum]

20 minutes ago, Frog Town said:

Got lots of laughs when posted but now it's not so funny.  When you've seen this happen so many times over the Winter, it doesn't take a MET degree to catch on.  

 

[Cary67]

First call 0.5"

[OHweather]

1 hour ago, RCNYILWX said:

I can confidently say that part of the problem with the ice storm forecast out there was the new ptype methodology we were forced into this winter. We had imo a much better system in place for several years up until last year.

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But here I was under the impression that if we just pulled in the WPC QPF and snow ratios and then ran Forecast Builder and pulled in the NBM temps and dews and clicked on a few buttons and ran the unconditional probability of weather type grids that I’d get a perfect snow and ice forecast in 5 minutes. In all seriousness, I think you folks in central region had a better ptype process than we did up through last winter in eastern region…I was training last winter and only touched mixed precip grids a few times, but it was impossible to get what we wanted with the old conditional wx type grids and top down method we were still using, and there were multiple different tools being used to get those grids by offices around us so it was hard to collab. A lot of hand waiving trying to manipulate grids. I feel like the methodology we use now IS somewhat easier to manipulate and get what you want, but I also feel like it’s rare that I don’t feel inclined to do some amount of editing to temp, dew point, and the various PoWT grids to get what I want in any sort of mixed/changing ptype scenario because the PoWT grids frankly aren’t meteorologically reasonable sometimes. Unfortunately, the level of willingness to make those grids edits seems to vary quite a bit from met to met and office to office, and I feel like those who are reluctant to make edits are prone to doing a less thorough analysis than they otherwise would (with a last second colder trend and unusually efficient accretion with decent rates and temps at or above freezing that recent ice storm was just difficult on the southern fringe, though poor starting grids from NBM/FB couldn’t have helped). 

Before I derail this thread too much more…my impression on this storm is that every model suggests that when the storm reaches maturity and peak intensity that very strong lift in the DGZ in the deform band will yield sufficient rates and large flakes to overcome any BL thermal issues. I’m pretty confident someone gets smoked. However, the big difference is regarding how quickly the storm deepens and reaches peak maturity which heavily impacts where the deform band reaches peak intensity and is best able to overcome any marginal thermals…as one would expect, the slower deepening favors the E/SE solution. 

I feel like the extremely sharp and rather anomalous subtropical shortwave, coupled jet structure, and high PWATs/low static stability argue for the quicker deepening, though it’s primarily a sub-tropical jet storm with little actual phasing with the polar jet, so both the track and shape of the precip shield on the northern/northwestern side will be quite sensitive to the amount of confluence to the north/northeast of the low. While I don’t think wholesale changes will occur at this range, subtle changes with that confluence could lead to track bumps to almost the last minute. My gut feeling is we don’t see a track any farther south than the GFS or CMC, but the NAM and Euro seemed to have inched a bit less amped so we’re probably narrowing the envelope. 

[Baum]

[Frog Town]

24 minutes ago, Baum said:

 

Just wait...

[RCNYILWX]

Very good agreement between the 18z EPS and GEFS actually with that shift south of the EPS. But that also means there's still a decent # of members north of the operational, similar to the 18z GFS/GEFS.

When the 18z Euro did shift south, it was a good reminder to me to not necessarily put too much stock even into a model I tend to trust more, particularly in this type of forecast that is sensitive to relatively small changes in the setup and the mass fields.

@OHweather, great post btw. Would you put more trust in the ensemble means at this point? Wondering if that may be the way to go since they've been generally more stable than the operational runs.

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[Harry]

2 minutes ago, RCNYILWX said:

Very good agreement between the 18z EPS and GEFS actually with that shift south of the EPS. But that also means there's still a decent # of members north of the operational, similar to the 18z GFS/GEFS.

When the 18z Euro did shift south, it was a good reminder to me to not necessarily put too much stock even into a model I tend to trust more, particularly in this type of forecast that is sensitive to relatively small changes in the setup and the mass fields.

@OHweather, great post btw. Would you put more trust in the ensemble means at this point? Wondering if that may be the way to go since they've been generally more stable than the operational runs.

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In the past I have found that way is a bit more reliable especially where qpf amounts is concerned. 

[Malacka11]

HRRR looks okay. Now we're just gonna have to hone this puppy in. 

[OHweather]

9 minutes ago, RCNYILWX said:

Very good agreement between the 18z EPS and GEFS actually with that shift south of the EPS. But that also means there's still a decent # of members north of the operational, similar to the 18z GFS/GEFS.

When the 18z Euro did shift south, it was a good reminder to me to not necessarily put too much stock even into a model I tend to trust more, particularly in this type of forecast that is sensitive to relatively small changes in the setup and the mass fields.

@OHweather, great post btw. Would you put more trust in the ensemble means at this point? Wondering if that may be the way to go since they've been generally more stable than the operational runs.

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I've been trying to pay the most attention to both the ensemble means, but also looking at the various threshold probabilities (for both QPF/snow), individual members and some of the new percentile stuff on WxBell (WxBell really has some pretty nice stuff for the GEFS, EPS and GEPS) to get a feel for what the "favored" solution is but also for trends on the fringes. The EPS has been disappointing to me with this one as it's tended to be under-dispersive and following the op, but the GEFS actually had a good spread several days out when the op Euro/CMC were well south and I think it's encouraging that the last couple of runs have tightened up the spread a bit (and seem to be converging on a slightly more amped solution than the op). I feel like I'd lean towards the more amped solution, but I have seen northern stream confluence mess with these sub-tropical jet storms before so the less amped solution is still on the table for now. 

[RogueWaves]

51 minutes ago, Stebo said:

Bit flatter of a track too, and definitely south and east a bit.

I'm ok with flat (storms)

[sbnwx85]

Bullseyed in the GFS, Euro and HRRR operational runs and still not at all confident in what will happen. Wild times.

[Sciascia]

[Stebo]

3 minutes ago, sbnwx85 said:

Bullseyed in the GFS, Euro and HRRR operational runs and still not at all confident in what will happen. Wild times.

We are as early as 36 hours out and have significant model discrepancies on location for the snow band.

[Malacka11]

The NAM is another 3 mb stronger at 09z Friday 

[Harry]

2 minutes ago, Stebo said:

We are as early as 36 hours out and have significant model discrepancies on location for the snow band.

 

MJO phase 7 usually delivers the goods to us in S.MI. Phase 6 further west/nw vs phase 8 se. 

[Stebo]

4 minutes ago, Malacka11 said:

The NAM is another 3 mb stronger at 09z Friday 

Both look like they may come in NW Meanwhile the HRRR is definitely in the south camp.

[Malacka11]

1 minute ago, Stebo said:

Both look like they may come in NW Meanwhile the HRRR is definitely in the south camp.

For sure but the 0z HRRR is a lightyear more amped than its 18z run. I'm sure that between now and radarcasting time it'll throw out at least one weenie chicago crusher because why not. 

[ILSNOW]

NAM hasn’t gotten the south and east memo (YET)

[Harry]

9 minutes ago, Stebo said:

Both look like they may come in NW Meanwhile the HRRR is definitely in the south camp.

 

It's actually a bit se. 18z took the slp over top my head while 00z keeps it south. 0 line stays near/just south of here vs 18z which got it up to Grand Rapids and kept it north of here. 

[Stebo]

Just now, Harry said:

 

It's actually a bit se. 18z took the slp over top my head while 00z keeps it south. 0 line stays near/just south of here vs 18z which got it up to Grand Rapids and kept it north of here. 

It started west but ended flatter.

[Lightning]

Just now, Harry said:

 

It's actually a bit se. 18z took the slp over top my head while 00z keeps it south. 0 line stays near/just south of here vs 18z which got it up to Grand Rapids and kept it north of here. 

Baby steps.  

[Cary67]

NAM loves dramatic shifts within this time frame 

[Harry]

Great thing about the site I use is it allows me to put county lines and interstates on top. Great for spotting smaller changes that may not as seem as obvious without that. 

[Harry]

1 minute ago, Stebo said:

It started west but ended flatter.

 

Any little thing helps us at this point with those kinds of trends atleast. 

[Harry]

3 minutes ago, Lightning said:

Baby steps.  

 

We may end up with the desired track for sure but I still worry a little about thermal profiles. Gonna need those heavier rates to get some decent totals. 

[Radtechwxman]

The amount of variability right now is laughable. Normally would have advisories or watches posted by now. My forecast is 0-8in. Should verify nicely. I'm in between every OP model suite, more centered on EPS and GEFS, and hi res either is a miss nw or se. Lol. This is about as good as the Xmas Storm watching it unfold on models. 

[RCNYILWX]

I try to avoid looking at the HRRR at this lead time because it's a hot start model and frequently all over the map for winter systems. I really don't think it was meant to be used for winter forecasting outside 18-24 hours. It's more useful inside 12-18 hours.

While it doesn't mean a particular solution in its extended runs can't have the right idea, it's much more often wrong than right this far out and therefore hard to put any stock in it. It was very bad for the ice storm (too warm) and also the event before that (too cold over northern IL). It may have performed decently for the pre Christmas storm at this lead time, but that's the only one that sticks out to me.

[Malacka11]

If the GFS crushes Chicago this next run you guys all have to zelle me $5.

[sbnwx85]

2 minutes ago, Malacka11 said:

If the GFS crushes Chicago this next run you guys all have to zelle me $5.

[Lightning]

3 minutes ago, Harry said:

 

We may end up with the desired track for sure but I still worry a little about thermal profiles. Gonna need those heavier rates to get some decent totals. 

Looking at the dynamics with this storm I believe heavier rates will be there!  Plus heavy wet snows seems to be the norm this winter here.