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From the GL section. Thanks! @OHweather

I'm just here to spread false hope of a pattern change that'll never come ;) (though we're already setting things in motion this week with a brief -EPO that does dump a good amount of cold into Canada and the eastern half of the U.S.)...

I don't totally hate the odds of a storm/event around the 23rd-25th across a good portion of the sub forum, with fairly strong ensemble support for a decent shortwave to eject out of the southwest.  With some bootleg blocking across Hudson Bay, lower heights over the southeast, and surface ridging over the top ahead of this feature, I think there's a good shot it's wintry.  850mb temperatures are near normal (after being cold for a few days prior) and are workable with the ensemble mean 0C line south of the Ohio River ahead of this wave.  If it deepens too quickly it would still cut and change the Ohio Valley to rain (or perhaps simply give them mostly/all rain), but places like Iowa/Wisconsin/Michigan, Chicago, Detroit, and maybe even Indy/Toledo/Cleveland would probably see a half decent amount of snow if an organized system can eject in this time-frame.  Places like Pittsburgh and Columbus/Dayton/Cincinnati still can snow but would likely need to root for a more strung out system, as the "blocking" to the north isn't strong enough to stop a stronger system from cutting too early for them.

1381407890_eps500.thumb.png.48036e8f30cb6e3e705cba396caf1256.png

1404831038_EPSsfc.thumb.png.54ed3e1a3fe6ca257192828c752ae0f6.png

1351583919_EPS850.thumb.png.f2862b0a8e33cd67e66d0a8e300c81aa.png

As for the "pattern change", both the tropics and extra-tropics don't really say it should be here yet...I think the ensembles several days ago (and hence those of us rooting for a pattern change) rushed the change a bit, but things suggest it's probably still 10-15 days away from really being "there"...

The MJO is at an extremely strong amplitude in phase 5/by tomorrow 6...these are not cold phases, though do usually end up being cold within 2-3 weeks of their occurrence.

92980003_CFSMJO.gif.959b69b78877786c8d52196b2a7b0abb.gif

Here are lagged composites of what happens after a phase 6 MJO at an amplitude of 1 or greater...although the MJO accounts for something like 25% of the sub-seasonal variability observed over a large sample, this is a very strong MJO and will influence the pattern.  Each lag is 5 days.

2122696592_phase6lagged.thumb.png.f59c86fc071d3275f267a6ddb4583520.png

This does not suggest a more legitimate pattern change that dumps cold into the CONUS for another 10-15 days (though does suggest slightly faster high-latitude changes, which we are seeing).  Phase 7, which we'll reach in 5-7 days, leads to cold by lag 1 which is 5-10 days (and supports the timeline from a current phase 6) and is typically cold thereafter for quite a while.  Phase 8 is cold immediately and for quite a while.  Here is a link to these composites for anyone interested: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/LaggedComposites/

Basically, tropical forcing says we should not yet be cold and probably shouldn't be for another 10-15 days, so it's probably not that surprising that the mid-range guidance has delayed a persistent cold pattern but still shows one developing past day 10.  This should start moving up in time as the MJO keeps propagating.

219121766_GWOlast120.thumb.png.bd8b72f8a1d0e31d435bcb6812a8c575.png

Global angular momentum (GWO, AAM, GLAAM, whatever your acronym) will rise soon, but it hasn't yet.  A low AAM is more typical of a La Nina, supports a strong stratospheric polar vortex/+AO, and trough over the western U.S.  We have been gradually climbing towards a more persistently positive AAM since the middle of fall, but it's been a slow climb, and I think the AAM slipping negative for most of December (after a couple of positive attempts in November) contributed to the strong stratospheric PV and +AO we are dealing with right now.  It spiked at the end of December, but the tropospheric pattern was horrible with a PV over Alaska and the stratospheric PV was too strong for that spike to significantly disrupt it.

The strong MJO over the next two weeks, along with a fairly strong East Asian Mountain Torque (high pressure east of the mountains) will add a lot of momentum over the next two weeks, and we will see the strongest positive AAM spike of the fall/winter by far.  Here is the EPS sea level pressure anomaly forecast for hour 264 showing this strong mountain torque, along with the CFS AAM forecasts for the next month:

895398534_EPS264.png.94f4c7bde3ac8f7dc6253849979385df.png

492379120_CFSAAM.thumb.png.e1ab314c956337e40148c70e401b87e9.png

This added momentum will help fuel an already active sub-tropical jet, will support some jabs to the stratospheric PV, and the MJO moving through the western Pacific as a +East Asian MT occurs will support significant amplification in the EPO/PNA domains.

Basically, I understand it's frustrating waiting a bit longer after over a month of really unfavorable conditions for snow for most of the sub and that it may seem like the models are perpetually pushing cold back, but there are reasons we didn't flip as quickly as the models suggested..basically the drivers didn't support it yet...and there are numerous reasons to expect it to still change soon.  The combination of factors we will see the rest of this month is unlike anything we've seen so far this fall/winter and I would be flabbergasted if it didn't result in a shakeup in the pattern.  I think the trick will be figuring out if we go back to warm in mid-late February, or if it's a more prolonged change that carries us through the rest of winter.  I don't know the answer to that yet.

After the potential system around the 23rd-25th (that favors the northwestern 2/3rds of the sub) there may be a similar opportunity a few days later.  Thereafter individual threats become murkier, but it should stay active and I think we see the EPO drop more than the EPS suggests in the 10-15, which will eventually push the baroclinic zone far enough south to favor the Ohio Valley over the Great Lakes. 

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4 minutes ago, TugHillMatt said:

Yeah, I saw talk of it in another subforum earlier this evening...OHWeather did a much better job of explaining it.

Weren't the EPS, for days, consistently showing a solid pattern change?

Yes, and the GEPS and GEFS. I still think it comes but with a lot less arctic air then modeled before.

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I think, which doesn't mean much, that the models are just not adept at picking up the new changes that drive our weather. It seemed years ago it was much more simple with forecasting...today we have no less than 10 to 15 different indices and drivers we need to monitor...get 11 right but 2 wrong and it may not end up how it should, or the indices could be showing worst case scenario but we have a great winter...both have happened in the past 10 years and I do not believe these models are good enough to be accurate.

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Just now, Thinksnow18 said:

I think, which doesn't mean much, that the models are just not adept at picking up the new changes that drive our weather. It seemed years ago it was much more simple with forecasting...today we have no less than 10 to 15 different indices and drivers we need to monitor...get 11 right but 2 wrong and it may not end up how it should, or the indices could be showing worst case scenario but we have a great winter...both have happened in the past 10 years and I do not believe these models are good enough to be accurate.

They've been pretty spot on with the warm weather the last month. All models showed it.

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