Chicago Storm

As has been mentioned, we are heading into a significant pattern change. Changes on the large scale really start to appear this weekend and into the beginning of this upcoming week. This new pattern, which may very well evolve over time, will extend through the first 1/3rd of January, and quite possibly the first 1/2 of January. Two big changes that we are seeing right off the bat and that have already begun are a progression of the MJO into the colder phases and a stratospheric warming event. The MJO recently entered the COD, after being in low-amplitude warmer phases from the very end of November through the first 2/3rds of December. The trip through those warmer phases is one of several reasons (Raging Pac Jet is another) that we have been stuck in a consistently mild (Sometimes very mild) regime. The MJO has now entered a colder phase, low amplitude phase 8, and is expected to make a trip at lower amplitude roughly through colder phases 1-2 over the next 1-2 weeks. Another thing that we will be watching unfold is stratospheric warming. This event is expected to disrupt the main SPV placement and strength during the potentially 1-3 week event. As is usually the case, any effects of the SSWE will not be seen right away; that is something to keep an eye on from around week 2 in January through early February. As mentioned above, there are a few reasons we have been seeing consistently mild (Sometimes very mild) conditions over the past several weeks. The raging Pacific jet is one of those bigger reasons. The Pacific jet is expected to break down soon, with increased troughy-ness (Wave breaks) developing. Canadian ridging, which will retrograde from Central to Western Canada and eventually Alaska, will also tend to lower Pacific influence as well. Getting beyond the MJO, SSW and Pac jet... We are likely to see a fairly consistent flow of waves/disturbances/troughs enter the CONUS along the West Coast, originating from the deep/mean trough from the Aleutians down into the Northeast Pacific. This is characterized by the lower-height anomalies from the Northeast Pacific and then across the southern 2/3rds or so of the CONUS. Additionally, with the Pacific jet breaking down and the retrograding ridging in Canada, this will lead to generally cooler/colder conditions overall than have been seen, with an airmass origin more often than not from the Northeast Pacific to Pole regions. All in all, with this pattern change... -While it may not be super/hyper active, there will be a steady stream of disturbances that traverse the CONUS. Will they all turn into something interesting? No. But having a feed is a start. -It is very clearly not going to be as significantly/consistently as mild as it has been. That's not to say there won't be any bouts of mild temperatures, but what we have been seeing will be in the past for now. -The chances for wintry storm potential are not amazing, but definitely an improvement compared to much of the past 1-2 months.

Cross-posting from the Chicago record thread... A few stats to watch for Chicago, for Christmas Eve and Christmas Day. Top 10, if not top 5, a lock for pretty much each list. Warmest Christmas Eve Max Temps 1. 64 - 1889 2. 62 - 1982 3. 59 - 1877 4. 58 - 1932 4. 58 - 1893 4. 58 - 1875 7. 57 - 2021 8. 55 - 2019 9. 54 - 1936 9. 54 - 1895 Warmest Christmas Eve Min Temps 1. 51 - 1982 2. 49 - 1877 3. 46 - 1893 3. 46 - 1889 5. 40 - 1888 6. 39 - 1931 7. 38 - 1932 8. 37 - 1979 8. 37 - 1875 Warmest Christmas Day Max Temps 1. 64 - 1982 2. 57 - 2019 3. 56 - 1936 3. 56 - 1895 5. 55 - 2021 5. 55 - 1971 7. 52 - 1994 7. 52 - 1893 7. 52 - 1891 10. 50 - 1940 10. 50 - 1877 Warmest Christmas Day Min Temps 1. 46 - 1936 2. 42 - 1940 2. 42 - 1877 4. 37 - 2019 5. 36 - 1982 6. 35 - 1957 6. 35 - 1941 6. 35 - 1888 6. 35 - 1881 10. 34 - 1973 10. 34 - 1923 10. 34 - 1913 10. 34 - 1891 Wettest Christmas Day 1. 0.50" - 1950 1. 0.50" - 1909 3. 0.47" - 1982 4. 0.46" - 2009 5. 0.38" - 1957 6. 0.35" - 1973 6. 0.35" - 1949 8. 0.34" - 1965 8. 0.34" - 1879 8. 0.34" - 1877

A few stats to watch for on Christmas Eve and Christmas Day. Top 10, if not top 5, a lock for pretty much each list. Warmest Christmas Eve Max Temps 1. 64 - 1889 2. 62 - 1982 3. 59 - 1877 4. 58 - 1932 4. 58 - 1893 4. 58 - 1875 7. 57 - 2021 8. 55 - 2019 9. 54 - 1936 9. 54 - 1895 Warmest Christmas Eve Min Temps 1. 51 - 1982 2. 49 - 1877 3. 46 - 1893 3. 46 - 1889 5. 40 - 1888 6. 39 - 1931 7. 38 - 1932 8. 37 - 1979 8. 37 - 1875 Warmest Christmas Day Max Temps 1. 64 - 1982 2. 57 - 2019 3. 56 - 1936 3. 56 - 1895 5. 55 - 2021 5. 55 - 1971 7. 52 - 1994 7. 52 - 1893 7. 52 - 1891 10. 50 - 1940 10. 50 - 1877 Warmest Christmas Day Min Temps 1. 46 - 1936 2. 42 - 1940 2. 42 - 1877 4. 37 - 2019 5. 36 - 1982 6. 35 - 1957 6. 35 - 1941 6. 35 - 1888 6. 35 - 1881 10. 34 - 1973 10. 34 - 1923 10. 34 - 1913 10. 34 - 1891 Wettest Christmas Day 1. 0.50" - 1950 1. 0.50" - 1909 3. 0.47" - 1982 4. 0.46" - 2009 5. 0.38" - 1957 6. 0.35" - 1973 6. 0.35" - 1949 8. 0.34" - 1965 8. 0.34" - 1879 8. 0.34" - 1877

we already have them in-ground. .

Will finally have something up tomorrow, but a few key points... -The pattern is changing, and significantly at that. -It is very clearly not going to be as significantly/consistently as mild as it has been. -There will be a steady/consistent flow of waves/disturbances moving into the Western US, and then across the country. -The chances for wintry storm potential are not amazing, but definitely an improvement compared to much of the past 1-2 months. -A SSWE is most definitely going to occur, with the effects TBD in the weeks after it occurs. -The MJO will make a 1-2 week pass through colder phases. -The raging Pacific jet is likely to break down to some degree.

There will be opportunity in January.

Top 5 warmest high, top 5 warmest low and top 5 wettest Christmas for Chicago is within reach based on current guidance.

This thread may get some work soon… .

i don’t think anyone in their right mind would ever forecast a +15 +/- departure for a given month. .

There were some snow showers/squalls that moved through the area yesterday morning/afternoon, associated with the ULL/cold front that swept through the region. The snow didn't amount to anything more than a trace at ORD, but some other areas picked up a few tenths of accumulation.

Given the location of the SW, the main/core of the cold will be on the other side of the NH. .

SW is most definitely going to occur, and the MJO is most definitely going to exit the COD somewhere into the 8-2 phase range (But yes, at low amplitude).

I know Ricky briefly touched on part of it...But why has it been so consistently mild/warm, and why will it generally continue into late month? The combination of a bigly/massive Pac jet, the MJO progressing through warmer phases, and the lack of consistent blocking of some sorts. Changes are in the future, though, including some significant stratospheric warming on deck. Will touch on that early next week...

Winds of change are on the horizon… .

your first mistake was subscribing to his blog. .

looking like the palm tree will go un-boxed into january. this will be the first such time since i've had it, which dates back to 2008 or so.

Solid agreement on ENS means for two weeks out. Merry Christmas. .

My in-depth thoughts... Punt till January.

I'd have waited another day or so on this one, due to the pattern. The 18z GFS is what you'd expect to get in this progressive pattern for much of our region...a glorified FROPA.

0.3" ORD, 0.1" MDW and 0.7" RFD with the snow overnight/this morning.

A dusting to 1.5" of snow is still on tap area wide through the morning, with the disturbance/storm system moving through.

For the stuff that isn't thread worthy...

I wouldn't get too caught up in the potential revolving around next weekend for several more days. We're shifting into a fairly progressive pattern, and there are several pieces that need to be well placed for things to work out. Guidance is a go for now...We'll see how things look come Wednesday/Thursday.

Everything favors a progressive pattern, so I wouldn't expect to see that cutoff idea come back and see reality.

that makes zero sense.