RCNYILWX

Long time lurker (and very occasional poster) in this sub. I know the ensembles don't equal the reality of what snow lovers want, but isn't the pattern offered by the 12z EPS for week 2 typically a decent one for New England, objectively speaking?

Neutralish EPO with a -PNA, -AO, -NAO, no semblance of well AN h5 heights nearby and 850 mb temp anomalies near to slightly above normal with the 850 mb 0C line in the vicinity of the Delmarva.

It's not a cold pattern, but the -PNA would provide a steady stream of shortwaves and the -NAO/-AO could modulate the storm track in a beneficial way and/or promote coastal re-development of primary shortwaves tracking inland.

Wasn't necessarily expecting that sort of look to be in play for this winter, but from my perspective (NWS Chicago forecaster), that projected pattern is typically a productive one here and have also been associated with snowy patterns into New England. Thinking 2010-11, temporarily in early Feb 2015, and mid-late January into February 2021 and 2022 as some noteworthy examples.

I'd go as far as saying that the projected EPS pattern doesn't look like a bad one even down into the NYC area (I'm originally from Queens).

Wanted to lay out some things happening with some larger scale pattern drivers now and over the next few weeks and look at how they may impact chances for cold and snow potential. Chicago Storm's post on the prior page touched on most of these things. Behavior of the Pacific jet and potential for high latitude blocking will determine much of how this goes...something that can probably be said most of the time in the winter months. 
Not to be a wet blanket here but I don't want to get expectations unrealistically high at this point. Much of the subforum is going to be in a rather substantial seasonal snowfall hole before any sort of sustained colder pattern develops. In a strong El Nino it's inherently harder to get into a polar jet dominated pattern with lots of cold, clippers, and lake effect snow...those are patterns that are productive for much of the Midwest and Great Lakes. The mid-Mississippi and Ohio Valley portion of this subforum has lower annual snowfall and may get lucky with an active subtropical jet in an El Nino, so on that I would say that region has the greatest potential to rally and finish near or somewhat above average snowfall at this point...if anyone can. For the rest of the sub a below average seasonal snowfall is by far the more likely outcome at this point, but the pattern will be colder and more conducive to snow at times so I don't think we're looking at another year without a winter. We should see some windows of more wintry conditions. 

A significant influence on the Pacific jet stream is East Asian Mountain Torque (EAMT). Remember that big cold blast in Siberia earlier this month? The Arctic high associated with that dropped across eastern Asia (and is still doing so early in the above loop). This denser airmass and higher pressure east of the Himalayas puts a torque against the planet's rotation, slowing it down an imperceptible amount. To conserve momentum, this is compensated for by speeding up the jet stream over the Pacific...promoting stormier conditions over the northern Pacific. The Rockies can have a similar affect on the jet stream over the north Atlantic.

Note how a strong positive EAMT event occurred over the last week or so as the Siberian high dropped into eastern Asia. EAMT will generally trend more negative over the next 2-3 weeks, though I'd say it's possible we see one last little push of +EAMT in the first few days of January which may be important to determining how quickly the Pacific jet retracts in the coming weeks. 
The strong +EAMT led to the dramatic intensification of the north Pacific jet ongoing now, though the jet will begin retracting over the coming days and continue retracting/weakening into early January as EAMT trends more negative (and as tropical forcing changes, will get into that below). The stronger jet leads to stronger ageostrophic flow within its embedded jet streaks, encouraging a stormier (and amplified) pattern, especially near the eastern edge of the jet where the upper-level flow is most diffluent. 
As the jet reached its easternmost extension over the last few days the stormy pattern was over the southwestern US with ridging amplifying northeast of that. As the jet begins retracting over the next several days the stormy pattern will shift west into the Pacific, allowing ridging to shift west towards the west coast and Alaska while continuing to amplify. This jet evolution has strongly contributed to our ongoing mild pattern and the change will contribute to a period of cooler conditions to start January. 

https://www.atmos.albany.edu/facstaff/awinters/realtime/Deterministic_NPJPD.php
Wanted to demonstrate how important the Pacific jet has been on the pattern we are seeing. Per the analysis, we went from a jet retraction in mid December to a recent poleward shift of the jet. The jet is expected to be more characteristic of the "jet extension" phase the rest of this month, before briefly moving through an Equatorward Shift space back towards jet retraction (due to the negative trend in the East Asian Mountain Torque). 
Poleward shift heights and resultant temperatures:


A very Pacific-dominated pattern with minimal polar/arctic influence and very mild conditions across a good portion of Canada and the northern CONUS. Very similar to what we're currently seeing. 
How about a jet extension, which is what we'll see over the coming days?


Supports increasing heights along the West Coast and into Alaska, less Pacific influence, and at least some polar and arctic influence into North America, with cooler anomalies over parts of the eastern U.S. Looks a bit like the pattern showing up on the models and ensembles over the next week.
An equatorward shift is inherently hard to sustain in an El Nino but is most conducive to EPO-induced cold shots into southern Canada and the CONUS:


Jet retractions favor flatting ridging farther west over the North Pacific...a -PNA pattern, which is showing up in the extended ensembles...


 
Tropical forcing is also influencing the pattern...the MJO is making a fairly amplified pass through phases 1-2 through early January:

This supports amplification of western North American ridging and at least some semblance of a -NAO (Phase 1 top, Phase 2 bottom):

https://www.atmos.albany.edu/facstaff/roundy/waves/rmmcyc/index200reg.html
So far the East Asian Mountain torque and tropical forcing do a good job of explaining the evolution of the Pacific jet and the recent/upcoming North American pattern. The troposphere and stratosphere have seemed to be relatively well-coupled so far this season, with an amplified pattern in the troposphere in late November and early December leading to increased upward heat and wave fluxes into the stratosphere. This has led to an ongoing stratospheric warming event that appears poised to downwell into the troposphere. 

https://stratobserve.com/anom_ts_diags
Not only do the mountain torque and tropical forcing support amplified ridging on the west coast into Alaska the rest of this month into early January, along with perhaps a -NAO, but the downwelling negative AO out of the stratosphere supports high-latitude blocking. Lots of factors supporting the pattern change that will be getting underway very soon. 
Here's a look at the EPS mean 500mb and surface temperature forecasts through the upcoming pattern change:

The 500mb evolution shown on the ensemble seems strongly supported by the various forcings described above over the next 10 days. The ongoing storm over the central U.S. starts carving out a trough over the eastern US over the next several days, with amplifying ridging on the west coast deepening the trough over the next 10 days as energy ejects out of the southwest U.S. in the subtropical jet. This leads to increased polar influence into Canada and the U.S., but the source region is currently very mild which will take quite a while to completely overcome. 
 

The result is a cooler trend over the CONUS, especially over the southern U.S. where the active subtropical jet keeps conditions more active. Over Canada it remains generally mild for the foreseeable future but certainly trends much less mild than recent conditions. It's worth noting that this is a change from temperatures well above freezing all the way to Hudson Bay to sub-zero temperatures (on the ensemble mean) down to at least that latitude:

The tug of colder air behind the current Plains storm is very meager but the colder air becomes much more "tappable" by the beginning of January, so any storms that develop will be able to pull in seasonally cold air. Nothing crazy but certainly much more wintry feeling that at the moment. Note those frames are all 12z which catches something close to the daily lows.
While the tropical forcing, mountain torque/Pacific jet, and stratospheric influence support upcoming amplification of ridging along the West Coast into Alaska and perhaps a -NAO, there are certainly hints at a more -PNA pattern taking hold in two weeks. Is that legit? 
Recall back to the SLP loop and the mountain torque discussion:

A sustained negative EAMT event appears likely in early January, supporting retraction of the Pacific jet (and a -PNA). Note how a similar evolution (about a week later) of Rocky Mountain Torque supports ridging over the North Atlantic, as a +RMT and strong North Atlantic jet to start January gives way to a -RMT and weakened North Atlantic jet by the second week of the month. 

https://charts.ecmwf.int/?facets={"Product type"%3A[]%2C"Parameters"%3A[]%2C"Type"%3A[]%2C"Range"%3A["Extended (42 days)"]}
There is some uncertainty regarding how the MJO evolves beyond the next 10 days. Many ensemble members have the wave weakening and moving into the "circle" in the day 15-20 range (blue and green dots, valid the 2nd week of January). A number of members maintain amplitude into phase 3 and some into phase 4 and 5. That seems unlikely but the ongoing stratospheric warming event may support a stronger and more amplified MJO moving across the Indian Ocean and into the western Pacific mid-late January...a trend worth monitoring. Even a phase 3 MJO in early January suggests a trend to a more -PNA/west coast trough:

To sum up where things are so far:
Tropical forcing, mountain torque/the Pacific jet and stratosphere support a pattern change over the next week. This will increase polar influence into Canada and the U.S. and favor development of an eastern U.S. trough during the first week of January. Mountain torque and tropical forcing suggest continued Pacific jet retraction in early to mid-January, which will encourage ridging to retrograde across Alaska as troughing over the eastern CONUS also retrogrades/shifts west. This will lead to conditions initially supporting any southern stream systems bringing a wintry threat to the interior Southeast/Mid Atlantic the first few days of January, but with wintry potential shifting west across this subforum in the January 4-10 range...perhaps lingering through the middle of January if ridging doesn't shift west towards the west coast too quickly. With generally mild conditions persisting over Canada the pattern won't favor strong clippers or huge arctic outbreaks that can set off days-long lake effect snow storms, but southern stream storms may be able to bring swaths of snow if they phase enough with the polar jet. And, a modest clipper and some lake effect could still be possible with Canada trending more seasonal. 

Looking further ahead, a number of EPS members have a significant stratospheric warming event (SSW) between January 5-15. If this occurred it would lead to greatly increased potential for sustained high-latitude blocking beginning in late January and persisting well into (and perhaps through) February. It is very common for a warm-up to occur over the central and eastern U.S. as a stratospheric warming event is ongoing, before any blocking it sets off can establish. This would line up with hints of a -PNA and +EPO towards the middle of January. 

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml 
Looking at tropical forcing, the forcing has generally been amplified over the central Pacific (near 180 longitude) and over the western Indian Ocean (near 25E), roughly outlined by the green boxes. Tropical forcing has generally been suppressed between these two areas. The tropical forcing has moved through the western hemisphere (phase 1 MJO and favorable for colder weather) every 3-4 weeks.
If this continued it would move back through the western hemisphere by the middle of January. However, it seems like the tropical forcing was more driven by faster-moving Kelvin Waves until the two most-recent orbits, which featured stronger and slower-moving anomalies more typical of the MJO. This most recent pass remained strong through the eastern Indian Ocean subsidence zone but also took closer to 4-5 weeks to return to the western hemisphere. If this more recent trend continues it will return to the western hemisphere in the ~3rd week of January and support a more favorable Pacific influence on the pattern, along with a -NAO. However, the stratospheric warming event over the pole leads to a colder lower stratosphere over the tropics, which may amplify and slow down the progression of the tropical forcing. I would say smart money is on tropical forcing becoming favorable for a western North America ridge to return during the last week of January. Potential exists for prolonged -NAO blocking by then if we do in fact see a major stratospheric warming event (which appears likely during the first half of January). 
After the cool down into early January, leading to a favorable pattern for any amplified southern stream system to bring snow potential to the region in the January 4-10th timeframe, along with perhaps a modest clipper and some lake effect, a trend towards a trough with colder air over the western U.S. and ridging farther east is supported for the middle portion of January. By the end of January potential appears to be there for impacts from a stratospheric warming event and tropical forcing to support a western North American ridge, eastern trough, and high-latitude blocking with an active southern stream. This would lead to a few week period of more wintry weather, and while unlikely to make up for seasonal snowfall deficits completely could salvage a semblance of a winter in the region. 

In a brief change from the mild and quiet nothingness that's typified this month, a PV lobe will bring a respectable (by December 2023 standards) shot of cold air and wind for Monday-Monday night.

The Euro and EPS suggest a decent LES response with inversion heights climbing to around 700 mb, so could see some accums into the Indiana and Michigan lake effect belts. While the temps won't be anything to write home about, the wind and seasonable cold combo will certainly feel unpleasant coming off the mild stretch we've had.

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We've grown accustomed to quiet patterns in December recently, but I think this stretch we're entering may take the cake.

If the end of the ensembles are to be believed, it'll take until at least the end of the month to see some retraction of the higher end Pacific jet extension that will flood much of North America with mild air over the next couple weeks.

Even then, if the pattern does eventually transition to colder in January, if it's driven by a +PNA, that would favor extending the drier than normal pattern.

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Still too early to lock in a certain scenario, but the 12z guidance consensus suggests less of a snow threat for the LOT CWA and a severe threat potentially extending into a portion of the CWA on Saturday PM.

You know, a casual 250 mile shift between runs. I wouldn't get too excited about anything...
And until I see something that changes it, I am riding the "weaker, south, strung out" multi-year trend. 

I like our placement between models but as always now, I fear a one-run transition to an event with a much lower ceiling. 
Question: why is it that, for example, the 06z GFS offered a pretty bland storm while the 06z GEFS was pretty crazy with the vast majority of members with a storm depicting a much more impressive event than the OP?

You want to see a change compare the 00z GFS vs 06z GFS for next week. A day 4-7 forecast is completely different, you can't get any more different to be honest.

We have gotten some, but they definitely have been less than years ago. The 1980s-90s were clipper heyday. Funny thing about the 1990s is that the 21st century has been much snowier but with noticeably less clippers.

Since 2009-10 is the only moderate to strong Niño winter since 1950 with above normal snow across the LOT CWA, not particularly optimistic for a snowy winter locally. That winter was a highly west based El Niño that peaked at 1.5 ONI and it had record strong AO/NAO blocking.

The issue for us is that in means, El Niños are more conducive to +PNA, so that when it does get cold, you have more of a CAD or clippers vibe vs. moisture laden systems. Need to cash in if you do get a good southern stream wave or two. 2015 had the November 22nd system and most of the metro *just missed* on the late Feb event that slammed the south suburbs and especially northwest Indiana.

I think if an element is going to diverge from the pre-season expectations (mild, and below average precip and snow), it'll be temperatures, especially if we get some good periods of blocking assuming the SPV isn't too strong (which appears possible in a -QBO/-PDO). Overall, outside of the super Niños (>2.0 ONI), the data is much more of a mixed bag for temps in moderate to strong Niños (1-2 range in the ONI).

The challenge with temps is that if snow ends up on the low side, need favorably timed snow cover leading into cold snaps to get good periods of negative anomalies. For this reason, I'd still lean toward temps ending up above normal.

Given the crappy winter we had last winter, here's hoping for an unlikely 2009-10 like outcome to this winter.

Will be back posting more regularly in here soon.

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ORD with a peak of 96° as of noon.

With clear skies, thermal ridge overhead, and compressional warming from the incoming front… 100°+ should be bank at this point.


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96/78 at ORD approaching noon, vs. 93 at this time yesterday. The highway construction on the west side of the airport may be contributing at ORD given that MDW is currently 94, but it's time to get this 100 at ORD.

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ORD is currently 88/78 as of 929am. For reference, it was 88/79 on the 10am ob yesterday. So it should be a degree or two warmer by the top of the hour today than it was yesterday. In our morning update, we bumped the forecast high at ORD to 100.

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Idk if it's on the radar yet since higher end patterns for severe weather in the east are not necessarily common, but holy moly at the 00z Euro for Monday.

Sub 1000 mb low pressure over the northeast is impressive for early August, let alone May or June. And 70+ dew points were forecast up to I-90 during the afternoon and evening, amidst strongly supportive low level and deep layer wind shear. The 12z GFS is honestly not too far off from that.

I'm originally from College Point in Queens, worked at OKX from Feb 2009 until July 2010 and been at NWS Chicago ever since. I'll be visiting my family Friday the 4th to Friday the 11th and staying in CP, so I'll be there on Monday if that setup holds.

The look on the 12z Euro for Sunday was likely the most impressive this summer at that range for a favorable large scale pattern for severe weather. Will be interesting to see if the Euro holds with its much slower s/w and cold frontal approach tonight.

Idk if it's on the radar yet since higher end patterns for severe weather in the east are not necessarily common, but holy moly at the 00z Euro for Monday.

Sub 1000 mb low pressure over the northeast is impressive for early August, let alone May or June. And 70+ dew points were forecast up to I-90 during the afternoon and evening, amidst strongly supportive low level and deep layer wind shear. The 12z GFS is honestly not too far off from that.

I'm originally from College Point in Queens, worked at OKX from Feb 2009 until July 2010 and been at NWS Chicago ever since. I'll be visiting my family Friday the 4th to Friday the 11th and staying in CP, so I'll be there on Monday if that setup holds.

The look on the 12z Euro for Sunday was likely the most impressive this summer at that range for a favorable large scale pattern for severe weather. Will be interesting to see if the Euro holds with its much slower s/w and cold frontal approach tonight.

I didn't even look at the day 3 until now, that is complete nonsense.

Say what you want about Broyles (he's not good in general), but for for my money, Goss is the worst performing SPC outlook forecaster. Those who are familiar with the 4/7/2020 wind driven sig hail event in eastern IA, southwest WI, and northern IL will remember that he issued one of the worst day 2 updates of all time (removed general TS in much of the sig hail area) on 4/6/2020.

He's on midnight shifts now and his outlooks have been bad as usual. The current day 3 he issued last night may take the cake in terms of silliness.

This afternoon was the first time I had any sort of excitement writing an AFD since one of the late season winter events. I was on a ski trip out west for March 31st and I worked April 4th but I don't think I wrote one of the AFDs for that. So yeah, it's been a while. Next couple weeks look potentially solid if you like mid summer RoF type stuff.

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Shit like this makes me think the Air Quality Alert issuance decision should be given to the NWS and taken away from the state idiots. 

Confirmed that the only reason we got an AQA is that the WCMs from LOT, ILX, and DVN pleaded for one.

My take from the mess today is that only if you're in a sensitive group do you deserve an AQA according to the IL EPA. For everyone else, take some responsibility, go to airnow.gov, and step outside to judge for yourself if the air quality is hazardous.

It would be like the NWS never issuing headlines for hazardous weather because people should be able to figure out it's unsafe.

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I'm off today but according to my coworker, we had to essentially beg the IL EPA to put out an AQA today. They hand out AQAs like candy on 90 degree days for ozone potentially impactful to sensitive groups, but then crickets most of this morning for the worst air quality in years (decades?) here.

And then they put in a dig at us in the 2nd paragraph of the AQA, basically implying that they didn't think they needed to put out a AQA because the air quality is obviously bad and the AQI is available at airnow.gov. Good stuff.

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drought about to flex, mid range chances ghosting