GaWx

2 minutes ago, Coach McGuirk said:

More common than you think.  We do get snowstorms in southeaster VA.  It's feast or famine.  Last year was 1 in, 2 in, 2 in, 8.5 inches.  The previous two years were nothing.  We average 8 in a year.  We could be zero or 20 inches.  Nor'easters can drop 8-12 inches on us. 

I forgot to mention that there’s a dedicated thread for today’s storm. For documentation purposes, you may also want to post your results in there:

 Today here I just got an invigorating walk in with low 40s and just enough breeze to give it a nice bite. Today’s high of only 51 (normal is 65) means that every day so far this month has had a high only in the 50s. We already had had the first time in recorded history (back to 1874) of no high reaching 60 for Dec 1-7. Now it’s also the first time for that for Dec 1-8 and tomorrow is going to make it the first time for Dec 1-9!

 Rainfall so far this month is over 2”, which is way above the normal of 0.75” for Dec 1-9. For the first time since at least Thursday we had no rain.

8 minutes ago, Coach McGuirk said:

Storm dying out, probably end up with 6 inches.  But 6 inches that came out of nowhere is fine with me. 

How often has your area received 6” or more from a single storm?

For the record regarding the main indices for today’s wintry event:

- The prior -PNA rose to the more favorable neutral PNA (-0.1)

- AO -1.9, one day after a short-term minimum of -2.2 was hit

- NAO -1.2, one day after a short-term minimum of -1.3 was hit

- MJO likely was inside the circle phase 8 (probably won’t know for sure for a couple of days)

- +EPO

- -WPO

55 minutes ago, snowman19 said:

As I’ve learned and I’m sure many others have…..They are going with persistence forecasting, which is really not advisable at all. When you do that, you are just assuming that a pattern is going to continue and models are all wrong and are just going to keep correcting to cold without any end or breaks. Persistence forecasting works until it doesn’t. Those guys are basically saying “yea, the models have been wrong so far and the pattern hasn’t broken yet, so we are just going to keep forecasting the status quo (cold) indefinitely, no matter what the forcing may do, no matter what in the long wave pattern changes and no matter what the models may show, we don’t care”. Not only unprofessional for mets, but a very bad idea and if it fails, you totally lose credibility and trust 

Good points. But if there were a clearly identified long time model bias,  adjusting for that would obviously make sense.

22 minutes ago, MJO812 said:

The questions are whether or not and, if so, how long these same model misses will continue. It isn’t black and white. Nobody knows including you and me.

Today’s Euro Weeklies for week 3+ are still lacking cold domination to return to most of the E US south of the N tier with a solid -PNA dominating through mid Jan along with no -NAO or -AO. If this verifies, it would likely be pretty mild in much of the E US and nothing like we’ve been experiencing the last 2 weeks. However, models the last 3 weeks have been too warm in the E US with too much SER and missing much of the -NAO and -AO. Also, Midwest snowcover is well above avg, there’s the potential lag effects from the 11/28/25 SSWE, and the MJO remains favorable for E US cold. Are the weeklies/models finally getting their act together or are they going to continue with the same errors? Opinions?

 A big reason the models have been much too warm in the E US are the horrible NAO/AO progs with this one from just 11 days ago having it go + just 1 week later:

11/28 AO prog for today: ~+1

Today’s AO verified way down at ~-2 (strong -AO) meaning a +3 miss:

There was a similar big miss for the NAO:

11/28 NAO prog for today slightly positive (~+0.2):

Today’s NAO verified way down at -1.2 (strong -NAO), meaning a +1.4 miss:

 OTOH: The natural gas market, which is down sharply (6%) currently feels the prospects for a warmer pattern Dec 16th and beyond have increased. Check out the 0Z EPS HDD, which is on left chart, as it shows HDD plunging from mainly AN through 12/14 to BN 12/16-21 along with a trajectory suggesting more BN HDD (meaning warmer than normal E US). We’ll have to see whether or not this will finally verify well as the EPS has been too warm for the last 3 weeks as it has continually been correcting colder as the periods get closer:

1 hour ago, stadiumwave said:

 

Go look at all -QBO La Nina's that had any early strat warming (not full blown SSW). January is the coldest month with thise analogs unlike the +QBO LA Nina's that basically all end winter early JAN. No way to know if it shakes out that way but it is interesting nonetheless. 

 Related to this is the -PNA Dec to +PNA Jan transitions for -ENSO that have been happening during the last 40 year period. That transition has been strongest when the Dec -PNA was strongest. Examples of cold Jans were during these winters: 1983-4, 1984-5, 2008-9, 2010-1, 2013-4, and 2021-2 where Jan was cold though not always colder than Dec.

3 hours ago, MJO812 said:

The models have been correcting colder so far this month after showing warmth in the long range. I believe it will continue as along as the WPO stays negative. 

Look at the gefs correcting in the bottom imaging.  This month will end up being a cold month. Now hopefully snow will eventually come with it for areas near the coast. 

Indeed, and look at the trend of just the last 3 GEFS for 12Z on 12/18: E trough deepening/W ridge strengthening. It’s important to keep watching these trends as the models in general have been much too warm in the E US since the runs starting 3 weeks ago though at some point this trend is likely to end at least temporarily:

3 hours ago, Spartman said:

Jonathan Wall apparently bringing up 2001-2002 regarding the Phase 8 MJO

https://x.com/_jwall/status/1997672498993762417

I’ll give him the benefit of the doubt and assume he’s not counting weak phase 8 (inside circle). But even so, these had outside the circle phase 8 in Dec since 2001:

2017: 

2009:

2007:

2002:

@mitchnick

5 hours ago, yotaman said:

Forecasted high 54, actual high 45. Clouds hung tight. Low was 31.

 There’s no question that the CAD wedge has been the big winner in the SE US so far this month.

 My area has had almost every day mainly cloudy, rain on most days, and every day 12/1-7 has had highs only in the 50s! That’s very hard to do on every day for a week in early Dec with normal highs 10 degrees warmer. As a matter of fact, it’s so hard that this is the first time on record that it has happened with records going all of the way back to 1874!

 Interestingly, the highs have ticked down each day this month: 59, 58, 55, 54, 53, 52, and 50.

 I see that GSO has had all highs only in the 40s Dec 1-7. I wonder if that’s ever on record happened there. Anyone know?

Edit: If that’s not enough, the forecast is calling for 2 more days of 50s highs, which will make it Dec 1-9! Same idea for GSO with 2 more sub 50 highs for Dec 8-9!

 Edit: I just checked GSO. Only once on record back to 1903 did they have not get out of the 40s Dec 1-7: 1910. However, they did get to 50+ on Dec 9th, So based on the forecast, Dec 1-9th, 2025 will be the first on record not having even one day get out of the 40s at GSO!

 Which are y’all going with for Saturday’s (12/13) low? 
 
 The GFS sticks out as much colder than the others at ATL with upper teens there, which tells me it’s likely too cold there. It has had a cold bias over snowcover in recent years (which is well above average in the Midwest). That’s probably a factor as I don’t know that that has been fixed.

6Z GFS: pipe busting cold with upper teens ATL/RDU: likely too cold

0Z Euro: slower with the cold and thus is much warmer on Sat AM with upper 30s: likely too warm though it has 20s the subsequent few days

0Z ICON: mid 20s RDU to upper 20s ATL: looks like a reasonable middle-ground

0Z CMC: coldest at RDU with mid teens (CMC has a well-known cold bias) though only down to mid 20s ATL

0Z UKMET: only down to low 30s though it has a warm bias/very likely too warm though it is headed for 20s on Sunday

54 minutes ago, PhiEaglesfan712 said:

Definitely agree with that. Plus, December 2023 was warm all the way through. Kind of like 2015 and 2021. All of those years had a regression to the mean in January, with snow and near normal temperature departures.

This year we have a cold December so far. We just need a snowfall, or otherwise, we might have a similar situation to December 2022.

 I’m not using Dec 2022 as a heavily weighted analog because of snowcover. On this date in 2022, there was only 1% snowcover in the Midwest:

Compare that to today’s 46%, the 3rd highest only to 2013’s and 2007’s 53% and just ahead of 2005’s 45%. The 2003-24 average is only ~15% meaning today’s is ~3 times the average for Dec 7th:

@donsutherland1you may want to keep this in mind for your forecasts.
 

https://www.nohrsc.noaa.gov/nsa/index.html?region=Midwest&year=2025&month=12&day=7&units=e

I created a new thread for tomorrow’s wintry event in mainly NC/VA:

 I created this for the Monday (12/8) wintry threat for mainly NC and VA so as to leave the longer term for the main Dec thread.

 @buckeyefan1please pin this. Thank you.

2 hours ago, donsutherland1 said:

If the WPO relaxes from its forecast values of -2.000 or below, other teleconnections can gain influence over the pattern. The EPS currently forecasts an EPO+/AO+/PNA-/NAO+ regime toward the end of its run. If the WPO rises, that could allow ridging to expand across the CONUS with warmth following after a few days lag.

December 30-31, 1999:

The December 30-31, 1999 composite 500 mb map is one example of how unfavorable teleconnections overwhelmed a weaker WPO-. Then, the WPO was still impressive (below -1.000) but it was not at the extreme values necessary to overwhelm the pattern.

Milder conditions rapidly spread into the East.  Despite much above normal temperatures to start January 2000, the month wound up colder than normal. Late January (January 24-27 timeframe) saw a major snowstorm in the Southeast and lower Mid-Atlantic region.

For now, it looks to remain generally colder than normal through around December 20th. Nothing is cast in stone for the remainder of the month, though some temporary relaxation is plausible. IMO, the odds remain against a complete breakdown of the pattern and the onset of a sustained warm pattern during the closing 10-11 days of December. Still, it's worth watching the evolution of the guidance.

I suspect that there could be an increased risk of a pattern breakdown after mid-January, which often happens during La Niña winters, but that's in the speculative range right now. The PNA could play a larger role in how January evolves.

 Regarding the Januaries overall in the NE US following the last 11 -ENSO -PNA Decembers, only 2 were mild (2017 and 2023) while 3 were within a few degrees of normal and 6 were cold (1984, 1985, 2009, 2011, 2014, and 2022). So, 3 times as many mild were cold.

*Edited for correction: 6 Jans were cold, not just 5.

1 hour ago, snowman19 said:

Day 14 on the operational 18z GFS 

 But the idea of a big Arctic plunge 12/12-17 deep down into the US (possibly from two highs per GFS) is becoming increasingly likely based on model guidance. This is very believable considering it would be during an EPS progged longest phase 8 in 50 years along with the highest % Dec 5th snowcover in the Midwest since at least 2002.

 This is also setting the table for a potential quite cold Dec/Jan considering the -PNA Dec -ENSO analogs suggesting a +PNA Jan, which would make it likely that DJF would end up colder than normal for much of the E US even if we get the favored mild Feb.

 The Euro Weeklies would have to bust badly to allow for a +PNA, but it’s been too strong with the SER since just before Thanksgiving.

18Z GFS:

2m anomalies for 0Z on 12/14:

Highest US snow-cover as of Dec 5th 2003-25 (%)(2003-24 avg 27%):

‘05 48 

‘25 45 

‘18 43

‘10 39

‘13 38

‘19 37

‘06 33

‘16 32

But more importantly for E US cold prospects is the Midwest snowcover: highest % as of Dec 5th (2003-24 avg 12%):

‘25 65

‘05 45

‘18 32

‘06 31

‘10 27

‘16 25

‘03 23

‘08 20

https://www.nohrsc.noaa.gov/nsa/index.html?region=Midwest&year=2025&month=12&day=5&units=e

4 hours ago, PhiEaglesfan712 said:

December 2016 and December 2022 seem like the best matches. We have a lot of the elements of those seasons this year: -ENSO, deep -IOD, la nina background, and strong Pacific jet. Plus, a cooler December. If we don't get the snowstorm, then I really like the 2016-17 and 2022-23 analogs even more (sorry Team Snow).

The only places I think that will do well in the East are places like upper New York (Buffalo to Albany), Vermont, and northern New Hampshire/Maine. Places near the coast are going to have a tough time getting snow.

US snowcover as of Dec 5th is way higher now than it was in ‘16 and even moreso vs ‘22.

10 hours ago, GaWx said:

 All 0Z ensembles are much colder in the E US 12/13-17 vs earlier runs.

Followup: this is only 8 days out

12Z GFS

 All 0Z ensembles are much colder in the E US 12/13-17 vs earlier runs.

New weeks 3-4 outlook makes sense since it’s similar to the Euro Weeklies. But hopefully they will end up too warm:

Chicago per model consensus is on track for a top tier cold Dec 1-20. Here are the 15 coldest Dec 1-20 at Chicago of the last 75 years (top 20 %) in reverse chronological order:

2016, 13, 10, 08, 05, 00, 89, 85, 83, 76, 72, 63, 58, 56, 50

 2025 appears at this time like it might compete with many of these.