GaWx

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.

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

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

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.

At 1PM, there was a whopping 26F diff. between Valdosta’s 76 and Tifton’s 50. Tifton is a mere 45 miles N of Valdosta!

The yucky rainy pattern continues here. Luckily during a short break in the light rains yesterday evening, I squeezed in a walk. Today so far has been different. The rains at times have been heavy, with my measurements suggesting ~0.75”. There’s been enough to be wary of hydroplaning if going too fast. This is the heaviest I’ve seen in several months. Thus, it’s the first minor test of my completed yard drainage projects as well as the city’s redug nearby street drainage ditch project. But it’s still not yet a complete tear as I need even heavier rains. Regardless, there will be more on and off rains through Sunday. My temps have been mainly in the mid to upper 50s after dipping to the rain cooled upper 40s last night. Temps are 12 warmer in Brunswick 75 miles to the S.

9 of the last 11 of the Jans following -PNAs in Dec for -ENSO were either cold or pretty close to normal. You’ve been harping on the only two warm Jans of the 11. Feb will more than likely be mild. It’s not necessarily Jan and Feb being similar as you’ve been thinking. This indicator suggests that’s unlikely as of now.

I’ll be rooting for a strong -PNA this month. Why? For -ENSO: Strongest -PNA Decs since 1983-4: -2021-2: -2.56; Jan was +1.01/cold -2010-11: -1.78; Jan was +1.29/cold -1984-5: -1.60; Jan was +1.63/cold -2008-9: -1.41; Jan was +0.61/cold ——— The Euro Weeklies continue with a pretty strong SER/-PNA in the first half of Jan. But it’s recently been correcting to a weaker one in late Nov/early Dec.

Agreed. But also keep in mind that the 15 days on that model (0Z EPS) preceding the map you showed are very cold in the NE 1/4 of the US and suggest one of the coldest 1st 19 days of Dec anomalies on record in the NE 1/4 of the US: Days 1-10: Days 11-15:

Today’s 2 week ensemble MJO forecasts: -12/5 EPS steady as a rock with a 17+ day long phase 8, second (back to 1974-5) only to the 18 days of 1975-6: a cold E US weenie couldn’t place it any better though keep in mind that the MJO, itself, is only one index of many despite it having notable tendencies: 12/5 GEFS: though not steady like EPS with only a 5 day phase 8 followed by 3 days of weak phase 1 (which also is often cold in Dec) followed by 5 more days in phase 8 and then 4 days barely in phase 7, this is on the whole still favoring dominating cold in the E US: Related to the very cold Dec forecasts, natural gas is up a whopping 6% today, alone! Knowledgeable NG investors don’t normally go long NG in winter unless the forecast is for a cold E US.

I still feel that Jan and Feb should be analyzed separately for the NE US. Since 1983-4 as regards -PNA Decs: -3 times as many -ENSO -PNA Decembers were followed by cold Jans as mild Jans including the recent Jan of 2022. In addition, there were cold Jans in 2014, 2011, 2009, 1985, and 1984. Related to this, 9 of 11 of these Jans were either cold or pretty close to normal. -But OTOH there were 6 times as many mild Febs vs the only cold Feb (2014) of these analogs in the NE.