Carvers Gap

And it could end up being warm. But in the end, it is just something none of us can control. The thing that will irritate me when tracking winter patterns....a model flip away from a cold, storm pattern. In this case, the chinook pattern has been well advertised. What I want to see is that pattern to be muted. Modeling is apparently going to miss at least two cold fronts...maybe more. Those fronts are getting colder as reality approaches. That is a sure tell that modeling is correcting. There is also a bit of a disconnect between 500 and the surface. So, interesting times ahead. Prim climatology is still almost a month away. And yes, I could use a few warm days just to thaw out. It has been BN here since Thanksgiving...I need a break from the cold. You won't hear me say that often!

The surface pressure anomalies are not bad throughout.

Have to look at the surface. 500 maps are missing cold shots. I think we are going to see a fairly normal pattern for December at this latitude. What I am looking for is not non stop chinooks. I am resigned to some chinooks mayhem. We were close to a winter storm that run.

The 18z GFS joins(?) the 12z Euro in muting the chinooks with multiple cold fronts. I did notice ensembles beginning to cool off at 12z (look at the run 2 run for reference). I hesitate to say the GFS joins the Euro since the GFS was the first to the party and then went and smoked a cigarette on the back porch at lunch.

I think the trough shifting back NW makes sense given climatology. I also know that LR models like to end winter with that....only to have the entire trough come crashing SE w/ one good cutter. I suspect we have a really big cold snap coming...timing TBD, but I would guess LC has this nailed to the wall.

12z suite highlights. The 12z Euro(surprise!) now carries the banner for cold. The Dec20-30th timeframe for NE TN is normal-ish. It has the least feedback over the PNW. The Dec 19-20 cold front is now a "go" with it being legit Canadian cold. Can we score another front on the 22nd per the Euro - the GFS lost it, but I bet it's real. The really interesting one is the backdoor cold front on the 27th. Yes, it looks like Christmas should be warm with the cycle of warm fronts and cold fronts seeming to have it locked in between cold fronts - but who knows really. At nine days out, anything can happen. Maybe the really big news is the NAO looks on steroids on both the GFS and Euro 12z runs. It is east based, but retrograding to the West. It doesn't take much imagination to see a full latitude trough developing over NA between the Aleutian and NA ridges. A true block w precedent.

The 0z Euro is much different w/ the Dec19-20 cold front potential. I think it likely wrong. The 6z AIFS has the cold front. It would not surprise me to see snow flurries or snow showers behind that front. If you watch the 6z GFS at 500, it makes sense. It pops a ridge in the East. It gets knocked down. The next ridge(chinook) pops further west. It gets knocked down. Each time the ridge goes up, it gets knocked down, and retrogrades westward. By the end of the run, it is a EPO ridge. Jax mentioned the atmospheric river. It may well be we are still in a base-cold pattern w/ the AR overwhelming the MJO signal which wouldn't be unprecedented (reference earlier discussion). As it retracts, that trough would slide right back into the East. I need to actually look at modeling in the Pac to see if that is happening. Interesingly, western Montana has had severe flooding when they should have had snow. Troy and Libby have lost several bridges in western Montana.

The 6z GFS is back to normal for Dec 19-29th after a warm run at 0z. Interestingly, the 0z run developed what appeared to be feedback over the PNW. When that occurs, the rest of the run is warm. When it doesn't occur...it is back and forth. For now, it looks like cold air masses will visit(24-48 hour duration) on the 19-20th, possibly the 22nd, possibly the 24th, and then too scrambled to even guess after that. In between the cool downs, there will be chinooks likely. I am really interested to see where this pattern settles after this transition timeframe. But the back and forth pattern might the the actual pattern for a few undetermined amount of weeks.

It looks like temps (not right by the river) are ranging rom 7-9F for my area of TRI. It is 8 at the airport. We had wind chills yesterday in the mid-single digits.

And be sure to keep posting! Great to have our input...I meant to add that.

Yep. Get rid of that feedback over the Pac NW, the vortices kick eastward, and deepen. For whatever reason, models are having a very difficult time (past 5-6 weeks) with infinite vortices over the West Coast. That error is rendering modeling almost useless after hour 200...not that it is super accurate after that during normal times. @John1122got me into watching Mammoth's snow cams during winter. I follow a bunch of their pages after the Carver Gap family visit over the summer. That place is beautiful at all times of the year. Anyway, they are stuck under that western ridge.

I think as soon as a model spins up a low over the Canadian Rockies, sends it SW to where is spins off the CA Coast until it strengthens anomalously, and then dies out...has to be tossed right at the point. The 18z GFS makes a lot of sense until it does that at 210. Those solutions haven't been materializing. When the feedback occurs, it spins up a deep trough in the eastern Pac(which originates in Canada!) and that deepens the AN heights over the EC and ensuing Chinook. Those western Canadian coastal lows are going to get kicked eastward - just how it goes in real life "most" of the time. I think that problem is over cooking the ensembles.

The 18z GFS does indeed find a Christmas Eve cold front. Chinook-then-cold front pattern in place. I actually don't mind that. That is a far better option than the standing ridge(which had rain into almost the Hudson Bay). It will be interesting to see if it intensifies that 24th cold front with time. Originally, it had an anafront on that day. Of course, it has also had sever as well! LOL

Great observations. I appreciate your input as always!

For whatever reason, deterministic global models are having a very difficult time seeing cold fronts in the d10-15 range. I think that is feedback(infinite loop stuff). The chinook looks plausible and is a pretty normal phenomenon in my book. The cold fronts pushing it back make a lot of sense as well. I doubt that pattern is very stable as it requires a lot of amplification to sustain that type of back and forth. I just read LC's writeup from last night. He is firm with his last 1/3 of January and most of Feb being cold. To me that is a 95-96 type of analog. But it fights winters which return with some fight - lots of analogs for those. If the QBO wasn't negative, I would be more solemn. I suspect we see the NAO fire, and as we know, the lead time on the NAO firing is very short.