December 2019 Weather Discussion for the PNW

[ShawniganLake]

Another mild month unfolding here. Sitting at +2.5F for December after finishing November at +1.3F. At least we got some decent rain tonight. Over 1/2” now which has doubled my monthly total

[SilverFallsAndrew]

Another mild month unfolding here. Sitting at +2.5F for December after finishing November at +1.3F. At least we got some decent rain tonight. Over 1/2” now which has doubled my monthly total

 

January...Hey a January 2005 redux would do you well!

[ShawniganLake]

January...Hey a January 2005 redux would do you well!

Yes it would. Snowfall this season here is already lagging behind 2004-2005 by about 2.25” to this point.

[TigerWoodsLibido]

Gotta love when the smoke detector goes off in the middle of the night for no reason...overnight GFS is a snoozer for the most part. The mountains get snow over the next 10 days tho so at least there’s that.

[TT-SEA]

Gotta love when the smoke detector goes off in the middle of the night for no reason...overnight GFS is a snoozer for the most part. The mountains get snow over the next 10 days tho so at least there’s that.

 

Except Saturday - Thursday now looks basically dry and the GFS showed rain below 5,000 feet after that.

 

This is not a 10-day mountain snow bonanza coming up.   Far from it actually.

 

We should also remember the GFS greatly exaggerates snowfall totals... particularly when looking at maps covering a long period of time.

[ShawniganLake]

Except Saturday - Thursday now looks basically dry and the GFS showed rain below 5.000 feet after that.

 

This is not a 10-day mountain snow bonanza coming up. Far from it actually.

 

We should also remember the GFS greatly exaggerates snowfall totals... particularly when looking at maps covering a long period of time.

Yea the models have totally caved on any major prolonged Mt snow event. The best looking snow pattern is happening right now.

[TT-SEA]

Yea the models have totally caved on any major prolonged Mt snow event. The best looking snow pattern is happening right now.

 

I know we are only supposed to talk about good things (i.e. lots of cold and snow and wind and rain) and be very positive though.  

[FroYoBro]

At least this week is great for the mountains. We aren’t talking about historic lows in snowpack.

[Front Ranger]

Christmas. Not a bad signal at this point.

 

[ShawniganLake]

Christmas. Not a bad signal at this point.

 

gfs-ens_z500a_namer_53.png

Was actually just going to post this. Pretty nice looking. Unfortunate that both GEPS and EPS seem to be sold on a very different outcome.

[ShawniganLake]

[TT-SEA]

Christmas. Not a bad signal at this point.

 

gfs-ens_z500a_namer_53.png

 

 

Here is the 00Z EPS for the week of Christmas.   Given its rock solid consistency... its probably best to assume it will be something close to this in reality.   Looks like a general western trough... but with signs of split flow as well.

 

 

[Gradient Keeper]

6z GFS Ensembles - Still seeing that dip in the mean temp and chilly members near/after Christmas. 500mb pattern has an amplified ridge around 160-150 W.  We do need to see the EURO/GEM latch onto this now. We never want to see the GFS out on its own like this.

 

Yakima ensembles increased potential for backdoor cold/arctic air into Eastern Washington and the Columbia Basin.

http://old.wetterzentrale.de/pics/MT8_Yakima_USA_ens.png

[Front Ranger]

One weakness of the LR EPS is that it sometimes tends to hold on to persistence too long.

 

I'm not assuming either model is close at this point.

[TT-SEA]

One weakness of the LR EPS is that it sometimes tends to hold on to persistence too long.

 

I'm not assuming either model is close at this point.

 

Hanging onto persistence has generally been the right way to go since mid-October.     It has been handling the situation quite well.

 

It interesting to watch the long range period on the EPS each run and track it... and then see the operational runs of all models swinging wildly in the long range but eventually close in on the solution that the EPS was showing all along. 

 

This is not always true of course.   As I have mentioned many times... the EPS was not good most of the summer.   It had no consistency and over-promised western ridging.   But it has been much better since about September and until it stops being consistent it seems unlikely that it will be wrong.  

[Brian_in_Leavenworth]

Except Saturday - Thursday now looks basically dry and the GFS showed rain below 5,000 feet after that.

 

This is not a 10-day mountain snow bonanza coming up. Far from it actually.

 

We should also remember the GFS greatly exaggerates snowfall totals... particularly when looking at maps covering a long period of time.

A dry pattern for sure, but NWS Seattle says snow levels at 2000 feet or lower through Wednesday, so whatever falls will be snow. After that is too far away to forecast anyway.

[Front Ranger]

Hanging onto persistence has generally been the right way to go since mid-October.     It has been handling the situation quite well.

 

It interesting to watch the long range period on the EPS each run and track it... and then see the operational runs of all models swinging wildly in the long range but eventually close in on the solution that the EPS was showing all along. 

 

This is not always true of course.   As I have mentioned many times... the EPS was not good most of the summer.   It had no consistency and over-promised western ridging.   But it has been much better since about September and until it stops being consistent it seems unlikely that it will be wrong.  

 

I'd like to see actual stats though for the periods of pattern change. I'm not convinced that it's picked up every pattern change perfectly.

 

Actually think I remember it struggling at times to pick up on the late October/early November pattern switch.

[TT-SEA]

I'd like to see actual stats though for the periods of pattern change. I'm not convinced that it's picked up every pattern change perfectly.

 

Actually think I remember it struggling at times to pick up on the late October/early November pattern switch.

Its easy to tell when its struggling... the long range will change (sometimes dramatically) from run to run.

 

Its very consistent right now. And has been consistent overall for the last 6 or 7 weeks.

 

Bottom line... ignoring the EPS when its consistent is probably not a good idea. You don't have to believe me. I know the EPS is far from perfect. But when I see consistency... it's usually a good idea to pay attention.

[Phil]

One weakness of the LR EPS is that it sometimes tends to hold on to persistence too long.

 

I'm not assuming either model is close at this point.

This. Models having problems handling the downwelling of the -U anoms after the CW last month, in tandem with the EAMT drawback and transition from +IOD to warm pool forcing.

 

Not an easy period to forecast, for humans or models.

[MossMan]

Looks fun at Stevens...Even though they are reporting a mix at the moment.

[MossMan]

I’m starting to sense a 2017 Christmas like miracle brewing...

[Phil]

Yea the models have totally caved on any major prolonged Mt snow event. The best looking snow pattern is happening right now.

Shocker...

[Gradient Keeper]

12z GFS Day 5-6 Noticing the upper low over Siberia holding back further this run and the WPAC up through the Bering looking ridgy/blocky

[MossMan]

Actual air movement going on...smells fresh and non smoky for the first time in a month...refreshing!

 

Currently 45 degrees.

[ShawniganLake]

Shocker...

Dry winter is back on.

[ShawniganLake]

Actual air movement going on...smells fresh and non smoky for the first time in a month...refreshing!

 

Currently 45 degrees.

I forgot and I know I asked before but why is it so smoky there?

[TT-SEA]

Looks fun at Stevens...Even though they are reporting a mix at the moment.

 

 

My son came over Snoqualmie Pass at midnight last night... he said it was intense.   I told him to wait until morning but he had his mind set on getting home last night.  

[MossMan]

I forgot and I know I asked before but why is it so smoky there?

Some controlled/slash burns going on in the area that have been left to smolder for weeks with little to no air flow in this split flow deadness. Probably clearing for housing developments...since we do not have enough of those...

[Gradient Keeper]

Of course by Day 7 not so favorable. Don't like that retrograding low over Northern Alaska either.

 

12z ECMWF in 1 hour 22 minutes

[Gradient Keeper]

Dumb pattern. No one likes dumb patterns.

[ShawniganLake]

Some controlled/slash burns going on in the area that have been left to smolder for weeks with little to no air flow in this split flow deadness. Probably clearing for housing developments...since we do not have enough of those...

Oh that’s right. Shitty. Winds have been unusually calm the past couple weeks here. My max gust for December is 7mph

[Phil]

Dumb pattern. No one likes dumb patterns.

That’s gonna turn into a -EPO blockfest in the clown range.

 

Watch. Much better scandi pattern.

[Phil]

Sometimes what looks like a dumb pattern at first is actually a much better pattern trying to organize.

 

Scandi block, quicker jet retraction, weaker Greenland vortex. All better. Should be good after D12!

[SilverFallsAndrew]

12z looks fairly cool at the surface. 

[TacomaWaWx]

Picked up 0.44” yesterday and another 0.02” so far this morning. We’re at 1.30” of rain for December.

[El_Nina]

Mt Hood snowpack is up to 29 percent from 28 yesterday.

[ShawniganLake]

Some chilly gorge outflow for Christmas on the gfs

[SilverFallsAndrew]

Mt Hood snowpack is up to 29 percent from 28 yesterday.

 

Early December snow pack does not mean a whole lot though. We had tons of mountain snow in December 2015 and lost pretty much all of it during the blow torch February. Last winter snow pack was abysmal through January and bounced back in a big way. 

[SilverFallsAndrew]

The 12z GFS may not deliver tons of mountain snow, or any valley snow chances, but it will feel like winter if it verifies. I give it the Snow Wizard memorial stamp of approval. 

[Gradient Keeper]

B E L I E V E ! ! ! !

 

It's coming....