We have a trend for an Arctic Outbreak by Christmas

[Valkhorn]

The GFS has now trended to surge arctic air into the country. So far these are how the last runs have turned out (yes or no for arctic outbreak):

12/11/03 - 18z - yes
12/12/03 - 00z - half and half
12/12/03 - 06z - no
12/12/03 - 12z - yes
12/12/03 - 18z - yes
12/13/03 - 00z - yes

I'm waiting for the GFS run to finish for 00z but so far to 276 hours it looks promising.

[Valkhorn]

The GFS is done. The trend is two arctic outbreaks this time for 00z, with a slight punctuation of warmer air.

Interesting maps:

http://www.ssd.noaa.gov/PS/SNOW/DATA/usa-1mo-loop.html
http://maps.wunderground.com/data/images/cn_st.gif

The Hudson Bay will be frozen completely in 10 days time and the snowcover is well to the south, and getting further south.

Something definately is on the horizon.

Interesting readings this hour from Canada:

Nunavut:
Cambridge Bay: -27F
Baker Lake: -31F
Eureka: -33F
Kuglugtuk: -33F
Rankin Inlet: -31F

Ontario:
Armstrong: -22F
Geraldton: -20F
Timmins: -20F

Yukon:
Komakuk Beach: -20F
Shingle Point: -22F

NW Territories:
Aklavik: -24F
Holman Island: -26F

...it is getting colder folks...

[JCT777]

Nice analysis, Valkhorn. It does appear as if there is going to be an Arctic outbreak (or 2) during the next few weeks. Anyone looking for mild weather in the Eastern half of the country in the last 10 days of December - especially north of 35 N - is not going to be happy.

[wxw]

Excellent post Valkhorn. You've been right on top of (and correct about) this outbreak, even though various models started to back away from it the last few days. CPC was very confident early in the week about the -NAO, +PNA setup favoring this setup, but even they started to back away from it Thursday and Friday, again probably due to the waffling of the GFS.

So, when this occurs, do you think it would also be a favorable setup for LES from GL into the Appalachian chain?

The GFS has now trended to surge arctic air into the country. So far these are how the last runs have turned out (yes or no for arctic outbreak):

12/11/03 - 18z - yes
12/12/03 - 00z - half and half
12/12/03 - 06z - no
12/12/03 - 12z - yes
12/12/03 - 18z - yes
12/13/03 - 00z - yes

I'm waiting for the GFS run to finish for 00z but so far to 276 hours it looks promising.

[wxw]

Actually, let me correct my last statement. Can't say your call is correct yet because it hasn't verified, but it does look more and more likely.

[Valkhorn]

Hehe thanks guys. I don't see how it could be any other way myself. Some runs of the AVN even call for rapid snowmelt despite temperatures cold enough to support snowcover so out beyond 3-4 days the snowcover maps must be taken with huge grains of salt.



The 12z run is very odd indeed. I'm going to wait for the next few runs to see what's happening. So far there is a trend for massive cold air to entrench to southern Canada and the northern tier. The latest run even puts the -30C line into northern MN. I knew the 480's would show up sooner or later for height values in the models.

One thing is clear, arctic air will invade the US in two weeks. The two things that are unclear:

1) Will there be a brief warmup in the US before this happens? The models are waffling on this back and forth a lot.

2) How far south will the cold air make it. Every other run has put the cold air into Florida practically and the others leave it in MN.

My take: (1) the brief warmup is being overdone. I really don't think it will do much to erase any snowcover and will for the most part only bring some temps near average. (2) I think the models are just now picking up on a possible cross polar flow and polar vortex gliding into southern Canada. I think once it gets a handle on that better it'll get a handle on where it goes in the US. I highly doubt though a pocket of -30C 850mb temps would stay up in MN for 3 days and not send temperatures below freezing south of the Mason-Dixon line. So far the 12z is showing a rediculous gradient by then.

We're talking heights from 486 to 570 on a line from ND and MN to Texas on this run. That's a little odd.

Now there is a third scenario. We could end up with only a cold air invasion in the North, but that hasn't happened often with this kind of cold air, so, so far I don't buy scenario 3.

[aep]

Geez, I sure hope we don't get that cold for Christmas. According to that map we would be right in the center of the -30 850mb temps. It will make this last cold spell feel like a walk in the park.

[Lindaloo]

Any chance we here on the Gulf Coast will see some of this bone chilling cold by Christmas?

A few years back it was 78 degrees on Christmas Eve. I wore shorts and had the AC on.

[Josephine96]

Nice and chilly in some spots. Warm and summerlike in others I like the warmer weather

[Valkhorn]

It's too early to tell how far south this cold air will get. Those of you in the upper midwest have a near 80% chance at seeing it, but that's the most certain part.

The rest (no pun intended) is still up in the air

[Valkhorn]

The 18z is in. Looks like it is the same as the 12z with an exception of it being much colder in Canada this time. I saw a few 480 and 486 values for 1000-500mb heights out by hour 200-300 over Canada.

The models are getting more and more sure of it now, only the question now is when will it cross the border.

[Lindaloo]

It's too early to tell how far south this cold air will get. Those of you in the upper midwest have a near 80% chance at seeing it, but that's the most certain part.

The rest (no pun intended) is still up in the air

Thanks for the info.

[wxw]

Valkhorn, Any chance of it pressing into GL region by xmas day based on the latest model runs? I'm trying to get an idea of LES potential in NW Ohio around the 25th.

Thanks.

The 18z is in. Looks like it is the same as the 12z with an exception of it being much colder in Canada this time. I saw a few 480 and 486 values for 1000-500mb heights out by hour 200-300 over Canada.

The models are getting more and more sure of it now, only the question now is when will it cross the border.

[Stormsfury]

Well, the 3 day average of the EURO gets quite interesting and exudes BIG potential ...

3 day average - US view

3 day average - Northern Hemisphere View -BIG NOTES: Confluent flow over the East and a huge Omega Block over the Northeast Atlantic ... Something could be a brewing just in time for Christmas ...

SF

[Valkhorn]

Wow... mucho impressive Stormsfury.

I think it's funny though that those that waffle with the models will probably waffle with this, even though it's very imminent.

My take is that even the models until it's ready to come down will not have a good hold of it. They never do until it's a good 5 days away or less.

[Valkhorn]

00z in for today. BIIIG Dissapointment.

It has mucho arctic air creeping into Canada, but keeps a zonal pattern for 3 weeks and has too many bizarre things going on.

1) Either there will be a crazy zonal pattern for a month or
2) It's only trying to get a grip right now on the connection to the cold air to Canada, and in as such anything beyond that, until it gets that connection nailed warm patters in the US should be totally ignored.

Things are getting very complicated.