Arctic Outbreak Mid January for the Plains?

[Jesse Risley]

That would be insanely high MSLP. The highest I've ever seen it was in Jan 2009 when it hit around 1050 when places in Iowa (don't remember the rest of the nation) were hitting -30...smashing a record for the date. I can only imagine the density/coldness of air that would result in MSLPs of 1055 to 1065 mb.

It looks like the 0z suite of model data has the MSLP a bit lower, with the ECMWF showing a high pressure region (1048 mb) extending from Saskatchewan to the OK/TX (panhandle) border at 12z on Wednesday, whereas the GFS is showing slightly lower values (1038 mb) with the ridge shunted slightly further east.

Though it may be a little far off at this juncture, both the ECMWF and the GFS are hinting at another intrusion of pretty cold air dipping down into the Plains by the close of the MLK Jr. holiday weekend, though the GFS is advertising a much more significant cold spell than the ECMWF is this far out. It's probably something to keep an eye on to see if that trend continues with future model runs on each suite of models.

 

[Tim Vasquez]

Looks like some changes with the latest GFS regarding our cold weather prospects. Instead of a high-amplitude ridge off the west coast synergizing with a cutoff high at the tip (McFarland pattern), the cutoff high ends up retrogressing into Siberia (Chukotka), which directs the bulk of the cross-arctic flow into Alaska rather than Canada, and leaves North America mostly with zonal flow.

On one hand, this decreases the likelihood of a classic dry, severe cold outbreak. On the other hand, the zonal flow brings more QGDs into the mix, and there will still be a strong cooling trend in northwest Canada. If some of this air manages to break off in northwest Canada and ooze southeast along the Rockies and has sufficient depth and intensity to steepen isentropic surfaces along the western edge of these cold air masses, then given the zonal flow it's a good pattern for snow production and snow cover from BC/AB southeast through MT, WY, CO, KS, and OK next week and reinforcement of those cold air masses. I've been doing some work to search for analogues to see how these situations play out... I haven't really found anything conclusive yet.

For what it's worth, the GFS still wants to paint bitter cold across the Great Plains and midwest (highs of 9F in OKC Tuesday) though I'm on the fence whether this is realistic since those kinds of temperatures usually involve channeling of cold air southward from the high arctic or lots of fresh snow across the northern Plains.

Tim

 

[Jeff Duda]

Newer GFS runs are reverting back to the previous forecast of having the cutoff high sit over Alaska for a few days. From then on it's just a matter of time as the Arctic air comes around the ridge, down along the western Canada coast, then hovers for a few days before a new trough swings it in over the CONUS. Although it still shows some very cold air, it is not bringing that air nearly as far south into the US as it was in previous runs.

However, it also appears that the model is predicting two shots of Arctic air. One arrives during the middle of next week (Wednesdayish) and does make it farther south into the central Plains, but it is short lived and there is much recovery before the big shot a few days later. This second punch is the one that does not make it as far south.

 

[Jeff Duda]

Looks like the arctic plunge did verify in some parts of the region. International Falls probably saw the brunt of it in the lower 48, hitting a record low of -46! Although some other sources say it wasn't quite that cold. At that level, I don't think it matters much. It's funny to see a sounding that is so cold that part of the profile won't fit on the skew-T (time sensitive):

I'm betting this does occur once or twice a year, but I found it entertaining to see surface theta-e values drop below 240 over widespread areas of southern Canada. I even saw some 235 K contours show up!

In my neck of the woods, this arctic outbreak and cold weather over the past week or so hasn't really been as bad as some of the models were predicting. I've been underforecasting the low temperatures in my local forecast contest pretty regularly over the past week or two. I'm glad it hasn't been as cold as predicted, though.

 

[Mike Smith]

Jeff,
Excellent followup!
Mike

 

[Alex Lamers]

International Falls probably saw the brunt of it in the lower 48, hitting a record low of -46! Although some other sources say it wasn't quite that cold.

Just an FYI that the official low was -46 at the ASOS. -46 was also recorded by a co-operative observer in Babbitt. Also, I thought it was pretty cool that the surface temperature on the INL sounding was colder than the 500mb temp. Event summary:

http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=dlh&storyid=63000&source=0

I wasn't looking too closely at all of Canada and Alaska, but I did notice some colder readings off to the northwest. Fort Yukon, Alaska had a low of -57.

At that level, I don't think it matters much.

Yeah, after you pass -20 (in my book), it is just really, really cold and unpleasant.

 

[Jeff Duda]

I'm going to revive this thread given the rash of cold air outbreaks across a large portion of the US over the last few weeks. The first few were covered earlier in this thread. The current outbreak was not discussed here, and apparently it is a record breaker for parts of the southern and southwestern US. However, the medium range models are not done with severe cold air outbreaks.

1) The first one is slated to strike the upper Midwest and Great Lakes regions early next week. It looks to be quite cold, but not as cold as other outbreaks so far this winter. Nonetheless, temps are predicted to sit in the -20 F below average range around central Iowa.

2) The second one looks to be much more menacing. If the attached 192-hr GFS surface graphic verifies, it will likely be epic cold for portions of the southeastern US. The GFS may be overdoing this especially since the FIM and ECMWF models are not predicting quite as severe an outbreak, but they all do predict the polar vortex shunting out shortwaves rapidly across the Upper Midwest/Great Lakes/Northeast US over the next 10 days or so, with this one scheduled to hit late next week (Thursday the 11th-ish).