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southerngale wrote:I see mets talking about bitter cold making it all the way to the Gulf coast, and I've seen '89 and '83 mentioned a few times. But then I see where some of the same mets are saying that the air isn't extraordinarily cold up there. Doesn't the Siberian air need to be particularly cold for this to be a significant Arctic blast, something that prompts wxman57 to send out a Special Weather Statement?
I understand the pattern setup is great, but can that alone with "ordinary" temperatures up there and not "extraordinary" temperatures bring this major Arctic blast that is being advertised?
You pose a good question. In order for a record-smashing cold air event across the Deep South, there needs to be a very cold airmass up north to begin with. Currently, temperatures in the source region, north-central Canada, are in the -20 to -45 degree range. There are likely colder temperatures farthere north where the Polar jet will track, but there are no obs there.
If you examine the ECMWF 850mb temperature contours then you can see how the cold air may develop over the coming week:
http://weather.cod.edu/forecast/loop.ecmwf850t.html
Note the current pool of cold air in SE Canada is forecast to wrap westward as the vortex gets established near SW Hudson Bay. Additional air flowing across the Pole into this Votex could build a mass of very cold air north of the U.S. Border by next Thursday. Temperatures of -32C or colder are indicated over a large area. Such temperatures would be significantly colder than with the last outbreak.
One other thing to consider with this outbreak (vs. Jan 13-16) is that this outbreak will have upper-level support to drive it southward. The cold air won't just sink southward down the Plains, it'll be driven southward with much more force. That, combined with a farther-south snow line means a greater risk of severe cold across the Gulf Coast states. And with an active southern stream liketly to continue, the threat of frozen precip would be there as well, likely farther south than with the last event, as the sub-freezing layer will likely be much thicker.
So, we're quite confident it's going to get MUCH colder across most of the U.S. from the Rockies eastward late next week through the first week or two of February. But we're not yet sure just HOW cold it will be down south. The cold outbreak COULD rival some big outbreaks (1989 for example), but that's a low-confidence forecast this far out. It's possible, though.
