Tuesday, 11:30 AM

While Alaska slips into the deep freeze, most of the U.S. continues to bask in unusual mildness for the middle of November. Okay, there are some exceptions, such as parts of extreme southeastern Nebraska and eastern Kansas, where as much as six to twelve inches of snow blanketed the region in the past 36 hours. But aside from that, most areas east of the Rockies are enjoying mild weather, in stark contrast to the chill of October.

The center of these warm anomalies is from the northern Plains and Upper Midwest into central Canada. The Great Lakes and Northeast remain on the high side of the norms, and will pretty much stay there through the weekend and into the first half of next week. The Southeast has been warm, but will trend toward normal the rest of the week into the weekend.

If you want to get a glimpse of the changes to come, take a look at areas farther west across the southern tier of states. In the wake of the cold front yesterday, temperatures dove into the 50s and lower 60s, and made little recovery in the afternoon even after the sun returned. And with high pressure gradually taking over from Texas to Mississippi and Alabama for the next 48 hours or more, the air mass will not only be cool, but also very dry with no Gulf moisture involved.

For one thing, this will lead to some frost that has heretofore been lacking in a lot of places, yet even this is hardly to be considered an air mass of arctic origin! Still, the combined effect of much chillier nights and day time highs that will be within a few degrees of normal will lead to a below normal day or two across these regions. Again, this is being accomplished over a relatively small area without any supply line of arctic air.

The system that has dumped the snow on parts of the Plains will lift out to the north and northeast over the next couple days as the weight of the western trough, if you will, grows and exerts a downstream 'push' on the system ahead of it.

Upstream, the vicious cold front that blasted into the Northwest over the past 24 hours with flooding rains along with hurricane-force winds along the Oregon coast will weaken as it presses farther inland this afternoon and tonight, and give the region a brief break between stormy onslaughts.

However, a piece of upper level 'energy', for lack of a better way to describe it, will help push the remains of the front into and through the southern Rockies tomorrow and tomorrow night. As it moves farther to the east and southeast, the atmosphere will suddenly spring into action with a response. At first, there will be what I would term a mid- and high-level moistening process that will lead to a noticeable increase in clouds across Texas Thursday. Then, as the the developing upper level trough approaches, it will elicit a response from the low levels, and suddenly overrunning rains will break out later Thursday and Thursday night over South and Southeast Texas, spreading north and east with time going into Friday.

Eventually low pressure will form near or off the Texas Coast, a system that will then traverse the northern Gulf Friday and Friday night into Saturday morning. An expanding area of rain with some embedded thunder will show up across the Gulf Coast region in the process, and this promises to bring rain across at least the Florida panhandle and southern Alabama into Georgia and the Carolinas Saturday and Saturday night.

As I mentioned in yesterday's post, watch out up the Eastern Seaboard, as this developing storm may try to turn up the coast and spread the rain up and east of the Appalachians Saturday night and Sunday, though the details of that have to be hacked out over the next couple days. And as posited yesterday, this may be the very kind of storm pretty much absent from the past couple winters. Yes, I know, it will be 100 per cent rain, and the snow geese won't be thrilled about it. But it's the type of classic 'Miller-A' storm coming across the Gulf, then heading up the eastern Seaboard that indicates an active southern branch for one thing, and could lead to a large of snow later in the winter once 1) the arctic air is liable to be in place, and 2) the water off the East Coast is nearly so warm. It may be some crumbs, but I'm at least throwing something out there for the geese to tie them over for a while until we dive headlong into winter in just a few short weeks.

Behind this storm, the Plains warm for the weekend, but not much longer. Farther upstream another potent system will attack the West Coast with a vengeance, and this one will be a two-parter. The first part is yet another powerful but fairly compact storm that will slam into British Columbia tomorrow night, dragging a cold front into the Northwest by Thursday morning. With it another round of gale-force winds and stronger and heavy rain for western Washington and western Oregon. No doubt there will be some flooding, too.

Part two follows farther south from the central Pacific, sending an area of heavy rain farther south, aimed more at southern Oregon and northern California. As this whole trough progresses inland to start the weekend, it will pull a little of the arctic air in Alaska into it, but not much. However, it will develop a new storm on the Plains that can squeeze a little snow out of the hybrid air mass for the northern Plains and Upper Midwest.

The attacks from the Pacific won't stop there, though, and this continued assault will bring another round of rain and wind and mountains snow into the Northwest later Saturday and Saturday night. It would appear as if the one right after it for the start of next week is the one that really sets up the pattern for change next week, as it heads more into British Columbia. The upper levels will be warming along the West Coast at this point, a sign of ridge-building, and as this early week storm goes inland and over the top of this little ridge, it is likely to turn southeastward, and beginning the process of trying to send a trough downstream into the East by the time we get to the end of next week. And again, while it may not bring the whole enchilada, or, in this case, turkey, along for the ride, it won't be the same kind of air mass change in the East we've seen this week nor into the early part of next week behind any storm or front. In fact, Canada will likely still be much above normal late next week, so unless we're developing a pipeline out of Alaska south over the Pacific, then over the Rockies and into the South and East, the air mass won't even then be truly arctic! That being said, it will end the run of anomalous warmth, and grease the skids, so to speak, for the heart of winter to come.

Posted by Joe Lundberg on Tuesday, November 17, 2009 11:30 AM
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