As mentioned in this blog space last week, the polar vortex has become weaker. This means that portions of it are more likely to move farther south, bringing cold arctic air. Still, it was also noted that indications were for the arctic cold to bypass much of the United States. Even with a night of subzero temperatures in the Northern Plains earlier this week, bitter cold has for the most part not been a featured item.
We have seen sustained temperatures below normal concentrating over the southern states during the last couple of months. But even though below normal, temperatures aren't of the arctic variety. An active southern jet stream has led to more Pacific air masses moving through this portion of the country, with storms arcing from the Pacific Northwest to the Southern Plains and through the Mid-Atlantic over the last few weeks.
The rain (and snow) that has accompanied these storms has been highly beneficial for winter wheat. Even if it is not realized at this time due to dormancy, the increases in soil moisture should help curb the harsh effects of La Nina. This tends to produce drier-than-normal conditions for the Central and Southern Plains, a large concern for winter wheat. The crop entered dormancy with most areas in some sort of dryness or drought category, according to the U.S. Drought Monitor, so anything will be a benefit. That will be especially true if DTN's long-range forecasters are correct in their assessment that late-winter will see the effects kick in the strongest.
So where has this arctic air been hiding? The answer is Russia, where significant pieces of the polar vortex have been meandering around for the last two weeks. Models do not note any significant intrusions of arctic air over the country through the end of the year.
There are some storms, however. This includes a storm across the middle of the country in the middle of next week, just before Christmas. Some areas will likely get some snow, but with the seven-day time frame, exact location is hard to pinpoint.
Still, with above-normal temperatures preceding and following the system, many areas are likely to be devoid of snow cover for Christmas. This will be abnormal for locations near the Canadian border, which see a white Christmas roughly 60% or more of the time. And with temperatures being above normal for many of the northern areas, grass is still green in spots, instead of the normal wintertime brown. I know it is around my home in south-central Minnesota.
John Baranick can be reached at firstname.lastname@example.org
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