Tales of Virginia drought and Canadian snowpack — mild and dry into next week, then perhaps some changes
The drought is growing and getting worse in Virginia, according to the latest U.S. Drought Monitor state map– I wrote a little about our local drought in Wednesday’s Weather Journal column. Virginia’s area of drought is part of a much larger area that extends through much of the inland Southeast, with the worst areas in Georgia. And nationally, the central U.S. still has a lot of real estate in extreme drought, an area that has actually been growing and intensifying steadily since some improvement in late summer and early fall. It will take some major changes in the weather pattern to change this map’s colors. Nothing of that nature is expected in the next 5-7 days, but beyond that, there are indications there may at least be some large low-pressure systems developing that can draw moisture from the Gulf of Mexico to moisten at least some of the dry regions. Those lows may also mark the beginning of cold air expansion into the U.S. More on that in a bit.
In the short term, the Pacific Northwest is continuing to get nailed by the “Pineapple Express,” bringing round after round of torrential rainfall and massive piles of high-mountain snows. The prevailing low-pressure spinning counterclockwise in the Pacific Northwest means a mild west-southwest flow will blow across much of the nation. For us, that will mean gradually milder afternoons, into the 60s this weekend and possibly scraping 70 at a few locations by Monday. No rainfall is expected at least through Tuesday.
Perhaps you may have heard on here or elsewhere about how Siberian snow cover had its third fastest spread on record this fall, trailing only 1976 and 2009, the latter preceding a cold and infamously snowy winter in Southwest Virginia (and the former, ’76, preceding an infamously cold winter). Take a look at Thursday’s updated snow cover map for the Northern Hemisphere, and you’ll see all of Russia and almost all of Canada are under a blanket of white. Comparing the U.S. snow cover maps between Nov. 29, 2012, (linked here ) and that of exactly a year ago, Nov. 29, 2011, (linked here) shows much more widespread and deeper snow in southern Canada and the northern tier of the U.S. this year than was there this time last year. The breadth and depth of snow cover north of us and on the other side of the pole remains one of the key factors that points to increased chances of intensely cold Arctic masses developing and recharging this winter before sinking south into the U.S. We have been seeing, and are continuing to see, Arctic air pool in Canada, awaiting something to tug it southward. The persistent Pacific Northwest low has resisted the cold air’s move the past couple of weeks, but in time, perhaps beginning as early as late next week, it appears on forecast models as if central U.S. storm systems moving over the Great Lakes into Canada will begin to help slide pieces of this Arctic air southward into the U.S. Don’t expect a sudden flip of the switch with full-bore winter suddenly materializing out of a mild start to December, but the jet stream will likely sink southward and more cold air park farther and farther south over the next couple of weeks, after next week’s mild start. There are no guarantees yet on whether the changing pattern will ultimately result in snowfall or even prolonged cold, but this winter does look to be a far cry from last winter’s long-lasting mildness, even though the first few days of “meteorological winter” starting with the calendar flip to December may feel otherwise.
Whatever your level of love or hatred for snow, enjoy the warmth while it lasts this weekend and early week.