Posted at 8:42 AM on January 12, 2010
by Paul Huttner
Twin Cities NWS graphical forecast shows temps approaching 30 today.
Where we're you on Christmas Day?
That's the last time you felt temperatures above freezing. It should happen again tomorrow. That marks 18 days with the mercury way below freezing.
So far January is running a full 11.2 degrees colder than average, and 9 of 11 days this month have featured sub-zero overnight lows. That's all about to change as an extended January thaw cranks up this week.
As is usually the case with Minnesota weather, the forecast isn't as clean as we'd like.
Yes warm air is gushing in from the west this week. But the warmest air is sailing in around 3,000 to 5,000 feet. That warm air aloft is called a temperature inversion, and it can trap pollutants and cold air near the ground where we live and breathe. Inversions can also create and trap low stratus and fog which can limit the warming trend, especially over dense snow pack.
Still, it looks like we'll have enough wind today to "mix out" some of the low clouds, and that should bring period of sun which will help boost temperatures. Computers are hinting at upper 30s to near 40 Wednesday if we get enough sun and keep the low clouds and fog at bay.
Thanks to El Nino?
It appears our weather pattern has changed for at least the next 10 days, and we may be able to thank El Nino. We're developing a "split flow" in the jet streams over North America, and that is a classic El Nino trade mark. As the polar front jet lifts north into Canada, we warm up. I expect we will be near or above 30 degrees for at least the next 10 days in much of Minnesota.
Then the sub-tropical jet gets cranking along the California and Gulf Coasts, and they get wet.
Weekend GFS 500 millibar chart shows classi "El Nino" split flow jet stream.
It looks like the Pineapple Express may be about to pay a visit to California in the coming days and weeks. For now, the flow off the Pacific is bringing a series of storms from the central and northern Pacific. But it's likely just a matter of time before the flow turns southwest from the tropics, and drenches southern California with heavy rain and mountain snow. Floods and mudslides to follow. From having forecast in the Desert Southwest for many years and watching weather patterns during El Nino events it is my experience that the El Nino storm train begins to peak in late winter in late January, February and into March.
Enjoy the thaw this week, but keep an eye out for any refreeze at night once we warm above freezing Wednesday.
Thank you for making me look up what "Pineapple Express" actually means.