Friday, January 22, 2010

Blame El Nino

Rain in late January? Where are we living - Little Rock? Memphis? Wichita? On some level it's a little hard to comprehend the notion of LIQUID precipitation falling during one of the coldest 10 days of the entire year (at least on paper). But to quote Vonnegut, "and so it goes." The current pattern is consistent with kinds of atmospheric symptoms observed during a moderate El Nino event, a warming of equatorial Pacific Ocean water, which tends to increase the frequency/intensity of storms hitting California - with a much more active storm track over the southern U.S. than usual during the winter months. During El Nino winters the deep south tends to be wetter and cooler than average, a more pronounced Pacific flow penetrating farther inland, keeping the northern tier states of the U.S. (including Minnesota) warmer than average. We sailed through December and the first week of January with no real El Nino signal showing up on the maps, but since about Jan. 7 North America has entered a milder, stormier, more Pacific-influenced pattern. Today's rain storm may, on some level, be a bi-product of this cyclical warming of Pacific water which kicks in every 4-6 years. As in all things meteorological - it's awfully tough connecting the dots, proving cause and effect.



An unfavorable track for statewide snow. A perfect track for snow runs across central Iowa over La Crosse and Eau Claire, Wisconsin. In the case of this weekend's storm the track will be a couple hundred miles too far west, dragging unusually warm air well north, sparking a cold rain instead of moderate/heavy snow. Colder air filtering in on the backside of the storm Sunday and Monday will spark a period of snow, but only the Dakotas and parts of the Red River Valley will see all-snow.

Watches, warnings and advisories. A glaze ice risk south/east of the Twin Cities (especially early Saturday morning). Although mostly-rain is expected Saturday over southern and even central MN, the farther north/west you drive, the better the odds of running into a wintry mix of rain/ice/snow. Warnings are posted for far western Minnesota, where much of the precipitation will fall as snow - and a good 6-8"+ is possible by Monday night.

The same storm that battered California with drenching rains, high winds, rare January tornadoes, thunder, lightning and hail - sparking a series of mudslides and precautionary evacuations in the suburbs of L.A. will churn northward across the Plains today, yanking unusually warm air unusually far north. Snow requires sub-freezing temperatures throughout the lowest mile of the atmosphere; even a shallow layer of air > 32 F can instantly melt snow and turn it into a cold rain - such will be the case today, highs reaching the low to mid 30s. Across far western and northern Minnesota cold surfaces may trigger a period of dangerous glaze ice, even a few hours of sleet (ice pellets). The Dakotas and much of the Red River Valley should remain cold enough for mostly snow, and it may wind up being quite an impressive pile by Monday, some 10-15" amounts aren't out of the question. But the main surge of moisture, coming today, will be rain for much of southern and even central Minnesota. Too bad for snow lovers. Conservatively, had temperatures been only 5 degrees colder, we'd be looking at over a foot for much of the area. I've said it before: this almost looks more like a March slop-storm, not something you'd expect to experience during the dead of winter. Odd.

Latest snowfall prediction. Rain/ice Saturday gives way to a changeover to wet snow Sunday, and despite a brief break (dreaded "dry tongue" sweeping in from the southwest) moisture wraps all the way around the storm, keeping light snow in the forecast from late Sunday into Tuesday morning. A couple inches of slush may pile up in the Twin Cities, closer to 2-5" for the St. Cloud area, 6-8" from Brainerd to Detroit Lakes, Wheaton and Moorhead.

PROVING that snow lovers in Minnesota lead quiet, desperate lives, by the time it's actually cold enough for snow (Sunday) a surge of dry air will sweep in from the Desert Southwest, what some geeky, socially-stunted meteorologists (no, not me!) lovingly refer to as the "dreaded dry tongue." Sounds like something you might see on the menu of a bad deli. It's nearly as disappointing, at least for a significant number of Minnesotans who LIKE snow! Seems like we're being cheated, punished by a preternaturally fickle Old Man Winter, but so it goes with big, mature storms. The bigger the storm, the higher the likelihood of dry air wrapping into the storm's circulation - causing the heaviest snow, rain or ice to taper off to a fine mist, drizzle or flurries. Eventually snow will wrap completely around the storm (approaching from the north!) and trigger an inch or two for MSP by midday Monday. But parts of central Minnesota may still experience a "plowable" snowfall, as much as 2-5" or more, with some 6-8"+ amounts west of Willmar, Alexandria, Wadena on north toward Brainerd, Pequot Lakes and Bemidji. A coold 10-12" may still pile up from Moorhead north to Grand Forks and Thief River Falls. In general, the farther north/west you drive across the state, the worse travel conditions will become, with more precipitation falling as snow, less ice and rain.

So close and yet so far. Oh well. There's always the next storm. And if you want to see a cool foot of snow load the kids up in the car and just drive west. Eventually you'll run into more snow than you know what to do with!

Paul's Outlook for the Twin Cities

Today: Winter Weather Advisory. Icy mix giving way to a period of rain, windy and raw. Winds: SE 15-25 High: 36

Tonight: Rain changes to wet snow by morning. Low: 33

Sunday: A changeover to mostly snow - starts to accumulate by PM hours. High: 34 (falling into the 20s by evening).

Monday: Windy and colder with periods of light snow, another inch or so (totals from 1-3" from this entire storm system). High: 23

Tuesday: Flurries taper. Cold sun returns - better travel conditions. High: 17 Low: -5

Wednesday: Bright sun, few degrees cooler than average. High: 18

Thursday: Mix of clouds and sun. High: 19

Friday: Sun giving way to increasing clouds. High: 17

The GFS is hinting at more 30s from Feb. 2 - 7. This next cold spell will NOT be as long (or as deep) as late December into early January.

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