Sunday, March 7, 2010

Snow To Go

Where did winter go? The calendar says March 8, but as far as the atmosphere is concerned we're enjoying the last week of March, possibly the first few days of April. As is often the case at this (northerly) latitude - winter is on an on-off switch. No such thing as a dimmer switch when it comes to the atmosphere draped over Minnesota. We went from a flurry of snowy clippers (early February) to an almost unprecedented streak of sunny, quiet, tranquil days, high pressure stalling out over the Upper Midwest, sparking a string of dry days with unusually light winds, trapping pollutants at ground-level, turning us (at least temporarily) into a chilly L.A. (with lakes). Saturday night's disturbance brushed southern Minnesota with light rain - another (better) chance of rain will come this week as a southern storm pushes moisture northward. The best chance of rain comes from late Tuesday into Friday, a few models hinting at some .50" rainfall amounts. That could - in theory - be enough rain (coupled with 45-50 degree F warmth) to accelerate snow melt to the point where river flooding becomes imminent in the weeks ahead, especially on the Red River, which seems to be the most at-risk tributary at this point. Hydrology, river forecasting, is literally a science within a science. I don't profess to know the details of how meteorologists at the NWS in Chanhassen track and model snow melt - there's a heavy reliance on computer models, and all of us realize that computers are as fallible as the people who program them. But some factors can be successfully modeled: the amount of water in the snow (and ground). The depth of the frost layer. The predicted highs, coupled with anticipated rainfall. All of these factors determine the rate of snow melt and subsequent flood risk. Bottom line: if you live along any of Minnesota's streams or rivers you'll want to stay alert i the coming weeks. April may be a very, very busy month for Minnesota's flood forecasters.

Probability of Flooding. Data provided by the National Weather Service North Central River Forecast Center shows a 60-80% risk of flooding along the Mississippi River in St. Paul and Hastings, and a 95%+ risk along much of the Red River, where the threat seems to be greatest. For the latest data click here.

Retire the parka, dig out the umbrellas. Models consistently bring a sloppy southern storm into Minnesota, the best chance of rain from late Tuesday into Friday. Relatively mild air passing over cold (rapidly melting) snow cover may spark dense "advection" fog, visibilities falling close to zero at times, the best chance of pea-soup conditions each morning.

Fleeting Snow. Saturday's high-res (visible) satellite image showed snow on the ground. The Twin Cities metro area shows up (far less snow - more asphalt/concrete/development) and the Minnesota River Valley shows up vividly. Most towns will have half as much snow on the ground by the end of this week as daytime highs consistently reach the 40s, coupled with moderate rain by midweek.

Nervous Meteorologists. Hopefully the 12z GFS forecast won't come to pass. It predicted over 1.4" of rain by Friday, which could be disastrous for Minnesota's flood scenario. Most of the models are forecasting significantly less, closer to .30 to .40" of rain. (Click the graphic to bring it full screen).

Weather & Climate Stories

Extreme weather on the rise? Are we really seeing more severe weather, or just doing a better job of documenting the wild gyrations that have always been there? Good question. Check out this story on crazy swings in weather around the planet from NBC.

Video of the 27' rogue wave that swamped a cruise ship in the Mediterranean Sea is here. Unbelievable footage.

Hail & high water. Click here to read about a freakish hailstorm that dropped several FEET of golfball-size hail on Melbourne, Australia.

Science stunner: vast East Siberian Arctic Shelf methane stores destabilizing and venting. This is beyond my pay-level, I don't pretend to know what (if any) implications this story might have. The amount of methane released from this Siberian methane source is roughly equivalent to what the world's oceans release. Remember, methane is approximately 30 times stronger than carbon dioxide, the most common greenhouse gas. The part that troubles me the most: none of the computer models factor in this rapid release of (intense) greenhouse gas into Earth's atmosphere. Once again we're in uncharted waters - literally. The complete story is here.

Kilted skiers set world record. After reading this story I think I need to wash out my eyeballs. Please don't try this at Buck Hill or Afton Alps.

Going. Going. Almost Gone. If you like snow get out there and roll around in it asap. Much of it will be gone by the end of this week, at the rate we're going. The maps looks like something out of the end of March or early April, including rain from late Tuesday into Friday. (Snowblowers optional for the foreseeable future, btw).

Paul's Conservation MN Outlook for the Twin Cities and all of Minnesota

Today: Dense fog advisory early. Peeks of sun, unusually mild. Winds: SE 5-10. High: 48

Tonight: Patchy clouds and fog. Low: 35

Tuesday: Mostly cloudy, rain arrives later in the day. High: 46

Wednesday: Periods of rain, patchy fog. Low: 36. High: 47

Thursday: More rain, still foggy and gloomy. Low: 39. High: near 50

Friday: Rain continues - down to 4" dirty snow? Low: 37. High: 48

Saturday: Drier day, more clouds than sun. Low: 36. High: 49

Sunday: Partly sunny, feels like April 3! Low: 39. High: 51

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