Sunday, March 21, 2010

Minnesota's Incredible Shrinking Winters

So here we are, two days into spring, snow pretty much gone, most of the frost already out of the ground, ice on area lakes already thin, unstable and unsafe. Note to self: unless you have a secret death-wish: stay off the ice. The last subzero night here at home: January 29. For the winter season: 15 subzero nights (the long-term, rolling 30-year average is 30 nights of negative numbers). The suburbs of Dallas, Texas have seen more snow than we have since mid February (Saturday's freakish storm dumped 3-5" on the suburbs of Dallas, the same storm that unloaded 9" on downtown Denver and 26" on the suburbs of Boulder, Colorado). Strange. March temperatures are roughly 9 degrees above average, to date, and there's every indication our milder-than-normal weather will hang on, at least looking out the next 10-15 days. Beyond that it's truly anyone's guess.

So what gives? Yes, we still experience arctic fronts, it still snows (although not nearly as often as Minnesota snow-lovers would like). "Hey Paul, when I was five I remember the snow coming up to my chin! True, but keep in mind you were only 2 feet tall at the time." Oh. Perspective is important, but easier said than done. Professor Mark Seeley at the U. of Minnesota reports a quadrupling of midwinter ice/rain events since 2003. NASA reports that the decade from 2000 to 2009 was the warmest ever recorded. Far northern Minnesota is seeing anywhere from a third to a quarter as many -40 F nights as it did as recently as the 1970s. Who cares? Well, pests are happy about this mild turn of events. Most tree-munching pests aren't killed off until the mercury falls close to -40 F. If it doesn't consistently get that cold during a Minnesota winter, those pests can survive, breed, and chomp away at our beloved North Woods. That's what seems to be happening across portions of the Rockies, Alberta, British Columbia and a vast swath of Alaska - millions of acres of hardwood trees and pines dying or dead because of this persistent pests that aren't being killed off every winter, because the arctic fronts aren't as cold as they were a generation ago. The bottom line: we're not seeing the volume or intensity of severe cold that we experienced 30-50 years ago in Minnesota. Since 1997 we've saved roughly 9% heating our homes and businesses, one pleasant upside to our statewide warming trend.

Average Duration of Ice on Lake Mendota (outside Madison, WI) since 1850. I'm no mathematician, but I see a distinct trend in the last 160 years; a similar trend shows up on most Minnesota lakes. This year the "ice-out" date should come 1-2 weeks earlier than normal. Here is more detail on Lake Mendota's icy tendencies, one of the longest, most reliable histories of ice on any lake in the Upper Midwest.

Growing Fire Risk. Until we green up (still 2-3 weeks away?) the risk of brushfires and grass fires will escalate. The fire risk is "high" to "very high" across much of central and southern MN. It's been unusually dry in recent weeks, adding fuel to the potential fires. I have a hunch that unless we see significant rain (or snow) in the next week or two we'll be tracking brushfires on the maps as we start the month of April. Click here to see the latest fire outlook from the USDA Forest Service.

Nagging Drought. Although conditions have eased in recent months (ample fall rains, and a snowy start to winter) the northern suburbs of the Twin Cities are still experiencing moderate drought conditions, much of northern Minnesota still characterized as "abnormally dry."

Today may wind up being the nicest day of the week, highs well up into the 50s to near 60 by late afternoon under a brilliant-blue sky. A weak cool front whips up patchy clouds tomorrow, a fleeting sprinkle or spritz can't be ruled out, but I don't see any significant precipitation through the weekend. We cool off a bit by midweek, then warm (slightly) by Friday before a more noticeable cool-down over the weekend, highs stuck in the 30s (north) and low 40s (south). I know I sound like a skipping record (remember those?) Ok, I'm sounding like a defective iPod, a garbled MP3 (doesn't sound nearly as good) but the next storm passes off well south of Minnesota next weekend, a slight chance of a light rain-snow mix by Sunday, but right now I can't get excited about amounts. The GFS long-range model is hinting at showery rains, even a few embedded thunderstorms, during the first week of April, highs mostly in the 50s.

We may sail through the month of March with NO ACCUMULATING SNOW. That hasn't happened during modern-day records, dating back to 1885 in the Twin Cities. The least snow I could find in March: 1/10th of an inch back in March, 1981. That's in stark contrast to 2008 (18" in March) and 2006 (20.4" in March). Welcome to Minnesota, Capital of All or Nothing.

Another Close Encounter of the Sloppy Kind? The latest GFS model, valid midnight Saturday night, showing another storm winding up over Oklahoma, tracking more east than northeast, capable of brushing Minnesota with a little very light rain Saturday, possibly a rain-snow mix by Sunday. Confidence level: low.

Latest Crest Outlook for St. Paul. The Mississippi River is forecast to crest Wednesday at 19.5', about 6 feet below the historical high-water mark. Still considered "major flooding" significant inundation of low-land areas is likely. The latest projection from NWS river forecasters is here.

Records since Saturday. Check out daily snowfall reports across southern and eastern Iowa, where 3-5" of snow fell Saturday. 65 outside Green Bay on Saturday - more like early May! See the latest interactive map and records for the USA at Ham Weather, a division of WeatherNation, right here.

Minnesota from Space. Area lakes are still ice-covered, some of the smudges of white south/west of the Minnesota River are areas of snow, but it's going fast. At this rate most lakes across central and southern Minnesota may be mostly ice-free within 1-2 weeks.

Ice jams near Sartell, on March 16. Click here for more photos of the flooding statewide, courtesy of the National Weather Service.

Downtown Delano, the Crow River out of its banks on March 20.

Credit River, the Minnesota spilling out of its banks.

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

Today: Bright sun, too nice to work (much). Winds: S 10-15. High: 58 (60 not out of the question).

Tonight: Partly cloudy. Low: 37

Tuesday: Clouds increase, very slight chance of a shower/sprinkle. High: 55

Wednesday: Partly sunny, still warmer than average. High: 53

Thursday: Mix of clouds and sun, a bit cooler. High: 49

Friday: Intervals of sun, probably dry. High: 47

Saturday: Mostly cloudy, slight chance of light showers/sprinkles. High: 46

Sunday: Cloudy, small chance of a light rain/snow mix. High: 44

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