Plowable Snow (4-7" north metro, 2-3" downtowns, 1-2" southern 'burbs)
- Blog Post by: Paul Douglas
- February 29, 2012 - 10:43 AM
Tough Winter To Be A Snow Lover. This thing isn't over yet. Although we saw a cold rain overnight (over an inch in some spots), a changeover back to snow is likely Wednesday - we may wake wake up to a couple inches of slush, in fact the northern suburbs could pick up 2-5" of snow before this thing winds down during the day Wednesday. Hey, I like snow as much as the next guy - I have a couple of (Polaris) sleds that haven't seen much action this winter. This upcoming weekend will be the best weekend of the entire winter season to hit the trails. Happy Leap Day!
- Most of the accumulating snow will wind down by midday, potential for another coating to 1/2" in some spots before the flurries taper off.
- Final snowfall amounts range from about 1" southern suburbs to 2-3" downtowns, to as much as 6-7" northern suburbs.
- Temperatures stay above freezing today; most major roads/freeways should be wet/slushy.
- Conditions on area highways will get (slightly) worse the farther north you travel. Again, the north metro picked up 2-3 times more snow than the southern suburbs.
Warning Downgraded To Advisory For MSP Metro. An advisory remains in effect for the metro, warnings posted just north of the Twin Cities, blizzard warnings in effect for the Duluth area. The latest from the local NWS office here.
How Much? Although the brunt of the snow is sailing north of MSP, we'll still have something to show for all the buzz and media hype: I'm thinking 2-5" north metro and maybe 1-2" southern 'burbs between 5 am and noon on Wednesday, just enough snow to gum up secondary roads, some bridges and side streets. From Alexandria to Brainerd over a foot is expected, maybe as much as 18-20" near Duluth. NAM solution above courtesy of WeatherCaster.
Probability Of 8 Inches Or More? According to NOAA much of the northern half of Minnesota stands a better than 70% probability of picking up a cool 8" or more. Many towns from Bemidji and Brainerd to Duluth will wind up with well over a foot.
Map and statistics courtesy of NOAA.
Eye Of The Storm. Big, powerful, mature storms often inhale vast quantities of dry, desert air - the "dreaded dry tongue" I mentioned back on Sunday. This surge of dry air sweeping in from the southwest can cut off heavy snow or rain, especially south of the storm track. Sure enough, dry air did wrap into this storm's circulation - notice a little "eye" of snow-free air just north of the metro area around midday today. Map courtesy of Weather Underground.
Snowmobile Alert. Have a sled and itching to get out on the trails - finally! Hard to believe we had to wait until March, but conditions should be excellent this upcoming weekend up north, from the Brainerd Lakes area to Duluth and the North Shore. I have a hunch this may be the last time we have a chance to fire up the sleds - highs reach the 40s by Tuesday of next week, 50s possible by the second weekend of March. Don't procrastinate - this may be our only chance.
Tornado + Snow. This is unusual - television video of a tornado on the ground Tuesday evening in Nebraska, with patches of snow still on the ground! I can't remember the last time I saw this. Thanks to meteorologist Dean Wysocki for passing this one along.
Ask Paul: Q&A.
This is one of the worse weather model failures I've seen in a while.
Usually 5-days out the track of these storms are set in concrete, but
this one moved a hundred miles north. Wow. I was looking for a snow
storm and we get rain.
With global warming won't there be:
1. increase temps in the upper levels
2. higher humidity
Won't this make squeezing moisture out of clouds more difficult because even if you get lift say from a front, warmer air will not yield water droplets as much as cooler air.
Vince - not our proudest moment, no. It's too easy to slam the computer models (which we rely on for anything beyond 24 hours). A typical forecast weighs what's happening now (at all levels of the atmosphere) with what the models are predicting (is there consensus? Are there trends in the models? Which models work best in this scenario?) And then there's experience. Gut feel. It's said that meteorology is a "black art". Part of the art is deciding when to toss the models out the window. But 72 hours ago nearly all the models (including European ECMWF) were hinting at a major snowfall for the metro. Within 24 hours all the models suddenly shifted the track 150 miles farther north, scrambling the forecast for MSP, turning it into a rain/sleet/ice/snow event.
We rely on math and physics to run these weather models, but there are two big problems: it's impossible to get a perfect snapshot of what's happening right now, worldwide. Sparce data over oceans, little reliable data over third world countries - it's like trying to finish a puzzle with most of the pieces missing. Junk in, junk out. And then you have the actual physics that drive the models, sophisticated calculus. The atmosphere is a fluid and behaves like a fluid, but our knowledge of how the weather really works is incomplete. Some things are difficult to model: moisture fluxes from the oceans, friction as air passes over mountains. The models are (usually) pretty good, but not perfect. There is always some level of disagreement among the various models; scores of them (The NAM only goes out 84 hours, while the GFS has some skill going out 16 days). Until about 24-36 hours before onset of precipitation Tuesday all the models were showing a southerly storm track, with (just) enough cold air in place for mostly snow in the metro. The question was "will the dry tongue" cut down on amounts over southern Minnesota" - not - "will we get 1" rain instead of heavy snow?" I don't want to diss NOAA or NCEP, the division that handles weather modeling in the USA, but it's amazing that (all) the models could simultaneously be so bad. Again, it makes me wonder if something bigger is going on. The models assume that it's late February, when - in fact - the maps look like something out of late March.
All the models have been especially bad this winter. Meteorologists are all scratching their heads. Not sure if this is a symptom of La Nina, or blocking patterns, but something has changed. Jet stream winds have been unusually strong (I've seen some reports as much as 20% faster than normal). I've said it before - it's no longer your grandpa's winter. The pattern is significantly different than it was in the 70s and early 80s. Last winter we got our winter-groove back, but cold, big-snow winters seem to be increasingly the exception, not the rule. I wish I had a smoking gun, an easy TV-sound-bite answer about why the models have been so terrible, but I don't. The other part of your question: a warmer atmosphere can hold more water vapor (and evaporate more water from the oceans), increasing the potential for flooding in the summer, and big snowfalls in the winter, at least in theory. With climate change moisture is distributed unevenly. Dry areas will become drier, wet areas wetter. That's climate, not day-to-day weather. We're loading the dice in favor of more (moisture) extremes, milder winters, and higher humidity levels & dew points. Thanks for a great question - sorry for the novella. - Paul
Paul's Star Tribune Outlook for the Twin Cities and all of Minnesota:
TODAY: Snow slowly tapers. 2-3" early, as much as 4-6" north metro, around 1" south metro. Winds: NW 7-12. High: 35
WEDNESDAY NIGHT: Flurries end, clouds linger. Low: 24
THURSDAY: Some sun. Flurries up north. High: 38
FRIDAY: Potential for accumulating snow, especially east of St. Paul. Low: 26. High: 35
SATURDAY: Slow clearing, cool breeze. Low: 21. High: 33
SUNDAY: More clouds than sun, brisk. Low: 19. High: 32
MONDAY: Intervals of sun, turning milder. Low: 18. High: 41
TUESDAY: Early case of spring fever? Nice with plenty of sun. Low: 31. High: near 50
A Very Close Call
Who was it who said "close" only counts in horseshoes and hand grenades? Doesn't matter. Metro snow lovers are not the least bit consoled by the 12-18" snow that fell up north. That could have been us. It SHOULD have been us!<p>Note to my readers: we do our best to predict the weather, using weather models, experience, and a sturdy west-facing window. We don't MAKE the weather. We're not in a back room pushing buttons and throwing switches.
A snowstorm is like a cool, creamy cake. Too much of any one ingredient spoils the recipe. On Sunday I was worried about the "dreaded dry tongue". Turns out the storm moved slower and farther north, pulling a warm layer into Minnesota. Instead of a foot of snow we got soaked with an inch of rain. We were 2 degrees F. away from a huge pile of snow.
Overnight the column of air overhead cooled, turning rain and ice back to snow, and a couple inches are still possible this morning before flakes begin to taper. At least we have something to show for all the media hype.
Friday's storm plasters Wisconsin with snow. No more close encounters here; 50 degrees by Tuesday?
"Hi Paul...just curious...when extreme events of the "great recession" made historical economic data useless to the point where predictive modeling completely broke down. I have always wondered if climate change could do the same with our weather models. Is anyone keeping track of their accuracy over the last couple years?"
- Peter Tharaldson, Best Buy (by way of Facebook)
Peter - thanks for your question. I turned to my good friend and local climate scientist John Abraham, Associate Professor of Thermal And Fluid Sciences at the University of St. Thomas:
Economic forecasting, climate forecasting, and forecasting of extreme weather events are very different animals. The climate responds to long-term forcings (solar energy, etc.) and while there are year-to-year fluctuations, and even decade to decade fluctuations, over time, these fluctuations tend to "average out". Consequently, long term climate prediction is possible and while not perfect, is improving.
Predicting extreme weather is more complicated because short term weather patterns are more dependent on the fluctuations in the climate. That said, some extreme weather is more easily predicted than others. For instance, it has long been predicted that the southwestern part of the US would get drier, with more droughts. Similarly, it has been predicted that there would be increased precipitation in some regions with associated increases in flooding. Those predictions are much easier than predictions of increases in hurricanes, tornadoes, etc.
Economic predictions are an entirely different beast. They don't rely upon well-understood equations of nature. They depend on humans, psychology, unforeseen events (like BP oil spill or Japan nuclear accident), and politics. So, I don't put much confidence in economic predictions when compared to climate predictions.
When predicting climate, models have to conserve energy, mass, momentum, various chemical species, etc. The economy is not encumbered by these conservation equations.
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