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Snowpocalypse 2012? (still on track for biggest snowfall of winter)

  • Blog Post by: Paul Douglas
  • February 26, 2012 - 9:40 PM

 

Sunday Night Update. Yep, it's still going to snow Tuesday and Wednesday - of that I have little doubt. Now the burning question is: a mere 6" of slush, or over a foot of traffic-snarling, airport-delaying, field-rejuvenating, trail-smothering (glorious) snow? With this blog I'm trying to show you, the weather enthusiast, how difficult it is to predict snow. Rarely is the scenario ever a true black and white situation - it's almost always some nebulous shade of gray. So it is with our potential mega-storm Tuesday into Wednesday. Latest ECMWF (European) model runs, which tend to do a better job than NOAA's GFS model overall, are hinting at a slightly more northerly storm track, into southern Minnesota - which means a surge of dry air (the dreaded "dry tongue") may poke into southern counties, possibly lowering snowfall amounts from the Twin Cities metro on south. Two complicating factors: a possible change to sleet Tuesday PM hours + dry tongue on Wednesday. Both factors would lower expected snowfall amounts from MSP on south to the Iowa border. I still suspect the heaviest zone of snow, the east-west deformation axis, will set up north/west of the Twin Cities. Translation: a much better chance of a foot or more of snow from Willmar and St. Cloud to Mille Lacs, even the far northern suburbs, like Cambridge and Princeton. We'll still get a pile, but I'm not convinced the MSP metro will see a foot, at least not yet.    - Paul Douglas

 

Storm Headlines

- No travel problems Monday. Consider getting errands done Monday or first thing Tuesday.

- Snow arrives Tuesday morning, and gets heavier/steadier as the day goes on. The heaviest snow should come Tuesday night.

- Snow tapers off during the day Wednesday (faster south of the metro area).

- Getting home Tuesday PM will be rough and slushy, but the worst travel conditions will probably be Wednesday morning.

- Expect a huge range in snowfall amounts across the MSP metro area: 3-5" south metro, but as much as 7-12" northern suburbs. This will be a wet snowfall with high water content, tough to get off your driveway or sidewalk.

- Anywhere from 1 to 2 feet of snow may accumulate over central Minnesota, from Willmar and Morris to St. Cloud, Mille Lacs and Hinckley.

- The farther north/west you travel on 7, 12, I-94, Highway 10 or I-35, away from the metro area, the worse travel conditions will be Tuesday into Wednesday.

- I expect Winter Storm Watches to be upgraded to a full-blown Winter Storm Warnings for much of Minnesota by Monday morning. That means it's imminent. Latest watches/warnings from NOAA's Twin Cities office here.

 

Hints Of A Dry Tongue. The 12z Sunday ECMWF (coutesy of Weather Underground) shows the storm track shifting about 75 miles farther north, reaching southern Minnesota. Dry, desert air tangled up in the storm circulation will approach from the south, turning off the heaviest snows south of MSP during the day Wednesday. If this trend continues the odds of MSP picking up a cool foot of snow will drop precariously. It could still happen, but I suspect the heaviest snow bands will set up 50-100 miles north of MSP, over central Minnesota.

NAM Precipitation Predictions for MSP On Sunday For Tuesay/Wednesday's Storm:

12z Run: 2.01" (snow changing to sleet, then back to snow late Tuesday night & Wednesday).

18z Run: 1.59" (profile aloft cold enough for all snow).

00z Run: 1.56" (latest NAM run shows mostly snow).

 

Latest NAM Output. The 00z run prints out 1.56" liquid, with temperatures throughout the lowest mile of the atmosphere cold enough for (mostly) snow. With an 8:1 or 10:1 snow/rain ratio that could still translate into 6-10" snow for much of the metro, more over the far northern and western suburbs. Not sure if the NAM is picking up on the northward trend for the storm track, and a possible intrusion of drier air aloft, which might shut off the snow faster on Wednesday. 1000-850 thicknesses stay below 1300, which is considered "critical", when snow begins to mix with rain/sleet.

 

More Likely Scenario: Plowable, but NOT Snowpocalypse. This is the GFS solution, which is coming in line with the more northward storm track trends of the ECMWF. It shows the heaviest axis of snow (deformation zone) from Morris and Alexandria to St. Cloud and Hinkley, with over 16" possible, which I think is realistic. There is still a huge snowfall gradient across the metro area, something like 3" southern Scott County to a cool foot for Anoka and White Bear Lake. I suspect this solution has a better chance of playing out than (widespread) one foot plus snowfall amounts across the entire metro area.

 

Northward Nudge To Projected Storm Track. Recent model runs have nudged the predicted storm track 50-100 miles farther north (the blue plus symbols over southern/central MN show the expected location of the storm within 72 hours; the models have a pretty good cluster south/west of MSP. So what? The farther north the storm tracks, the greater the potential of a dry intrusion, the dreaded dry tongue, which can shut off significant snow like a light switch when it arrives. With this trend I honestly don't think most of us will see a foot of snow, at least not in the metro. My gut: 3-4" south metro, maybe 6-10" north metro, with a foot still possible far northern and western suburbs. I suspect there will be a huge north-south contrast in final snowfall tallies across the immediate metro area. I'd get locked up if I predicted 2-20", but that's exactly what may unfold between Northfield and Little Falls. Storm track prediction courtesy of NOAA.

 

Less Likely Scenario: Snowpocalypse 2012. The NAM solution assumes all snow, and no "dry tongue" to cut off the heaviest snowfall on Wednesday. Although still possible I'm leaning against this solution. The key reason? Both the GFS and ECMWF seem to be crystallizing around a more northern storm track, which would lead to a very sharp snow cut-off across the metro. Naturally. Living on the edge...

 

Model Convergence. Meteorologists are reassured when the models agree (which happens very rarely, come to think of it). Although there's still a pretty good range in amounts, you can see a pretty strong cluster around 10", give or take. Yep, it'll be plowable, but I'm still not convinced we'll all pick up a cool foot. Let's not get too greedy...

 

Latest Watches. Check out the latest here, courtesy of NOAA. Most of Minnesota is under a Winter Storm Watch (which implies a potential for 6" or more of snow in a 24 hour period). A Blizzard Watch is posted for a big chunk of west central Minnesota. In general, the farther north/west you drive, away from MSP, on Tuesday and Wednesday the worse travel conditions will be.

 

From The Local National Weather Service. I think this is a pretty reasonable forecast, based on the latest data. The heaviest snow bands setting up just north/west of the metro area Tuesday PM into Wednesday morning. Click here to read more from the local NWS office in Chanhassen.

 

Blizzard Potential. NOAA's experimental winter graphics show the greatest chance of blizzard criteria (visibility under 1/4 mile with sustained winds of 35 mph+ in falling/blowing snow) over parts of central and northern Minnesota around midnight Tuesday night.

 

Potential For All Snow? The 00z NAM keeps the temperature profile above MSP just below 32 F. for the duration of the storm. The Skew T forecast above is for 11 pm Tuesday night, when the profile seems to be closest to being warm enough for sleet. Earlier runs warmed up the atmosphere about 4,000 to 6,000 feet aloft, implying a period of sleet (ice pellets) Tuesday afternoon and evening. If the NAM is right and we do see (all) snow, that increases the potential for significant snowfall amounts by Wednesday.

 

Timing The Storm. The latest 18z Bufkit analysis tool shows marginal conditions for dendritic snow crystals, which are most likely to form when temperatures are close to -10 or -12 C. Maximum vertical velocities, when the air is predicting to be rising most violently, capable of producing the heaviest snow, comes from Tuesday evening into the morning hours Wednesday. Snow should cut off fairly quickly by Wednesday midday/afternoon as drier air surges into southern MN.

 

No, We Won't See This Much Snow. This is file from Romania a couple weeks ago - one of the more amazing photos I've seen this winter. I'll wash (and wax) Ken Barlow's car if we pick up this much snow.

 

4th Warmest. So far this winter has been the 4th warmest for the lower 48 states in 117 years of record-keeping. Source: NOAA.

Look At The Bright Side: No More Subzero Air. The map above shows the southward extent of subzero air predicted for the next 8 days, courtesy of policlimate.com. We'll still experience plenty of cold fronts between now and April, but with a sun angle as high in the sky as it was on October 15, the odds of negative numbers are dropping off rapidly with each passing day.

 

An Historic Winter For The Twin Cities. Only 3 nights below zero? Only the winter of 2001-2002 had fewer nights of subzero fun (2). The average number of nights below zero at KMSP every winter season? 28. Data above courtesy of the MN State Climate Office.

 

A Celestial Treat. Thanks to D.J. Kayser and Rebecca Boos who snapped this photo of the moon, Venus and Jupiter from St. Cloud Sunday evening. Hey - why aren't you watching The Oscars?

 

"Isn't it interesting that the same people who laugh at science fiction listen to weather forecasts and economists?" - Kelvin Throop III

 

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