Advisory: Icy Mix Today – Plowable Snow Tonight – Arctic Melt Down – Minneapolis Star Tribune

 In Science

Weather Goes From Minnesota Nice to Minnesota Ice

Over the years I’ve learned a few things the hard way. The timing of a storm is obviously critical. So is the surface temperature. We tend to get hung up on snow amounts (“Hey Paul, where’s that 4 inches you promised me!”) when air temperature often determines how bad rush hour will be.

Colder storms tend to be more dangerous. Snow falling at 15F compresses into ice, and chemicals take time to melt this dangerous, slippery crust. In fact an inch at 17F can be far more hazardous to drive on than 6 inches of slush at 33F.

A layer of mild air aloft may result in a mixed bag of snow, sleet (ice pellets), even freezing rain – the most dangerous form of wintry precipitation. MnDOT-treated freeways may stay wet and slushy during the daylight hours today, but I expect roads to become icier everywhere tonight with a changeover back to snow. 2-4 inches falls by Wednesday in the metro with more over central Minnesota.

Light snow brushes southern Minnesota Thursday night; ECMWF guidance hints at a few more inches of slush Sunday night as rain changes back to snow.

Dig out the parkas – December looks good and cold.


Winter Weather Advisory. No watches or warnings, but the local Twin Cities office of the National Weather Service has issued a Winter Weather Advisory for much of the state, including the immediate MSP metro. Details:

 WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 2 PM TUESDAY TO 6 AM CST WEDNESDAY... * EXPECT WET SNOW TO DEVELOP AROUND 2 PM TUESDAY AND THEN DIMINISH AROUND 6 AM WEDNESDAY. * THE HEAVIEST SNOWFALL RATES WILL OCCUR BETWEEN 6 PM TUESDAY AND MIDNIGHT WEDNESDAY. * TOTAL WET SNOW ACCUMULATIONS OF 2 TO 5 INCHES ARE EXPECTED. * LOOK FOR REDUCED VISIBILITIES AT TIMES. * PLAN ON SLIPPERY ROAD CONDITIONS.


Rainy, Icy Mix Changes to Snow – Potential For 2-4″ By Wednesday Morning. Models are converging on a solution for total snowfall at KMSP, probably in the 2-4″ range (on lawns) – less on freeways and city streets. I suspect rush hour Wednesday will be more problematic than getting home later today.


Future Radar. 4km NAM data shows a mix of rain, sleet and snow pushing across the state; mostly snow north of St. Cloud. A changeover to mostly snow occurs tonight and Wednesday morning before tapering off. A few inches of slush may pile up on lawns, while (treated) roads remain mostly-wet. Loop: AerisWeather.


WRF Snowfall Totals. The same 4km weather model from NOAA still prints out some 6″+ amuns,especially east metro to Lake Mille Lacs. A rainy mix during the daylight hours tomorrow should help to keep totals down – still leaning more toward 2-4″ of heavy, wet, slushy snow on lawns by Wednesday morning. Source: WeatherBell.


84-Hour Snowfall Potential. There is the 12km NAM model predicted snowfall product into Friday; more lake effect for upstate New York, a plowable snow from central Minnesota into Wisconsin, and snow for the highest peaks from Colorado into the Pacific Northwest. Source: AerisWeather.


Above Average By Next Weekend. Yes, it’s been a few degrees colder than average, but ECMWF guidance warms us into the low 40s by Saturday and Sunday. And suddenly our definition of a “warm front” takes a radical turn. Source: WeatherBell.


Cold Start to December – Moderating by Mid Month. Much of the southern USA will get a taste of Canadian air by the first week of December with potential snow from north Texas into the Midwest and Ohio Valley. But there’s some evidence that milder, Pacific air may return for much of the USA by the second week of December.


Wednesday Travel Weather. Models print out showers from the Great Lakes and Ohio Valley to the Gulf Coast. No major problems getting hom on Wednesday. Map: Aeris AMP.


Thursday Travel Weather. Heavy rain pushes into the Pacific Northwest, otherwise relatively dry, quiet weather prevails on Thanksgiving Day with pleasant temperatures over the southern half of the USA.


Instant Winter. Reports of serious, lake effect snows for upstate New York and much of New England:




A Raw Thanksgiving Parade. Conditions are ripe for rain showers in New York City Thursday – not a steady, heavy rain, but it will definitely look and feel like late November.


Tropical Storm Otto Forms In Southwest Caribbean. Packing 65 mph sustained winds, Otto is forecast to track westward, passing over Costa Rica and Nicaragua into the Pacific. Details via CIMSS Satellite Blog at the University of Wisconsin: “…Infrared (10.7 µm) imagery from GOES-13, above, from 1315 through 1715 UTC on 21 November, shows periodic deep convection over the Depression; the grey regions in the deepest convection over the system correspond to brightness temperatures colder than -75 C. The environment surrounding this system, shown below, is marginally favorable for strengthening; sea-surface temperatures are warm, although the oceanic heat content suggests the warmth does not extend through a deep column of water. Wind shear over the storm is modest (but far stronger north of the storm)…”


An Unlikely Track. Check out the predicted track for Tropical Storm Otto, courtesy of NOAA NHC. By the way, if Otto regains strength in the Pacific it may undergo a name change (different list of names in the eastern Pacific than the Caribbean). As if we weren’t all confused enough…


Rain Triggers 570% Surge in Los Angeles Country Freeway Crashes. Did we mention it’s only rain? I know – I know. Oil accumulating on freeways mixing with rain or even drizzle can create ice-like conditions on the highways, but good grief people. Here’s an excerpt from The Los Angeles Times: “…Over Sunday and Monday, the storm dumped more than two inches of rain in San Luis Obispo County and more than an inch at Brentwood’s Getty Center in Los Angeles County, where a surge in car crashes left freeways intermittently jammed, authorities said. According to statistics from the California Highway Patrol, between 9 p.m. Sunday and 1 a.m. Monday there were 201 reported crashes on L.A. County’s freeways — a 570% increase from the same period last week when the CHP counted 30 crashes…”


The Big Melt: Sea Ice Hits Record Lows at North and South Poles. Here’s a snippet from The Christian Science Monitor: “Sea ice levels in both the Arctic and the Antarctic have hit record lows, NASA climate scientists report. The northern record, while bleak, isn’t all that surprising – Arctic sea ice has been on a consistent decline for years. But until recently, Antarctic sea ice was actually expanding. Climate change skeptics have often pointed to ice gain in the Southern Hemisphere, which hit record highs between 2012 and 2014, but now that trend appears to be reversing. “[It] certainly puts the kibosh on everyone saying that Antarctica’s ice is just going up and up,” Walt Meier, a research scientist with the Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center, told CNN…”


Something Really Crazy Is Happening In The Arctic. Have we reached a tipping point? I don’t pretend to know, but Tom Yulsman at Discover Magazine ImaGeo isn’t the only one who is alarmed: “Sea ice in the Arctic has been trending at record low levels since the third week of October — and now, something really crazy is happening up there. The Arctic is heading into the dead of winter, and across a vast swath of territory, the polar night has descended, with 24 hours of darkness each day. This is when temperatures should be plunging, and sea ice should be expanding rapidly. Instead, temperatures are soaring, and sea ice is actually shrinking. This shouldn’t be happening…”

Animation credit: “Changes in the concentration of Arctic sea ice between Nov. 12 and 19, 2016 are seen in this animation of satellite data. The North Pole is at the center. Areas with 100 percent coverage of ice are depicted in white. Lighter to darker blue tones are indicative of decreasing concentrations. And areas with no ice are in gray. Ice actually decreased within the area circled in red in the first frame of the animation.” (Data: University of Bremen. Images: Polar View. Animation: Tom Yulsman).


Crazy Cryosphere: Record Low Sea Ice, An Overheated Arctic, and a Snowbound Eurasia. Bob Henson has an informative post with more information about what’s happening at the top of the world at WunderBlog: “There are weather and climate records, and then there are truly exceptional events that leave all others in the dust. Such has been the case across Earth’s high latitudes during this last quarter of 2016, on track to be the planet’s warmest year on record. Sea ice extent and area have both plummeted to record lows for this time of year in both the Arctic and Antarctic. Such dramatic losses rarely occur at the same time, which means that the global total of sea ice coverage is phenomenally low for this time of year. The weirdness extends to midlatitudes: North America as well as the Arctic have been bathed in unusual mildness over the last several weeks, while Eurasia deals with a vast zone of above-average snowfall and below-average temperatures…”

Graphic credit: “The normalized value of global sea ice area as of November 17, 2016, was so far from any other total in the 37-year record that it represented a departure of about 8 standard deviations below the average! Image credit: Wipneus, using data from National Snow and Ice Data Center.” (NSIDC was not involved in producing this image.)


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