Kansas Ice Storm of 2017

There is a chance of freezing rain across the Midwest and central Great Plains this weekend.  It will primarily be a travel nuisance in places like Indiana and Ohio and a bit more disruptive in Missouri and Iowa.  But in central Kansas, residents are likely to face severe travel difficulties and widespread, long-lasting power outages.

Forecasted accumulations of ice, courtesy NWSFO Wichita.  Notice the large area where more than 1/2″ of ice is forecasted (much of it is off the map toward Dodge City and Hays).

From my research, around 3/4″ to 1″ of accumulation is when ice storms turn catastrophic and the effects last for weeks as opposed to days, so this storm is a big deal.  While this part of Kansas doesn’t have lots of trees, there are plenty of power lines, and the trees are in populated areas where most people live anyway.  On the plus side, the storm is well forecast and occurring on a 3-day weekend.  Utilities have had time to get workers, equipment, and supplies positioned, and there won’t be a lot of people on the roads.  The area where more than 0.50″ of ice is expected (blues and reds) on the map is moderately-large but not gigantic so they should have enough workers available (assuming the forecast is correct).

Likelihood of 0.5″ of ice or more. Blues and reds generally indicate >50% likelihood.  The highest probability is just south of Dodge City.

Ice storms are caused when warm (>0°C) moist air rises above a colder layer of air below freezing.  Falling snow melts into rain and then freezes in the air (sleet) or on contact with ground-based objects (freezing rain).  Equally important, a strong high pressure system nearby provides a fresh supply of cold, dry air right at the ground.  Obviously the cold air is necessary, but so is the dry component.  While it reduces precipitation amounts because some rain evaporates, evaporation helps sustain the cold air by chilling it (just like when you step out of a shower) and prolongs the ice storm by keeping temperatures below freezing.  Notice the strong high pressure anchored between Sioux Falls, SD, and Sioux City, IA.

surface pressure map

1038 mb is a considered a strong high pressure center.

Finally, the low pressure center is going to move slowly through Sunday evening (“0Z Mon” on the nearby map), allowing precipitation to fall in the same areas for a longer time.

Forecast location of the low pressure over time. The yellow circles indicate the range of possibilities for each time step. Times are in UTC (0Z = 6 PM CST or 7 PM EST.)

Everything is coming together for a major ice storm in Kansas and other nearby areas.  Hopefully everyone out there is prepared!

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