UAL off Runway in SFF
 

Apparently the airport is closed...

https://twitter.com/airlivenet/statu...402433?lang=en

Yep - it's KGEG...

Looks well "off-piste" :*

Are you sure it's not KGEG?

Indeed. SFF is Felts Field, general aviation field east of Spokane.

KGEG
 

!geg 01/211 geg ad ap clsd 1601051544-1601051642

!geg 01/210 geg twy c2, h, k, j, d, twy c btn apch end rwy 7 and
twy a ficon patchy ice observed at 1601051056. 1601051056-1601061056

And, just to be clear, it looks like UA 812, GEG-DEN, slid off taxiway A, not the runway. They were planning to depart runway 3.

FedEx 1476, an MD-10, reported good braking action on the runway, taxiways slippery after landing a short time earlier.

Living near GEG, we had a massive change in WX overnight, temps went from 0F to 0C with early a.m. rain after a week of snow, would imagine RWYs 21 and 3 there got greasy in a hurry. Glad nobody hurt.

Some pictures and a nice pax interview in this news story, sounds like the United crew and staff handled things well:

Plane slides off taxiway at Spokane Airport

From the marks in the snow, looks like the aircraft slid sideways into the snow bank, hopefully no damage.

And speaking of B-737's going sideways on the ground, here's some PPRuNe discussion of why they sometimes seem to taxi with a crab:

http://www.pprune.org/tech-log/18831...ng-ground.html