I flew into Memphis Tennessee last week during the middle of a major
cold outbreak in the American Mid-West. The temperature at Memphis
(35.9 degs N) when I landed at 1800 local was 21F accompanied by a
stiff breeze.

The flight over The Great Lakes was interesting as streets of cumulus
cloud were forming over ice-free portions of the lake depositing snow
on the eastern shore. Some streets of lake-effect cumulus and very
shallow Cb were visible approaching the eastern shore of Lake Michigan
pasting the area around Grand Rapids. The cruise altitude of the
Airbus 330 I was on was 41,000ft so we would have been well into the
stratosphere in this deep cold air - the Cb tops were way below us,
probably no more than 10-15,000 ft.

Flying down the Mississippi the snow cover petered out near St Louis.
There as none in Memphis itself until Tuesday, when warmer air started
pushing in and there were a few flurries.

News bulletins in the US were all about the severe cold snap, the
worst since 1982 or something. Several places in the north -
Minneapolis for example - were reporting daytime maxima of -20F or
thereabouts. The TV forecasters were doing all the usual cold snap
things - chucking a cup of water in the air or hammering nails into
wood using frozen bananas etc.

Martin