On Aug 19, 8:11*am, A1C Watkins wrote:
On Aug 16, 3:41*pm, wrote:

Why is the 540 isopleth significant on a 1000-500 thickness chart?

Thickness below 540 generally indicates a zero percent chance of
frozen precipitation (i.e. snow) so that is pretty significant.

The dartboard shown in such charts indicate heights I take it. Thus
the dots joined are for pressures on one plane and heights on the
other so (not counting my own) what does thickness mean?