Weather It Is (What did he mean?)

For those who are wondering: 500 mb means 500 millibars of pressure. For your reference, the pressure is around 1000 mb at sea-level,

and you have to go up around 5500 m to get there (on a very tall ladder).

The colder it is at 500 mb the better chance for snow (at least here) because it means that the temperature decreases pretty quickly with

height from the surface and this scenario favors thundersnow.

Lastly, an ensemble forecast is a group of forecasts based (in our case) on similar -- but not the same -- initial conditions. In other words,

since there is always some error in the observed weather, we assume that the actual conditions of the atmosphere are not exactly what

we measured. In fact, we change the measurements a bit and then see how this affects the forecast. If you look at the GEFS forecast on the site,

you  can see that this can be quite a lot!  (At least beyond a couple of days.)

Barry Lynn