An interesting satellite picture

This is a satellite picture from yesterday at one point in the afternoon (I'm still lost on the 19:15Z - is the Z for Greenwich Mean Time???). Anyways there are a couple of interesting things going on here.
1. The colors, here the purple is for low clouds and the colors progress through green and yellow to indicate higher cloud tops (i.e. colder temperatures). If you look off of the Maine coast up into the Canadian Maritimes, you will see an odd arragement of clouds that appear to be almost vertical. Normally coastal lows take on more of a vortex like shape commonly called a "comma". This shape is not forming because of an extremely strong southern branch of the jet stream that is shearing the western edge of this storm (you can draw a line where the cold and warm air meet which is the trajectory of the jet stream).
2. A very strong fetch of extremely cold air off of Hudson Bay in Canada is filtering south due to the counter-clockwise flow about the very large coastal low and the strong polar high pressure over the Midwest. The moisture needed for lake effect snow in the eastern US is result from this cold flow (usually due to a pressure gradient between a strong high and low that are on either side of the great lakes) across the unfrozen Great Lakes. This cold dry air, as it progresses across the lakes, picks up humidity (simple thermodynamics) and then this air is shoved up the spine of the Appalachains. What is very interesting is that the patterns in the clouds in Pennsylvania reflect the topography, i.e. the Appalachains run from SW to NE across PA and you can see (if you look closely) the underlying ridge structure reflected where the air is compressed when pushing over these ridges and leading to the patterns in cloud formation.
(Note: The underlying thermodynamics for cloud formation in this case are that air that is rising (in this case due to the change in elevation of the earth) is cooled. This cooler air has a reduced capacity to hold moisture (again this is a basic thermodynamic property) and this moisture which is in the gaseous form is then converted to a liquid form in the phase transition to make clouds.)
3. Yesterday in the afternoon it was snowing in Cumberland MD but it was mostly sunny and dry in DC. The satellite image shows that the clouds over W Va and PA and western MD vanish as you progress eastward to the front range of the Appalachains. Well once the air gets across the mountains, it can now expand as the elevation of the earth drops and this expansion allows for the air to now take up liquid moisture as a gas, so any clouds (which are acutally big bags of liquid in sky) now vanish because the liquid goes through another phase transition to gas (and you can no longer see it). Additionally, most of the moisture was wrung out in the form of snow in the mountains. The line of clouds right down the W Va and Va border with W Va socked in with clouds and the Virgina piedmont as no clouds at all.
4. You can see the jet stream (using the clouds) across the southern states and the 90 degree turn it makes over Bermuda and heads due north to the Canadian Maritimes.

Pretty cool picture!