Tonight's homework: Study for
1. District Benchmark Assessment (DBA) Friday Nov. 8
2. Which means you are also studying for the Weather Unit  Assessment:  Friday Nov. 15.
WHAT should you study? Review your:

• study guide from last week
• science notebook since the second week of school; and
• check this blog.  

Part A. An air mass is a "packet" of air with the same temperature, pressure and humidity throughout.  (Think of a giant ziploc bag filled with air. Now, take away the ziploc bag).  An air mass gets its properties  (temperature, pressure and humidity) from the Earth's surface. For instance, a warm and humid air mass can move into Texas or the central U.S. from the Gulf of Mexico.
1)  Where could we get a cold, dry air mass from? 
2)  Where could we get a hot, dry air mass from? 
3)  Challenge: Find a fact about air masses from an internet site.

Part B. The leading edge of an air mass is called a "front".  If you look at this webpage, you'll see fronts, or leading edge of air masses as of this time:  
http://www.weather.com/maps/maptype/currentweatherusnational/uscurrentweather_large.html?clip=undefined&region=undefined&collection=localwxforecast&presname=undefined

                                              Image above courtesy of the Weather Channel, from 11/7/13 at approximately 5:03 p.m.
 In the picture, the curved line with the blue "spikes", or icicles, is a cold front with high pressure zones behind it.  Way back west, over Montana and Wyoming, see the warm front? It's a red line with symbols that look like a half-sun.
1) Why would the cold front move from west to east? Hint: we discussed this in class.
2) When a cold front hits a warm humid air mass, we get a change in weather, like a storm.  Why?  Pick one of the following answers:
      a) the warm front sinks to the bottom of the cold air mass and rains down to the ground;
      b) the warm air mass dissolves the cold front;
      c) cold air makes the humidity in the warm air mass condense into clouds and storms.