3-10. Air mass stability can be changed thermodynamically or mechanically. 1. True 2. False 3-11. Over  the  midlatitudes  of  North  America  in winter, an air mass exhibiting surface temperatures  of  -18°C  or  colder  is  generally classified as 1. cPk 2. mPk 3. cAk 4. cPw 3-12. Much can be gained from knowing the path cP and cA air masses take on leaving their source regions   in   North   America.   Which   of   the following   statements   pertains   to   the   winter outbreaks of these air masses when their path is cyclonic? 1. Good flying conditions are the rule 2. Cloud   cover   lingers   along   the   Atlantic coast until the air mass clears the Appalachian mountains 3. Frequent and widespread snow squalls can be  expected  on  the  leeward  side  of  the Great Lakes 4. Unrestricted  visibilities  are  common  on the   windward   side   of   the   Appalachian mountains 3-13. Weather along the U.S. west coast in winter is predominantly the result of which air mass? 1. mP 2. cP 3. cA 4. mT 3-14. What   air   mass   is   generally   responsible   for relatively   mild   weather   across   the   U.S.   in winter,  and  is  often  incorrectly  referred  to  as mT? 1. cP with a short cyclonic trajectory over the Pacific 2. cP with a long cyclonic trajectory over the Pacific 3. mP  with  an  anticyclonic  trajectory  along the northern border of the Pacific high 4. Highly modified equatorial (E) air 3-15. The heaviest precipitation recorded in Southern California in winter is produced from what air mass? 1. mP 2. cP 3. mT 4. cT 3-16. Maritime  polar  (mP)  air  is  far  more  frequent along  the  west  coast  of  the  U.S.  than  the  east coast. Why? 1. mP air of the Atlantic and Pacific are both more apt to move in an easterly direction, and  in  the  Atlantic,  this  movement  takes mP air away of the U.S. east coast 2. cP air is heavier and more dense than mP air,  and  it  acts  as  a  barrier  over  North America 3. The Greenland ice cap blocks mP air from moving    west    to    the    North    American continent (U.S. east coast) 4. The  very  warm  water  temperatures  of  the Gulf    Stream    rapidly    modify    mP    air requiring it to be reclassified as mT air 3-17. After a week of colder than average temperatures,   the   southeastern   U.S.   comes under  the  influence  of  much  warmer  mT  air over   the   Gulf   of   Mexico.   Which   of   the following   types   of   weather   will   likely   be produced by the mT air? 1. Snow flurries 2. Thunderstorms and tornadoes 3. Widespread advection fog 4. Copious rain 3-18. True    mT    air    does    not    have    dew    point temperatures below what value? 1. 60°F 2. 65°F 3. 70°F 4. 75°F 3-19. Which  of  the  following  air  masses  dominates most of the U.S. during the summer season? 1. mT or cP 2. mT or mP 3. mT or S 4. E or mP 14