Causes of Lake-Effect Precipitation Enhancement	Relative Importance
1.  Atmospheric destabilization is caused by cold air flowing       across warm water.	Most important by far.
2.  Roughness of land versus water leads to surface convergence       and uplift on the downwind side of a body of water.	Second most important around lakes in flat land area.
3.  There is at least some orographic uplift near every lake       shore.	Second most important in mountainous terrain.  This factor is very different in different locations.
4.  Evaporation of lake water by wind flowing over surface.	Not at all important.

Other Lake-Effect Facts

• Is generally strongest in late fall and early winter when the temperature differential between lake water and overlying air is likely to be greatest.
   

• Is stronger where the fetch (path length of wind over water) is greater.
   

• Is greatly weakened if the associated lake is ice-covered.
   

• Precipitation is usually concentrated in bands parallel to the wind direction.
   

• Location of greatest enhancement varies with wind direction.
   

• Is strengthened by increased wind velocity and lower temperatures of the air mass.
   

• Can enhance rainfall as well as snowfall but enhancement is generally less because of warmer air temperature.
   

• Only downwind sites are affected.