Winter storms continued    Another contributing factor to the snow process is the elevated terrain. As air from the lower elevations to the east rises over mountains of New Mexico and western Texas, further cooling takes place which further enhances the production of snow. Finally when low pressure in the upper atmosphere moves into Arizona or northwestern Mexico, it causes the jet stream to become more southerly to the east with strong winds aloft transporting moisture from the Pacific or Baja into the southern Rockies. The approach of the upper low and jet stream acts to strengthen the surface cyclone plus provides another source of moisture to  increase the potential for heavy snow.   A more common weather pattern over the southwestern United States during the late winter and early spring induces a process called lee cyclogenesis. During lee cyclogenesis, a strong upper-level low moves eastward across Arizona with an associated strong  jet stream extending across northern or central New Mexico. In response

The development of a strong surface low over northeastern New Mexico,         eastern Colorado or the Texas panhandle often produces dry but very windy weather over New Mexico and far western Texas.

a strong  surface cyclone will develop along the eastern slopes or lee of the Rockies over northeastern New Mexico, eastern Colorado or the Texas panhandle.  As the surface cyclone to the east intensifies, and as the upper-level low moves eastward, southwestern New Mexico and far western Texas often experience strong gusty winds with widespread blowing sand and dust but little or no rain or snow. Concurrently southeast of the lee cyclone,  southerly winds transport warm moist unstable air into the southern plains. As a result these weather systems often produce severe thunderstorms over central Texas, Oklahoma and Kansas with large hail, damaging winds and even violent tornadoes.   return to page 1                                                                                                                   page 4

Lee cyclones often bring strong winds with blowing sand and dust over southern New Mexico and western Texas ( photographed by Charlotte Rogash ).                                      go to page 5