Nighttime thermospheric winds and temperatures have been measured over Fritz Peak Observatory, Colorado (39.9¿N, 105.5¿W), with a high-resolution Fabry-Perot spectrometer. The winds and temperatures are obtained from the Doppler shifts and line profiles of the (OI) 15,867 K (6300 ¿) line emission. Measurements made during three large geomagnetic storms, when Kp exceeded 8, have shown large-scale thermospheric waves that are probably generated by impulsive heating at high latitudes. These waves are observed to propagate equatorward over the observatory, and on one occasion a poleward traveling disturbance was observed several hours later. The characteristc features of the observed waves during the three storm periods are described, and the global properties of these waves are examined by using a numerical model of the zonally symmetric thermosphere. The model calculations show reasonable agreement with the observations over Fritz Peak Observatory, thus enabling an estimate to be made of the high-latitude energy input that launched the waves.