B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Other / Unknown; Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action
Weather
Rapidly lost 45 KTS at FL370. The maximum continuous thrust was set at the onset of the shear. We descended to FL350 to stop the speed degradation and restore airspeed. The non-flying pilot advised ATC immediately and got acknowledgment after the third transmission. There was no conflicting traffic and the ride was smooth. No turbulence.
A B737-NG encountered a high altitude windshear in the southeastern Cascade Mountain Range which caused the loss of 45 KTS at FL370. The Captain exercised his emergency authority and began a descent to FL350 with maximum continuous thrust.