## 1 Introduction  
Downslope wind storms sometimes occur on the lee of mountain ranges such as the Rocky Mountain Front Range (e.g., [1; 2; 3; 4]). Such terrain-induced non-linear flow phenomena can result in damaging surface winds as well as severe turbulence both near the ground and at higher levels, thus affecting flight safety (e.g., [5; 6]). The strong near-surface downslope winds may halt in a narrow convergence zone, resulting in a deep, turbulent updraft. Several aircraft accidents have been attributed to turbulence associated with downslope wind storms [3; 7]. A rich array of instruments was deployed in the 2006 Terrain-induced Rotor Experiment (T-REX) to study downslope wind storms and related phenomena in the Owens Valley, California, in the lee of the Sierra Nevada [8]. Several theories have been proposed for the downslope acceleration of flow and the sudden, steep ascent further downwind [9; 10]. The main theories assume either an internal hydraulic jump [5; 11; 12], or gravity wave energy reflection on a self-induced critical level and local resonance (resonantamplification theory) [13; 14; 15]. Both theories require strong low-level flow across the mountain range, and a weakly stratified layer overlying a stable layer that immerses the terrain. The stable layer is squeezed over the terrain crest and then plunges into the lee, much like supercritical water flows over a barrier before encountering a hydraulic jump to transition back to subcritical flow. The high-amplitude hydraulic jump or wave energy reflection typically results in wave breaking and turbulence over a depth that usually exceeds the height of the terrain crest, and even the height of the equilibrium level of the potentially warm air carried down in the lee. The tremendous shear along the upper edge of this plunging flow, as well as near the surface, can produce severe turbulence. The breaking of waves aloft near the top of the hydraulic jump, and occasionally the release of static instability due to overturning isentropic streamlines [16], may also cause severe turbulence. The hydraulic jump is associated with intense low-level convergence. The opposing low-level flow (encountered sometimes further downwind of the mountain) is part of a horizontal vortex referred to as a rotor, which poses an additional threat to aircraft during landing or take-off. Rotors form due to boundary layer separation that may develop in association with the leading updraft in hydraulic jumps, but may also be associated with high-amplitude trapped lee waves [17]. A counter-rotating vortex (or local horizontal vorticity maximum) is also found on the opposite side of the hydraulic jump; it is a reflection of the negative shear at the upper margin of the plunging current [17]. The strength and depth of the upstream stable layer strongly affect the amplitude of the downslope wind storm and the intensity of lee rotors [18; 19; 20; 12]. The present study documents a downslope wind storm, a deep updraft and rotors in the lee of the Medicine Bow Mountains (MBM) in southeast Wyoming, USA (Figure 1). This range is lower and narrower (in the cross-wind direction) than the Sierra Nevada or the Rocky Mountain Front Range, but like those ranges it is asymmetric, with a steeper lee side than the windward side. Recent observational [21] and modeling [22] studies focused on boundary layer separation, rotor formation and wave breaking in the lee of the MBM. [PERSON] et al. [21] used the same aircraft and airborne radar as used herein (i.e., the Wyoming Cloud Radar or WCR), but their observations are relatively limited since they lacked radiosonde data on the windward side and were collected in a brief period. This brief period of data collection was sufficient to capture rapid dynamic evolution of the downslope windstorm [21]. A follow-up study by [PERSON] et al. [23] analyzed WCR and flight-level vertical velocity data to quantify turbulence intensity (more specifically, the cubed root of the energy dissipation rate) in breaking mountain waves.