Closer analysis of the Rostov upper air ascent for 00Z 19 March 2016 (for what it is worth!) reveals to me the following air temperature readings at the bottom:
Surface +5.2C
2063ft +0.6C
916mb (c2333ft) -0.3C
4275ft -2.3C
FZ level c2200ft
At 180 knots the ram rise would be about 4 deg C so "practical"height of 0 deg c isotherm would be higher than this.