MSA

[India Four Two]

Extract from the Canadian AIM - AIR 1.5 Pressure Altimeter:

1.5.8 Pressure Drop
The “drop” in pressure associated with the increase in wind speeds extends throughout the mountain wave, that is downwind and to “heights” well above the mountains. Isolating the altimeter error caused solely by the mountain wave from error caused by non-standard temperatures would be of little
value to a pilot. Of main importance is that the combination of mountain waves and non-standard temperature may result IN AN ALTIMETER OVERREADING BY AS MUCH AS 3 000 FT. If the aircraft in our example had been flying upwind on a windy day, the actual ground separation on passing over the crest of the ridge may well have been very small.

TP 14371 - Transport Canada Aeronautical Information Manual (TC AIM) - Transport Canada