METEOROLOGIST JEFF HABY
An upslope wind occurs on the windward side of a mountain range. Some mountain ranges, such as the Sierra
Nevadas in California have the west side of the mountain range as the windward side the great percentage of the
time. Other mountain ranges such as the Rocky and Sangre de Christo Mountains have the west side as the windward
and in some circumstances have the east side as the windward side. When the winds are from an easterly component,
upslope slope occurs in the high plains. The best upslope conditions develop when there is a strong area of low
pressure in the southern plains. To the north of the low, winds have a strong easterly component. This upslope
enhances snowfalls that occur in the lee of the Rockies. An upslope flow causes the air to rise. This results
in an increasing of
relative humidity (lowers vapor deficits) because the air cools
adiabatically as it rises.
The
dewpoint and temperature convergence upon each other when the air is rising (temperature decreases faster
with height than the dewpoint decreases with height in a rising parcel of air). Upslope flow is responsible for
phenomena such as mountain summertime convection and upslope enhanced snow.
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