Valley Breeze: An upward flow of air which developes during the day in the mountains.
Vapor Pressure: The pressure exerted by the water vapor in the atmosphere.
Vapor Pressure:The amount of moisture the atmosphere is holding at a given temperature.
The portion of air pressure exerted by the water vapor content of air. Expressed in
"Grams" of water vapor per "Kilogram" of dry air also called: "Mixing Ratio".
Vapor Trail: Same as contrail.
Veering: A clock-wise movement in wind direction. Example: East to Southeast.
Vertical Wind Shear: Wind direction change & speed with height.
VFR Weather: Ceiling greater than3,000 ft. and visibility greater than 5 miles.
VFR: In flying: Visual Flight Rules
VHF: Very High Frequency. 30 to 300 MHz radio frequency.
VIP: Video Intergrator & Processor: Radar Reflewctivity.
Virga: Precipitation in the form of rain, snow, sleet etc, falling from clouds and
evaporating before reaching the ground.
Visibility: The greatist distance at which objects can be seen with the naked eye.
Visibility: Prevailing: Visibility throughout half the horizon circle.
Visibility: Sector: Visibility within a centern area of the horizon circle.
Visibility: Surface: Visibility observed from a definite location.
Visibility: Tower: Visibility observed from a control tower.
Visibility: Virtical: The Distance one can see up to clouds or through an obscuration: The distance from which a pilot can see the ground through clouds or an obscuration.