UKMET - A medium-range numerical weather prediction model operated by the United Kingdom METeorological Agency.

Updraft - A small-scale current of rising air. If the air is sufficiently moist, then the moisture condenses to become a cumulus cloud or an individual tower of a towering cumulus or Cb.

Updraft Base - Alternate term for a rain-free base.

Upper Level System - A general term for any large-scale or mesoscale disturbance capable of producing upward motion (lift) in the middle or upper parts of the atmosphere. This term sometimes is used interchangeably with impulse or shortwave.

Upslope Flow - Air that flows toward higher terrain, and hence is forced to rise. The added lift often results in widespread low cloudiness and stratiform precipitation if the air is stable, or an increased chance of thunderstorm development if the air is unstable.

Upstream - Toward the source of the flow, or located in the area from which the flow is coming.

UVM (or UVV) - Upward Vertical Motion (or Velocity).