U
U/S - Unservicable
UAB - Until advised by ...
UCP - Unit Control Position
UDDF - Up and down drafts
UFN - Until further notice
UIR - Upper flight information region
UKMET - United Kingdom METeorological Agency
ULJ - Upper Level Jet
UN - Unable
UNA - Unable
UNAVBL - Unavailable
UNEC - Unnecessary
UNKN - Unknown
UNL - Unlimited
UNREL - Unreliable
UNRELBL - Unreliable
UNRSTD - Unrestricted
UNSATFY - Unsatisfactory
UNSBL - Unseasonable
UNSTBL - Unstable
UNSTDY - Unsteady
UNSTL - Unsettle
UNSTLD - Unsettled
UNUSBL - Unusable
UPDFTS - Updrafts
UPR - Upper
UPSLP - Upslope
UPSTRM - Upstream
URG - Urgent
USACE - U.S. Army Corps of Engineers
USBL - Usable
USBR - U.S. Bureau of Reclamation
USFS - U.S. Forest Service
USGS - U.S. Geological Survey
UT - Utah
UTC - Coordinated Universal Time
UV - Ultraviolet
UVM - Upward Vertical Motion.
UVV - Upward Vertical Velocity
UVVS - Upward vertical velocities
UWNDS - Upper winds
