AFTAfterAfterbayIn hydrologic terms, the tail race of a hydroelectric power plant at the outlet of the turbines. The term may be applied to a short stretch of stream or conduit, or to a pond or reservoir.AFTNAfternoonAFTRafterDowndraft(Abbrev. DWNDFT) - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm. A downburst is the result of a strong
downdraft.DRFTDriftDrifting IceIn hydrologic terms, pieces of floating ice moving under the action of wind and/ or currents.Drifting SnowDrifting snow is an uneven distribution of snowfall/snow depth caused by strong surface winds. Drifting snow may occur during or after a snowfall. Drifting snow is usually associated with blowing snow.DWNDFTDowndraft - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm. A downburst is the result of a strong downdraft.Dynamic LiftingThe forced uplifting of air from various atmospheric processes, such as weather fronts, and
cyclones.Forward Flank DowndraftThe main region of downdraft in the forward, or leading, part of a supercell, where most of the heavy precipitation is.
FTFeet (or foot)FTHRFurtherFTPMAILAn Internet server application which provides access to Internet FTP server files via e-mail. The National Weather Service operates an FTPMAIL server which provides e -mail access to any product available on the tgftp.nws.noaa.gov FTP server including marine text and graphic forecasts. For further information see: http://weather.noaa.gov/pub/fax/ftpmail.txt, or send an e-mail to firstname.lastname@example.org with the word "help" in the body. Ground Water OverdraftPumpage of ground water in excess of safe yield.Isentropic LiftLifting of air that is traveling along an upward-sloping isentropic surface.
Isentropic lift often is referred to erroneously as overrunning, but more accurately describes the physical process by which the lifting occurs. Situations involving isentropic lift often are characterized by widespread stratiform clouds and precipitation, but may include elevated convection in the form of embedded thunderstorms.Left Exit RegionUsed interchangably with Left Front Quadrant; the area downstream from and to the left of an upper-level jet max (as would be viewed looking along the direction of flow). Upward motion and severe thunderstorm potential sometimes are increased in this area relative to the wind speed maximum. See also entrance region, right rear quadrant. Left Front QuadrantUsed interchangably with Left Exit Region; the area downstream from and to the left of an upper-level jet max (as would be viewed looking along the direction of flow). Upward motion and severe thunderstorm potential sometimes are increased in this area relative to the wind speed maximum. See also entrance region, right rear quadrant.Left MoverA thunderstorm which moves to the left relative to the steering winds, and to other nearby thunderstorms; often the northern part of a splitting storm.LFTLiftLifted Index(abbrev. LI)- A common measure of atmospheric instability. Its value is obtained by computing the temperature that air near the ground would have if it were lifted to some higher level (around 18,000 feet, usually) and comparing that temperature to the actual temperature at that level. Negative values indicate instability - the more negative, the more unstable the air is, and the stronger the updrafts are likely to be with any developing thunderstorms. However there are no "magic numbers" or threshold LI values below which severe weather becomes imminent.Lifting Condensation Level(LCL) - The level at which a parcel of moist air becomes saturated when it is lifted dry adiabatically.LoftingA pattern of plume dispersion in a stable boundary layer topped by a neutral layer, in which the upper part of the plume disperses upward while the lower part of the plume undergoes little dispersion.Marine Small Craft Thunderstorm AdvisoryA marine warning issued by Environment Canada
Atmospheric Environment Branch when the possibility of thunderstorms is greater than 40
percent.Marine Small Craft Wind WarningA marine warning issued by Environment Canada
Atmospheric Environment Branch for winds which are forecasted to be in the 20-33 knot range
inclusive.Orographic LiftingSame as Upslope Flow; occurs when air is forced to rise and cool due to terrain features such as hills or mountains. If the cooling is sufficient, water vapor condenses into clouds. Additional cooling results in rain or snow. It can cause extensive cloudiness and increased amounts of precipitation in higher terrain.Orographic UpliftSame as Orographic Lifting; occurs when air is forced to rise and cool due to terrain features such as hills or mountains. If the cooling is sufficient, water vapor condenses into clouds. Additional cooling results in rain or snow. It can cause extensive cloudiness and increased amounts of precipitation in higher terrain. Rear Flank DowndraftA region of dry air subsiding on the back side of, and wrapping around, a mesocyclone. It often is visible as a clear slot wrapping around the wall cloud. Scattered large precipitation particles (rain and hail) at the interface between the clear slot and wall cloud may show up on radar as a hook or pendant; thus the presence of a hook or pendant may indicate the presence of an RFD.SHFTShiftSmall CraftThere is no precise definition for small craft. Any vessel that may be adversely affected by Small Craft Advisory criteria should be considered a small craft. Other considerations include the experience of the vessel operator, and the type, overall size, and sea worthiness of the vessel. See Small Craft Advisory.Small Craft Advisory(SCA) - An advisory issued by coastal and Great Lakes Weather Forecast Offices (WFO) for areas included in the Coastal Waters Forecast or Nearshore Marine Forecast (NSH) products. Thresholds governing the issuance of small craft advisories are specific to geographic areas. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats. There is no precise definition of a small craft. Any vessel that may be adversely affected by Small Craft Advisory criteria should be considered a small craft. Other considerations include the experience of the vessel operator, and the type, overall size, and sea worthiness of the vessel.
Exact thresholds may be found in NWSI 10-303:https://www.nws.noaa.gov/directives/sym/pd01003003curr.pdf.
For a list of NWS Weather Offices by Region, refer to the following website: http://www.nws.noaa.gov/organization.php Small Craft Should Exercise CautionPrecautionary statement issued to alert mariners with small, weather sensitive boats. Sustained OverdraftIn hydrologic terms, long-term withdrawal from the aquifer of more water than is being recharged.THRFTRThereafterTilted UpdraftA thunderstorm updraft which is not purely vertical but instead exhibits a slanted or tilted character. It is a sign of vertical wind shear, a favorable condition for severe storm development.UpdraftA 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.VALDRIFTAn air pollution transport and diffusion model developed to determine pesticide drift from aerial spraying operations in valleys.Wind ShiftA change in wind direction of 45 degrees or more in less than 15 minutes with sustained wind speeds of 10 knots or more throughout the wind shift.Wind Shift LineA long, but narrow axis across which the winds change direction (usually veer).WSHFTWind Shift
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