Subj : Wx Terms (F)(3) To : All From : Daryl Stout Date : Mon Aug 07 2017 12:04 am Flood Warning (FLW) In hydrologic terms, a release by the NWS to inform the public of flooding along larger streams in which there is a serious threat to life or property. A flood warning will usually contain river stage (level) forecasts. Flood Wave In hydrologic terms, a rise in streamflow to a crest and its subsequent recession caused by precipitation, snowmelt, dam failure, or reservoir releases. Flooded Ice In hydrologic terms, ice which has been flooded by melt water or river water and is heavily loaded by water and wet snow. Floodproofing In hydrologic terms, the process of protecting a building from flood damage on site. Floodproofing can be divided into wet and dry floodproofing. In areas subject to slow-moving, shallow flooding, buildings can be elevated, or barriers can be constructed to block the water' approach to the building. These techniques have the advantage of being less disruptive to the neighborhood. It must be noted that during a flood, a floodproofed building may be isolated and without utilities and therefore unusable, even though it has not been damaged. Floodwall In hydrologic terms, a long, narrow concrete, or masonry embankment usually built to protect land from flooding. If built of earth the structure is usually referred to as a levee. Floodwalls and levees confine streamflow within a specified area to prevent flooding. The term "dike" is used to describe an embankment that blocks an area on a reservoir or lake rim that is lower than the top of the dam. Floodway In hydrologic terms, (1) A part of the flood plain, otherwise leveed, reserved for emergency diversion of water during floods. A part of the flood plain which, to facilitate the passage of floodwater, is kept clear of encumbrances. (2) The channel of a river or stream and those parts of the flood plains adjoining the channel, which are reasonably required to carry and discharge the floodwater or floodflow of any river or stream. Flood\/Flash Flood Warning Issued to inform the public that flooding is imminent or in progress. Flood\/Flash Flood Watch Issued to inform the public and cooperating agencies that current and developing hydrometeorological conditions are such that there is a threat of flooding, but the occurrence is neither certain nor imminent. Flow (abbrev. FLW) Wind. In meteorology, a qualitative reference of an air parcel(s) with respect to its direction of movement, sometimes specified at a certain height or pressure elevation, e.g. westerly flow at 500 mb. In hydrology, the volumetric flow of water past a given point on a stream or river, usually in cubic feet per second (cfs) Flow Duration Curve In hydrologic terms, a cumulative frequency curve that shows the percentage of time that specified discharges are equaled or exceeded. Flow Separation The process by which a separation eddy forms on the windward or leeward sides of bluff objects or steeply rising hillsides. Flow Splitting The splitting of a stable airflow around a mountain barrier, with branches going around the left and right edges of the barrier, often at accelerated speeds. Flowing Well In hydrologic terms, a well drilled into a confined aquifer with enough hydraulic pressure for the water to flow to the surface without pumping. Also called an Artesian well. FLRY Flurry FLS River Flood Statement Fluence Time integrated flux Fluid Matter which flows; gas or liquid. Flurries Snow flurries are an intermittent light snowfall of short duration (generally light snow showers) with no measurable accumulation (trace category). Flux The rate of transfer of fluids, particles or energy per unit area across a given surface (amount of flow per unit of time). FLW Follow (or) Flow- Wind FM From or Fathom fMin In solar-terrestrial terms, the lowest radiowave frequency that can be reflected from the ionosphere. FNT Front FNTGNS Frontogenesis FNTLYS Frontolysis Foehn A warm, dry wind on the lee side of a mountain range, the warmth and dryness of the air being due to adiabatic compression as the air descends the mountain slopes. In the United States, the term chinook is used for Foehn winds in the Rocky and Sierra mountains. Foehn Pause A temporary cessation of the foehn at the ground due to the formation or intrusion of a cold air layer which lifts the foehn off the ground. foEs In solar-terrestrial terms, the maximum ordinary mode radiowave frequency capable of reflec- tion from the sporadic E region of the ionosphere. foF2 In solar-terrestrial terms, the maximum ordinary mode radiowave frequency capable of reflection from the F2 region of the ionosphere. Fog (abbrev. F) Fog is water droplets suspended in the air at the Earth's surface. Fog is often hazardous when the visibility is reduced to ¬ mile or less. Fogbow A rainbow that has a white band that appears in fog, and is fringed with red on the outside and blue on the inside. Forced Channeling Channeling of upper winds along a valley's axis when upper winds are diverted by the underlying topography. Compare pressure-driven channeling. Forebay In hydrologic terms, the water behind (upstream) of the dam. Forecast A statement of prediction. Forecast Crest In hydrologic terms, the highest elevation of river level, or stage, expected during a specified storm event. Forecast Guidance Computer-generated forecast materials used to assist the preparation of a forecast, such as numerical forecast models. Forecast Issuance Stage The stage which, when reached by a rising stream, represents the level where RFCs need to begin issuing forecasts for a non-routine (flood-only) forecast point. This stage is coordinated between WFO and RFC personnel and is not necessarily the same as action or alert stage. The needs of WFO/RFC partners and other users are considered in determining this stage. Forecast Periods Official definitions for NWS products: Today...............................Sunrise to sunset This afternoon..................noon till 6 p.m. This evening.....................6 p.m. till sunset Tonight.............................sunset till sunrise Tomorrow.........................sunrise to sunset of the following day Forecast Point In hydrologic terms, a location that represents an area (reach of a river), where a forecast is made available to the public. Each NWS river forecast point has an associated E-19a, Abridged Report on River Gage Station, and E-19, Report on River Gage Station. Forecast valid for The period of time the forecast is in effect beginning at a given day, date and time, and ending at a given day, date and time. Foresight In hydrologic terms, a sighting on a point of unknown elevation from an instrument of known elevation. To determine the elevation of the point in question, the foresight is subtracted from the height of the instrument. Forward Flank Downdraft The main region of downdraft in the forward, or leading, part of a supercell, where most of the heavy precipitation is. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .