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.



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