Weather Glossary – F


FA – Forecast Area.

FAA– the Federal Aviation Administration.

FAHRENHEIT – the standard scale used to measure temperature in the United States; in which the freezing point of water is thirty-two degrees and the boiling point is two hundred and twelve degrees.

FAIR – Less than 4/10 opaque cloud cover, no precipitation, and no extremes in temperature, visibility or winds.

FCST– Forecast

FIRE UP– A favorite phrase of forecasters. It means storms are developing or will develop.

FLASH FLOOD – A flood that occurs within a few hours (usually less than six) of heavy or excessive rainfall, dam or levee failure.

FLOOD – High flow, overflow or inundation of a normally dry area which causes or threatens damage.

FLOOD STAGE– The level of a river or stream at which considerable inundation of surrounding areas will occur.

FLY IN THE OINTMENT– A favorite phrase of some forecasters. Refers to a forecast problem or a potential forecast problem. Could also be in reference to a forecasting problem that caused a “busted” forecast.

FOEHN – A warm dry wind on the lee side of a mountain range. The heating and drying are due to adiabatic compression as the wind descend downslope.

FOG – Water droplets which are suspended in the air near the Earth’s surface and causing reduced visibilities.

FORECAST PERIODS – Routine forecasts issued before noon contain three forecast periods: Today (or this Afternoon), Tonight, and the Next Day. Routine forecasts issued after noon contain four forecast periods: Tonight, the Next Day, the Next Night, and the following Day.

FREEZE – When the temperature at or near the surface is expected to be 32 or below, during the growing season. Adjectives, such as “killing,’ “severe,” or “hard,” are used when appropriate. A freeze may or may not be accompanied by the formation of frost.

FREEZING LEVEL The altitude in the atmosphere where the temperature equals 32F.

FREEZING RAIN (DRIZZLE) – Rain (drizzle) which freezes on contact to produce a coating of ice on the ground and other exposed surfaces.

FRONT – The transition zone between two distinct airmasses. The basic frontal types are cold fronts, warm fronts and occluded fronts.

FROPA– Frontal Passage

FROST – The formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures are colder.

FUJITA SCALE – System developed by Dr. Theodore Fujita to classify tornadoes based on wind damage. Scale is from F0 for weakest to F5 for strongest tornadoes.

FUNNEL CLOUD – A rotating column of air forming a pendant from a cumulus/cumulonimbus cloud with circulation not reaching the ground.

FWC– Forecasted Weather Conditions