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Cloud forecasts indicate the prevailing flight conditions. An
open magenta circle with an 'X' indicates Low Instrument Flight Rules (LIFR, ceilings less
than 500 feet and/or visibilities less than 1 statute mile). A red circle indicates
Instrument Flight Rules (IFR, ceilings 500 to less than 1000 feet and/or visibilities 1
to less than 3 statute miles), a blue circle indicates Marginal Visual Flight Rules
(MVFR, ceilings 1000 to 3000 feet and/or visibilities 3 to 5 statute miles), and no
circle (background color) indicates Visual Flight Rules (VFR). See the following table.
| Category |
Ceiling |
|
Visibility |
| LIFR |
below 500 feet |
and/or |
less than 1 mile |
| IFR |
500 to below 1,000 feet |
and/or |
1 to less than 3 miles |
| MVFR |
1,000 to 3,000 feet |
and/or |
3 to 5 miles |
| VFR |
greater than 3,000 feet |
and |
greater than 5 miles |
Wind forecasts use wind barbs to indicate forecast winds to the
nearest 5 knots. Standard meteorological convention for plotting winds is used. The tail
of the barb indicates the direction of the wind. Click
here for sample wind barbs with explanations. On the wind gust graphic, forecast
wind gusts of 20 knots or greater are plotted.
Weather forecasts are plotted using standard weather symbols.
Click
here for a graphic with weather symbols explained.
'Prevailing conditions' at a forecast location means the weather is expected to occur
over 50 percent of the time during the forecast period. 'Temporary conditions' means
weather conditions with at least 40 percent probability of occurrence at the forecast
location. It is important to remember TAFs are made for a 5 mile radius around an airport.
The forecast made for the airport location may not be representative of conditions in
nearby areas. The Area Forecast, along with AIRMETs, SIGMETs, and Convective SIGMETs
provide information for en-route weather and weather between airport locations.
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