As in the METAR, winds greater than 99 knots are  given in three digits. From 1500Z, winds from 160° at 15 knots, gusting to  25 knots, visibility greater than 6 statute miles, clouds  scattered at 4,000 feet and broken at 25,000 feet. From 0000Z wind from 140° at 12 knots; visibility  greater than 6 statute miles, clouds broken at 8,000  feet, overcast at 15,000 feet between 0000Z and  0400Z, there is 40 percent probability of visibility 3  statute miles thunderstorm with moderate rain showers  clouds broken at 3,000 feet with cumulonimbus  clouds.  From 0400Z winds from 140°at 8 knots visibility  greater than 6 miles clouds at 4,000 scattered and  overcast at 8,000 temporarily between 0400Z and  0800Z visibility 3 miles, thunderstorms with moderate  rain showers clouds overcast at 3,000 feet with  cumulonimbus clouds. Becoming between 0800Z and 1000Z wind from 320°  at 7 knots end of report (=). The aviation area forecast (FA) gives a picture of clouds,  general weather conditions, and visual meteorological  conditions (VMC) expected over a large area encompassing  several states. There are six areas for which area forecasts  are published in the contiguous 48 states. Area forecasts are  issued three times a day and are valid for 18 hours. This type  of forecast gives information vital to en route operations as  well as forecast information for smaller airports that do not  have terminal forecasts. Inflight weather advisories are forecasts provided to en route  aircraft, and detail potentially hazardous weather. These  advisories are also available to pilots prior to departure for  flight planning purposes.  AIRMETs (report type designator WA) are issued every  6 hours with intermediate updates issued as needed for a  particular area forecast region. The information contained  in an AIRMET is of operational interest to all aircraft,  but the weather section concerns phenomena considered  potentially hazardous to light aircraft and aircraft with limited  operational capabilities. An AIRMET includes forecast of  moderate icing, moderate turbulence, sustained surface winds  of 30 knots or greater, widespread areas of ceilings less than  1,000 feet and/or visibilities less than 3 miles, and extensive  mountain obscurities. Each AIRMET bulletin has a fixed  alphanumeric designator, and is numbered sequentially for  easy identification, beginning with the first issuance of the  day. SIERRA is the AIRMET code used to denote IFR and  Routine TAF for Pierre, South Dakota on the 11th day  of the month, at 1130Z valid for 24 hours from 1200Z  on the 11th to 1200Z on the 12th wind from 150° at  12 knots visibility greater than 6 statute miles, broken  clouds at 9,000 feet, temporarily, between 1200Z and  1400Z, visibility 5 statute miles in mist. TAF KPIR 111130Z 111212 15012KT P6SM BKN090  TEMPO 1214 5SM BR FM1500 16015G25KT P6SM SCT040 BKN250 FM0000 14012KT P6SM BKN080 OVC150 PROB40  0004 3SM TSRA BKN030CB FM0400 1408KT P6SM SCT040 OVC080 TEMPO0408  3SM TSRA OVC030CB BECMG 0810 32007KT= 10. Probability forecast—a given percentage that describes  the probability of thunderstorms and precipitation  occurring in the coming hours. This forecast is not  used for the first 6 hours of the 24-hour forecast. 9. Forecast change group—for any significant weather  change forecast to occur during the TAF time period,  the expected conditions and time period are included  in this group. This information may be shown as  From (FM), Becoming (BECMG), and Temporary  (TEMPO). “From” is used when a rapid and  significant change, usually within an hour, is expected.  “Becoming” is used when a gradual change in the  weather is expected over a period of no more than 2  hours. “Temporary” is used for temporary fluctuations  of weather, expected to last for less than an hour. 8. Forecast sky condition—reported in the same manner  as the METAR. Only cumulonimbus (CB) clouds are  forecast in this portion of the TAF report as opposed  to CBs and towering cumulus in the METAR. 7. Forecast significant weather—weather phenomenon  is coded in the TAF reports in the same format as the  METAR. If no significant weather is expected during  the forecast time period, the denotation “NSW” will  be included in the “becoming” or “temporary” weather  groups. 6. Forecast visibility—reported in statute miles, in whole  numbers or fractions. If the forecast visibility is greater  than 6 miles, it will be coded as “P6SM.” Area Forecasts (FA) Inflight Weather Advisories Example: Airman’s Meteorological Information (AIRMET) Explanation: 4-39