INSTRUMENTS FLIGHT PLANNING
Area of thunderstorms cover 40% or more
Icing, turbulence and low-level wind shear are implied with and
Since in-flight weather advisories are designed for in-flight planning, they must be transmitted to
aircraft enroute. FAA Flight Service Stations broadcast in-flight weather advisories when they
pertain to an area within 150 NM of the Flight Service Station. In-flight weather advisories are
transmitted at 15 and 45 minutes past the hour during the first hour of their valid time. In
addition, convective SIGMETs are transmitted on the hour and at 30 minutes past the hour.
After the first hour, only an altering broadcast is transmitted at 15 and 45 minutes past the hour.
Example: "Washington SIGMET (or AIRMET) BRAVO 3 is current." Refer to the Flight
Information Handbook for more information on SIGMETs and AIRMETs.
Frequencies available for receiving in-flight weather advisories are found in the IFR or VFR
Enroute Supplement. Flight Service Stations are responsible for transmitting in-flight weather
advisories. Flight Service Stations are indicated in the Enroute Supplement by the word RADIO.
In-flight weather advisories are transmitted over all frequencies that are listed after the word
RADIO with the exception of those frequencies that are followed by the letter R.
Example: 122.3R. The R indicates the Flight Service Station is equipped to receive only on
that particular frequency.
Flight Service Stations
Direct pilot-to-weather briefer service is available by making radio contact with any FAA Flight
Service Station. Flight Service Specialists may not make original weather forecasts, however,
they have the latest weather reports and terminal forecasts (PLATES or TAFORS) available for
relay and are authorized to interpret weather reports and describe the weather conditions you can
expect to encounter. Similar pilot-to-weather briefer service can usually be obtained from the
ARTCC controller. Remember, Flight Service Stations are not weather forecasters.
Scheduled Weather Broadcasts
NAVAIDs providing scheduled weather broadcasts are indicated by radio class B. For example,
if the RADIO/NAV REMARKS section of the IFR Enroute Supplement listed a NAVAID as a
BVORTAC, then it is a VORTAC providing scheduled weather broadcasts. These stations
broadcast weather information at 15 minutes past the hour. An ABVORTAC provides
continuous automatic transcribed weather broadcasts. Exceptions to these times are listed in the
7-6 IN-FLIGHT WEATHER ANALYSIS