aeronautical information in the cockpit helps pilots
plan more safe and efficient flight paths, as well as
make strategic decisions during flight to avoid
potentially hazardous weather.
Pilots are encouraged to provide a continuous
exchange of information on weather, winds,
turbulence, flight visibility, icing, etc., between pilots
and inflight specialists. Pilots should report good
weather as well as bad, and confirm expected
conditions as well as unexpected. Remember that
weather conditions can change rapidly and that a "go
or no go" decision, as mentioned in paragraph
7-1-4b2, should be assessed at all phases of flight.
g. Following any briefing, feel free to ask for any
information that you or the briefer may have missed
or are not understood. This way, the briefer is able to
present the information in a logical sequence, and
lessens the chance of important items being
overlooked.

7-1-6. Inflight Aviation Weather Advisories
a. Background
1. Inflight Aviation Weather Advisories are
forecasts to advise en route aircraft of development of
potentially hazardous weather. Inflight aviation
weather advisories in the conterminous U.S. are
issued by the Aviation Weather Center (AWC) in
Kansas City, MO, as well as 20 Center Weather
Service Units (CWSU) associated with ARTCCs.
AWC also issues advisories for portions of the Gulf
of Mexico, Atlantic and Pacific Oceans, which are
under the control of ARTCCs with Oceanic flight
information regions (FIRs). The Weather Forecast
Office (WFO) in Honolulu issues advisories for the
Hawaiian Islands and a large portion of the Pacific
Ocean. In Alaska, the Alaska Aviation Weather Unit
(AAWU) issues inflight aviation weather advisories
along with the Anchorage CWSU. All heights are
referenced MSL, except in the case of ceilings (CIG)
which indicate AGL.
2. There are four types of inflight aviation
weather advisories: the SIGMET, the Convective
SIGMET, the AIRMET (text or graphical product),
and the Center Weather Advisory (CWA). All of these
advisories use the same location identifiers (either

Meteorology

VORs, airports, or well-known geographic areas) to
describe the hazardous weather areas.
3. The Severe Weather Watch Bulletins (WWs),
(with associated Alert Messages) (AWW) supplements these Inflight Aviation Weather Advisories.
b. SIGMET
G-AIRMET)

(WS)/AIRMET

(WA

or

SIGMETs/AIRMET text (WA) products are issued
corresponding to the Area Forecast (FA) areas
described in FIG 7-1-4 and FIG 7-1-5. The
maximum forecast period is 4 hours for SIGMETs
and 6 hours for AIRMETs. The G-AIRMET is issued
over the CONUS every 6 hours, valid at 3-hour
increments through 12 hours with optional forecasts
possible during the first 6 hours. The first 6 hours of
the G-AIRMET correspond to the 6-hour period of
the AIRMET. SIGMETs and AIRMETs are considered "widespread" because they must be either
affecting or be forecasted to affect an area of at least
3,000 square miles at any one time. However, if the
total area to be affected during the forecast period is
very large, it could be that in actuality only a small
portion of this total area would be affected at any one
time.
1. SIGMETs/AIRMET (or G-AIRMET) for the
conterminous U.S. (CONUS)
SIGMETs/AIRMET text products for the CONUS
are issued corresponding to the areas in FIG 7-1-4.
The maximum forecast period for a CONUS
SIGMET is 4 hours and 6 hours for CONUS
AIRMETs. The G-AIRMET is issued over the
CONUS every 6 hours, valid at 3-hour increments
through 12 hours with optional forecasts possible
during the first 6 hours. The first 6 hours of the
G-AIRMET correspond to the 6-hour period of the
AIRMET. SIGMETs and AIRMETs are considered
"widespread" because they must be either affecting
or be forecasted to affect an area of at least 3,000
square miles at any one time. However, if the total
area to be affected during the forecast period is very
large, it could be that in actuality only a small portion
of this total area would be affected at any one time.
Only SIGMETs for the CONUS are for non-convective weather. The U.S. issues a special category of
SIGMETs for convective weather called Convective
SIGMETs.
2. SIGMETs/AIRMETs for Alaska

7-1-11