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AIM

10/12/17

7−1−18

Meteorology

NOTE−

1. Terminal control facilities have the option to limit the

AWW, convective SIGMET, SIGMET, or CWA broadcast as

follows: local control and approach control positions may

opt to broadcast SIGMET or CWA alerts only when any

part of the area described is within 50 miles of the airspace

under their jurisdiction.
2. In areas where HIWAS is available, ARTCC, Terminal
ATC, and FSS facilities no longer broadcast Inflight
Weather Advisories as described above in paragraph a. See
paragraphs b1 and b2 below.

b. Hazardous Inflight Weather Advisory Ser-

vice (HIWAS). HIWAS is an automated, continuous

broadcast of inflight weather advisories, provided by

FSS over select VOR outlets, which include the

following weather products:  AWW, SIGMET,

Convective SIGMET, CWA, AIRMET (text [WA] or

graphical [G−AIRMET] products), and urgent

PIREP. HIWAS is available throughout the contermi-

nous United States as an additional source of

hazardous weather information. HIWAS does not

replace preflight or inflight weather briefings from

FSS. Pilots should call FSS if there are any questions

about weather that is different than forecasted or if the

HIWAS broadcast appears to be in error.

1. Where HIWAS is available, ARTCC and

terminal ATC facilities will broadcast, upon receipt,

a HIWAS alert once on all frequencies, except

emergency frequencies. Included in the broadcast

will be an alert announcement, frequency instruction,

number, and type of advisory updated; for example,

AWW, SIGMET, Convective SIGMET, or CWA.

EXAMPLE−

Attention all aircraft. Hazardous weather information
(SIGMET, Convective SIGMET, AIRMET 

(text [WA] or

graphical [G−AIRMET] product)

, Urgent Pilot

Weather Report [UUA], or Center Weather Advisory

[CWA], Number or Numbers) for (geographical area)

available on HIWAS or Flight Service frequencies.

2. Upon notification of an update to HIWAS,

FSS will broadcast a HIWAS update announcement

once on all frequencies except emergency frequen-

cies. Included in the broadcast will be the type of

advisory updated; for example, AWW, SIGMET,

Convective SIGMET, CWA, etc.

EXAMPLE−

Attention all aircraft. Hazardous weather information for

(geographical area) available from Flight Service.

3. HIWAS availability is notated with VOR

listings in the Chart Supplement U.S., and is shown

by symbols on IFR Enroute Low Altitude Charts and

VFR Sectional Charts. The symbol depiction is

identified in the chart legend.