Section 8. Center
Weather Advisory (CWA)
A Center Weather Advisory (CWA) is an unscheduled weather advisory for conditions meeting or
approaching national inflight advisory (WA, WS,
or WST) criteria. It is primarily used by aircrews to
anticipate and avoid adverse weather conditions in
the en route and terminal environments.
a. CWAs are valid for up to 2 hours and may
include forecasts of conditions expected to begin
within 2 hours of issuance. If conditions are expected
to persist after the advisory's valid period, a statement
to that effect is included in the last line of the text.
Additional CWAs will subsequently be issued as
appropriate. The CWSU will issue a CWA:
1. When necessary to supplement an existing
WS, WST, or WA for the purpose of refining or
updating the location, movement, extent, or intensity
of the weather event relevant to the ARTCC's area of
2. When an inflight advisory has not yet been
issued, but the observed or expected weather
conditions meet WS, WST or WA criteria based on
current pilot reports and reinforced by other sources
of information concerning existing meteorological
3. When observed, or developing weather
conditions do not meet WS, WST or WA criteria but
current pilot reports or other weather information
sources indicate that an existing, or anticipated,
meteorological phenomena will adversely affect the
safe flow of air traffic within the ARTCC's area of
b. The CWA will describe the location of the
phenomenon using ARTCC relevant points of
reference, such as VORs, and will include the height,
extent, intensity, and movement of the phenomenon.
Each CWA will have a phenomenon number.
c. The format of the CWA communications header
is: (ARTCC designator)(phenomenon number) CWA
(date/time issued in UTC)/(ARTCC designator)
CWA (issuance number) VALID UNTIL (date/time
in UTC)/(FROM) (affected area)/(text).
ZOB1 CWA 032141
ZOB CWA 101 VALID UNTIL 032300
FROM 10S DET TO 40N DJB TO 40E SBN TO 80SE MKG
LN SEV TSTMS WITH EXTRM PCPN MOVG FROM
2525 3/4 INCH HAIL RPRTD LAST 5 MINS 20 SW YIP.
TSTMS WITH HVY TO EXTRM PCPN CONTG DTW
AREA BYD 2300
ZKC1 CWA 121528
ZKC CWA 102 VALID UNTIL 121728
STL DIAM 30 NM. NMRS RPTS OF MOD TO SEV ICG
080/090.. LGT OR NEG ICG RPTD 040/120 RMNDR OF
ZKC AREA AND NE OF AREA.
The CWA will be distributed to ARTCC area
supervisors and traffic management coordinators and
will be entered through FAA AISR and other
communications media to make it available for
dissemination to other FAA and NWS facilities.