METEOROLOGY FLIGHT PLANNING
WSUS41 KMKC 221855Z
MKCC WST 221855
CONVECTIVE SIGMET 20C
VALID UNTIL 2055Z
FROM 90W MOT-GFK-ABR-90W MOT
INTSFYG AREA SEV TS MOV FROM 24045KT. TS TOPS ABV FL450.
WIND GUSTS TO 60 KT RPRTD. +FC...HAIL TO 2 IN...WIND GUSTS
TO 65 KT POSS ND PTN.
CONVECTIVE SIGMET 21C
VALID UNTIL 2055Z
ISOLD SEV TS D30 MOV FROM 24020KT. TS TOP ABV FL450.
HAIL 2 IN...WIND GUSTS TO 65 KT POSS.
OUTLOOK VALID 222055-230055
AREA 1...FROM INL-MSP-ABR-MOT-INL
SEV TS CONT TO DVLP IN AREA OVR ND. AREA IS EXP TO RMN SEV AND SPRD
INTO MN AS STG PVA MOV OVR VERY UNSTBL AMS WTH -12 LI.
AREA 2...FROM CDS-DEW-LRD-ELP-CDS
ISOLD STG SEV TS WILL DVLP OVR SWRN TX AND WRN TX THRU FCST PD AS
UPR LVL TROF MOV NEWD OVR VERY UNSTBL AMS. LI RMNS IN -8 TO -10
RANGE. DRY LN WILL BE THE FOCUS OF TS DVLPMT.
Figure 3-4 WST Example
For WSTs, a line of thunderstorms is defined as being at least 60 miles long with thunderstorms
affecting at least 40 percent of its length. Embedded thunderstorms, for the purpose of WSTs, are
defined as occurring within and obscured by haze, stratiform clouds, or precipitation from stratiform
clouds. WSTs for embedded thunderstorms are intended to alert pilots that avoidance by visual or
radar detection of the thunderstorm could be difficult or impossible. Note that the presence of
thunderstorms implies the associated occurrence of severe or greater turbulence, severe icing, and
low-level wind shear.
All issued and valid WSTs for a specified geographic area are collected and listed in one place: a
Convective SIGMET Bulletin. The three Convective SIGMET bulletin areas are the Eastern (E),
Central (C), and Western (W) US, separated by the 87 and 107° W lines of longitude (with
sufficient overlap to cover most cases when a phenomenon crosses the boundaries). These area
letters can be found in the heading portion of the message, after the message type (e.g., WSTC),
and after the WST bulletin number (e.g., 20C). Each of these three bulletins is transmitted hourly
(at +55 minutes) and is valid for up to 2 hours. If there are no conditions within a region meeting
Convective SIGMET criteria at the time of issuance, then a negative bulletin is sent.
SEVERE WEATHER WATCHES, MILITARY ADVISORIES, AND PIREPS