Area forecast discussion
National Weather Service St Louis MO
500 am CST Sat Jan 20 2007

the closed low which was over Southern California now comes under
an old rule called "henry's rule" which says that when an upstream
short wave moves to within 1200 miles of the closed low it will
kick it out...and kick it is! The closed low located over Southeast
Arizona yesterday evening shows up on the satellite water vapor
picture beginning to eject east northeast. This trough has
captured some tropical moisture with it and the plume can be
seen overspreading the Panhandle areas early this morning.