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1921 J. Bjerknes & H. Solberg in Geofysiske Publikationer II. iii. 12 In the first case, the boundary line at the ground will be the front of advancing cold air, or, to introduce a shorter expression, a ‘cold front’. In the latter case, the boundary line will be the front of advancing warm air, or simply a ‘warm front’.

1923 W. N. Shaw Air & its Ways vii. 74 The polar front is regarded as being a bank of air with stream lines..over which the equatorial air is advancing gradually upward by motion directly transverse to the line of motion in the front.

1938 Nature 29 Oct. 804/1 Any pressure system, such as a cyclone, an anticyclone, a trough or a front.

1956 Weather May 147 The front is not a surface but a zone of rapid temperature transition between air masses.

1957 Times 11 May 7/1 A depression near Ireland will be slow moving and associated weak fronts will move slowly N.E. to E. districts.

1970 R. W. Longley Elem. Meteorol. x. 223 A frontal surface is the bounding surface between two air masses... The front is the intersection of such a frontal surface with the ground.

1921 J. Bjerknes & H. Solberg in Geofysiske Publikationer II. iii. 12 In the first case, the boundary line at the ground will be the front of advancing cold air, or, to introduce a shorter expression, a ‘cold front’. In the latter case, the boundary line will be the front of advancing warm air, or simply a ‘warm front’.

1969 A. G. Forsdyke Weather Guide 49 The rain belt ahead of a warm front is often 200 to 300 miles wide.