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A medium-sized moth (3.6-3.8 cm wingspan) with powdery grey forewings with black markings and dirty white hindwings. There is a prominent black basal streak that extends just through the antemedian line. The antemedian line is oblique, angled distad toward the lower margin, and is doubled and filled with lighter grey scales. The postmedian line curves outward on the upper half, and is crossed by a fine black streak in the anal angle. The orbicular spot is round, light grey and partially outlined in black scales. The reniform is less clearly defined, and is also partially outlined in black scales. The hindwings are dirty white, darkening toward the outer margin. Sexes are similar, with females having more dark scaling on the hindwings. Very similar to the much commoner Grey Dagger-moth (A. grisea), which is slightly broader-winged and smaller-bodied. The best character for separating radcliffei and grisea is the postmedian line; in radcliffei it runs straight to the margin, whereas in grisea it angles sharply distad and then basad at the lower margin.

No Alberta data; elsewhere in Canada it has been recorded from a variety of deciduous trees and shrubs, with most records from white birch (Betula papyrifera (Prentice, 1962). Rings et al (1992) summarized a number of host records reported in the literature, most in the family Rosacea, including apple (Malus), serviceberry (Amelanchier, and various cherries (Prunus), but also mountain ash (Sorbus), elm (Ulmus, and willow (Salix).