My gardener was right: winter aconite (Eranthus hyemalis) and snow drops (Galanthus nivalis) are blooming on this client's slope.
This natural planted area in Queens gets afternoon sun and is snow free now — unlike many other areas, especially north-facing slopes, which still have ample snow cover. My guess is the snow cover moderated soil temperatures, and when the afternoon sun finally melted through, it began to warm the soil, speeding these little gems along.
Whatever the mechanism, this is the only site I see in bloom just now — although I'm sure there must be others. 'Arnold Promise' witch hazels (Hamamelis x intermedia 'Arnold Promise') are about to pop and paperbush's (Edgeworthia chrysantha) odd buds are quite swollen, but neither is yet truly in bloom.
Bright color has returned to the landscape!