threatening

approaching, coming, forthcoming, future, near, nearing, oncoming, upcoming

brewing, gathering

likely, possible, probable

inevitable, unavoidable

apocalyptic (also apocalyptical), lowering, menacing, ominous, portentous

anticipated, awaited, expected, foreseen, predicted

black, bleak, cheerless, chill, Cimmerian, cloudy, cold, comfortless, dark, darkening, depressing, depressive, desolate, dim, disconsolate, dismal, drear, dreary, dreich [chiefly Scottish], elegiac (also elegiacal), forlorn, funereal, gloomy, glum, godforsaken, gray (also grey), lonely, lonesome, lugubrious, miserable, morbid, morose, murky, plutonian, saturnine, sepulchral, somber (or sombre), sullen, sunless, tenebrific, tenebrous, wretched

discouraging, disheartening, hopeless, unfavorable, unpromising, unpropitious

ill-fated, ill-starred, star-crossed, troubled, unfortunate, unlucky

evil, malign, malignant

dicey, insecure, precarious, treacherous, uncertain

ultrahazardous

chance, haphazard, random

distressing, sickening, unpleasant

ugly, wicked

adverse, bad, baleful, baneful, deleterious, detrimental, evil, harmful, hurtful, ill, inimical, injurious, malignant, nasty, noxious, pernicious, pestilent

deadly, deathly, destructive, dire, fatal, fateful, fell, killer, lethal, mortal, murderous