21.   Isolated but potent thunderstorms will erupt across parts of Nebraska and Kansas as the southern end of the cold front lifts very warm surface air.

22.   Isolated, strong thunderstorms will flare up from eastern Oregon to the northern Rockies as a cool front lifts warm surface air.

23.   Instead, pockets of surface air, heated by the warming earth, ascend through a cold upper atmosphere, often resulting in the showery days of spring.

24.   It uses the current surface air temperature and surface wind speed.

25.   Just as ice skaters spin faster with arms tucked inward, surrounding surface air spins as it rushes in toward the updraft core.

26.   Lifting of surface air will be enhanced by a sluggish disturbance at jet stream altitudes.

27.   Limited sun will lead to cumulus clouds as warmed surface air rises through the cold pool.

28.   North of the system, rain and ice will fall in northern Illinois and southern Wisconsin as moist air flows north above cold surface air.

29.   On Tuesday afternoon, a cold front arrived in western Pennsylvania after partial to full sunshine had boosted surface air temperatures to their maximums.

30.   The cave interior tends to be warmer and moister than the surface air.