1.   As the intense rays of the June sun heat the interior, rising currents develop, resulting in a lowering of the surface air pressure.

2.   As the intense rays of the June sun heat the interior, rising currents of hot air develop, resulting in a lowering of the surface air pressure.

3.   A deep snow cover helped chill the surface air.

4.   A typical hurricane lowers surface air pressure a few percentage points below normal levels.

5.   Clusters of showers and thunderstorms will flare over the southern Appalachians as a jet stream disturbance lifts moderately humid surface air.

6.   Cool ocean waters also moderate surface cold air associated with Pacific fronts, thereby weakening the fronts.

7.   Despite the chill in the surface air across the Northeast, the upper levels of the atmosphere will begin a warming trend Sunday.

8.   Farther east, scattered showers and thunderstorms will develop over parts of Utah and Nevada as the arriving jet stream disturbance vigorously lifts warm surface air.

9.   Farther south, rain will develop in eastern North Carolina and Virginia later Saturday as a formidable jet stream disturbance lifts moist surface air.

10.   For starters, the sloping terrain can augment the lifting of humid surface air, thereby energizing thunderstorms.