Well defined upper level jet stream. If thunderstorms break through the cap, they will likely form in the maximum dew point gradient from dry to moist air. Formation along and 200 miles to the right of the upper level jet and from the maximum low level convergence downstream, to a point where the air is too dry to produce severe weather. Bulges in dry line. Convergence near the bulge can initiate severe weather .
Storms form from late afternoon to mid evening, and normally last two to six hours.
Favorable area for severe thunderstorm development is the triple point of the surface low, warm front, and dry line. Numerical models typically forecast limited precipitation with a large upper level ridge to the west of the forecast area. However, short waves, especially at 500 mb come off the front side of the ridge and produce large clusters of thunderstorms. 500 mb flow over the geographical midpoint is 280 degrees or greater. Troughs approaching the apex of the upper level ridge from 600- 400 mb.