Much of the Midwest will pick up some precipitation today as a disturbance aloft runs along a frontal boundary. Thunderstorms are likely early in the day around Kansas City and St. Louis, while cities like Chicago and Detroit will see much of the action during the afternoon hours. Severe thunderstorms will be isolated with the main threat from southern Kansas to southern Illinois. High temperatures on Tuesday should range from the 70s around the Great Lakes to the 90s across the Plains. Temperatures will increase through the week across the Plains and highs may eclipse 100 degrees all the way up through the northern Plains to the Upper Midwest. Heat will gradually expand eastward, as well.
A cold front is likely to trigger afternoon thunderstorms from Maine to the Middle Atlantic region today. A few thunderstorms may turn severe from Maine to Delaware. Large hail and gusty winds are expected with the stronger storms. Scattered thunderstorms will approach the Pittsburgh area by Tuesday evening but hopefully they will hold off until after the All-Star Game. This situation will have to be monitored. Temperatures remain warm with moderately high humidity levels Tuesday and Wednesday. Another cold front will slide southward through the region later Wednesday and Thursday continuing the threat of thunderstorms in the region.
Parts of the South will see thunderstorms on Tuesday. The most likely area will be from Arkansas to extreme northern Georgia. The rest of the region will see only widely scattered thunderstorms. By later in the week, high pressure aloft will build westward from the Atlantic. The high should limit shower and thunderstorm activity to only 20-30% coverage, which will allow high temperatures to climb into upper 80s and 90s. A few areas in Oklahoma and central Texas could eclipse the 100-degree mark.
Much of the West will be rather quiet for awhile but temperatures will be hot through the interior. Look for some isolated afternoon thunderstorms across the Rockies, however. During the late afternoon and early evening hours the storms should try to roll off the mountains into the valleys. A new cold front will send more showers into coastal sections of the Pacific Northwest late Tuesday and Wednesday. Look for cool temperatures along the northern and central coast of California but it will be hot in the central and southern Sacramento Valley. The Desert Southwest will continue to bake.