The remnants of Tropical Depression Debby will move out over the western atlantic, with showers and thunderstorms coming to an end by early Thursday morning. A front over the upper Great Lakes that extends to the Central Rockies will move eastward to the Northeast coast by Friday evening. A few showers and thunderstorms will develop near the front over parts of the middle Missouri Valley on Thursday morning. Later on Thursday showers and thunderstorms will develop along and ahead of the front from the Great Lakes to the Mid-Mississippi Valley moving eastward. Monsoonal moisture and afternoon heating will trigger showers and thunderstorms over parts of the Southern/Central Rockies during the afternoon and evening hours on Thursday and Friday. A front approaching the West Coast will produce scattered light rain along parts of the Pacific Northwest coast and parts of northern California coast beginning Thursday afternoon.
A strong upper level ridge of high pressure building over the Plains and spreading eastward will bring excessive heat to much of the central and eastern U.S. over the next several days. Hundreds of high temperature records have been tied or broken across the central U.S. over the past week. More records are expected to be broken as the heatwave continues. Excessive Heat Warnings, Heat Advisories, and Excessive Heat Watches are in effect from the Southern and Central Plains to the Great Lakes region, and reaching the Mid-Atlantic.
Critical Fire Weather Conditions are forecast for southeastern Missouri, southern and eastern Illinois, much of Indiana, western Ohio and the western half of Kentucky. Red flag warnings are also in effect for portions of eastern Idaho, western and southern Wyoming, portions of eastern and southern Nevada, and western Colorado.
The Minnesota Pollution Control Agency issues health advisory due to wildfire smoke and ozone pollution for the Twin Cities metro area and Rochester. In Colorado, Wildfire Smoke Health Advisories continue for four of the fires in the state including the fire west of Boulder and an Ozone Action Day Alert is in effect for the Front Range Urban Corridor. The Air Quality Index is forecast to be in the Unhealthy range in the South Bend Indiana area on Thursday.