612 FXUS01 KWBC 300442 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 1240 AM EDT Tue Jun 30 2026 Valid 12Z Tue Jun 30 2026 - 12Z Thu Jul 02 2026 ...Severe thunderstorms possible across the north-central and northeastern U.S. through Wednesday... ...Severe thunderstorms possible across central/southern Plains through Wednesday... ...Dangerous heat for the central and eastern U.S.; below normal temperatures for the West... A broad upper-level troughing over western U.S. will support unsettled weather as facilitates the eastward movement of a frontal boundary across north-central U.S. The strengthening cyclone tracking across southern Canada will drag a cold front southeastward through the Northern Plains and Upper Midwest before reaching the Great Lakes by late Tuesday into Wednesday. The frontal boundary will interact with warm and unstable air mass, which will promote repeated rounds of showers and thunderstorms from the central High Plains into the Upper Midwest on Tuesday. Adequate deep-layer shear and moderate to strong instability will support organized convection capable of severe thunderstorms, large hail, damaging winds, and excessive rainfall. The severe weather and excessive rainfall threat shifts eastward into portions of the Great Lakes and Northeast late Tuesday as a warm front lift northward. Showers and thunderstorms will continue into Wednesday across much of the central Plains into the Great Lakes, but a quasi-stationary front and surface trough over the Intermountain West/Northern Rockies will bring a chance for scattered showers and thunderstorms across the area. Farther south, scattered to numerous diurnally enhanced thunderstorms are expected along the slow-moving frontal boundary across the Southeast that will bring concerns for localized flash flooding. Additionally, convection will develop across eastern New Mexico and west Texas, where persistent southeasterly low-level flow will maintain moisture convergence along the southern High Plains. While storm converge should remain scattered, localized heavy rainfall may lead to isolated flash flooding concerns, particularly in terrain-favored locations and urban corridors through Wednesday. A surface trough will extend southward across central and southern Plains, bringing isolated showers and thunderstorms on Tuesday. With the combination of southerly flow and instability, the storms may also produce supercells that may bring a severe thunderstorm threat with damaging winds and large to very large hail over central/southern High Plains through Wednesday. The dominate weather hazard during this week will continue to be dangerous heat across much of central and eastern U.S. Strengthening mid-level heights beneath the expansive ridge will support afternoon highs temperatures in the 90s and lower 100s. Increasing humidity values will produce peak heat indices between 105-115 degrees across portions of the Midwest and Mississippi Valley through Thursday, and expanding into the Mid-Atlantic and Ohio Valley by late week. With the combination of warm overnight lows, generally remaining in the 70s, providing limited relief and prolonged daytime, there is an increased risk of heat-related illnesses, especially for vulnerable populations and those without adequate cooling. In the West, persistent upper-level troughing will result in below normal temperatures across the region through the week. Oudit Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php $$