Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Mon Jul 15 2024 Valid 00Z Tue Jul 16 2024 - 00Z Thu Jul 18 2024 ...The combination of 100-degree heat and high humidity will keep Heat Risk at major to extreme levels over the Mid-Atlantic to southern New England through Wednesday, as well as over portions of the Ohio Valley on Tuesday... ...Triple-digit heat will be replaced by damp and cooler weather over the central Plains on Wednesday but will continue over the interior Pacific Northwest, the Desert Southwest and Southern Plains... ...A cold front will bring areas of heavy rain and strong to severe thunderstorms from the central Plains to the Midwest, into the lower Great Lakes and interior Northwest over the next couple of days... The widespread heat wave that has gradually intensified over the mid-section of the country as well as the East Coast over the past couple of days will begin to be replaced by a dome of cool air which is currently entering the northern border of the U.S. Before the cool air has a chance to dip farther south into the central Plains by Wednesday, much of the central and eastern U.S. will remain in the midst of a major heat wave. High temperatures well up into the 100s in the central Plains this afternoon will be repeated on Tuesday but only shifted slightly farther south. Meanwhile, the combination of high humidity and temperatures topping the century mark will keep the Heat Risk at major to extreme levels for much of the Mid-Atlantic states into southern New England through Wednesday. Portions of the Ohio Valley into the Midwest will also be under major to extreme Heat Risk levels on Tuesday but showers and thunderstorms arriving ahead of a cold front will keep temperatures at bay by Wednesday. This cold front will also bring bouts of heavy rain and potentially severe weather across the northern tier states. The first round is forecast for the Midwest through tonight. Another round is forecast farther south from the central Plains to the mid-Mississippi and Ohio Valleys Tuesday night into Wednesday morning. These heavy rain and severe weather potentials are in response to the cool air mass from Canada colliding with the heat dome across the central and eastern U.S. A refreshingly cool and pleasant air mass with highs in the 70s will overspread the northern Plains by Wednesday. In the meantime, widespread heat advisories and areas of excessive heat warnings remain in effect across the central to eastern U.S. Please continue to practice heat safety through the next few days in these areas. The cool air is forecast to reach as far south as the central Plains on Wednesday where high temperatures will be lowered by 20 degrees, with afternoon readings reaching only into the 80s. Meanwhile, triple-digit heat is forecast to persist in the interior Pacific Northwest, the Desert Southwest and the southern Plains. Monsoonal moisture will support scattered thunderstorms from the central Rockies to much of the Four Corners region through the next couple of days. A slight chance of thunderstorms is expected to extend north into the interior Pacific Northwest. Mainly dry conditions will prevail in California and Nevada. The Sunshine State will remain in the 90s with summertime thunderstorms. Kong Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php