Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 339 AM EDT Fri Jun 25 2021 Valid 12Z Fri Jun 25 2021 - 12Z Sun Jun 27 2021 ...Unprecedented and dangerous heat likely throughout the Pacific Northwest and Northern Great Basin this weekend... ...Several rounds of showers and thunderstorms to create numerous instances of flash flooding today between the Central Plains and Middle Mississippi Valley... ...Heavy rain and severe weather chances linger from the Southern Plains to the Great Lakes through Sunday... Today is expected to be the first of many extremely hot days felt across the northwestern United States. An anomalous upper-level ridge is forecast to slowly meander over the region and nearby southwest Canada through this weekend. Coinciding with the longest days of the year and widespread severe drought conditions, high temperatures are forecast to soar well into record-breaking territory beginning on Saturday and lasting through at least the middle of next week. High temperatures are expected to increase each day this weekend and top out near 20 to 30 degrees above average on Saturday and Sunday over Washington and Oregon. This equates to widespread temperatures in the upper-90s and triple digits, including the major metropolitan areas of Portland, OR and Seattle, WA. High temperatures into the 110s are possible across the Columbia Basin in western Washington and north-central Oregon. Starting on Saturday, several high temperature records should fall throughout the Northwest, with monthly and even all-time records in jeopardy by Sunday and Monday. Excessive Heat Warnings have been issued for nearly all of Washington and Oregon, as well as much of Idaho and northern California. Heat of this magnitude can be extremely dangerous if proper precautions aren't taken. Residents are urged to stay hydrated, avoid extended amounts of time outdoors, and stay in air-conditioned rooms. Nighttime temperatures are only expected to briefly cool into the 70s throughout the lower elevations, which can significantly increase the threat for heat related illnesses. Elsewhere, active weather is set to be found across the central U.S. over the next couple of days. A stationary front is forecast to extend from the Great Lakes to the Southern Plains by this evening and be the focus for multiple rounds of heavy rain and thunderstorms. Given the stalled frontal boundary, sufficient atmospheric moisture, and the slow-moving nature of thunderstorms in the area, flash flooding will be a major concern from southeast Kansas to west-central Indiana. Thunderstorms have already led to significant flash flooding and over 7 inches of rain in far northeast Kansas early this morning, with the threat slowly pushing southward today. WPC has issued a Moderate Risk (level 3/4) for Excessive Rainfall through Saturday morning that covers parts of the Central Plains, Middle Mississippi Valley, and western Ohio Valley. This means numerous instances of flash flooding are expected, with significant events possible. Flash Flood Watches have been posted for this region as well. Severe weather is also possible throughout the central U.S. today. The Storm Prediction Center has issued a Slight Risk (level 2/5) for severe thunderstorms that extends from the central/southern High Plains to central Illinois. Isolated tornadoes, damaging winds gusts, and large hail are all a possibility as storms form and strengthen along the stalled frontal boundary this afternoon/evening. By Saturday, the severe weather threat is forecast to shift southward and into the southern High Plains as the cold front surges south. Meanwhile, additional downpours and flash flooding will remain possible from the Rolling Plains of Texas, throughout central Oklahoma and the Middle Mississippi Valley, to the Great Lakes. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php