Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 348 AM EDT Tue Jun 01 2021 Valid 12Z Tue Jun 01 2021 - 12Z Thu Jun 03 2021 ...Record-breaking heat found across the western United States to start the month of June... ...Flash flooding and severe weather possible across portions of the Lower Mississippi Valley and Southern Plains today... ...Scattered showers and thunderstorms advance eastward into the Ohio and Tennessee valleys on Wednesday... The western United States is wasting no time to start meteorological summer as high temperatures are forecast to soar well above average from the Desert Southwest to the Pacific Northwest through at least Thursday. Simmering and record-breaking heat will be particularly likely today from central California to northwest Oregon, before expanding into the northern Great Basin on Wednesday. Highs are expected to reach into the triple digits across the Sacramento and San Joaquin valleys of California, as well as portions of southwest Oregon and the Desert Southwest. High temperatures into the 90s should spread as far north as central Washington and potentially north-central Montana on Wednesday. A few locations at risk of experiencing daily record high temperatures today and Wednesday include: Fresno and Redding, CA; Medford and Portland, OR; as well as Spokane, WA and Boise, ID. Excessive Heat Warnings and Heat Advisories have been issued for areas where heat-related illness is possible if simple precautions are not taken. Farther east, a weak area of low pressure currently located over northeast Texas is forecast to slowly move east-northeast over the next few days and enter the Ohio Valley by Thursday morning. Showers and thunderstorms will likely develop along and ahead of an associated cold front as in influx of moisture streams northward from the Gulf of Mexico. Thus, severe weather and flash flooding will remain a concern today across the Lower Mississippi Valley and portions of the Southern Plains. WPC has issued a Slight Risk of Excessive rainfall that stretches from southern Missouri to Louisiana, where chances of downpours leading to flash flooding are greatest. By Wednesday, showers and thunderstorms are forecast to shift into the Ohio and Tennessee valleys, while also lingering throughout central and southern Texas. A few thunderstorms will be capable of producing damaging wind gusts and isolated tornadoes between northern Mississippi and southwest Ohio. Isolated instances of flash flooding are also an anticipated concern throughout the aforementioned regions due to high rainfall rates and the potential for local rainfall amounts over 2 inches. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php