Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 336 PM EDT Wed Jun 16 2021 Valid 00Z Thu Jun 17 2021 - 00Z Sat Jun 19 2021 ...Dangerous and record-breaking heat to continue across portions of the West and Central Plains... ...Heavy rain and severe thunderstorms possible throughout the Midwest on Thursday and Ohio Valley on Friday... ...Thunderstorms and scattered flash flooding expected across Florida this evening, as tropical rains approach the central Gulf Coast by Friday... The persistent and extreme heat wave being felt across the western U.S. is set to continue and even expand over the next couple of days. A strong upper-level ridge over the Southwest is expected to remain in place through Friday, while only slightly weakening. High temperatures 10 to 20 degrees above average will spread into central and northern California on Thursday, before reaching portions of the northern Great Basin by Friday. Dangerous and potentially deadly heat will continue throughout the Southwest and Intermountain West during this time period as well. Highs into the 110s and low 120s are likely throughout the Desert Southwest. Meanwhile, widespread triple digits will be felt throughout California and lower elevations of the central Great Basin and central Rockies. A brief period of sweltering heat will also impact areas farther east across the central Plains to end the workweek. High temperatures into the upper 90s and low 100s will stretch from eastern Colorado to southern Illinois. Much of the aforementioned regions from the West to Midwest will see dozens of daily record high temperatures set. A few monthly and even all-time records have already been tied/broken this week associated with the current stretch of heat. Widespread Excessive Heat Warnings and Heat Advisories are in effect throughout California, Nevada, Arizona, and Utah. Residents enduring the abnormal heat are urged to stay hydrated and avoid extended periods of time outdoors if possible. With warm temperatures and dry soil in place, an elevated fire risk is in effect throughout portions of the Rockies and Intermountain West. A weak area of low pressure and associated frontal boundaries will fuel scattered showers and thunderstorms over the Midwest on Thursday. A few of these storms will be capable of producing damaging wind gusts, large hail, flash flooding, and isolated tornadoes. The Storm Prediction Center has highlighted an area that includes northern/central Iowa, southern Minnesota, northern Illinois, and southern Wisconsin as having the greatest chances for severe weather on Thursday. By Friday the severe weather and flash flooding threat is expected to shift eastward into the Ohio Valley. SPC has issued a Slight Risk of severe thunderstorms that extends from central Illinois to western Pennsylvania. WPC has issued a Slight Risk of Excessive Rainfall for Friday over a very similar area throughout the Ohio Valley. Active weather is also in store for the Gulf Coast States over the next few days and potentially into the weekend. Scattered thunderstorms across the Florida Peninsula will potentially lead to flash flooding this evening, particularly throughout the southern half of the Sunshine State. Meanwhile, the National Hurricane Center has highlighted an area of unsettled weather currently located over the southwest Gulf of Mexico as having a 70 percent chance of forming into a tropical cyclone over the next 48 hours. Regardless of formation into an organized system, heavy rain is likely to encroach upon the central Gulf Coast by Friday afternoon/evening. Much of southern Louisiana has received double their normal rainfall over the last month; therefore, if any tropical moisture enters the region it would likely exacerbate flooding concerns. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php