Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Wed Aug 08 2018 Valid 12Z Wed Aug 08 2018 - 12Z Fri Aug 10 2018 ...Unsettled weather expected to shift across the south-central and eastern U.S. through much of the work-week... ...Excessive heat and air quality concerns will persist for much of the Western U.S. as well as parts of the Mid-Atlantic and Northeast.... ...Red Flag Warnings continue across southern California and the Cascades of Washington... ...Hurricane John will track northwest near the Baja California Peninsula... Scattered to widespread showers and thunderstorms can be expected for central and eastern portions of the country as a slow-moving cold front shifts east and southeast. The trailing end of the front will slow considerably across the central U.S. Slow storm motion along this portion of the front will increase the likelihood of heavy rainfall and the risk for flash flooding. WPC has highlighted a portion of the Southern and Central Plains (including the Leeward side of the Central and Southern Rockies), as well as along the Ohio River and into the Middle Mississippi Valley as being in a slight risk of excessive rainfall. The remaining regions along the frontal boundary are in a marginal risk of excessive rainfall and flash flooding. Additionally, the Storm Prediction Center has issued a slight risk for severe storms for the leeward portions of the Southern/Central Rockies. A Flash Flood Watch and Severe Thunderstorm Watch are also currently in place for this region as well. The risk of excessive rainfall will slowly shift southward with the front each day. Hurricane John is tracking northwest and is expected to pass offshore the Baja California Peninsula. Moisture associated with this system will feed northward into the Desert Southwest, with will steadily increase the possibility for higher rainfall thus WPC has a slight risk for excessive rainfall and flash flooding in effect for portions of Arizona and New Mexico. Meanwhile, the rest of the West will continue to hot and mostly dry as a ridge extends from the Southwest northward. Excessive Heat Warnings are in effect for much of the Southwest and southern California. Excessive Heat Watches and Advisories are also in effect for the Northern Great Basin and portions of the Pacific Northwest. Many locations will observe daily maximum temperature readings exceeding 100 degrees. Additionally, an elevated threat for the spread of wildfires will persist. Red Flag Warnings are currently in place across Southern California as well as across the Cascades in Washington. Air Quality Alerts also continue across portions of the Southwest, California, and Northwest as wildfires continue to infuse the air with copious amounts of smoke. On the east coast, strong southerly flow will pump hot and humid air inland. This will result in above normal temperatures and even higher heat index values ahead of the approaching cold front. Heat Advisories and Air Quality alerts for excessive ozone concentrations are in effect across much of the Northeast and the northern extent of the Mid-Atlantic region through this evening. Heat Advisories have also been issued for portions of the Deep South through this evening. Expect conditions to begin improving once the cold front passes through in the coming days. Campbell/Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php