Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 403 AM EDT Sat Sep 22 2018 Valid 12Z Sat Sep 22 2018 - 12Z Mon Sep 24 2018 ...Heavy to excessive rainfall shifts from eastern Texas/Oklahoma to the Lower Ohio Valley this weekend... ...Elevated to critical fire weather threat continues across the Central Great Basin and Central Rockies... The heavy rainfall and flash flood threat overnight across Texas and Oklahoma will shift slowly south and eastward into the lower Mississippi and Ohio Valleys this weekend as above normal moisture streaming northward into this region interacts with a nearly stationary frontal boundary. Areal averaged rain amounts on the order of 1 to 3 inches, with locally higher amounts, is forecast today and on Sunday from eastern Texas to the Tennessee and lower Ohio Valley. Given significant rainfall already impacting parts of Texas/Oklahoma/Arkansas, much of this area was placed within a moderate risk for flash flooding/excessive rainfall today. From eastern Texas to the lower Ohio Valley, a slight risk is in effect through the weekend. Expect showers and thunderstorms to reach portions of the Mid-Atlantic by Sunday, while on the backside of this boundary, conditions are rather chilly, with afternoon high temperatures forecast to be as much as 5 to 10 degrees below normal for this time of the year from the southern Plains to the Mid-Atlantic. Elevated to critical fire weather concerns continue across much of the central Great Basin and portions of the Central Rockies where warm and dry conditions will persist through the weekend underneath of upper level ridging. Afternoon high temperatures could be as much as 10 to 15 degrees above normal with numerous red flag warnings in effect across portions of Nevada and Idaho, as well as much of southern Wyoming. See products issued by the Storm Prediction Center and the local forecast offices for additional information. Elsewhere across the country, an upper level system moving into the Pacific Northwest today may bring some light and scattered showers to western Washington and Oregon, while the remainder of the interior Northwest remains dry. Once this system pushes into the Plains by late weekend/early Monday, it should tap into additional moisture increasing the threat for rainfall along a frontal boundary setting up in the northern Plains by the end of the short range period. Down across the Southeast and Florida, expect mainly scattered showers and thunderstorms all weekend within a warm and humid airmass. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php