Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 311 AM EDT Fri Sep 11 2020 Valid 12Z Fri Sep 11 2020 - 12Z Sun Sep 13 2020 ...There is a slight risk of excessive rainfall over parts of the Middle Mississippi Valley... ...Temperatures will be 10 to 15 degrees above average over inter portions of the Pacific Northwest while temperatures will be 10 to 20 degrees below average over the Plains and parts of the Upper/Middle Mississippi Valley... ...Fire weather conditions improving across the western U.S. An upper-level low over the Northern/Central Rockies will aid in drawing a plume of moisture northward from the Western Gulf of Mexico over the Upper/Middle Mississippi Valley on Friday into Saturday. The upper-level dynamics associate with the upper-level low will aid in producing rain with embedded thunderstorms over the Upper/Middle Mississippi Valley and parts of the Upper Great Lakes on Friday into Saturday. The WPC has issued a slight risk of excessive rainfall over parts of the Middle Mississippi Valley. The rain associated with the system will be heavy enough to produce mainly localized scattered areas of flash flooding over the region on Friday into Saturday morning. The rain will move into the Upper Great Lakes later on Saturday into Sunday. Temperatures associated with the upper-level low will be 10 to 20 degrees below average over the Plains and parts of the Upper/Middle Mississippi Valley that will moderate slowly. Meanwhile, tropical moisture over the Gulf Coast and the Southeast into parts of the Mid-Atlantic with the aid of embedded impulses will produce showers and thunderstorms over the region through Sunday morning. Elsewhere, upper-level ridging will allow temperatures to become 10 to 15 degrees above average over inter portions of the Pacific Northwest. In addition, under the upper-level ridge downward moving air will allow for limited mixing of the air. The limited mixing will aid in developing areas of stagnate air prompting air quality alerts over the Pacific Northwest dense fog over the Central Valley of California, and dense smoke advisories over parts of California and Nevada. Furthermore,areas of the Western U.S. that has been plagued by wildfires, improving conditions can be expected over the weekend as winds should remain relatively weak although cautions should not be relaxed as the air remain very dry across the interior sections such as the Great Basin. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php