Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 247 AM EDT Fri Sep 21 2018 Valid 12Z Fri Sep 21 2018 - 12Z Sun Sep 23 2018 ...Heavy rain expected for the southern plains and much cooler weather for the northern tier states... Heavy rain and flooding are expected to make weather headlines for the end of the week across parts of Texas, Oklahoma, and Arkansas. A deep surge of tropical moisture, with much of this from former Tropical Depression Nineteen, will advect northward and be lifted by a cold front approaching from the central plains and further aided by a shortwave arriving from the southern Rockies. WPC currently has a Moderate Risk of excessive rainfall from north-central Texas to southern Oklahoma for the potential for several inches of rain through Saturday afternoon, and high rainfall rates will likely lead to instances of flash flooding over this region. Other areas that will likely have enhanced rainfall are parts of western Washington state and the Upper Midwest. A Pacific low pressure system is forecast to reach southern British Columbia Friday night with a plume of heavy showers ahead of it that would affect the greater Seattle area and mainly points north and west. The rapidly developing surface low over the Great Lakes region early Friday will also result in widespread rain from northern Minnesota to the Upper Peninsula of Michigan, and thunderstorms extending from central Michigan to the Gulf Coast. Windy conditions are expected across the Great Lakes region on Friday owing to the increasing pressure gradient from the strong surface low. Temperatures are expected to be below normal across the north-central U.S. on Friday behind the strong cold front, with readings only reaching the 50s from Montana to Wisconsin with autumn making its presence known. It's still summer-like across the Deep South and extending eastward to the southeast coast with highs in the upper 80s and lower 90s with high humidity as the upper level ridge continues to govern the weather pattern. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php