Issued 355 AM EDT Thu Sep 20 2018 Valid Thu Sep 20 2018 - Sat Sep 22 2018 ...Severe weather and a threat for flash flooding across the Upper Midwest today... ...Moderate Risk for flash flooding in place over central Oklahoma on Friday into the overnight hours... ...Substantial temperature contrast on the order of 40-50 degrees F from the Dakotas into the central U.S... ...Wet conditions likely across sections of western Washington up into British Columbia... As an upper tro...