Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 410 PM EDT Fri Sep 07 2018 Valid 00Z Sat Sep 08 2018 - 00Z Mon Sep 10 2018 ...Excessive rainfall associated with Tropical Depression Gordon will impact portions of the Lower and Middle Mississippi Valley and the Ohio Valley into Saturday... ...Heavy rain is also forecast for portions of the southern Plains and Mid Atlantic... ...Excessive heat and fire weather concerns possible across portions of the Western U.S. this weekend... Tropical Depression Gordon is currently located over Arkansas and is expected to weaken to a Post Tropical Cyclone as it slowly shifts northward this evening. It will then merge into a stalled frontal system which is draped across the southern Plains, Middle/Lower Mississippi Valley, Ohio Valley, and Mid Atlantic and regain strength over the next few days. The combination of these two systems is resulting in a strong pull of warm and moist air across much of the southeast third of the country, which is promoting thunderstorms and heavy rain. The Weather Prediction Center has issued an area of Moderate Risk for flash flooding through tonight near the low pressure system, encompassing northeast Arkansas, much of Missouri, and portions of Illinois. A Slight Risk area has also been issued for the areas surrounding, as well as across a portion of the Southern Plains and northern Middle Atlantic along the frontal boundary. Ongoing Flash Flood Watches and Warnings are currently in effect for large portions of the Southern Plains, Lower and Mid Mississippi Valley and the Ohio Valley. Expect the flash flooding risk areas to shift with the movement of the low pressure center and frontal system over the coming days. A strong ridge located across the Southwest is promoting above normal temperatures across this region. Excessive heat warnings are in effect for Saturday across portions of southern California and southwest Arizona as a result. These above normal temperatures will also be felt across other portions of the western U.S., which may promote fire weather concerns. A Fire Weather Watch has been posted for southwest Wyoming and eastern Idaho for during the day Saturday due to expected low humidities, unseasonably warm temperatures, and the potential for dry thunderstorms resulting in lightning and erratic winds. Meanwhile, a much colder airmass is setting in across the far Northeast. Overnight temperatures are expected to drop to near freezing in portions of the high terrain during the weekend, which has led to the issuance of Frost Advisories for Saturday night into Sunday morning. Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php