Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 314 PM EDT Sun Oct 21 2018 Valid 00Z Mon Oct 22 2018 - 00Z Wed Oct 24 2018 ...Heavy rainfall threat continues for South Texas... ...Widespread freeze warnings and frost advisories are in effect from the Tennessee Valley to the Mid-Atlantic overnight tonight... Moisture overriding a stagnant frontal boundary in the northern and western Gulf of Mexico will keep showers and thunderstorms across the Florida Keys and the Gulf Coast the next several days. The best signature for heavy rain will be across far south Texas, where a handful of flash flood watches are in effect, particularly in the Brownsville region. Showers and thunderstorms will continue the next few days as well across Southern Texas as moisture from Hurricane Willa in the Eastern tropical Pacific eventually gets pulled northward towards the region. Given several days of wet weather already, there's a marginal risk for flash flooding. To the west, expect rain across the Great Basin this evening (with snow in the highest elevations) shifting slowly eastward by Monday and Tuesday underneath and ahead of broad upper level troughing across the Southwest U.S.. Localized flash flooding may be a threat in regions which are sensitive to heavy rainfall. Finally, a surface low traversing the region on Tuesday, will allow for mainly light rain and snow showers across the Great Lakes and the Northeast. Regarding temperatures across the country, reinforcing shots of cold air will keep temperatures below normal from the Great Lakes/Northeast to the Southern Plains through the short range period. Overnight lows tonight could be near or below freezing from the Tennessee/lower Ohio Valley to the central Appalachians and Mid-Atlantic where widespread freeze warnings and frost advisories are in effect. In the Southern Plains, daytime highs in the 50s and 60s are possible, which would be as much as 10 to 20 degrees below normal for this time of the year. Meanwhile, out west, temperatures above normal are expected to continue, and stagnant airflow and light winds within the valleys of eastern Washington and north-central Oregon have prompted air quality alerts. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php