Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 355 AM EDT Wed Jun 20 2018 Valid 12Z Wed Jun 20 2018 - 12Z Fri Jun 22 2018 ...Flash flooding threats exist along the Texas coast as well as over the Middle Mississippi Valley... ...Record warm minimum temperatures possible across the southeastern U.S. and Pacific Northwest... ...Excessive heat expected over the Desert Southwest... A slow moving, meandering upper low will loom large along the Texas coast through roughly Thursday morning. Most recently, this system has a history of producing flash flooding, including some water rescues across Corpus Christi, Texas. With abundant tropical moisture in place and numerous slow moving thunderstorms, additional flash flooding is likely to occur somewhere along the Texas coast. A widespread 3 to 5 inches of rainfall is possible over this region through Thursday morning with isolated pockets of heavier amounts expected. Gradually the parent upper low is forecast to sink southward and position itself over central Mexico by the end of the work week. Another region which can expect a decent threat for flash flooding is the Middle Mississippi Valley. The prominent issues will likely extend from eastern sections of Nebraska/South Dakota out into Iowa and adjacent locations. A myriad of disturbances aloft will work in conjunction with a slow moving surface cyclone to afford multiple episodes of organized showers and thunderstorms. This combination will set a focus for a broad axis of heavy rainfall extending over the mentioned stretch of states. Like the Texas Gulf coast, sections of the Middle Mississippi Valley are also within the moderate risk for excessive rainfall as shown in the latest graphics. Not withstanding, areas farther downstream are not out of the woods as a wavy frontal zone sprawling eastward into the Ohio Valley and mid-Atlantic will be a site for organized heavy precipitation. A slight risk for excessive rainfall is being advertised, generally along I-70. South of the mentioned wavy frontal zone, it will be quite warm and muggy with low temperatures not dropping appreciably. As such, expect widespread mid 70s with localized upper 70s the next couple of nights across the southeastern U.S. Based on daily records, some observed minima may approach or locally exceed these extrema. During the daytime, while records are not likely, hot conditions should prevail across the Carolinas as highs soar into the upper 90s. Meanwhile, north of the boundary, highs in the 70s will be commonplace over New England. Looking to the western U.S., the Pacific Northwest can also expect fairly warm overnight temperatures for mid/late June. Current forecast lows are in the mid 60s across interior Washington/Oregon while upper 50s are more likely closer to the I-5 corridor. If such temperatures are achieved, some daily records may be broken. Farther south, excessive heat warnings and watches are in effect across the Desert Southwest. This well advertised increase in the temperatures is in response to a building upper ridge. By Thursday, highs will likely push into the 110s across many spots including Las Vegas, Needles, and Phoenix. And the current forecast high at Death Valley, California is 124 degrees on Thursday. As an upper ridge erodes across the northwestern U.S., a number of disturbances advancing from the Pacific will enhance chances for precipitation across the Pacific Northwest, Upper Intermountain West, and Northern Rockies. Somewhat limited moisture should keep overall rainfall amounts on the lower end with general maxima focusing over areas of local upslope effects. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php