Heavy rain, flash flooding and severe weather threat associated with astrengthening storm system to continue this afternoon and tonight in theSoutheast......Powerful storm system to foster heavy rain and high wind potential overmuch of the eastern U.S. on Thursday; severe weather and flash floodthreats forecast in parts of the Southeast and upper Ohio Valley......High winds along with widespread moderate to heavy rain expected toimpact the entire Eastern Seaboard into the Great Lakes Thursday nightinto Friday; warming up in the West...The second half of the work-week features an impressive early-mid Aprilstorm system, currently tracking through the Deep South, that will headnortheast through the Lower Mississippi Valley this evening and head forboth the Tennessee and Ohio Valleys come Thursday morning. The centralGulf Coast is the focus for the most dangerous weather this afternoon andevening as organized thunderstorms track east through the region. TheStorm Prediction Center and Weather Prediction Center both issued ModerateRisks for severe storms and Excessive Rainfall respectively, implying thatnot only is flash flooding anticipated for parts of the central GulfCoast, but so are severe thunderstorms capable of producing tornadoes,damaging wind gusts, and large hail. Meanwhile, periods of rain will becommon from the ArkLaTex and Ozarks this afternoon to the Ohio Valley andLower Great Lakes overnight.By Thursday morning this strengthening storm system will direct its shieldof rain north into the eastern Great Lakes and Mid-Atlantic, then finallyinto the Northeast by Thursday afternoon. Numerous showers are also stillexpected in parts of the Lower Mississippi Valley and for much of the Ohioand Tennessee Valleys. In terms of severe weather the upper Ohio Valley ismost at-risk, as evident with an expansive Slight Risk area and a smallerEnhanced Risk area that is focused in eastern Ohio and western WestVirginia. Tornadoes and damaging winds are the primary modes of severeweather of greatest concern through Thursday afternoon. Farther south, thestorm's cold front will act as a trigger for severe storms from theMid-Atlantic on south to northern Florida. SPC has a Slight Risk thatstretches from southern South Carolina on south to the Tampa, FL metroarea. There is also the threat for Excessive Rainfall and resulting flashflooding from the Upper Ohio Valley on east through the northernMid-Atlantic. WPC has a large Slight Risk area in place for portions ofthese regions, with metro areas such as Pittsburgh, Washington D.C.,Baltimore, and Philadelphia all within the Slight Risk zone. In additionto the rain and thunderstorms, gusty winds will be felt across much of theeastern half of the U.S., especially in the central Appalachians and partsof the Southeast where Wind Advisories are in place for tomorrow. ByFriday, while the severe threat backs down, there is a Slight Risk forExcessive Rainfall in portions of northern New Hampshire and westernMaine. Gusty winds, as well as widespread showers are anticipated in theGreat Lakes and Mid-Atlantic during the day Friday.In the West, a tranquil weather pattern this afternoon and throughThursday along the West Coast will conclude as the next Pacific stormsystem delivers showers and mountain snow to the Pacific Northwest byThursday night. The storm system dive south along the West Coast and afrontal boundary will set up over the Northern Rockies. This will lead tohit-or-miss showers from the Sierra Nevada and Oregon Cascades on eastthrough most of the northern Rockies Friday afternoon. Temperature-wise,an expansive swath of unusually warm temperatures for mid-April will groweast from the West Coast and the