Heavy rain, significant flooding, and severe weather concerns remainacross parts of eastern Texas and the southern Plains through theweekend...Heavy mountain snow and gusty winds to enter much of the West, GreatBasin, and Rockies over the next few days...Below average temperatures and showers impact the Mid-Atlantic andNortheast into the end of the weekend...Slow-moving thunderstorms containing intense rainfall rates are ongoingthis afternoon throughout parts of southeastern Texas just north of theHouston metro area, which are leading to a continuing threat of flashflooding. Ongoing significant to catastrophic flooding throughout parts ofeastern Texas from prior heavy rain will only exacerbate the flash, urban,and river flooding threat from additional rainfall into this evening.Newly formed thunderstorms developing off a southern High Plains drylinecould lead to isolated to scattered flash flooding across central Texas aswell tonight, but the main hazard associated with these storms areforecast to be associated with giant hail, damaging wind gusts, and a fewtornadoes. Farther north, a potent cold front exiting the central HighPlains and progressing into the mid-Mississippi Valley by Saturday is alsoexpected to spark a line of showers and thunderstorms capable of producingheavy rain and severe thunderstorms, mainly throughout parts of Kansas andNebraska.By this weekend, the aforementioned cold front is expected to continueprogressing eastward through the Midwest and Ohio Valley. The tail end ofof this frontal boundary reaching westward to the southern Plains will bethe focus for additional thunderstorm activity and the potential for flashflooding. A Slight Risk (level 2/4) of Excessive Rainfall has been issuedfor central and north-central Texas on Saturday, with the threat areashifting east on Sunday, extending from eastern Texas to southwestMissouri and far southeast Kansas. Additionally, severe thunderstorms arepossible, with the greatest risk anticipated on Saturday in the PermianBasin of West Texas. Several storms may produce large to giant hail and acouple strong tornadoes.An anomalously strong upper-level low entering northern California onSaturday night is forecast to spread moderate to heavy precipitation andgusty winds into the western U.S. and Great Basin this weekend. Heavymountain snow in the Sierra Nevada and Oregon Cascades is likely to add upto over a foot (mainly above 6000 feet) on Saturday. As the systemcontinues to swing eastward, gusty southerly winds up to 60 to 80s mph arepossible in the central Great Basin and the Sierra Nevada, where High WindWarnings have been issued. The associated precipiation and gusty windswill shift eastward as the upper-level low crosses the Intermountain Weston Sunday. Residents and visitors through are advised to check localconditions before traveling, especially throughout exposed elevatedroadways.Showers are also expected to dampen the first weekend in May throughoutmuch of the Great Lakes and eastern United States. Most precipitationshould remain scattered, with thunderstorm chances in the Southeast, Ohioand Tennessee valleys. A backdoor cold front sinking through theMid-Atlantic today will allow for additional shower activity and belowaverage temperatures this weekend. Highs are only expected to reach the50s and 60s as cloud cover and cool air streaming off the Atlantic keeptemperatures 10 to 20 degrees below average between the Mid-Atlantic andNew England when compared to climatology for the dates.