The active spring pattern continues across much of the Plains into theGreat Lakes/Ohio Valley......Severe weather threat Monday afternoon into Monday night from theCentral to Southern Plains into the Lower Missouri Valley, spreading intothe Ohio Valley Tuesday......Heavy rains and flooding possible across portions of the Northern HighPlains and eastern portions of the Central to Southern Plains......Elevated to Critical Fire weather conditions across the Southern HighPlains......Late season heavy snows for the Northern Rockies......Much below average temperatures expected across the Great Basin,Central to Northern Rockies, while above average temperatures are forecastacross much of the Plains to the east coast...There is no let up in sight for the active Spring time weather patternacross large portions of the nation.  The next strong frontal boundary isforecast to push into much of the Plains tonight and into the UpperMississippi Valley, Great Lakes and Ohio Valley regions on Tuesday. Thunderstorm activity currently beginning to develop across portions ofthe Central Plains is expected to continue strengthen and expand acrossportions of the Central to Southern Plains late this afternoon into Mondaynight and spread eastward into the Lower Missouri Valley by early Tuesday. There is a moderate to high risk of severe weather across portions of theCentral to Southern Plains with large hail, high winds and tornadoespossible.  Along with the severe weather threat, heavy rains are alsolikely across eastern portions of the Central to Southern Plains from fromthe eastern Dakotas, south through southwest Minnesota, much of Iowa,western Missouri, eastern Nebraska, eastern Kansas and northeast Oklahoma. Across these areas the expected heavy rains may lead to areas of flashand river flooding.  Heavy rains and flooding also possible acrossportions of the Northern High Plains from eastern Montana into farnortheast Wyoming.  This next batch of heavy rains will be falling well tothe north of portions of Texas that have seen very heavy amounts over thepast week. The heavy rain, flooding and severe weather threat will be pushing fartherto the east during Tuesday with areas from the Ohio Valley, northward intothe Great Lakes having the potential for highly impactful weather.  Thisimpactful weather will likely continue across the Ohio Valley region onWednesday and expand into the Tennessee Valley and Mid to LowerMississippi Valley as addition heavy rains, severe storms and floodingdevelop ahead of the next strong system to push into the MississippiValley by mid week.No precipitation is expected over the next few days across the SouthernHigh Plains.  This along with lower relative humidities and windyconditions will support an elevated to critical fire weather threat overthe next several days from southeast Colorado, the Texas/OklahomaPanhandle region, south through much of New Mexico and far West toSouthwest Texas.  Red Flag warnings are currently in effect across thesearea for the extended period of fire weather danger.