Heat wave focus shifts from the Mid-Atlantic to portions of theSoutheast/Southern Plains by Monday......There's a Slight Risk of Severe Thunderstorms over portions of theNorthern High Plains......Severe storms for portions of the Upper Midwest on Monday......Monsoon-like conditions persist for the Southwest...A broad and well entrenched upper ridge centered over the Southern HighPlains/Southwest will eject shortwave energy across the northern tierstates through the early work week. A low pressure system will slideacross the Northeast and potentially into the Canadian maritimes tonight.Scattered to isolated showers and thunderstorms will focus around anattendant cold front propagating through much of the Northeast andnorthern Mid-Atlantic coast. Remnant moisture from Tropical CycloneAlberto, will bring early monsoon-like conditions to the Southwest andFour Corners region over the next few days. Scattered to isolated showersand thunderstorms will occur with some instances of flash floodingpossible, particularly over slot canyons and favorable terrain. There's aSlight Risk (at least 15%) of Excessive Rainfall leading to Flash Floodingover portions of southeastern Arizona on Monday with Marginal Risks (atleast 5%) persisting through mid-week.Elsewhere, shortwave energy propagating across southern-central Canada andthe northern tier CONUS will influence more thunderstorm activity over theUpper Midwest/Great Lakes beginning Monday afternoon. There's a SlightRisk of Severe Thunderstorms (level 2/5) over parts of the Upper Midwestlate Monday afternoon. Severe/destructive wind gusts are possible forparts of Minnesota into Wisconsin. A cold front at the surface will act asa focus for showers and thunderstorms across portions of the MiddleMississippi Valley and Midwest on Tuesday. There's a Slight Risk of SevereThunderstorms for parts of Iowa/northern Missouri into northern Illinois,southern Wisconsin, southwest Lower Michigan, northern Indiana andnorthwestern Ohio. There's potential for an MCS to move across parts ofWisconsin/Michigan into northern Illinois/Indiana Tuesday morning, theoutflows of which should set the stage for afternoon evening convection totake place after diurnal heating occurs. There's also a targeted SlightRisk of Excessive Rainfall over parts of eastern Iowa, southern Wisconsinand northern Illinois, where storms yielding high rain rates could causeflash flooding.A mid-level trough moving off into the Atlantic will promote widespreadrecord warm low temperatures across the Northeast/Mid-Atlantic Coasttonight. Lows in the 70s will be of particular concern to those withoutadequate cooling or hydration. Heat Advisories are in effect for much ofthe aforementioned areas. Upper ridging centered over the Southern HighPlains will produce warmer than average temperatures across the West andCentral U.S. this week. Troughing over the northern tier will keeptemperatures at or below average for parts of the Upper Midwest/GreatLakes.