Flash flooding possible for parts of the Upper Midwest, along withsevere weather...Burgeoning heat wave for the Great Lakes into the Ohio Valley andNortheast starting Monday and continuing through the week...Heavy rain and flash flooding possible for the central and northwestGulf Coast through Tuesday...Late-season wet snow for the northern Rockies Monday and Tuesday...A very active pattern is in store for the Lower 48 this week which willfeature a variety of weather hazards: Heavy rain and flash flooding: two areas are noted for the potentialfor flash flooding/heavy rain along with severe weather. The first overthe Upper Midwest as multiple rounds of heavy rain push through theDakotas into Minnesota, where there is a Moderate Risk of excessiverainfall (central MN) and a Slight Risk of severe weather (per SPC) onMonday (Nebraska northward to MN). The second will be near the Gulf ofMexico. Tropical moisture will surge northward and westward from southernLouisiana westward into Texas through Tuesday (and into Wednesday),including in and around the Houston metro area. In addition, the NationalHurricane Center is monitoring the southwestern Gulf of Mexico forpossible future tropical development over the next few days. Rising temperatures over the northeastern 1/4 of the CONUS willapproach and exceed record highs (including record warm overnight lows)over the Midwest/Great Lakes into the Northeast Mon/Tue (and beyond). Hightemperatures will climb well into the 90s for many areas, with upper 90spossible in the lower elevations in the East on Tuesday. Overnight lowsmay only drop into the upper 60s to mid 70s, offering little relief fromthe heat. The experimental HeatRisk outlooks shows Major to Extreme levelsfor many areas, owing to the duration of the upcoming heat wave. This isin stark contrast to the record cool temperatures Sunday morning overparts of the Northeast. Cool and snowy conditions will be impacting parts of the NorthernRockies over the next couple of days as a broader upper trough movesthrough the West. Temperatures will be well below normal for mid-June, andeven near record cold for the date. The snow will be limited to higherelevations in Montana (especially above 7000ft), but accumulating snow islikely even down to 5000ft or so. This heavy and wet snow may cause sometree damage and power outages, and will likely make travel difficultacross some of the passes. Hot/dry/breezy conditions over parts of the Southwest will result in ahigh fire danger over the next day or so, especially over northeasternArizona, southeastern Utah, and into western New Mexico. Critical fireconditions are forecast for these regions per SPC, with a broader Elevatedrisk for much of the Four Corners and even into the Sacramento/San JoaquinValley on Monday.