Severe thunderstorms and flash flooding possible across portions of thecentral Plains and Midwest today......Unsettled weather with the potential for heavy rain and strong stormsenter the Lower Great Lakes and Upper Ohio Valley on Saturday......Dangerously hot conditions will continue from parts of the southernPlains to the Southeast this weekend...A low pressure system is pushing across the northern and central Plainsthis afternoon. The low pressure center is moving east along theU.S.-Canada border with a trailing cold front extending south and westfrom the Upper Mississippi Valley through the Central Plains and a warmfront lifting north across the Midwest ahead of the system. Conditionswill be favorable for scattered severe thunderstorms to develop throughthis evening, and potential storm hazards may include large hail, damagingwinds, and a couple of tornadoes. Strong storms may also produce locallyheavy rainfall that could lead to instances of flash flooding,particularly in areas where soils are saturated from recent heavy rainsand areas where training/repeating storms develop.  The low pressure system will track eastwards on Saturday, slowly movingacross the Upper Great Lakes region, with the trailing cold frontextending back through the Ohio and Middle Mississippi Valleys to thecentral Plains and southern Rockies and with the leading warm frontlifting across the Mid-Atlantic into the Northeast. Shower andthunderstorm chances will shift east with the system, and some storms maybecome severe on Saturday. The main storm hazards will include scattereddamaging winds, a couple of tornadoes, and locally heavy downpours. Due tothe slow moving nature of the showers and storms, isolated to scatteredinstances of flash flooding will be possible along the entire length ofthe cold front.On Sunday, the system will gain a bit more momentum, and the central lowwill push into southeastern Canada while the trailing cold front movestowards the East Coast. Meanwhile, another low pressure system willdevelop over the Pacific Northwest/southern Canada, which will bringprecipitation chances back to the Pacific Northwest on Sunday that willspread into the northern and central Plains on Monday.Dangerous heat will continue to be a major weather story through the lastcouple days of June as an upper level ridge strengthens over thesouth-central U.S. and the Southeast. This will lead to above averagetemperatures impacting areas from the central/southern Plains to theSoutheast, with summer heat also building across the Southwest andnorthern High Plains by Sunday. High temperatures are forecast to reachthe upper 90s and low 100s in the southern Plains and Lower MississippiValley today, where Excessive Heat Warnings and Heat Advisories are ineffect. Scattered afternoon thunderstorms may keep the sizzling heat atbay across the Southeast, but highs into the mid-90s can still be expectedthis weekend. If spending time outdoors be sure to follow proper heatsafety by taking frequent breaks, staying hydrated, and checking onneighbors.