Monsoon-like conditions persist for the Four Corners Region......There is an Enhanced Risk of Severe Thunderstorms across portions ofthe Northern/Central Plains on Thursday...An upper-level trough will move into the Canadian Maritimes, while anupper low glides across the Northwest and an upper ridge expands acrossthe southern tier of the country late this week. Scattered thunderstormactivity is forecast to develop along a surface front extending from theNortheast/Ohio Valley down to the Lower Mississippi Valley and back upinto the Great Plains. The Storm Prediction Center issued Slight Risks ofSevere Thunderstorms for portions of the; Ohio Valley, Northeast andMid-Atlantic; ArkLaTex and Lower Mississippi Valley; and theCentral/Southern High Plains tonight. Damaging winds will be the mainconcern in the Northeast while hail and gusty/damaging winds may causeissues in the High Plains. Some storms in the Ohio Valley could producehigh enough rain rates to generate flash flooding tonight. Thus, there's aSlight Risk (at least 15%) of Excessive Rainfall for portions of thefavored terrain of the Central Appalachians, eastern Ohio, westernPennsylvania and northwestern Ohio. Monsoonal moisture will continueflowing into the Four Corners region tonight with mid-level energy aloftenhancing potential for thunderstorms and heavy rainfall. There's a SlightRisk (at least 15%) of Excessive Rainfall leading to Flash Flooding forportions of northeastern Arizona and much of New Mexico, as a result.The focus for Severe Weather and Flash Flooding shift into the GreatPlains and Mississippi Valley on Thursday. The once stationary frontdraped over the Great Plains will turn warm and move into the NorthernPlains. A deepening surface low pressure system beneath a potentupper-level low will promote scattered thunderstorm activity across theNorthern/Central Plains throughout the day. Storms should pick up inintensity by Thursday afternoon/evening. SPC issued an Enhanced Risk(level 3/5) of Severe Thunderstorms across portions of eastern Montana,western Dakotas, northeastern Wyoming, western Nebraska and northeastColorado, where wind gusts exceeding 80 mph, large hail greater than 2.5inches and a couple of tornadoes will be possible. There's isolatedpotential for Excessive Rainfall over parts of the Northern Plains andLower Missouri Valley where Slight Risks are in effect. Monsoon conditionsare expected to continue over the Four Corners with a Slight Risk ofExcessive Rainfall in effect for portions of western Colorado down intonorthwestern/central New Mexico. Some slow moving pieces of mid-levelenergy will slowly make its way across the Carolina coast and promoteSevere Storm potential early Thursday evening.Diffluent energy associated with the upper-level low moving through theNorthern Plains will help advance the strong surface low pressure systeminto the Mississippi Valley on Friday. A rising warm front out of thesouth will promote additional thunderstorm activity across theUpper/Middle Mississippi Valley. Excessive Rainfall and SevereThunderstorm chances pick up over parts of the aforementioned areas Fridayevening. Temperatures remain below average across the South while belowaverage conditions expand over the Northern Plains behind the cold frontthis weekend.