Northern New England remains the best location for clear viewing of thetotal solar eclipse this afternoon......Lingering wet snow across the Northern Plains expected to taper offlater today while locally moderate rain moves across the Upper Midwest......Heavy rain, flash flooding and severe weather threat emerging acrossthe Southern Plains to the lower Mississippi Valley on Tuesday......Critical fire danger shifts southward into western Texas by Tuesday...As the long-anticipated total solar eclipse scheduled to take place thisafternoon, the weather pattern across the U.S. is entering a transitionperiod from one that consists of a winter storm across the North to heavyrain and severe thunderstorms across the South.  The low pressure systemthat has brought snow, high winds, and severe weather to various locationsacross the northern and central U.S. will continue to weaken and tracknortheast across the upper Midwest today, and then move into southernCanada on Tuesday.  Lingering wet snow across the Northern Plains isexpected to taper off later today while locally moderate rain moves acrossthe Upper Midwest.Monday morning will feature showers and embedded thunderstorms across theGreat Lakes down into the Ohio Valley, Tennessee Valley and the lowerMississippi Valley well in advance of the low pressure system and near thetrailing cold front.  Meanwhile, moisture from the Gulf of Mexico isbeginning to return to the western Gulf states.  Southern Texas willlikely wake up to fair conditions this morning but will likely followed bya rapid untimely increase of clouds this morning into the afternoon priorto the arrival of the solar eclipse.  In contrast, northern New Englandremains to be the region where cloud cover will likely be minimized alongthe path of totality this afternoon as the nor'easter moves farther outinto the Atlantic.  It appears that other locations in between will have afair chance of cloud covers at various levels, although locations acrossArkansas to the Midwest could see breaks in the clouds or high thin clouds during the time of totality.  Monday night into Tuesday will likely see the threat of heavy rainblossoming across the South from eastern Texas/eastern Oklahoma expandingeastward into the lower Mississippi Valley in response to a potent uppertrough approaching from the southern Rockies that will interact with theinflux of Gulf moisture.  A few inches of rain will likely be common fromnorthern Louisiana into southern Arkansas through Wednesday morning withthis setup.  In addition, severe thunderstorms are also expected todevelop within the heavy rain area from Tuesday morning onward intoWednesday morning when a low pressure system is forecast to develop overTexas.  The heaviest rains and severe storms should begin to head farthereast by Wednesday morning into the Mid-South as the low pressure systemintensifies and tracks toward the east-northeast.