Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 420 PM EDT Wed May 18 2022 Valid 00Z Thu May 19 2022 - 00Z Sat May 21 2022 ...Low pressure system will spread showers/thunderstorms across the Northeast and Mid-Atlantic with more severe storms to follow over the upper Midwest next couple of days... ...Early-season heat continues in southern/central Plains while heat begins to build and expand up the East Coast... ...Cold air surges into the West on Thursday followed by snow down into the central Rockies/High Plains by Friday... ...Critical fire danger continues over portions of the Southwest into the central/southern Plains... An increasingly active weather pattern is in store through the next couple of days as a deep low pressure system pushes onshore over southwestern Canada followed by a strong surge of cold air through the western U.S. Precipitation associated with the low pressure system will continue to spread into the Pacific Northwest and reach into the northern Rockies in the form of showers and a few thunderstorms across coastal Washington/Oregon and snow over the higher elevations. This system is forecast to be re-invigorated over the northern Plains and into the Canadian Prairies on Thursday, with showers and thunderstorms expanding across the region, some of which are expected to be heavy and reach severe criteria. By Thursday night, additional energy arriving from a cold upper trough in the western U.S. will trigger another round of showers and a decent chance of severe thunderstorms, mostly likely across the upper Midwest as a low pressure wave intensifies along a front. The front is forecast to stall on Friday, keeping the best chances of showers and storms from across Missouri through the Midwest and into the Great Lakes. Behind the low pressure system, a strong surge of cold air is forecast to sweep through much of the western U.S. for the next couple of days. In addition to the arrival of much colder air, dynamic interactions with the associated upper trough will bring an episode of mountain snows down the northern and central Rockies as well as the nearby foothills/High Plains. The most notable location will be over Colorado where near record high temperatures in the 90's on Thursday will be followed by a drastic cool down and the development of wintry precipitation on Friday. Meanwhile, showers and thunderstorms will be focused around and ahead of a low pressure system moving through the Ohio Valley and into the Mid-Atlantic by tonight. Localized heavy rainfall leading to flash flooding is possible over much of Kentucky, where a Slight Risk of excessive rainfall is in effect. Some thunderstorms may turn severe, especially over west-central Kentucky where a Slight Risk of severe thunderstorms is in effect. Upper-level ridging will continue a trend of record warmth in the central/southern Plains over the next couple of days. High temperatures in the 90s and 100s will be 20-30 degrees above average for many parts of north-central Texas, Oklahoma and the central Plains through Thursday. These temperatures will either tie or break many existing records for the day. There will be little respite for parts of north-central Texas and central Oklahoma in the evenings as lows are forecast to remain in the 70s over the next couple of days. A retrograding ridge will jut into the Southeast from the western Atlantic late Thursday into Friday leading the East Coast to experience a significant warm up heading into the weekend. Much of the West will be warmer than normal today and Thursday, as well. Strong winds will overlap a very dry airmass over the Southwest leading to a Critical Risk of fire weather for much of the Four-corners region into Friday. On the other hand, an intense surge of cold air will engulf much of the western U.S. and reach into much of the northern and central Plains by Friday, along with the development of a late-season winter weather event over Colorado. Kong/Kebede Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php