Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Fri Aug 23 2024 Valid 12Z Fri Aug 23 2024 - 12Z Sun Aug 25 2024 ...Monsoonal thunderstorms could lead to excessive rainfall for much of the Four Corners region today and into the weekend... ...Record heat begins to relent over the Southern Plains this weekend but near record cool in the eastern U.S. and California... ...Critical Fire Risk and Red Flag Warnings in effect across much of the Great Basin... An anomalously amplified weather pattern across North America will continue to bring sharply contrasting weather conditions across the U.S. as we head into the weekend. This weather pattern will feature a warm upper high over the southern Plains sandwiched in between two deep and cold upper lows/troughs on either side of the West and East Coasts. A deep and unstable southwesterly flow between the ridge and the upper low near the Pacific Northwest will support monsoonal showers and thunderstorms across the Four Corners region through the next few days, especially early this morning when severe thunderstorms are advancing farther downstream into the central Plains. Slot canyons and burn scars are particularly vulnerable to flash flooding. The flash flooding threat dwindles a bit heading into the weekend as the upper-ridge shifts slightly eastward and the main energy associated with the upper low will be directed farther north toward the northern High Plains where a new low pressure system is forecast to form by Saturday night. Meanwhile, critical fire weather danger is forecast for the Great Basin under gusty and dry conditions behind a cold front. The large upper low dipping into the Pacific Northwest will continue to provide very cool and damp conditions into the West Coast today. In fact, record cool high temperatures can be found today across California. The anomalous cool conditions will penetrate farther inland during the weekend, overspreading much of the western U.S. by Sunday morning. In contrast, another afternoon of record high temperatures are forecast for portions of Texas into Oklahoma under the warm upper high where 110s are possible in portions of Texas Panhandle into nearby Oklahoma. This heatwave is showing signs of relenting by this weekend as the cool air from the western U.S. upper trough begins to erode the upper ridge. However, heat indices are forecast to reach into the upper 90s to the mid 100s during the weekend while the heat begins to spread northward into the central Plains. Meanwhile, very cool and pleasant weather for August will continue to prevail across much of the eastern U.S. under the cool upper trough together with a cool high pressure system at the surface. In fact, record cool temperatures are possible this morning across portions of the Mid-Atlantic, central Appalachians, and interior Southeast with temperatures dipping as cold as the 40s. A gradual warming trend is expected through the weekend for the eastern half of the country as the high pressure system begins to slide off the East Coast. Kong Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php