Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 304 PM EDT Wed Aug 21 2024 Valid 00Z Thu Aug 22 2024 - 00Z Sat Aug 24 2024 ...Record heat continues into the end of the week across the Southern Plains... ...Record cold develops across California Friday into Saturday... ...Active monsoonal showers for the Southwest into the Southern Rockies... ...Showery weather on tap for Florida into the coastal Southeast and across northern New England... The mid to upper level flow is expected to remain highly amplified across the Lower 48 over the next two days, comprised of a deep upper low moving slowly across New England into the Canadian Maritimes, another strong closed low dropping south along the Pacific Northwest coast and the seemingly ever present closed upper high across the Southern Plains. This mid to upper level pattern will be setting the stage for some big temperatures contrasts across the CONUS over the next few days. The persistent closed upper high over the Southern Plains will keep the dangerous heatwave going across the Southern Plains as the week ends the weekend begins. The recent batch of record high temperatures over the Southern Plains will continue over the next two days with numerous record highs possible from southeast New Mexico into large portions of Texas. High temperatures across this region will be in the 100 to 110 degree range producing widespread areas that will experience major to extreme heat risks over the next two days. Excessive Heat warnings and heat advisories are currently in effect across large portions of the Southern Plains, affecting nearly 25 million people. In contrast to the heat, both the eastern U.S. and western U.S. will see below average temperatures over the next two days. For the east, an area of high pressure will stretch from the Mississippi Valley to much of the eastern seaboard, except for the coastal Southeast and Florida and northern New England. This will produce below average temperatures and dry conditions, although temperatures will begin to moderate back toward seasonal norms by this weekend. The exceptions to the dry weather across the eastern half of the nation will be across Florida into the coastal Southeast and over northern New England. A stationary front is expected to lie across north central Florida through the end of this week and into this weekend, supporting showery conditions for Florida into the coastal Southeast. Showery conditions also likely across northern New England near the aforementioned strong closed upper low moving slowly eastward across this region over the next two days. While the below average temperatures will be waning across the east over the next few days, the magnitude of below average temperatures will be increasing across much of the west to the west of the Rockies. This is in association with the above mentioned strong closed low moving southward along the Pacific Northwest coast. This closed low will help push a strong cold front inland from the eastern Pacific into the Pacific Northwest on Thursday-Friday and southward into California and the Great Basin Friday and Saturday. Much below average temperatures likely across these areas Thursday, Friday and continuing into this weekend. There is the potential for record cold afternoon high temperatures across large portions of California on Friday, continuing into Saturday. Between the Pacific Northwest closed upper low and the closed upper high over the Southern Plains, above average monsoonal moisture values will be transported northeastward between these two circulations, bringing the potential for widespread scattered monsoonal shower and thunderstorms for portions of the Southwest, Great Basin and Southern Rockies. Locally heavy rains across these areas will also pose the risk of flash floods, especially in areas of steep terrain and in slot canyon regions. Oravec Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php