159 FXUS02 KWBC 221943 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 343 PM EDT Fri May 22 2026 Valid 12Z Mon May 25 2026 - 12Z Fri May 29 2026 ...Heavy rain and thunderstorms expected to continue across much of the Southern U.S... ...Overview... A couple of southern stream upper troughs will pass through the southwestern and south-central U.S. next week, providing lift for widespread rain and thunderstorms in a moist and unstable environment. The heaviest rain should generally affect the Lower Mississippi Valley and Southeast into Memorial Day, and potentially get renewed in Texas and vicinity into the workweek over areas that will already have wet antecedent conditions. Out West, a more amplified pattern starts to emerge as a stronger upper trough likely becoming a closed low enters the Pacific Northwest and envelops more of the Intermountain West by mid to late week, yielding cooler temperatures and precipitation. An upper ridge should develop downstream in the east-central U.S., reaching into the Upper Midwest/Great Lakes and bringing above average temperatures. ...Guidance/Predictability Assessment... The latest models and guidance show good agreement on the overall pattern evolution through the period, which should gradually trend more and more amplified through next week. GFS and GEFS runs from today (Friday) have fortunately caught back onto a solution of showing a deeper and slower upper low moving across the West like the non-NCEP guidance has shown, unlike yesterday's GFS/GEFS runs. There remains some minor spread with just how far south the low will get, with the 12Z CMC the farthest south by late week while other guidance has the low centroid farther north. There is good agreement for upper ridging downstream, oriented from the Southeast northwestward into the Midwest, as southern stream energy cuts into it in the south-central U.S., with typical model differences in the details. Meanwhile, there is some uncertainty by Thursday and Friday with a potential upper low retrograding into the Northeast and the potential for multiple waves of troughing. The details are yet to be determined but will continue to be monitored as it does affect sensible weather for temperatures and QPF. A multi-model blend worked well for the medium range forecast early on. As the week progressed, used more of the ensemble means for the fronts/pressures to mitigate individual model differences, with the means reaching about half by Day 7. ...Weather/Hazards Highlights... On Monday, northern stream troughing over the Northeast and southern stream troughing over the southern Plains/Lower Mississippi Valley will allow for a large swath of rain and thunderstorms through the south-central U.S. stretching across the East. Areas farther south should see heavier rain in a more unstable environment, so a Marginal Risk remains in place in the Day 4/Monday ERO from eastern Texas through much of the Mid-South and Southeast for potential flash flooding from heavy rain rates. Additionally, the next southern stream upper low moving across the Southwest will help spark convection in the Four Corners region, especially New Mexico, on Monday. These storms should have good dynamical lift but less instability and faster movement than would likely cause flooding issues, so will keep this area out of a Marginal Risk. As the southern stream upper low moves east, this should renew convection with heavy rain potential in Texas and vicinity, and maintain rain/storm chances farther east. A broad Marginal Risk is also in place for Day 5/Tuesday. It is possible embedded Slight Risks may be needed as models converge on better potential for where heavy rainfall may occur. This is especially true for parts of Texas and vicinity (Tuesday and beyond) where recent rains and short term rainfall has lead to rather saturated grounds. The wet pattern looks to remain in place across the southeast quadrant of the country through the rest of the week as the overall pattern aloft stagnates. Upper troughing moving into the Northwest early next week and a frontal system ahead of it will allow for increased precipitation reaching the Pacific Northwest and spreading south and eastward with time through the week. Snow is possible at the highest elevations of the Cascades to Rockies. With a deepening trough over the West, temperatures should trend cooler in this region through about Wednesday, with some moderating back towards normal as the trough weakens and drifts. The upper ridge to its east will allow for warmer than average temperatures across the north-central U.S. through much of next week, with daytime highs 10-20 degrees above normal, especially for the early part of the week. Tate/Santorelli Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$