640 FXUS02 KWBC 210754 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 354 AM EDT Thu May 21 2026 Valid 12Z Sun May 24 2026 - 12Z Thu May 28 2026 ...Heavy rain and thunderstorms expected to continue across eastern Texas into the lower Mississippi River valley... ...General Overview... An active weather pattern will continue to remain in place across the south-central U.S. going into the upcoming weekend and into early next week, with multiple shortwave disturbances and a weak frontal boundary producing multiple rounds of heavy rain and storms. An upper trough over the Great Lakes this weekend should reach northern New England by Monday night, with widespread showers from the Ohio Valley to the Northeast ahead of this feature. Out West, a more amplified level pattern starts to emerge as a stronger upper trough and then closed low enter the Pacific Northwest and enveloping more of the Intermountain West by the middle of the week, and a downstream upper ridge develops over the Ohio Valley and western Great Lakes with above average temperatures. ...Guidance/Predictability Assessment... The 00Z model guidance suite has a good solidified depiction of the amplifying trough across the West late in the period, and forecast confidence has increased in this pattern change evolving, even though the GFS is a little weaker with this trough by next Thursday. Across the southern tier states, the guidance continues to show a weak closed southern stream low over Texas and Oklahoma for the beginning of the forecast period. The NBM is likely too warm with temperatures across the northwestern quadrant of the country going into the Tuesday to Thursday time period, so the WPC forecast reflects a cooler scenario more in line with the latest deterministic guidance, and also a slight increase in QPF across this same general region given better ascent. The ensemble means were increased to about 50% by next Thursday for fronts and pressures. ...Weather/Hazards Highlights... Heavy rain will continue to make weather headlines going into Sunday and Memorial Day from eastern Texas to the Deep South with multiple mesoscale convective systems developing. These will be in response to enhanced ascent from a weak upper trough in the southern stream flow, coupled with a weak front in the region and plenty of moisture and instability. A Slight Risk for excessive rainfall will be valid on Sunday from eastern Texas to western Louisiana, where the potential exists for a few inches of rainfall with the most persistent storms over soils that will be becoming increasingly saturated. The coverage becomes less concentrated going into the Day 5/Monday time period, so a broad Marginal Risk area is valid across much of the South and extending eastward to include portions of southern Virginia. Scattered showers and thunderstorms are likely to develop, and some of these could be locally heavy. More precipitation returns to the Pacific Northwest to start next week with a cold front moving in and a building upper level trough, and this moves inland through the middle of the week. A gradual warming trend can be expected for the Mid-Atlantic and the Northeast to start next week after a few days of cooler weather from cold air damming. Slightly below average temperatures are likely across the Gulf Coast region given the widespread rainfall that is expected. With the upper low developing over the northwestern U.S., a return to colder conditions is also likely here going into Tuesday and Wednesday, with some higher elevation snow likely for portions of the northern Rockies. The greatest positive anomalies will likely be over the northern Plains and Upper Midwest with the upper ridge axis Monday through Wednesday, with readings up to 20 degrees above average. Hamrick 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 $$