603 FXUS02 KWBC 201914 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 314 PM EDT Wed May 20 2026 Valid 12Z Sat May 23 2026 - 12Z Wed May 27 2026 ...Heavy rain and thunderstorms expected to continue across eastern Texas into the lower Mississippi River valley... ...Overview... A slow-moving upper low will track across the south-central U.S. this Memorial Day weekend, while moisture and instability feed into a weak frontal boundary. This will produce widespread showers and thunderstorms for that region, and flooding will be a concern as rain totals pile up. Meanwhile a northern stream upper trough is forecast to push across the north-central U.S., bringing rain to the northeastern quadrant of the U.S. for the weekend and potentially lasting into Monday. A deeper upper trough/low is forecast to arrive in the Northwest early next week, yielding cooler temperatures and precipitation, as well as developing a more amplified pattern as a downstream upper ridge develops across the east-central U.S. by midweek. ...Guidance/Predictability Assessment... Model guidance shows reasonable agreement through the weekend with the primary features of note, including the north-central and south-central upper troughs mentioned above. Typical smaller scale differences could cause sensible weather differences like placement of QPF, but these will likely remain uncertain into the short range. The northern stream trough will shift across southeastern Canada Monday-Tuesday while the southern stream trough erodes during that time. A multi-model blend worked well for the early part of the period. The primary larger scale model variations are with the upper trough moving toward and into the Northwest early to mid-next week. The 00/06Z model guidance suite was rather agreeable with its track and timing of the trough and embedded low. However, the newer 12Z suite has diverged somewhat, with the GFS a bit farther east and the CMC farther southwest by Tuesday-Wednesday. The 12Z ECMWF seems to be located the closest to previous consensus, so would favor that position, which is a good middle ground and in line with the ensemble means. ...Weather/Hazards Highlights... Heavy rain will continue to make weather headlines going into the Memorial Day weekend across much of the south-central U.S. as multiple mesoscale convective systems develop. These will be in response to enhanced ascent from a southern stream upper trough coupled with a weak front in the region and plenty of moisture and instability. Slight Risks for excessive rainfall remain in place for southern/southeastern Texas and western Louisiana on Day 4/Saturday and shifted a bit east on Day 5/Sunday, where the potential exists for several inches of rainfall over this time period over soils that will be becoming increasingly saturated. Another corridor of moderate to heavy rainfall is possible across northern portions of the Mid-Atlantic and southern portions of the Northeast on Saturday, where instability will be limited but moisture anomalies will be high and a frontal system is in place to focus the moisture. A Marginal Risk remains in place for the Day 4 ERO in that corridor, but its position could continue to shift around as model spread persists. Farther south, scattered showers and thunderstorms are likely to develop across the Southeast and Carolinas this weekend into next week. Despite drought conditions, there may be a nonzero chance of flash flooding in these areas where rain rates are high, but will keep this sub-Marginal Risk for now. 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 Sunday and spreading southeast on Monday and Tuesday. Snow is possible at the highest elevations of the Cascades to Rockies. The Four Corners states can also expect increasing rain and thunderstorm chances by Monday. Lingering cloud cover and rainfall with residual cold air damming across portions of the Mid-Atlantic and Northeast should continue to keep temperatures on the cool side on Saturday, with highs running 10-20 degree below average before a gradual moderating trend ensues by early next week. It should also be slightly below average across Texas given the widespread rainfall that is expected through the weekend. With the upper low developing over the northwestern U.S., a return to colder conditions is also likely in that region going into Tuesday and Wednesday. The greatest positive temperature 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. Tate/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 $$