179 FXUS02 KWBC 191945 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EDT Tue May 19 2026 Valid 12Z Fri May 22 2026 - 12Z Tue May 26 2026 ...Multiple days of heavy rainfall expected for the south-central U.S. through early next week... ...Overview... Southern stream energy is forecast to move across the Southwest Friday and slowly across the southern Plains this weekend and early next week, bringing multiple rounds of showers and thunderstorms to the region, potentially leading to flooding concerns. Meanwhile a northern stream upper trough crossing the northern Plains and Upper Midwest will push a frontal system through those regions into the East, producing ample rain chances there as well. Then by early next week, a stronger trough is forecast to arrive in the Northwest, yielding cooler temperatures and precipitation. ...Guidance/Predictability Assessment... Model guidance shows reasonable agreement through the weekend with the primary features of note, including the north-central and southwest to 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 primary larger scale model variations are with the trough moving toward and into the Northwest early next week. The EC/CMC/AIFS and even the AIGFS and AIGEFS generally show a slower track of the trough and potential embedded upper low compared to the fast GFS runs. Continue to favor the larger consensus rather than the progressive GFS. Note that the 12Z ECMWF and CMC came in with around the same timing for the upper trough/low Monday-Tuesday, but centered slightly north of their 00Z runs, which may affect the southern extent of cooler temperatures and rain. Thus the early medium range forecast period used a multi-model blend favoring the ECMWF and GFS for mass fields. As the period progressed, lessened the proportion of the GFS and increased the EC ensemble mean and AIFS. ...Weather/Hazards Highlights... Multiple days of heavy rainfall are likely across the south- central U.S. as upper-level energy provides lift atop a warm and unstable airmass. Widespread thunderstorms and mesoscale convective systems are possible and will likely peak this weekend across eastern Texas into the Lower Mississippi Valley. Farther north and east, moisture will be drawn ahead of the north-central U.S. trough and spread across much of the Plains and Mississippi Valley to the East Coast on Friday, with potential heavier amounts in the Mid- South to Ohio Valley and Pennsylvania where a frontal system could focus rain. Instability is lesser farther north, but moisture anomalies are still above average. The Midwest should gradually dry over the weekend, but rain chances are likely to persist across the Ohio Valley and East into early next week. Due to these features, the Day 4/Friday ERO features a Marginal Risk from the Gulf Coast through the Mid-South and parts of the Ohio Valley into Pennsylvania, with another Marginal centered over Oklahoma where an MCS is likely and SPC also shows a severe threat. Then Day 5/Saturday, a Slight Risk is in place for southeast Texas into Louisiana given the increasing rainfall totals likely by then. A Marginal Risk surrounds the Slight while there is also another Marginal Risk in the northern Mid-Atlantic and parts of the Northeast, where recent models favor heavier rain, but this Marginal looks especially prone to shifting around given the amounts of model spread. Troughing moving into the Northwest early next week will allow for increased precipitation reaching the Pacific Northwest Sunday and spreading east on Monday. 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. In terms of temperatures, a cold air damming type event will likely become established east of the Appalachians with overcast skies and periods of mainly light rain at times to close out the week, yielding cooler than average highs in the Mid-Atlantic and southern parts of the Northeast into the weekend. Meanwhile, relatively cool conditions across the central/northern Plains are expected to gradually warm to above average through the forecast period. The West should see warmer than average temperatures through the weekend, but should cool west to east into Monday- Tuesday underneath the trough. Tate 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 $$