957 FXUS02 KWBC 140738 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 338 AM EDT Thu May 14 2026 Valid 12Z Sun May 17 2026 - 12Z Thu May 21 2026 ...Central U.S. Heavy Rainfall/Runoff and Severe Weather Threat... ...Guidance/Predictability Assessment... Guidance continues to show a similar larger scale flow pattern evolution over our fine nation in transition from near zonal into this weekend to a more amplified solution all next week. There's significant uncertainty as to the timing and amplitude of certain embedded shortwaves within the broader digging trough in the West next week and downstream ejection. However, there's consensus on a broad diffluent pattern setting up over the Central U.S., which will support severe storms and heavy rain potential. There's also a strong signal for an strong upper ridge to set up over the East. The WPC medium range product suite was primarily derived from a composite blend of GFS/ECMWF/Canadian models and ensemble means along with the National Blend of Models in an effort to mitigate system variances as consistent with individual predictability. WPC product continuity is well maintained in this manner. ...Weather/Hazards Highlights... Energetic upper trough/deepened surface low ejection over eastern Canada will lay down a trailing front with from the north-central U.S to the Northeast this weekend. Multiple shortwave impulse passages, favorable right entrance region upper jet lift and moisture/instability focus into the Upper Midwest portion of this front may support emerging convective development and potential for local training has prompted an WPC Excessive Rainfall Outlook Marginal Risk areas valid for Day 4/Sunday and Day 5/Monday, with the latter more expansive area stretching from the Upper Midwest to the southern Plains favorable convective pattern uptick/growth. Farther upstream system energies subsequently work into the West and downstream up across the central U.S. with less certainty this weekend into next week in amplifying flow. Passage may yield enhanced weekend winds and wildfire threat potential across the southern Rockies/high plains. There is also then an increasing signal that ample Plains cyclogenesis/frontogenesis, upper jet support and growing lead Gulf return flow will further set the stage to fuel an expanding central U.S. convective rainfall/runoff and severe weather threat pattern to monitor as indicated by SPC. Meanwhile, an eastward spreading upper ridge will spread well above normal pre-frontal temperatures across the Central to Eastern U.S. downstream this period that may support some local high temperature values. To the south, low level onshore flow will bring showers into Florida in proximity to upper low development near/east of the Bahamas. Schichtel 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 $$