764 FXUS02 KWBC 130759 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 359 AM EDT Wed May 13 2026 Valid 12Z Sat May 16 2026 - 12Z Wed May 20 2026 ...Central U.S. Heavy Rainfall/Runoff and Severe Weather Threat... ...Guidance/Predictability Assessment... Guidance forecast clustering remains good valid for this weekend into Monday, bolstering confidence in a GFS/ECMWF/UKMET/Canadian model composite blend that seems well supported by ensembles in this timeframe. Model forecast clustering steadily increases across longer time frames as varied upstream systems/energies work into the western to central U.S., but a generally more compatible GEFS/ECMWF/Canadian ensemble means composite seems to provide a decent forecast basis, but possibly not quite amplified enough given guidance pattern trends. This has been adjusted manually and WPC product continuity is decent despite these uncertainties. ...Weather/Hazards Highlights... Energetic upper trough/deepened surface low ejection over south- central then eastern Canada will lay down a trailing front with from the north-central U.S to the Northeast. Impulses, 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 despite detail uncertainty prompted the introduction of WPC Excessive Rainfall Outlook Marginal Risk areas valid for Day4/Saturday and Day 5/Sunday. 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 Plains cyclogenesis/frontogenesis, upper jet support and growing lead Gulf return flow may 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 shower 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 $$