Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 AM EDT Fri May 20 2022 Valid 12Z Mon May 23 2022 - 12Z Fri May 27 2022 ...Heavy rain and strong storms from Texas to the Ohio Valley and Great Lakes early-mid next week... ...Weather Pattern Overview... A cold front is forecast to exit the East Coast by early Monday after a hot weekend for much of the eastern U.S., with a cooler and more comfortable airmass settling in behind it for early in the week. Meanwhile, a rather active weather pattern is expected to develop across the continental U.S. going into next week, as multiple waves of low pressure develop along a frontal boundary situated over the Plains and extending to the Great Lakes. This will be in response to a building upper level trough over the western High Plains that will slowly move eastward through the week. ...Guidance Evaluation/Preferences... The 00Z model guidance suite is in decent synoptic scale agreement for the beginning of next week, with differences becoming more apparent by Wednesday as the trough amplifies over the Plains. The past few runs of the GFS have been slower and stronger with the trough over the south-central U.S. and developing a closed upper low, whereas the CMC/ECMWF and many of the ensemble members were more progressive and had the trough axis reaching the East Coast by the end of the week. It is interesting to note that the 00Z CMC trended more towards the GFS for this trough, with overall forecast confidence for the Thursday-Friday time period limited and thus subject to potential noteworthy changes in future forecasts. There is also a good model signal for an amplifying trough in the general vicinity of the Pacific Northwest by next Friday. The WPC fronts/pressures forecast was primarily derived from a multi-deterministic model consensus through Tuesday, and then incorporated more of the 12Z CMC/ECMWF and increased use of the ensemble means for the Wednesday-Friday time period. ...Sensible Weather/Threat Highlights... Temperatures behind the cold front exiting the East Coast next week should return to near seasonal levels after a potentially record setting early season heatwave. Low pressure forming along the trailing front as it meanders near the Southeast Coast may continue a moderate to heavy rainfall threat into Monday as well for parts of the Carolinas and the southern Appalachians. The next system developing over the south-central U.S. into early-mid next week is expected to become the main weather headline of this forecast period. There will likely be widespread convection and heavy rainfall from Texas to the Ohio Valley with moist return flow into another slow moving and wavy frontal system. There is the potential for some flash flooding with the slower moving storms within a very moist and unstable atmosphere. The latest WPC experimental Excessive Rainfall Outlook indicates a Slight Risk area for Monday into Tuesday morning across portions of central Texas, and this could be expanded in later forecasts, and the potential exists for additional heavy rain going into Tuesday and Wednesday across the Mississippi River Valley, albeit with greater uncertainty in placement of MCS activity. Some severe storms are certainly within the realm of possibility for these same general areas. The western-central U.S. trough should keep temperatures below normal across Rockies and Plains through at least Tuesday. Much of the Western U.S. should remain mainly dry through the middle of next week as upper ridging builds over the region and warmer temperatures expand across the region, with the exception of some showers entering the Pacific Northwest by Friday. This may lead to an excessive heat episode over interior California and the Desert Southwest for the end of the week. 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, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices 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