Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 AM EDT Sat Jun 01 2019 Valid 12Z Tue Jun 04 2019 - 12Z Sat Jun 08 2019 ...Heavy Rainfall Threat from South-Central Plains to the Mid-Lower Mississippi Valley, Tennessee Valley and lower Ohio Valley next week... ...Overview and Weather/Threats Highlights... Potent North Pacific upper-level jet energies split in approach to the West Coast of North America. In the southern stream, an upper-level low/trough will linger over southern California and the Desert Southwest, only very slowly moving eastward after midweek. This will nudge eastward a lead hot subtropical ridge over the south-central U.S. and the Gulf of Mexico. A persistent and amplified upper low over southeastern Canada will position to the lee of central Canadian upper ridging. This will allow incoming northern stream shortwaves to periodically amplify from the Great Lakes to the Mid-Atlantic/Northeast. Relatively slow-progressing southern stream shortwaves will periodically eject eastward from the Southwest low early next week, reaching the central U.S. and potentially interacting with amplifying northern stream energy. These waves along with return flow across a persistent baroclinic zone may continue to support areas of increased convective risk from the Southern/Central Plains into the mid-lower Mississippi Valley, Tennessee Valley and lower Ohio Valley. This offers a risk of episodes of locally heavy rainfall/flash flooding as well as strong to severe thunderstorms/MCS activity. This threat may become more widespread when the upper low/trough over the unsettled Southwest ejects more bodily to the central U.S. to spawn lead Gulf of Mexico/tropical moisture return. System ejection is in response to the amplified approach of kicker Pacific energy upstream across the West Coast. Kicker trough height falls themselves will support the spread of moderate and terrain enhancing precipitation across the Northwest/West later next week in unseasonably cooling and unsettling late Spring flow. ...Guidance/Uncertainty Assessment... The WPC medium range product suite was mainly derived from a composite blend of well clustered 18/00 UTC GFS/FV3/GEFS mean and 12 UTC UKMET/ECMWF/ECMWF ensemble mean guidance in a pattern with average to below average mass field forecast spread. A main heavy convective rainfall focus is less predictable within this pattern, but there is a growing signal supporting a threat from the south-central Plains to the mid-lower Mississippi Valley, Tennessee Valley and lower Ohio Valley in a region already inundated with heavy rainfall and flooding issues. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml