Extended Forecast Discussion NWS Weather Prediction Center College Park MD 205 AM EDT Sat Jun 20 2020 Valid 12Z Tue Jun 23 2020 - 12Z Sat Jun 27 2020 ...Overview and Weather/Hazard Highlights†The medium range period begins next Tuesday with amplified troughing/possible closed low settling south of Hudson Bay and drifting slowly northeast through the week. This brings height falls and a cold front down across the east-central U.S. and eventually the East. Above normal temperatures are likely in advance of the cold front next Tuesday and Wednesday across the lower Great Lakes to northern New England. The trailing end of the frontal boundary is expected to stall back through the South and linger through much of the week, serving as a focus for shower and thunderstorm development. Precipitation should slowly shift farther south and east from the Southern Plains/Lower Mississippi Valley to the Ohio Valley/Appalachians and Eastern Seaboard. Guidance continues to suggest the Southern Plains and Lower Mississippi Valley may have the greatest potential for locally heavy rainfall and runoff issues. Additionally, upper level energy across south Texas/northwest Gulf may fuel some enhanced precip along the Texas Gulf Coast region mid to later next week, with at least locally heavy rainfall possible. Meanwhile out West, upper-level mean ridging should dominate over the Southwest for much of next week and early week Northwestern U.S. upper ridging should keep conditions mostly dry. A cold frontal passage from the Northwest through the Northern Rockies/Plains later next week though may bring some showers over the region, with organized activity most likely to focus along a lingering boundary in the northern Rockies/High Plains. Temperatures across much of the West are forecast to be above to well above normal the first half of the period, with daytime highs ranging 10 to 15+ degrees above average. Temperatures should moderate back towards normal the second half of the week as height falls move into the Northwest/Great Basin. ...Guidance/Predictability Assessment... Guidance continues to struggle somewhat with placement and intensity of the Great Lakes/Hudson Bay low, although a general model compromise with the ensemble means provides a good starting point. Out West, significant differences in trough evolution start by day 5/Thursday with the 12z/June 19 ECMWF coming in much stronger/amplified and presenting a closed low solution over the northern Rockies/High Plains by day 7. Significant run to run differences remain, especially with the ECMWF, so any solution at this point in the Northwest would be low confidence. WPCs blend trended quickly towards the more agreeable ensemble means on days 6 and 7 across the West. There also remains some variability with upper energy along the Western Gulf Coast, with the latest run of the ECMWF remaining the most robust with this and the QPF. Again, a general model/ensemble compromise serves this area well for the medium range. Santorelli 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