Extended Forecast Discussion NWS Weather Prediction Center College Park MD 109 AM EDT Thu Jun 20 2019 Valid 12Z Sun Jun 23 2019 - 12Z Thu Jun 27 2019 ...Weather Highlights/Threats... The persistent upper ridge over the southeast continues to advect warm air east across the southern Mississippi Valley and the Southeast/TN Valley/Oh Valley/Appalachians on Sunday, and continuing into the Northeast early next week. Expect high warm sector temperatures under this ridge, with most areas several degrees above normal. Another area of warmer than normal temperatures develops as the upper ridge build north across the Plains, with anomalies as much as ten degrees above normal day 7 Thu 27 Jun in eastern MT and ND. After initial cold in the high Plains, temperatures moderate early next week. the developing low in the northwest leads to a cooling trend next week, with widespread temps several degrees below normal, focused on northern CA day 6 Wed 26 Jun and day 7 Thu 27 Jun. Forcing ahead of the trough crossing the Rockies this weekend presents a threat of strong to severe/MCS convection and locally heavy rains in areas with pooling moisture/instability. The rainfall focus Sunday and Monday is forecast to be from eastern Kansas and Oklahoma across the Mississippi Valley into the Great Lakes and the Midwest. On Tuesday 25 Jun /Wednesday 26 Jun the showers/storms are expected to focus from east Texas across the Arklatex to the lower MS Valley, Florida and the Northeast. ...Guidance/Predictability Assessment... The WPC medium range product suite was derived from a blend of the 18z UTC GEFS and 12 UTC ECMWF ensemble mean guidance, with minimal weighting on the operational GFS/ECMWF. The 18 UTC deterministic GFS returned to its long term bias of moving the 500 mb wave out of the central US faster than the ECMWF/Canadian and the ECMWF and GEFS Means starting on Mon 24 June. This continues across the Great Lakes Mon night-Tue. The 12z ECMWF had a different issue with the same system, producing a more amplified 500 mb trough and possible embedded closed low across the upper MS Valley Mon and Great Lakes Tue that caused the ECMWF to be on the slow end of the guidance envelope. Given most ECMWF and GEFS members cluster in between the ECMWF and GFS, the preferred solution was weighted heavily towards the means. Next week, a new closed low develops and moves southeast from offshore British Columbia into the Pacific northwest or adjacent coastal waters by the middle of next week. This persistent and slow moving circulation allows the deep layer ridge to rebuild over TX and NM, and then extend north into the northern Plains. There is less spread than normal for this consensus, lending the situation to a consensus based approach. Petersen 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