Extended Forecast Discussion NWS Weather Prediction Center College Park MD 243 AM EDT Tue Jun 08 2021 Valid 12Z Fri Jun 11 2021 - 12Z Tue Jun 15 2021 ...Locally Heavy Rainfall Threat Continues Friday Across Central Appalachians and Mid-Atlantic... ...Much Above Normal Temperatures Return Late This Weekend and Early Next Week Across Northern Rockies/Northern Plains.... ...Guidance/Predictability Evaluation... The latest model guidance offers average to above average predictability for the Nation during the medium range period (Friday-Tuesday) and is driven by the amplified upper level pattern featuring a western U.S. trough with ridging across the southern to central U.S. and some troughing becoming established over the Northeast this weekend. By early next week, this pattern becomes asserted and persistent with heights building through the central U.S./Rockies while upstream troughing off the western U.S. deepens. There is some question on how the Northeast/Great Lakes troughing will evolve, whether it'll be more progressive/zonal like the GFS suggests or more amplified with a closed low forming like the 07.12Z ECMWF advertises. An ensemble mean approach supports the more progressive/zonal flow idea and this is also supported by the teleconnections driven by positive height anomalies over the northern U.S. and negative height anomalies off the West Coast. So for this cycle, the WPC blend favored the deterministic models for days 3-5 consisting of the 12Z ECMWF/CMC and 18Z GFS followed with mostly ECENS/GEFS means for days 6-7 to account for some of the model spread on either coast. This resulted in a blend forecast trending well with continuity. ...Weather Highlights/Hazards... The amplification of the upper ridge over the central U.S. is expected to bring another round of much above normal to possibly record warm temperatures to the northern Rockies and northern Plains late this weekend and early next week. Temperature departures from normal of 20F to 30F are likely with some triple-digit readings possible across central/eastern Montana Monday and Tuesday. Nighttime lows will also remain unseasonably warm for the region and likely stay 10F to 15F above normal for middle of June. Elsewhere across the Nation, no significant temperature anomalies are expected for the medium range forecast period. The threat of locally heavy rainfall capable of producing flash flooding will linger on Friday across portions of the central Appalachians and Mid-Atlantic as higher moisture interacts with a southward dropping cold front. For the weekend and early next week, the dominant upper ridge over the central U.S. will keep much of the Nation on the drier side with any substantial precipitation confined to the Pacific Northwest as well as portions of the Southeast and Florida along a residual frontal boundary. Taylor 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, 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