Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Fri May 29 2020 Valid 12Z Mon Jun 01 2020 - 12Z Fri Jun 05 2020 ...Much above normal temperatures for the Rockies/Plains... ...Overview and Guidance/Predictability Assessment... Models and ensembles agree in showing a persistent and highly amplified/blocky large scale flow pattern over the lower 48 and vicinity highlighted by mean upper troughs over the West Coast and Northeast that sandwich a hot south-central U.S. upper ridge. Predictability in the large scale regime is above average, but not so especially days 4-7 with the timing of small-mid scale embedded features embedded within the flow. Accordingly, the WPC medium range product suite was primarily derived from a well clustered guidance blend Mon. Prefer a reasonably compatible GEFS/ECMWF ensemble mean blend Tue-next Fri in an effort to mitigate the less predictable smaller scale model timing and detail differences that increase over time. Ensemble means favor slower ejection of closing southern stream trough energy over southern CA next week, especially compared to the GFS/Canadian late week. The generally blocky pattern nature seems to favor the slower half of guidance spread. Ensemble means also agree better than individual model runs for energy that reaches the Northwest by Wed-Fri. The means all show some degree of trough arriving versus a wide variety of shortwave amplitude/timing in the operational runs. Guidance continues to have difficulty downstream with the path/evolution of lead shortwave energies that eject from the West and track on/into the northern periphery of the central U.S. upper ridge and into the Northeast U.S. upper trough position. Feature predictability is low due to their small scale, but they will drive locally organized diurnal convection and meso-boundaries/fronts across the broad region. ...Weather/Hazard Highlights... Highest anomalies within the area of much above normal temperatures centered over the west-central U.S. should be over the north-central Rockies/High Plains Sun-Tue with readings up to 15-20F or so above normal and some daily record highs/warm lows possible. Temperatures should become a little less extreme by Wed-Thu but a fairly broad area of plus 5-15F anomalies for highs may persist through the end of the period from parts of the central U.S. into/near the Great Basin, with single-digit warm anomalies possibly returning into California if an upper low remains offshore through Thu. Portions of the East will see a couple days or so of temperatures about 5-12F below normal during Sun-Tue followed by a warming trend to within a few degrees on either side of normal. The evolving pattern should favor multiple episodes of showers/thunderstorms over the northeast quadrant of the lower 48. Best potential for this activity, which could be locally moderate to heavy, extends between the Midwest/Upper MS Valley and central Appalachians/Mid-Atlantic. The uncertainty in surface wave/frontal specifics keeps confidence fairly low for details on magnitude and location of highest rainfall totals. Farther west a wavy front extending into the Northern Plains/Rockies may provide a focus for rainfall but there is still poor agreement on the specifics. The upper trough expected to approach the Northwest around or after midweek may start to generate some rainfall, while diurnal rainfall should continue over the central/southern Rockies. Other parts of the West may see scattered activity depending on shortwaves within the overall West Coast mean trough aloft. Southern parts of Texas and Florida may also see some rain as they may remain near/south of a front that settles into the northern Gulf of Mexico. 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