Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 AM EDT Sun Jul 28 2019 Valid 12Z Wed Jul 31 2019 - 12Z Sun Aug 04 2019 ...Overview and Guidance/Predictability Assessment... Upper pattern will be driven by a closed high over the Four Corners as well as upstream over southern Alaska. This favors positively-tilted troughing over the northeastern Pacific into WA/OR and again over the eastern states. The models/ensembles have really struggled with the Pacific flow including the timing/track of a pair of systems Wed and again around Friday. The 12Z/18Z guidance split between quicker (ECMWF and most ensembles) and slower (deterministic GFS/Canadian/UKMET). Ensemble trend was decidedly quicker but was odd that only the ECMWF followed suit. Glance at the 00Z guidance showed a trend quicker but still not as quick as the ECMWF. However, this fit well with the blend using the pre-00Z guidance; namely, the ensemble mean consensus. Used a 50/50 GEFS/ECENS mean consensus to round out the forecast which allows some shortwave energy to crest atop the upper high through Canada and maintain the trough in the east (albeit with above average heights). Confidence was low in the Northwest but about average elsewhere. ...Weather Highlights/Threats... Temperatures below average in AZ/UT due to monsoonal moisture (and in increase in clouds/showers/storms) will moderate a bit with time as the upper high drifts just enough eastward to focus rainfall over CO/NM next weekend. Frontal boundary in the east will be a focus for convective rainfall including some locally heavier downpours/runoff issues through the period, but drifting eastward/southward day by day. East of Florida, a trough may bring a somewhat expanded area of rainfall through the Bahamas and perhaps into eastern North Carolina next weekend just south of the front. Finally, coastal Washington will see an increased chance of rain later in the week but this will be dependent on details yet to be determined. Fracasso 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