Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1151 AM EDT Sat Jul 27 2019 Valid 12Z Tue July 30 2019 - 12Z Sat Aug 3 2019 16Z Update: Very good deterministic model agreement exists across the continental U.S. for Tuesday and Wednesday. The upper low near British Columbia mid-week introduces more uncertainty into the forecast going forward to the end of the week, especially across southern Canada. The GFS and ECMWF indicate a shortwave originating from this low to track near the southern border of the Northwest Territories, with the GFS the faster solution. However, teleconnections with the broad upper low expected over northeast Canada and the upper level ridge over the Four Corners region next weekend are more supportive of a broad ridge axis extending northward into Canada, which limits the level of confidence on this feature being noteworthy. By the end of the forecast period next Saturday, confidence is greatest with the upper level high over Colorado and the broad upper trough over the eastern third of the U.S., and lowest with the eventual breakdown of the trough near the Pacific Northwest. The deterministic ECMWF, GFS, and some of the CMC was incorporated early in the forecast period, followed by some of the ensemble means and previous WPC continuity for Thursday through Saturday. D. Hamrick ...Overview and Guidance/Predictability Assessment... An upper high will meander around the Four Corners region as troughing digs into the eastern states as well as the Pacific Northwest. The models/ensembles largely agree for the first few days of the period (Tue into Thu) and a general model blend sufficed. For later next week into next Saturday, 18Z GFS and 12Z ECMWF showed reasonable agreement though displaced a bit from the ensemble means in the northeast Pacific where the guidance has had trouble settling on a solution. Trend seems to be for a bit slower progression which favors the GFS/ECMWF more than the slightly quicker ensemble means, so shifted the forecast in that direction but with limited confidence. Downstream result may be for a bit deeper troughing and a farther southward push of a cold front into the TN Valley. ...Weather Highlights/Threats... Temperatures in the Southwest will trend cooler as monsoonal moisture increases and clouds/showers/storms expand in coverage. Convective rainfall including some locally heavier downpours/runoff issues will focus along and ahead of the frontal boundaries from the Great Lakes to the Northeast and southward to the southern Plains/lower MS Valley/Southeast. Florida may see an enhanced period of rainfall with a dissipating surface boundary over the central peninsula early next week. The Pacific Northwest will see an increased chance of rain with an approaching system later in the week. 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