Extended Forecast Discussion NWS Weather Prediction Center College Park MD 250 PM EDT Mon Aug 01 2022 Valid 12Z Thu Aug 04 2022 - 12Z Mon Aug 08 2022 ...The Southwest Monsoon Resumes a Very Active Phase Late This Week... ...Heavy Rain Likely from the Ohio Valley Through The Northeast Late This Work Week*** ...General Overview... Active upper level flow pattern will continue across southern Canada/near the U.S. border over the next week as the persistent Hudson Bay low is dislodged east around Thursday. A well defined cold front will slow/stall as it tracks east across the eastern Great Lakes Thursday and cross New England on Friday. The next cold front crosses the northern Great Plains Thursday night/Friday and the Upper Midwest/Great Lakes this weekend. Meanwhile, the core of the upper ridge intensifies as it drifts east to the central Plains Thursday into Friday Friday before drifting back west this weekend. As a result the monsoonal pattern across the Four Corners region re-intensifies Thursday with a rather active period through at least the weekend. ...Guidance Evaluation/Predictability Assessment... Above average forecast confidence continues for late this week into the weekend among global deterministic guidance on the upper flow pattern. A general deterministic model blend is used for the Days 3-5 progs. The timing of the ejection of the low from BC was in question with the 06Z GFS being slower than the preferred 00Z ECMWF/CMC, though the 12Z GFS has slowed to be much like the EC/CMC, so we will see if that agreement continues. Days 6/7 of the forecast have increasing usage of ensemble means from the CMCE/GEFS/ECENS which is typical, particularly after the end of the 5-day UKMET output. For QPF, the NBM was enhanced with the 06Z GFS and 00Z ECMWF/CMC over the Southwest for Monsoonal precip. Considerable increases in QPF over the NBM were done mainly from the 00Z ECMWF/CMC for the eastern half of the CONUS Days 5-7 due to their similarities with cold frontal timing over the Northeastern quadrant (less progressive than the 06Z GFS). The 12Z GFS did slow in the Northeast and was an influence on the Slight Risk of excessive rainfall for the Northeastern urban corridor ending 12Z Saturday. ...Weather/Hazards Highlights... Another eastward moving wave of anomalous heat is expected to cross the northern Plains Thursday - Saturday which will be similar to the wave crossing the first half of this week. This with Meanwhile, maximum temperatures will likely be near to slightly below normal across much of the western U.S. for most of the forecast period. This wave looks to reach the Northeast by Sunday with another brief wave of high temperatures expected to continue ahead of a cold front into Monday. Meanwhile, monsoonal clouds and rain offer below normal max temps for the Desert Southwest to the Great Basin to southern Rockies. For precipitation, two general rounds of heavy rain are expected ahead of the two cold fronts over the central and northern portions of the eastern CONUS - Thur/Fri and Sun/Mon. A second Slight Risk of excessive rainfall was added to the Day 4 outlook over the eastern Great Lakes and one was added for the Bos-Wash megalopolis for Day 5 - both have decent agreement among global deterministic guidance for heavy rain focus there ahead of a slow moving cold front. The Monsoon reinvigorates in the Southwest as the ridge strengthens after a midweek period of more diffuse monsoon. Slight Risks were expanded over the Southwest for both Days 4 and 5 for this increased threat. Jackson 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, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml