Extended Forecast Discussion NWS Weather Prediction Center College Park MD 349 AM EDT Tue Aug 02 2022 Valid 12Z Fri Aug 05 2022 - 12Z Tue Aug 09 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 Lower Great Lakes Thursday and New England on Friday. The next cold front passes through the Northern 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... A relatively straightforward synoptic pattern, with high pressure stationed over the central/southern U.S. and waves of low pressure swinging across the northern tier, was captured well by the guidance through the medium range. A consistently slower EC appeared to be the main source of uncertainty during the medium range period. A general model blend of the 12z EC/UK/CMC and 18z GFS were utilized on days 3 and 4. The 12z EC was weighted less on day 4 due to the slowness noted in the mass fields with respect to the upper trough moving through Southern Canada and the Northern Plains. The 12z ECE and 18z GEFS were introduced to the blend on days 5 and 6 to account for timing and intensity discrepancies between the deterministics with respect to a second trough moving through the southern Canada. 12z EC/ECE/CMCE and 18z GEFS were favored by day 7 to account for standard spread in the pattern. ...Weather/Hazards Highlights... Another eastward moving wave of anomalous heat is expected to cross the Northern Plains Friday - Saturday which will be similar to the wave that crossed earlier this week. 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, monsoonal moistures in the southwest and heavy rainfall focused along a cold front will be the main threats for flash flooding. Heavy rainfall caused by monsoonal moisture will impact the Desert Southwest up into the Central Great Basin on Saturday and Sunday where Slight Risks of Excessive Rainfall leading to Flash flooding is in effect. Meanwhile additional moisture makes its way up into central Colorado on Sunday prompting a separate Slight Risk area for portions of the Colorado Rockies and foothills. A cold front stalling over the Northeast/Mid-Atlantic may lead to additional flash flooding risk, although, that risk is marginal due to spread in the guidance. Kebede/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