Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Thu Aug 4 2022 Valid 12Z Sun Aug 7 2022 - 12Z Thu Aug 11 2022 ***Monsoonal pattern remains active across the Southwest with additional heavy rainfall expected*** ...General Overview... The core of the westerlies aloft will be over southern Canada, with a trough and cold front crossing the Northern Plains and Great Lakes region by early next week. The core of the upper ridge is expected to retrograde westward and become established over the Intermountain West by Monday, and likely persisting there through next Thursday. Meanwhile, a broad upper level trough is expected across the northeastern quadrant of the nation as the upper level pattern becomes a bit more amplified. The upper low well off the West Coast is forecast to continue slowly lifting northward next week. ...Guidance Evaluation/Predictability Assessment... The 00Z model guidance suite is initially in good synoptic scale agreement across the nation through at least Monday. There are some minor timing differences with the shortwave crossing the northern Great Lakes, with the 00Z ECMWF slightly ahead of the CMC/GFS, but still close enough to merit a three-way blend of these models. Model differences become more significant by the middle of next week, with the ECMWF farther inland with the closed low over British Columbia, and the GFS/CMC are stronger with the trough building in across the eastern U.S. by next Thursday. The upper ridge across the Rockies still has very good agreement through the forecast period. The WPC forecast was primarily based on a CMC/ECMWF/GFS/some ensemble means through Tuesday, followed by gradually increasing contributions from the GEFS/ECENS whilst still keeping some of the deterministic guidance. ...Weather/Hazards Highlights... Temperatures are expected to be slightly above normal across portions of the Northeast and also the Pacific Northwest on Sunday, but no major heat waves are currently expected at this time. Readings will be running a few degrees below normal across much of the Southwest and the Rockies with the additional clouds and showers. By the middle of the week, heat builds again across the central and northern Plains, but the anomalies should be ten degrees above average or less in most cases. For precipitation, the main threats for flash flooding will be associated with enhanced monsoonal moisture over the Southwest and Four Corners region, in addition to fronts/shortwaves from Michigan to the Northeast U.S. as northern stream shortwave troughs progress down stream. The combined signals for rainfall and already wet conditions over the Desert Southwest into the central Rockies/Great Basin late into the weekend support a few Slight Risk areas for the Day 4 Excessive Rainfall Outlook. Despite frontal progression, deep moisture and instability also merits maintaining the Slight Risk area across the northern Great Lakes in a region with enhanced/ongoing short range QPF. Hamrick 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