Extended Forecast Discussion NWS Weather Prediction Center College Park MD 605 PM EDT Thu Jul 14 2022 Valid 12Z Sun Jul 17 2022 - 12Z Thu Jul 21 2022 ...Heat Threat to loom over much of the Western and Central U.S.... ...Pattern Overview and Weather/Hazards Highlights... A hot upper high/ridge will settle near Four Corners to support high heat across much of the West well into next week, but predictability is also high for widespread heat to encompass across much of the central U.S. as ridging/heights build downstream. Scattered local record values are possible in these broad areas. In this pattern, moderating monsoonal moisture flow across the Southwest into the central Great Basin/Rockies under the upper ridge will alternately offer daily chances for showers with some locally heavier downpours/runoff issues with slow cell motions. Meanwhile, a series of uncertain upper troughs/impulses will work inland from the Pacific and from southern Canada to track over-top the ridge with associated frontal systems to periodically focus progressive and potentially strong convection from the north-central U.S. and Midwest/Great Lakes to the East where a mean upper trough is reinforced. Deeper moisture will also fuel showers/thunderstorms farther southward down across the Southeast/FL and central Gulf Coast states. ...Guidance Evaluation/Predictability Assessment... The overall synoptic pattern of high pressure across the southern tier states and waves of low pressure spinning through the northern tier is captured reasonably well by the deterministic models through day 5 and the ensemble means through day 7. A general model blend of the 00z EC/UK/CMC and 06z GFS were utilized for days 3 and 4 though the EC and UK were favored due to their reluctance to spin a wave up over the Southeast coast. By day 5, the 06z GEFS and 00z ECE are incorporated into the blend to moderate the intensity displayed by the deterministic suite with respect to an upper low spinning through the Northern Plains. The de-amplification of the northern trough and the otherwise quasi-zonal pattern is captured well by the ensembles on day 7. Kebede/Schichtel Hazards: - Excessive heat across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, and the Southern Plains, Sun-Thu, Jul 17-Jul 21. - Excessive heat across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, and the Southern Plains, Mon-Wed, Jul 19-Jul 21. - Excessive heat across portions of the Northern Plains and the Northern Rockies, Sun, Jul 17. - Excessive heat across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Sun-Mon, Jul 17-Jul 18. 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