Extended Forecast Discussion NWS Weather Prediction Center College Park MD 433 PM EDT Tue Jul 19 2022 Valid 12Z Fri Jul 22 2022 - 12Z Tue Jul 26 2022 ...Dangerous heat to persist over the Central U.S. through early next week... ...Overview... Guidance shows the axis of a strong upper ridge stretching across much of the south-central U.S. during the period, albeit with some uncertainty over exactly where the highest heights will be on a day-to-day basis. This ridge will keep hot and humid weather over the central/southern Plains for a majority of the period. Some southern locations could see readings approach or break daily records for highs and very warm nighttime lows. With somewhat less extreme anomalies, areas from the Tennessee/Ohio Valleys through the Mid-Atlantic and New England will experience multiple hot days as well. The West should see moderate temperatures relative to normal late week through the weekend with the approach/ejection of eastern Pacific upper trough energy, followed by higher readings over the Northwest early next week. The initial Pacific energy and other features across southern Canada and the northern tier U.S. will flow around the ridge and feed into a broad northeastern U.S./eastern Canada mean trough, supporting one or more waves/frontal systems and episodes of showers and thunderstorms from the northern tier into the East. Monsoonal moisture over the Southwest/southern Rockies will promote daily chances of showers and storms, some of which could lead to flash flooding. This activity may increase in coverage and intensity during the weekend and early next week. ...Guidance Evaluation/Predictability Assessment... The overall synoptic pattern over the lower 48 was captured well by a general model consensus through the medium range period. Waves of low pressure riding along the northern tier of the country and high pressure settled across the south posed little in the way of pattern uncertainty. A general model blend of the 00z EC/UK/CMC and 06z GFS were utilized through day 5 as they handled the evolution of a upper-level low moving across the Northwest very well, despite some timing/intensity differences. Heavier weighting was given to the 00z EC and 06z GFS on day 3 due to notable differences between the GFS/EC trends and those of the UK/CMC with respect to the timing/intensity of the Northwest trough. By days 6 and 7 more ensemble mean products were incorporated into the blend with some 00z EC and 06z GFS to help scale back unreasonable amplification of a trough over the West. ...Weather/Hazards Highlights... Continue to expect most of the greatest temperature anomalies to be over and near the central Plains through the period, with multiple days of highs 10-15F above normal. Some of the heat may also extend into parts of the Tennessee Valley. By Sunday-Monday a cold front may suppress the heat over the north-central Plains. Typically hotter southern Plains locations will see less extreme anomalies but overall there will be a broad area with highs reaching or exceeding 100F for highs, while very warm lows in the upper 70s to low 80s will provide little nighttime relief. This heat wave should bring scattered records, most likely over the southern Plains to lower/mid Mississippi Valley. Over the West, monsoonal moisture and associated diurnally favored showers/storms with locally heavy rainfall may keep parts of the Four Corners/Great Basin region within a few degrees on either side of normal during through the period. There is a general signal in the guidance that rainfall should increase in coverage and intensity during the weekend and early next week but with considerable uncertainty over the specifics. The initial shortwave ejecting from the Northwest and then lingering weak trough energy should keep that region near or a tad below normal through the weekend. The majority scenario of some degree of upper ridging building into the Northwest by next Tuesday should lead to a warming trend, with some highs possibly reaching up to 10-15F above normal. The combination of shortwaves aloft and surface waves/fronts will likely produce one or more episodes of showers and storms from the northern tier states into the East during the period, with some heavy rainfall possible. Currently the best signal for enhanced rainfall extends from the Midwest through the Lower Great Lakes into the Mid-Atlantic, but recent guidance inconsistency with important details at the surface and aloft temper confidence in the specifics for now. The Mid-Atlantic and Northeast will be on the very warm to hot side from late week through the weekend, with some locations possibly seeing more consecutive days of plus 5-10F or so anomalies for highs than previously experienced so far this summer. Temperatures should trend closer to normal from north to south by early next week as a couple fronts arrive. Persistent moisture will allow for multiple episodes of showers/thunderstorms over the Southeast/Florida and central Gulf Coast region. Best organization may be late this week. Highs should stay near normal over the Southeast. Rausch/Kebede Hazards: - Heavy rain across portions of the Central Great Basin and the Southwest, Sat-Tue, Jul 23-Jul 26. - Heavy rain across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Sat-Sun, Jul 23-Jul 24. - Heavy rain across portions of the Great Lakes, the Central Appalachians, and the Ohio Valley, Sun-Mon, Jul 24-Jul 25. - Excessive heat across portions of the Central Rockies, the Central Great Basin, and the Southwest, Fri, Jul 22. - Excessive heat across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Fri-Tue, Jul 22-Jul 26. - Excessive heat across portions of the Southeast, the Mid-Atlantic, the Southern Appalachians, and the Tennessee Valley, Sat-Mon, Jul 23-Jul 25. 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