Extended Forecast Discussion NWS Weather Prediction Center College Park MD 213 PM EDT Sat Jul 16 2022 Valid 12Z Tue Jul 19 2022 - 12Z Sat Jul 23 2022 ...Dangerous heat to persist over much of the Western and especially Central U.S. next week... ...Overview... Hot temperatures will prevail across a large area of the central/western U.S. underneath a strong upper ridge centered over the Four Corners region. Near or record highs will be possible at times, and very warm morning lows may also challenge daily records over some areas. Toward the end of next week and the weekend a potential eastward shift in the upper ridge and arrival of a weak Pacific trough to the West Coast may bring western U.S. high temperatures closer to normal. Flow around the ridge will carry shortwaves that will help to reinforce the long term mean trough over the northeastern U.S. and produce episodes of showers and thunderstorms from the northern tier into the East. For the Southwest U.S. into the Rockies, some monsoonal moisture under the ridge will provide daily chances of showers and storms, some of which could lead to flash flooding. ...Guidance Evaluation/Predictability Assessment... For this forecast cycle, the model guidance remain largely agreeable and consistent giving way to average to above average forecast confidence in the large scale synoptic pattern. The latest guidance is clustered nicely on the center of the Four Corners upper ridge through about mid-week with a strong, compact upper low tracking across the northern tier / Canadian border toward the Great Lakes. The 00Z CMC was a slower outlier with this feature that translated through the rest of the period and as a result, its weight in the model blend was considerably lower though wasn't entirely discounted given a slight slowing trend overall. Other aspects of the forecast show varying degrees of spread and variability. By mid to late week, the western U.S. trough begins to push onshore where there is still some timing and depth issues, with the typical model biases showing up. The 06Z GFS (and 12Z as well) remain a bit faster compared to the consensus while the 00Z (and now 12Z) ECMWF show some slower progression. By the end of next week into next weekend, the upper ridge over the Southwest begins to shift to the east and flatten out but the center axis remains uncertain among the various deterministic models. Given some of the increasing model spread late next week into next weekend, the forecast cycle this update incorporated mostly the 00Z ECMWF/06Z GFS/00Z UKMET through day 5 then nearly 50 percent of a ECENS/GEFS mean. This resulted in a forecast with good continuity overall with only typical run to run detail/timing adjustments. ...Weather/Hazards Highlights... While much of the country will see above normal temperatures to start the period (Tuesday July 19), the greatest departures from normal will be found across the Plains to Upper Midwest where daytime highs 10 to 15 degrees above normal are expected. This puts triple digit readings across the southern and central Plains and 90s over a large percentage of the country. Scattered daily record highs are possible through the week with morning lows likely to challenge records as well mid to late week. 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 close to normal for highs through the period. Other parts of the West inland from the Pacific Coast should start the period up to 5-10F above normal for highs but then decline more toward normal as an upper low/shortwave eject from the Pacific and the Four Corners upper high eventually shifts eastward. Locally heavy rainfall will be possible with a fairly vigorous system forecast to track from the northern Plains through the Great Lakes and eastern Canada/Northeast U.S. Tuesday onward. Uncertain specifics of energy ejecting from the Pacific may play a role in convective details along a trailing front that may settle into the far northern tier late week into the weekend. The Mid-Atlantic and Northeast will be on the very warm to hot side, with some locations possibly seeing more consecutive days of plus 5-10F anomalies for highs than previously experienced so far this summer. Persistent moisture will allow for multiple episodes of showers/thunderstorms over the Southeast/Florida and central Gulf Coast region. Temperatures should be near normal over those areas. Rausch/Taylor 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