Extended Forecast Discussion NWS Weather Prediction Center College Park MD 240 PM EDT Fri Jul 15 2022 Valid 12Z Mon Jul 18 2022 - 12Z Fri Jul 22 2022 ...Dangerous heat to persist over much of the Western and 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. Meanwhile, the flow around the ridge will bring periodic episodes of showers and thunderstorms and help to reinforce the long term mean trough over the northeastern U.S. through the period. 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. Finally, the West Coast will tend to see weak troughing. ...Guidance Evaluation/Predictability Assessment... In a fairly typical summer-time pattern, the large scale pattern showed fairly good agreement and consistency between the various global models and WPC continuity. The center of the upper ridge is forecast to remain centered over the Four Corners through late next week while troughing prevails over the Great Lakes and Northeast. The latest guidance shows fairly good agreement in the surface evolution of a strong wave of low pressure tracking across the northern Plains early next week through the Great Lakes by mid-week, with its trailing cold front advancing across the central U.S., reaching the Mid-MS, Tennessee Valley and East Coast by the end of next week. The timing and progression of this feature still has model agreement issues, with the GFS being a fast progressive outlier compared to the other guidance. The updated forecast based on guidance through the 12Z/18Z cycles emphasized the operational runs for about the first half of the period, with GFS input tilted toward the 12Z run for its better clustering with the northern tier upper low early in the week. General agreement on the mean pattern but increasing detail uncertainties led to a transition toward nearly half total input from the ensemble means by late in the period. GFS input reverted back exclusively to the 18Z run for its incoming northeastern Pacific trough while ensemble mean input was split among the ECens/CMCens/GEFS to downplay the less desirable GEFS evolution over eastern Canada and vicinity. ...Weather/Hazards Highlights... Expect the greatest temperature anomalies to be over the central/northern Plains early next week where highs 15 to 20 degrees above normal are likely. Triple digit highs are expected from Texas northward through portions of the Dakotas and a few daily temperature records are possible. Monsoonal moisture and associated diurnally favored showers/storms with locally heavy rainfall may keep parts of the Four Corners/Great Basin region closer to normal for highs while other parts of the West should be somewhat warmer than normal. Exceptions will be over the far northern Rockies under the initial upper low/trough as well as along the immediate West Coast with readings closer to normal. Locally heavy rainfall will be possible with a stronger system forecast to track across the northern tier, Great Lakes, and Northeast mid week with warmer than normal temperatures likely ahead of that frontal passage. 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