Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EDT Fri Jun 24 2022 Valid 12Z Mon Jun 27 2022 - 12Z Fri Jul 01 2022 ...Overview... Guidance still agrees that a broad upper level ridge over the southern half of the CONUS will be in place through much of the medium range period, forcing storm tracks mainly through the northern tier. A vigorous shortwave through the Upper Midwest/Great Lakes will amplify some as it moves into the Mid-Atlantic and the Northeast early next week, pushing a surface cold front across the East and helping produce showers and thunderstorms. Behind this, amplified ridging should build over the Northwest U.S., and slide into the northern Plains as a closed low/upper trough could settle over the Pacific Northwest, perhaps by around Wednesday. Meanwhile, monsoonal moisture will continue to persist into the Four Corners region through much of the period, with the best potential for heavier to excessive rains to remain across the south-central Rockies into early next week. ...Guidance Evaluation/Predictability Assessment... Recent model guidance remains in good agreement through the medium range time frame for the large scale pattern described above and its evolution. This includes a couple of rounds of troughing over the northeastern U.S. and ridging shifting from the northwestern to north-central U.S. behind. Some slightly larger differences are indicated in model guidance with the track of an eastern Pacific upper low that should shift into southwestern Canada/northwestern U.S. around Wednesday, and CMC runs have been most consistent in leaving energy farther west. Then there are some placement differences with the centroid of a central Canada/Hudson Bay upper low, with the GFS on the western side Wednesday-Friday, which could cause minor differences over the northern U.S. with troughing and surface frontal placement. But the overall good agreement allowed for the updated WPC forecast to use a multi-model deterministic blend of the 00/06Z GFS runs and 00Z ECMWF, CMC, and UKMET, phasing in the 00Z EC ensemble mean in place of the UKMET by days 6-7, but with a majority deterministic blend. This created a middle ground solution with decent continuity from the previous issuance. ...Sensible Weather/Threat Highlights... Anomalously high monsoonal moisture for this time of year, likely tied at least in part to Tropical Storm Celia in the East Pacific, will continue streaming into the Four Corners states into early next week. Locally heavy to excessive rainfall will be possible each day, particularly over sensitive burn scar areas and considering the multiple day repeating nature of this activity. The best chance for impactful rainfall looks to be over parts of southern Colorado/New Mexico with favorable upslope flow interacting with the moisture already in place. A Slight Risk was maintained across northern New Mexico on the experimental day 4 excessive rainfall outlook for Monday where good model agreement overlapped with areas that have seen anomalous rainfall already. Activity then wanes around Tuesday-Wednesday, but there may be another uptick in moisture by the latter part of next week. A cold front should be fairly progressive through the East Monday, but should focus enough moisture and instability to fuel convection with possibly locally heavy rainfall. A settling of the front across the Gulf Coast, as well as the next cold front dropping into the region, should allow for enhanced rainfall into the middle of next week from Florida to along the Gulf Coast as aided by protracted onshore fetch of moisture. Elsewhere, progressive fronts tracking across the Upper Midwest into the Upper Great Lakes should produce a couple of rounds of rain and storms through the workweek there, and rain may also focus over the central Plains/Mid-Mississippi Valley by late week as a front shifts into that area. By early next week, temperatures all across the South should finally trend back towards normal. Relatively cooler temperatures with well below normal highs are likely to be most persistent over parts of New Mexico and Colorado given the monsoonal clouds and rain coverage. In the West, ridging through the region should present an excessive heat threat across parts of especially the Northwest into Monday with the above normal temperatures then working through the northern half of the Rockies, Plains, Midwest and then East Tuesday-next Friday as we head into July. Tate/Schichtel 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 Hazards: - Heavy rain across portions of the Southern Rockies, the Central Rockies, the Southern Plains, the Central Plains, and the Southwest, Mon, Jun 27. - Flooding occurring or imminent across portions of the Upper Mississippi Valley, the Northern Plains, and the Northern Rockies. - Excessive heat across portions of California, the Central Great Basin, the Pacific Northwest, the Northern Great Basin, and the Southern Plains, Mon, Jun 27. 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