Extended Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Wed Jun 22 2022 Valid 12Z Sat Jun 25 2022 - 12Z Wed Jun 29 2022 ...Excessive heat threats for the South and Northwest this weekend will moderate next week... ...Overview... The broad upper level ridging over the Southern U.S. will finally begin to weaken and break down this weekend as a shortwave through the northern tier to the north begins to amplify as it reaches the Great Lakes and especially the Northeast early next week. Meanwhile, monsoonal moisture will continue to persist into the Four Corners region through much of the period with potential for heavier to excessive rains along the southern half of the Rockies this weekend with the arrival of a surface front and trailing low level upslope flow. The pattern looks to become more amplified by early next week across the CONUS with troughing in the East and the arrival of a closed upper low towards the West Coast, and ridging building in between over a warmed interior West. ...Guidance/Predictability Evaluation... The WPC medium range product suite was primarily derived from a composite blend of well clustered model guidance of the 06 UTC GFS, 00 UTC ECMWF/UKMET/Canadian and 13 UTC National Blend of Models days 3-5 (Saturday-Monday). Guidance solutions remain well clustered at mid-larger scales into days 6/7, but the GFS/ECMWF and GEFS/ECMWF ensemble means seem to offer the best combination with agreed upon embedded features at these longer time frames and mesh seemingly well with the NBM as well in a continuing pattern with above normal predictability. ...Sensible Weather/Threat Highlights... Anomalously high monsoonal moisture for this time of year, likely tied at least in part to an eastern Pacific tropical system, will continue streaming into the Four Corners states into early next week. Locally heavy to excessive rainfall is possible, particularly over sensitive burn scar areas and considering the multiple day repeating nature of this activity. Rainfall may trend heavier over parts of Colorado/New Mexico by the weekend as a front dropping south through the region and trailing low level upslope flow could interact with the moisture already in place. Models showed enough agreement for the inclusion of a slight risk in northeast New Mexico on the experimental day 4 and day 5 ERO. Moisture will continue rounding the top of the ridge through the Plains, while interacting with a cold front through the Upper Midwest, where some increased threat for organized showers is possible. The cold front should be fairly progressive through the Midwest and into the East this weekend, but with enough moisture and instability along the boundary present, some locally higher totals seem likely, specific amounts and locations tho remain highly dependent on still uncertain timing of the front. A front settling across the southeast into Saturday should also bring a period of enhanced rainfall to parts of the Florida peninsula. Excessive heat across the Southern U.S. should finally begin to wane some, especially in parts of the Southeast, by this weekend. Anomalies averaging 10 to 15 degrees above normal will continue across the lower Mississippi Valley and Southern Plains with another few days of records both for daytime highs and warm overnight mins. 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. The northern High Plains may also see cool highs from Saturday into Sunday. The West Coast states should see highs 5-15F above average through about Tuesday as upper ridging moves through the region, with the interior Northwestern U.S. having an excessive heat threat this weekend in particular. Santorelli/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 Central Plains, the Central Rockies, the Central Great Basin, the Southern Rockies, the Southern Plains, and the Southwest, Sat-Sun, Jun 25-Jun 26. - Flooding occurring or imminent across portions of the Upper Mississippi Valley, the Northern Plains, and the Northern Rockies. - Excessive heat across portions of the Lower Mississippi Valley, the Tennessee Valley, the Southern Plains, the Middle Mississippi Valley, California, the Southeast, the Pacific Northwest, and the Ohio Valley, Sat-Sun, Jun 25-Jun 26. - Excessive heat across portions of California, the Central Great Basin, the Pacific Northwest, and the Northern Great Basin, Sun-Mon, Jun 26-Jun 27. - Excessive heat across portions of the Southeast, the Lower Mississippi Valley, and the Southern Plains, Sat-Mon, Jun 25-Jun 27. - Excessive heat across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, the Southern Plains, and the Ohio Valley, Sat, Jun 25. 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