Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Fri Jun 17 2022 Valid 12Z Mon Jun 20 2022 - 12Z Fri Jun 24 2022 ...Expansive area of heat to shift from the northern Plains/Midwest into the South next week... ...Overview and Guidance/Predictability Evaluation... The latest guidance stays consistent in showing a transition from an amplified trough-ridge-trough pattern on Monday towards a more typical summer-like pattern through the rest of next week. This features strong upper ridging expanding across the South as weaker and more progressive systems ride over top through the northern tier states. The models show good enough agreement for a general deterministic model blend the first half of next week as a closed low exits the Northeast and a shortwave lifts through the northern Plains. After Wednesday, uncertainties begin to arise with respect to timing and details of flow off the East Coast and in the West. The GFS seems an outlier on both ends as it is strongest and farthest south to cut off a lingering upper low off the Northeast coast, and also slowest/farther north with a possible closed low near the Northwest U.S. next Thursday-Friday. The CMC seems much to quick with the trough off the Northeast coast into the Canadian Maritimes, compared to the ensemble means, so it was excluded from the blend beyond Wednesday. Out West, the ECMWF is the closest proxy to the ensemble means showing a closed low over southern British Columbia (the GFS keeps this system still offshore). A majority blend of the ensemble means (with some modest weighting of the deterministic ECMWF) was used for days 6-7 to help mitigate these differences. ...Sensible Weather/Threat Highlights... The biggest weather hazard during the medium range period will be a dome of heat and anomalous warmth expanding from the Upper Midwest on Monday into the Southern states by Wednesday-Friday. The greatest anomalies are expected from parts of the central Plains to the Upper Midwest with daytime highs as much as 20 to 25 degrees above normal. This equates to high temperatures in the mid to upper 90s and low 100s with overnight lows in the mid to upper 70s struggling to provide much relief. Record high max and min temperatures are likely in many places. By Tuesday to Friday, the heat suppresses south with the upper ridge into the Midwest and eventually the south with several days of high temperatures near or exceeding 100F from central Texas to the Southeast and widespread high temperature records likely to be challenged. To the north, systems moving through the northern tier will focus some areas of locally moderate to heavy precipitation, with the best potential over/near the northern Rockies and Plains on Monday. Highest elevations may see some light snow as well with this system. Northward streaming anomalous moisture west of the ridge will bring an unusually early monsoon type pattern to parts of the Four Corners states and vicinity, mainly early in the week, supporting an increase in coverage and intensity of rainfall across the region. By mid week, there are still mixed signals over how much rainfall the interaction of this moisture with the western front advancing into the Plains will produce. However the potential for some training/repeat activity may have to be monitored as consensus shows this Plains front becoming aligned west-east along the southern edge of the westerlies by Wednesday-Thursday. Farther east, an area of showers and thunderstorms may push across the Great Lakes and possibly into the Northeast ahead of an advancing warm front, with some activity possibly on the heavy side. The Florida Peninsula should see multiple days of diurnal showers/storms from the weekend into next week as a front pushing into area decelerates and eventually dissipates. Santorelli 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