838 FXUS02 KWBC 201752 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 152 PM EDT Sat Jun 20 2026 Valid 12Z Tue Jun 23 2026 - 12Z Sat Jun 27 2026 ...Heavy rainfall expected for the Central Plains and very hot conditions for the Desert Southwest... ...Overview... A quasi-zonal upper level flow pattern will be in place across the country for the beginning of the period Tuesday. An upper level ridge will build across the Desert Southwest into portions of the Intermountain West, with increasing heat through the end of the week. A lingering frontal boundary draped across the Mid-South to the central Plains, coupled with some shortwave energy aloft, will fuel the development of multiple thunderstorm complexes that will bring episodes of heavy rainfall. By next Saturday, an organized low pressure system and cold front cross the northwestern quadrant of the country and will herald the arrival of cooler weather. ...Guidance/Predictability Assessment... Model guidance remains in good agreement on the large scale pattern through the period, with uncertainty in some of the details in the second half of the period. The GFS has trended closer to the ECMWF and CMC over the past 24 hours, but continues to be a bit of an outlier, showing a strong shortwave trough cutting through the ridge over the West late this week. The ECMWF, CMC, AIGFS, and EC- AIFS all maintain the strength of the ridge and bring a much weaker shortwave into the Central U.S. Thursday into Friday, which seems more likely at this time. However this feature evolves, it could have significant implications for precipitation amounts and location. The WPC forecast was initiated using a near even blend of the deterministic guidance, but the GFS was phased out by mid-next week and the GEFS and ECENS were added in increasing amounts to smooth out model differences. In terms of the NBM, it is likely underdone with the coverage of afternoon/evening showers and storms across the Four Corners regions mid-week, so QPF values were raised a little to better reflect the deterministic guidance. ...Weather/Hazards Highlights... The weather pattern will remain quite unsettled from the central Plains to the ArkLaTex region through Wednesday night with multiple rounds of thunderstorms with heavy rainfall expected. This is in association with a frontal boundary that will be in place across this region, with anomalous moisture surging north and fueling the convection that develops. Going into the end of the week, the heaviest rainfall is expected from eastern Kansas to Illinois where additional thunderstorm complexes are expected to develop and lead to periods of heavy rainfall. Temperatures are expected to be very pleasant by late June standards across a large expanse of the north-central states through much of next week, with highs generally in the 70s and comfortable humidity levels. Most of the Mid-Atlantic and Northeast should be close to seasonal averages with highs mainly in the upper 70s to middle 80s. With the upper ridge over the West through Friday, heat is expected to build from the Desert Southwest to the Pacific Northwest, with highs running 5 to 10 degrees above normal in many cases. A pattern change is expected to arrive next Saturday as a cold front drops south across the Pacific Northwest and brings an end to the heat wave there. Hot and humid conditions will continue unabated across the Deep South and Gulf Coast region. Dolan/Hamrick 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw $$