257 FXUS02 KWBC 231959 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Tue Jun 23 2026 Valid 12Z Fri Jun 26 2026 - 12Z Tue Jun 30 2026 ***Additional heavy rain for the Midwest and Ohio Valley*** ***Heat and humidity increases across the Central and Southern U.S. starting this weekend*** ...Pattern Overview... A zonal upper-level flow pattern at the start of the medium-range period is forecast to become more amplified by early next week with a pronounced upper low/trough traversing the northwestern quadrant of the country. The deep troughing in the West will be in contrast with an upper ridge building over the east-central U.S. by early next week. A return to heat and humidity is expected for much of the central and southern U.S. which will be in stark contrast with late-season mountain snows in the northern Rockies. ...Guidance/Predictability Assessment... Much of the variability seen in the morning suite of model guidance was found from the Midwest and Ohio Valley to the Great Lakes. The QPF axis this Friday into the weekend has been extending faster and farther eastward across the Midwest to the Ohio Valley given a faster ejection of a couple of shortwaves along the stationary/warm front. From this weekend into early next week, the most recent model trend has been to lift the elongated low- pressure system faster northeast toward southern Canada in response to a stronger upper ridge extending north across the Midwest. This stronger ridge implies an increasing chance for heat to build into the upper Midwest early next week. The faster northeastward motion of the low in the north-central U.S. would also imply an earlier departure of the rain/storms from the northern Plains into southern Canada early next week. The WPC prognostic charts were based on the consensus of the 06Z GFS/GEFS, 00Z EC/EC mean, and the 00Z CMC/CMC mean. The NBM was a reasonable starting point for most areas of the country, although a smoother QPF field was used to replace some of the high QPF blobs as well as with a smoother drop-off gradient. In addition, temperatures were lowered for coastal areas of the Mid-Atlantic, Northeast, and the Great Lakes. ...Weather/Hazards Highlights... Multiple mesoscale convective systems are likely to affect much of the Midwest and extending eastward to include the Ohio Valley through the end of the week and into Saturday, with some areas getting an additional 1-3 inches of rain over already saturated grounds from recent heavy rainfall. A lingering frontal boundary with shortwave energy aloft and strong moisture convergence will provide enough instability and lift to sustain these thunderstorm complexes, and some of these storms possibly producing flash flooding, including the potential for some strong to severe thunderstorms. A Marginal Risk of excessive rainfall is highlighted on the WPC excessive rainfall outlook across the east-central U.S. Friday to the weekend. Elsewhere across the nation, rainfall is forecast to increase for Washington and Oregon to close out the work week with the storm system moving through the region, with a larger area of heavier rainfall develops across Montana and then the Dakotas as the main surface low ejects eastward over the northern Plains by the weekend. A Marginal Risk of excessive rainfall is highlighted across the far northern Plains for Day 5 on the WPC excessive rainfall outlook. In addition, late-season high elevation snow is likely for the highest ranges of the northern Rockies as the colder upper low moves in. Scattered showers and thunderstorms are also expected for the East Coast through Saturday with increasing low level moisture in place. The widespread above average heat levels across the western third of the nation are expected to abate considerably going into the weekend. A strong cold front brings relief from the heat starting Friday followed by more appreciable cooling going into the weekend as highs return to below average for late June standards, whereas overnight lows should be less anomalous. The opposite holds true for the southern High Plains where temperatures are likely to increase by the weekend with highs well into the 100s for western Texas, and building heat and humidity for much of the central and eastern U.S. going into Sunday and Monday as the upper ridge dominates the weather pattern. Widespread major heat risk is currently depicted across much of the central to southeastern U.S. where heat advisories are likely for many areas for early next week. Kong/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 $$