512 FXUS02 KWBC 010659 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Wed Jul 1 2026 Valid 12Z Sat Jul 04 2026 - 12Z Wed Jul 08 2026 ...Significant heat wave expected to last into at least Saturday for the Midwest to Eastern U.S. before waning early next week.. ...Pattern Overview... The strong ridge supporting a significant and dangerous heat wave during the short range period should finally begin to weaken somewhat by the medium range period, however hazardous heat may still continue through the weekend, especially for parts of the East. Energy from the West should eventually work its way into the Northern Plains and Great Lakes suppressing the ridge completely by early next week. Ridging then looks to build back into the Four Corners region next week. Showers and storms will expand across the Ohio Valley and the South/East next weekend and early next week as the ridge weakens. ...Guidance/Predictability Assessment... Guidance continues to show good agreement with the synoptic scale pattern through the period, but uncertainty remains with the details/evolution of energy traversing the flow in the West and the timing of ridge break down over the East. Most of the guidance show the peak of the Heat Wave during the short range, and by the medium range period energy from the West should work into the Midwest/Great Lakes weakening the ridge and overall oppressive heat. How quickly and how much the ridge is suppressed is still in question, which leads to uncertainty in maximum temperatures for this weekend. Amplitude of this feature as it crosses into the Northeast next week is still somewhat uncertain, but there has definitely been a trend towards a bit flatter flow. Upstream, a ridge builds over the Four Corners region through the weekend and early next week. Models show agreement on a deeper shortwave or upper low moving into the Northwest, which may eventually displace the ridge a bit eastward with time next week. The WPC fronts/pressures progs was based on a blend of the deterministic and machine-learning guidance for the first half of the period, increasing weighting of the ensemble means to just over half by the latter half of the period. This generally maintained good agreement with the previous WPC forecast and the NBM, albeit with sensible weather adjustments to the NBM focused primarily for Max T and afternoon Dewpoints underneath the ridge early period. ...Weather/Hazards Highlights... A significant and major heat wave set to begin by the middle of this week may still continue into next weekend for parts of the Midwest and much of the East. Widespread and daily record breaking maximum temperatures into the 90s to low 100s, combined with high humidity, will result in heat indices approaching or exceeding 105-110 in many places, especially for Saturday. This equates to widespread Major to Extreme HeatRisk from the Midwest/Mississippi Valley eastward to the East Coast. Overnight lows will linger and also be quite warm, with numerous record high minimums possible, bringing little to no relief from the heat in the nighttime hours. Heat may finally begin to abate by Sunday, with upper temperature limits through the weekend possibly restricted by increasing clouds/convection as ridge breakdown begins. Above normal temperatures should expand westward into the Southern and Central Plains as well, with temperatures out West near to below normal underneath of general/weakened troughing. Rain and thunderstorms should expand in coverage across much of the eastern half of the nation this weekend within a very warm, moist, and unstable air mass. Fairly weak overall flow may also help to support at least a localized flash flood threat across much of this region, with possibly some better convection focus near a wavy frontal boundary from the Midwest to the Mid-Atlantic. WPC Marginal Risks are in place from the north-central Plains into parts of the East for the Days 4/Saturday and 5/Sunday Excessive Rainfall Outlooks. Elsewhere, diurnally driven showers and storms are expected from parts of the central Gulf Coast to Florida most of the period with increasing moisture. Showers may refire again later in the period for parts of the Southern/Central Rockies and High Plains, as well as the northern tier ahead of additional shortwave energy. The West looks to remain mostly dry through the entire period. 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 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 $$