268 FXUS02 KWBC 280612 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 212 AM EDT Sun Jun 28 2026 Valid 12Z Wed Jul 01 2026 - 12Z Sun Jul 05 2026 ...Significant, dangerous, and record breaking heat wave expected next week for the Central to Eastern U.S... ...Pattern Overview... The period begins Wednesday with a strong ridge anchored over the eastern half of the country, supporting a sprawling and dangerous heat wave. Meanwhile an amplified trough will be over the West becoming reinforced as multiple impulses move through within the flow, with some energy possibly acting to suppress the Eastern ridge slightly by next weekend. Showers and thunderstorms will be most likely across the Gulf Coast/Florida region, the southern Rockies, and the Upper Midwest to Great Lakes/Northeast. ...Guidance/Predictability Assessment... Good agreement continues amongst the latest guidance for at least the large scale pattern, but the details remain uncertain across the West with various shortwave energies reinforcing the trough. Confidence and predictability is high for the large upper ridge centered over the Tennessee Valley later next week. Out West, a strong shortwave will drop into the Northwest early period, with the GFS continuing to be much more amplified and slower with this system as it slowly drifts east-northeastward. By next weekend, there is some consensus for this energy to ride over the top of the ridge, acting to suppress it slightly, with an expansion of ridging westward into the southern Plains as well. The ECMWF remains less enthused with this late period evolution, wanting to maintain a stronger ridge over the East than some of the other guidance would suggest. The WPC forecast used a consensus of the deterministic and machine-learning guidance early in the period. Removed the GFS completely by Day 5, and increased weighting of the ensemble means into the mix to help tone down the less predictable late period details. Overall, maintaining good continuity with the previous WPC forecast. ...Weather/Hazards Highlights... The most impactful weather hazard during the medium range period will be a long lasting heat wave affecting much of the central to eastern U.S. spanning the short to medium range period. Widespread 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. This equates to widespread Major to Extreme HeatRisk from the Midwest/MS Valley eastward to the East Coast. Overnight lows will 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 slightly by the end of the period, with above normal temperatures expanding westward into the Southern and Central Plains as well. Out West, temperatures will be below to well below normal underneath of the upper trough. Rain and thunderstorms associated with a slow moving frontal boundary will impact parts of the Upper Midwest and Great Lakes into late next week. Moisture anomalies and instability within fairly weak flow may support at least a localized flash flood threat. WPC highlights much of this region within a Marginal Risk for both the Day 4/Wednesday and Day 5/Thursday Excessive Rainfall Outlook. Some of this activity will likely make its way into parts of the Northeast as well as it rounds the northern periphery of the mid/upper level ridge. Elsewhere, moisture funneling between the western trough and the eastern ridge should support showers and thunderstorms across parts of the southern Rockies and southern High Plains into Wednesday. Diurnally driven showers and storms are also expected from the central Gulf Coast to Florida with moisture increasing south of the upper ridge. Showers may increase across parts of the Ohio Valley and East late week/next weekend as the upper ridge slightly weakens and upper level energy tries to intrude into the region. 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 $$