431 FXUS02 KWBC 281857 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EDT Sat Jun 28 2025 Valid 12Z Tue Jul 01 2025 - 12Z Sat Jul 05 2025 ...Guidance/Predictability Assessment... The latest model and ensemble guidance continues to show relatively good agreement on the overall large scale very summertime-like pattern for the medium range time frame. There are some minor small scale detail differences, much of which will take until the short range to resolve anyways, but also does not have much impact on sensible weather at this point. To note though, the GFS was faster with the trough as it exits the East late week and a bit different with energy distribution across the West. The WPC forecast for today used a blend of the non- GFS blend early in the period, transitioning towards a 50/50 blend of the ECMWF/CMC with the ensemble means. Overall, this maintained good continuity with the previous WPC forecast. ...Weather/Hazards Highlights... Organized thunderstorms with favorable moisture/instability will bring locally heavy convective downpours ahead of an upper trough and a well defined summer surface frontal boundary to progress into the East and South/Southeast by Tuesday and into late next week. An elongated WPC Day 4/Tuesday Excessive Rainfall Outlook (ERO) Marginal Risk area remains from the Northeast/Mid-Atlantic back through the Appalachians and broadly across the South. An ERO Marginal Risk area is also highlighted for Day 5/Wednesday with focus across the Southeast. One area of focus for some heavier rain is across the central to eastern Gulf Coast region. Areas will dry out and moderate to the north post-frontal, but activity will linger along/ahead as the front slows and slowly loses influence across the South/Southeast into late next week. Even before the front nears, moist scattered thunderstorms are likely farther south in the broad warm sector as well. There will initially be less forcing for organization and sustaining of storms deeper down across the southern tier away from the upper jet, but instability could allow for heavy rain rates that may cause localized flash flooding, as likely dependent on smaller scale boundaries. Monsoonal moisture with some connection to possible Pacific tropical development is likely to increase next week in the southern Rockies/High Plains with southerly flow under the upper ridge, thus increasing coverage of rain amounts in storms. Marginal Risks remain planned there for Day 4/Tuesday and also for southern Arizona into Day 5/Wednesday. Areas like the Sacramento Mountains, where the steep terrain and burn scars cause the area to be particularly sensitive to rain and most vulnerable to potential flash flooding, especially with wet antecedent conditions there. Elsewhere, afternoon and nocturnal storm clusters may develop from the Northern Rockies Tuesday onward across the northern Plains and Upper Midwest Wednesday into Friday as moisture/instability pool along/overtop a retreating front. A Day 5/Wednesday WPC ERO Marginal Risk area continues given potential for training of these strong to severe cells. Santorelli/Schichtel 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 (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 $$