319 FOUS30 KWBC 050051 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 851 PM EDT Sat Jul 4 2026 Day 1 Valid 01Z Sun Jul 05 2026 - 12Z Sun Jul 05 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST KANSAS INTO OKLAHOMA AND PORTIONS OF INDIANA AND OHIO... Scattered areas of convection continue to pose at least a localized flash flood risk across portions of the central and eastern part of the country. Embedded within this we will carry two Slight risk areas into the overnight hours. One across portions of IN and OH where an MCV is focusing convection this evening. Still seeing enough cell mergers to drive some flash flood risk over the next few hours. While activity may generally weaken thereafter, the HRRR has been consistent at indicating a potential for continued convection near the MCV center as it tracks from northern IN into northern OH tonight. Some flash flood risk could thus continue through much of the night over this region. The other Slight risk is across portions of central/northern OK into southeast KS and immediate adjacent areas of southwest MO and northwest AR. Generally expect this activity to start forward propagating off to the southeast, which should limit the extent of the flash flood risk. Nonetheless, high rainfall rates are likely, and brief cell mergers could be enough to result in some flash flood impacts, especially across any more sensitive urban areas. Also, as the system transitions into an MCS, a comma head feature on the northern extent could slow and locally increase rainfall totals across the northeastern portion of the Slight risk area. Chenard Day 2 Valid 12Z Sun Jul 05 2026 - 12Z Mon Jul 06 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID-ATLANTIC... The east to west oriented frontal boundary will slowly drop southward into the Mid-Atlantic during the period. The warm, moist, and unstable airmass is expected to produce widespread slower moving thunderstorms. The atmosphere will be quite favorable for heavy rainfall and flash flooding, both for intense rain rates and repeating/back-building thunderstorms. The latest guidance has come into better agreement focusing the highest probabilities for the intense rain rates and higher QPF over central to eastern PA, portions of central to northern NJ, and far northern Maryland. 12Z HREF has 30-50 percent probabilities for localized 5" totals, with a broader footprint for 3" amounts. The combination of some terrain areas and the highly urbanized corridor makes this area much more vulnerable to flash flooding. While there remains some spatial uncertainty to exactly where the greatest rainfall will occur, the setup favors some locally significant flash flooding will be possible. The Slight Risk was maintained but a future upgrade to a Moderate Risk may be needed over portions of PA if trends continue. A broad Marginal Risk area spans from eastern Oklahoma/Kansas eastward to the Mid- Atlantic/southern portions of the Northeast. Taylor Day 3 Valid 12Z Mon Jul 06 2026 - 12Z Tue Jul 07 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID-ATLANTIC/NORTHEAST ON MONDAY... The threat for excessive rainfall and scattered areas of flash flooding will remain for portion of the Mid-Atlantic for this period. Rainfall occurring during the Day 1 and Day 2 periods may lead to increased soil saturation and lowered flash flood guidance for this region, thus making it more sensitive for additional heavy rainfall. Near and just south of this front instability of 2000 J/kg or greater and PWs over 2" are forecast, an environment supporting efficient rainfall and high hourly rates. The Slight Risk was adjusted minimally with the latest guidance, focusing primarily on the Mid-Atlantic from northern Virginia to southern New York. Stronger low level convergence will be capable of producing a broader area of moderate to locally heavy rainfall across New York into southern New England.; however, with less available instability rainfall rates will likely not peak as high as those further south. Thus, this area is covered by a broad Marginal Risk from portions of Upstate New York to the Cape, south to the Carolinas and then southwest into Arkansas and northern Louisiana. ...Montana... Along and ahead of frontal system, isolated instances of heavy rainfall will be possible capable of producing localized flash flooding. First will be across portions of northeastern Montana as a shortwave trough rounds the base of the building southwestern ridge. Storms will be capable of producing intense rain rates, so a Marginal Risk was added. Chenard/Campbell/Taylor Day 4 and Day 5 Valid 12Z Tue Jul 07 2026 - 12Z Thu Jul 09 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE NORTHERN PLAINS TO UPPER GREAT LAKES TUESDAY AND WEDNESDAY... 20z Update: Only minor changes made to the inherited Slight risk on days 4 and 5, as the areas are still aligned with the overall model consensus. Higher confidence on the day 4 (Tuesday) area, with more spread and uncertainty on the heavy rainfall axis by day 5 (Wednesday). Did go ahead and add a Marginal risk for portions of the Mid- Atlantic on Tuesday. Quite a bit of uncertainty on convective details, but troughing should persist into Tuesday, with PWs over 2" and instability remaining in place. The threat of organized heavy rainfall looks lower than Sunday and Monday, but the ingredients in place still support isolated to scattered convection capable of heavy rainfall rates. Westerly flow will try to bring in some drier air, so the northern and western extent of this risk area is subject to change, but at the moment pretty good model consensus that higher instability/moisture will at least persist across the coastal Mid-Atlantic. Chenard ...Previous Discussion... Slight Risks of Excessive Rainfall have been introduced across portions of the Northern Plains into the Upper Great Lakes Tuesday- Wednesday. A seasonably moist, unstable airmass will be in place along the northern side of an upper-ridge building over the western to central U.S. early next week. An upper-level wave rounding the ridge will help trigger scattered to widespread thunderstorm development at the leading edge of the deeper moisture over the northern High Plains. Propagation ahead of a developing surface wave along a quasi-stationary frontal boundary and developing low- level jet will help maintain storms into the overnight hours through the northern Plains with the potential for at least organized clusters of storms if not a mesoscale convective system. A similar scenario will play out Wednesday as ongoing/renewed storm development will continue eastward into the Upper Great Lakes. Typical uncertainty on the exact location and coverage of convective development remains a concern particularly as the storm evolution Tuesday will likely impact storm development/evolution Wednesday. However, good consensus amongst the deterministic model guidance on areal average totals in the 1-2" range and locally higher amounts of 3-4" supports the threat for scattered flash flooding with potential areal adjustment of the risk in subsequent outlooks. Putnam Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt $$