601 FOUS30 KWBC 230038 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 838 PM EDT Wed Jul 22 2026 Day 1 Valid 01Z Thu Jul 23 2026 - 12Z Thu Jul 23 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR SOUTHEASTERN VIRGINIA INTO NORTH-CENTRAL NORTH CAROLINA... ...Southeast... In spite of little rain thus far over Hampton Roads, the Moderate Risk is maintained given the combination of ample moisture (PW around 2") and elevated instability ahead of the slow moving cold front. The heaviest activity in the southern Mid-Atlantic has been farther north near the cold front over southern Maryland and in a corridor over far south-central VA and back over the southern Appalachians. The main threat for heavy rain in Hampton Roads is after midnight. A considerable flash flood threat remains for eastern Tennessee through northern North Carolina overnight. This is from flow parallel to the front drifting south allowing for repeating activity. A slug of 2" PW is across west-central NC along with some elevated MLCAPE of 2000 J/kg currently over western NC. This corridor is considered to be in a higher end (or "enhanced") Slight Risk overnight. ...Intermountain West onto the Central Plains... The well-defined mid-upper level vorticity max is lifting up the northern UT/CO border and will lift into WY overnight. The Intermountain West activity has generally peaked with further activity this evening focused over western WY and western CO into northwest NM. East of the Front Range are propagating multi-cell clusters feeding on strong southeasterly flow of Gulf enriched moisture streaming up the Great Plains. Expanded the Slight Risk over northeast CO and southeast WY where FFG is a little lower and ongoing activity should track (based on extrapolation and recent HRRR runs). Overnight activity over central Nebraska tracking southeast into northeastern Kansas is still expected as well (generally after 08Z). ...Gulf Coast/Tropical Storm Bertha... Center of Bertha has tracked south of New Orleans. The main threats are now ahead of the low center. Light scattered banding will continue behind the system over the central Gulf Coast overnight, but this does not warrant a Marginal Risk anymore, so that is pulled. The Upper and Middle Texas are ahead of the low and banding there is more potent, so a Marginal Risk is raised for the overnight around and and south of Galveston Bay where PW is currently peaking around 2.8". Heavy activity and isolated flash flooding are the main rainfall threats for overnight. Jackson Day 2 Valid 12Z Thu Jul 23 2026 - 12Z Fri Jul 24 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF FAR SOUTHEAST VIRGINIA AND EASTERN NORTH CAROLINA... ...Southeast... Convection may be ongoing at the start of the period along or just south of a slow-moving cold front. Hi-res guidance has slowed the southward progression slightly relative to previous model cycles, and the main change with the outlook was to pull the risk contours north to account for where there may be active flash flooding around 12Z Thursday. This is most likely from far northeast North Carolina into the Hampton Roads area of southeast Virginia, as well as the southern Appalachians from southeast Tennessee into southwest North Carolina, and perhaps far northern Georgia. Low-mid level flow parallel to the front, with PWATs over 2 inches, should be conducive to backbuilding and training, and the potential for narrow corridors with persistent hourly rain rates reaching 2 inches per hour. As diurnal heating commences, and especially toward the 18-00Z period, convection is likely to refocus a bit further south where more instability will be building, and perhaps along outflow boundaries that will push away from the synoptic front. This would likely shift the flash flooding threat into the remainder of the Carolinas, north Georgia, and northern Alabama for the remainder of the period, especially during the afternoon and evening. PWATs will generally be around or just over 2 inches, and should continue to support high rain rates at least approaching 2 inches per hour at times. This should lead to scattered instances of flash flooding, and could include some of the larger urban areas in the Southeast. ...Eastern Colorado... A Slight Risk was introduced in Eastern Colorado, as there is emerging signal in guidance for an area of more concentrated convection on Thursday afternoon and evening. HREF and REFS probabilities of rain rates over 1 inch per hour increase to around 30-50 percent between 20Z and 04Z, and probabilities of exceeding 1hr FFG are around 10-20 percent. Precipitable water values above the 95th pecentile for July would be conducive to those higher rain rates in areas where instablity builds. Although convection is likely to steadily progress to the east, rain rates are likely to be high enough to pose a risk for some flash flooding. ...Central Plains... Multiple MCSs will develop across the Central Plains over the next 40 hours -- one late tonight (Day 1 period) into Thursday morning (beginning of the Day 2 period), and another one Thursday Night into Friday (late in the Day 2 period into the Day 3 period). EAS probabilities from the HREF and REFS show much better agreement that the first MCS is most likely from south-central Nebraska into east-central Kansas, and this is where the Slight Risk was maintained. For the second MCS, EAS probabilities are lower, indicating lower confidence and more spread on placement. Therefore, it's not certain that the rainfall footprints of both will overlap to a considerable degree; if that does happen, it would make flash flooding more likely. However, rain rates in the first MCS may be sufficiently high (1-2 inches per hour) to pose a flash flooding threat on its own. ...Bertha/South Texas... 16Z UPDATE: No major changes were made to the outlook with this update, other than small tweaks to account for the latest observational trends and new 12Z hi-res model runs. A slow-moving front will continue to act as a focus for training convective rain bands and thunderstorms from the Upper Tennessee Valley into North Carolina, southeast Virginia, and the far southern Delmarva Peninsula. Although hi-res guidance now indicates less persistence and focus to the convective activity overnight, with somewhat lower rain threshold and FFG exceedance probabilities, the Moderate Risk was maintained for continuity and a favorable pattern for training convection. Within the Moderate Risk area, signals remain strongest in the Hampton Roads area. Meanwhile, the level of concern is increasing for later tonight for the southern Appalachians, in particular the mountainous areas of eastern Tennessee and western North Carolina, and perhaps far northern Georgia. Deep moisture is expected to increase over the next 12 hours as a more direct connection is made with some of the low-mid level moisture associated with Bertha along the Gulf Coast. This can be seen in the CIRA layer precipitable water products from the Surface to 850mb, as well as 850-700mb. There has already been a concerted northward push of anomalous moisture, and the PWAT at BMX increased from 1.86 inches to 2.10 inches between the 06 UTC and 12 UTC balloon launches. As this reaches the stalling front tonight, with increasing westerly low-level flow parallel to that front, ingredients will become favorable for reinvigoration of a training and backbuilding convective band in the vicinity of the southern Appalachians. QPF signals in the hi-res models have increased, with some chances of rain rates reaching 2 inches per hour if organized thunderstorms can become established. Therefore, although the risk level is being held at Slight, this area will be monitored closely in case a targeted upgrade is needed. Models continue to show a coherent signal for heavy rainfall through South Texas, related to a convective cluster well displaced from Bertha's center. A Slight Risk upgrade was considered given the deep tropical moisture that is likely to be present, however this is also mitigated by extremely dry antecedent conditions (rainfall less than 25 percent of normal in the past month). FFG in South Texas is among the highest in the country at the moment. Finally, all models show a steady westward progression of the convection, such that it doesn't linger in any one spot for more than a few hours. Considering that, and in collaboration with WFOs in Corpus Christi and Brownsville, the risk level was held at a Marginal Risk for now. Lamers Day 3 Valid 12Z Fri Jul 24 2026 - 12Z Sat Jul 25 2026 ..THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHEAST AS WELL AS FOR MUCH OF MISSOURI... ...Southeast... The continued presence of the stalled front in the Southeast should continue to focus additional rounds of convection on Friday, although given the lead time the placement is more uncertain. While the front itself may become more diffuse, this may be counteracted by decreasing deep layer mean flow as an upper level ridge axis builds in (potential for slower storm motions) and increasing precipitable water. Models actually show a much larger area of PWATs in excess of 2 inches than prior days, and combined with relatively strong instability, the environment would be very supportive of intense rain rates exceeding 2 inches per hour at times. If these more intense rain rates intersect (and persist) over areas that received heavy rain in prior days, or some of the major urban centers in the Southeast, then some locally significant flash flooding could result. Portions of the region will be monitored for a potential upgrade to Moderate Risk. Right now that seems most likely from north-central Alabama into north Georgia, and the eastern Carolinas, but it's important to stay tuned for future updates as a lot will likely depend on convective evolution over the next two days. ...Eastern Kansas and Missouri... The Slight Risk was maintained and is still centered on much of Missouri. This will be a continuation of convective activity from the Day 2 period. It should be noted there is considerable spread in the position of a potential MCS among available reliable guidance members. For example, the 12Z ECMWF has the rainfall maximum centered in northeast Missouri, to the north of St. Louis. Meanwhile, the 12Z AI-GFS and RRFS are as far away as southeast Kansas, a displacement of around 200 miles. These different model scenarios depict dry or nearly dry conditions where the other has a corridor of very heavy rain. This obviously has implications for narrowing down the risk area. For now the Slight Risk was kept fairly broad to account for model spread, and a large area with at least a 15 percent chance of flash flooding as a result. This may get narrowed with time. Lamers Day 4 and Day 5 Valid 12Z Sat Jul 25 2026 - 12Z Mon Jul 27 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE MID MISSISSIPPI VALLEY THROUGH THE CAROLINAS DAY 4, A PORTION OF THE UPPER MIDWEST ON DAY 5, AND ACROSS PORTIONS OF THE WESTERN U.S. DAYS 4 AND 5... ...Mid Mississippi Valley to the Southeast... The trend with Carolina Coast QPF on Saturday went slower meaning more rain along the Coast. It seems fine to continue with just a Marginal Risk for Day 4, though that was expanded back inland a bit to encompass all of eastern NC. Given the high amounts of rainfall forecast over eastern NC over the next few days, any further trend inland would warrant a reintroduction of a Slight Risk. Widened the Day 4 Marginal Risk over southeast Missouri given some uncertainty on the frontal placement there. The 12Z RRFS is also farther west over south-central MO Saturday afternoon. Otherwise, the expectation is still for elevated storms to then propagate southeast through the Mid South/TN Valley with deepening moisture and training activity likely. Additional activity further downstream along the front is likely over northern AL/much of GA where the Marginal Risk remains. ...Southwest to the northern Rockies... Monsoonal flow through the Intermountain West continues this weekend. EC/GFS PW anomalies are lacking over AZ for Saturday, but elevated over NM/CO/UT into WY. Moisture is more anomalous over all these states on Sunday. The Day 4/5 Marginal Risks are similarly drawn for both days with less coverage in northern AZ maintained for Day 4. Furthermore, the Sacramento Mtns of NM were added to Day 5 given model QPF there along with some added moisture. ...Great Lakes... Decent agreement among guidance for anomalously high moisture shift to shift east from the northern Plains through the Upper Midwest on Sunday on the top side of the upper high centered over the TX Panhandle. This is a northwest flow scenario and where it parallels any boundaries, repeating convection should occur. As of now the heavy rain threat area seems centered on Wisconsin per recent EC-AIFS and PW anomaly positioning from the EC/GFS. The placement should be refined with time, but the presence of repeating heavy thunderstorms has enough confidence to raise a Day 5 Marginal over Wisconsin into the LP of Michigan. Jackson/Pereira 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 $$