FOUS30 KWBC 230714 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 314 AM EDT Thu Jul 23 2026 Day 1 Valid 12Z Thu Jul 23 2026 - 12Z Fri Jul 24 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF CENTRAL TO NORTHEASTERN NORTH CAROLINA INTO FAR SOUTHEASTERN VIRGINIA... ...Southeast... Very few changes were needed with this morning's update across the Southeast, and the forecast remains on track. Unfortunately what also remains on track are these very persistent lines of showers and thunderstorms tracking across central North Carolina and into the Hampton Roads area of Virginia. This is being driven by a strong but essentially stalled out front over Virginia. Anomalous moisture streaming northeastward along the front is originating out of the Gulf and T.S. Bertha. Thus, the constant moisture supply is effectively replacing any moisture lost to heavy rain, so the storms can persist. The front could make a bit more southward progress down the Piedmont of southern Virginia and central North Carolina. This should gradually diminish areal rainfall totals with increasing longitude. Thus, the inherited Moderate Risk targeting northeastern NC and nearby areas remains in place, since the rain is likely to persist into that area right through the day today and the night tonight. Urban concerns into Virginia Beach, Norfolk, Chesapeake, and Portsmouth will remain front and center for the risk of potential impacts from flash flooding. Thus, despite some agreement that most of the heaviest rains eventually push south of those cities tonight, the urban areas lowering FFGs could still result in numerous flash floods today into tonight. The western extension of the front into the western Carolinas through northern Georgia, Alabama, and Mississippi will continue to promote localized instances of flash flooding due to training storms, following the exact same mechanisms as described above. The only difference is the storms are likely to struggle a bit more to organize, so fewer extreme rainfall amounts are expected from the Atlanta Metro west. The Slight Risk is primarily for urban areas. ...Central Plains... The inherited pair of Slight Risks were only tweaked to match with the latest guidance around the edge of the risk areas with this update. Across the east, an MCS will impact portions of Nebraska into Kansas early this morning, but should generally be fast moving and the rain will fall over dry soils. The primary concern for the Slight Risk is for tonight as a new MCS develops. This one will be significantly slower-moving. The MCS will have a robust LLJ tracking due north up the Plains to replenish all rain lost to rainfall. Thus, expect more instances of flash flooding tonight. Across the west, over eastern Colorado, the flash-flood risk will be in the late afternoon and evening during peak heating, as the upper level support and monsoonal moisture will promote more widespread but less organized convection as compared to the MCS impacting areas further east. Guidance has been consistent on the location of the heaviest rains, with little change in the magnitudes as well. Thus, few changes were needed. ...Bertha/South Texas... T.S. Bertha will continue tracking west into Texas. There is expected to be a period of time where the center remains over water over the far northwestern Gulf. This should allow the associated convection, which has always been displaced well southwest of center due to strong northeasterly shear, to eventually move into portions of south Texas. Therefore, the heaviest rains with the entire storm are likely to impact south Texas. There remains some potential that coastal areas such as around Corpus Christi could eventually need a Slight, or locally see Slight level impacts. But since most of south Texas remains dry, much of Bertha's rains in the area will be beneficial, with only isolated instances of flash flooding. Thus, the Marginal Risk in this area was left little changed with this update. ...Southwest... Both available monsoonal moisture and forcings will diminish today as compared to the scattered convection seen on Wednesday. Thus, a Marginal Risk was left in the areas where convection will be most prevalent, generally for Colorado, Wyoming, and Utah. While some showers and storms may impact areas further west, into Arizona, Nevada, and into Idaho, both coverage and intensity there will be much less, so the threat should be less than 5% for most areas of those states. Wegman Day 2 Valid 12Z Fri Jul 24 2026 - 12Z Sat Jul 25 2026 ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST AS WELL AS FOR MISSOURI AND NORTHEASTERN KANSAS... ...Southeast... The front impacting the Carolinas remains solidly in place on Friday as steadily training bands of showers and storms track along the front along the coast of the Carolinas. The heaviest rainfall totals do shift a bit from Thursday, focusing right along the coast from central South Carolina through much of the Outer Banks to Albemarle Sound. Hopefully, that southward shift allows for areas to the north very hard hit both now and on Thursday to get far less rainfall by Friday, albeit not quite none. Localized intrusions of warmer air over southern Virginia may allow for brief showers and storms to impact some of the hard-hit areas, but total rainfall does not look to be impactful, especially as those hard hit areas will still be recovering from today's rainfall. This general lack of overlap of the heaviest rainfall from Wednesday to Thursday, and the focus over generally flood-resistant areas of the Low Country to the Outer Banks allowed for the risk area to remain at a Slight, and a Moderate upgrade was not considered. Once again, the front extends back to the west over northern Georgia, Alabama, and Mississippi, so the Slight was continued a second day from Birmingham through Atlanta. ...Missouri and Kansas... An ongoing MCS at the start of the Friday period will be the primary animus for flash flooding across northeastern Kansas and extending across much of northern and central Missouri on Friday. The MCS is likely to persist through midday, diminishing through the afternoon. Comparatively very little convection is expected Friday night over this area, so the flooding focus will be almost entirely Friday morning. Urban concerns in Kansas City and eventually into St. Louis will pose the biggest impact concerns. ...Southwest... Convection remains very widely scattered across the 4 Corners region on Friday. Nominally higher flash flooding threat will exist over eastern New Mexico and into the Texas Panhandle. The area is very dry going in, so most of the rain will be beneficial for impacted areas. An isolated flash flooding threat will remain. Wegman Day 3 Valid 12Z Sat Jul 25 2026 - 12Z Sun Jul 26 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE COASTAL CAROLINAS... ...Southeast through the Tennessee Valley... A deepening longwave trough pushing south down the East Coast on Saturday will finally provide a push to the stalled out front over the Carolinas to allow it to push through the coast and offshore by Saturday night. Thus, Saturday will be the last day where heavy rainfall will threaten the coastal Carolinas. However, given prior days' rains, especially the rain expected on Friday, a Slight Risk upgrade was introduced with this update. Fortunately, outside of urban areas such as Wilmington, Myrtle Beach, and perhaps Charleston, SC on the south side, flat terrain, sandy soils, and vegetation should all help to suppress the flooding risk a good bit, despite the heavy rainfall from Friday continuing into Saturday. Further west across the Tennessee Valley, the front will remain stuck, as the aforementioned longwave trough only advances east of the Appalachians, so the Tennessee Valley will remain in a warm advection regime, allowing for periodic showers and thunderstorms to move over cities such as Nashville, Chattanooga, and Huntsville again on Saturday. In addition to topographic concerns, it's probable this area may also need a Slight Risk upgrade in coming days once the events move into CAMs range and amounts (typically) rise. ...Southwest... The monsoon recharges and resets across the 4 Corners region on Saturday. A westward moving shortwave moves up the Rio Grande, which when added to renewed monsoonal moisture, will make for a renewed round of afternoon showers and thunderstorms capable of flash flood producing amounts of rain across central and western New Mexico and into southeastern Arizona. Given the recent wet weather and the expected intensity and organization of the storms in this region on Saturday, here too appears probable to need a Slight Risk upgrade for some areas as the event moves into the CAMs range. Wegman Day 4 and Day 5 Valid 12Z Sun Jul 26 2026 - 12Z Tue Jul 28 2026 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE WESTERN U.S. AND ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION INTO THE OHIO VALLEY AND CENTRAL APPALACHIANS SUNDAY THROUGH TUESDAY... ...Southwest to the northern Rockies... Monsoonal flow through the Intermountain West continues into early next week. EC/GFS PW anomalies are highest (closer to 2 standard deviations above normal) across AZ, especially southern AZ on Day 4 (12Z Sun-12Z Mon) with PWs between 1.75-2.00". Suspect southern AZ could eventually see a Slight Risk area during this period, especially considering the higher likelihood of more vigorous shortwave activity rotating westward south of the mid/upper level ridge. For now however will maintain the Marginal Risk, given the spread in the global guidance and current low probabilities of greater than 1-2" of QPF within the 24hr period. For Day 5 (12Z Mon-12Z Tue), essentially minor adjustments to the broad Marginal Risk area across the 4-Corners, Southwest, central Rockies, and central High Plains. The globals (ECMWF, GFS, and CMC) all show convectively-aided shortwave activity traversing W-E overtop the flattening mid-upper ridge, into the central High Plains, which would explain the eastward expansion of the Marginal Risk area from the Day 4 ERO. Global ensembles also show an uptick in PW anomalies into the central High Plains as well during this time, along with an increase in areal-average QPF. ...Upper Midwest-Great Lakes-Ohio Valley-Central Appalachians... Global guidance, to varying degrees, continues to show convectively-aided shortwave activity riding down the top side of the upper ridge. The guidance shows these ridge crawlers becoming a bit better organized through the day 4-5 period, with an uptick in deep-layer QG forcing (Qs convergence) and increasing low-level moisture transport. For now, have maintained the relatively compact Marginal Risk on Day 4, while introducing a broader Marginal Risk on Day 5 stretching through the Great Lakes, OH Valley, and Central Appalachians. At this point, given the spread in the guidance QPFs, along with the strong low-mid level shear with the deep northwest flow and progressive north-northwest MBE/Corfidi Vectors, will cap the ERO risk at Marginal. Hurley 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 $$