FOUS30 KWBC 192016 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 416 PM EDT Sun Jul 19 2026 Day 1 Valid 16Z Sun Jul 19 2026 - 12Z Mon Jul 20 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHWESTERN U.S. FROM WEST TEXAS TO SOUTHWESTERN UTAH, AND EASTERN NORTH CAROLINA AND THE VIRGINIA TIDEWATER REGION... ...Southwestern U.S... Overall, the synoptic pattern remains much the same, with the monsoon ridge remaining favorably aligned. PW anomalies of 2-3 standard deviations above normal will remain across much of the highlighted area. This moisture, along with sufficient instability, and areas of enhanced ascent afforded by easterly-drifting mid- level energy will support another day of scattered to widespread convective activity. Slow storm motions along with cell mergers will raise the threat for locally heavy amounts and flash flooding concerns, particularly for slot canyons, dry washes, burn scars, and low desert areas via mountain outflows. The Slight Risk highlights the area where HREF and REFS guidance indicate the threat for 1-2 inch amounts is greatest. The main change from overnight is a reduction in the northward extent of the Slight Risk area over Utah, now confined to far southwestern Utah. Warmer 700mb temperatures north of the Grand Canyon will likely limit the areal coverage of convection, with a broad Marginal Risk remaining valid. ...Lower Missouri Valley to Southeastern Virginia and Eastern North Carolina... A targeted Slight Risk remains centered over eastern North Carolina and extends into southeastern Virginia. Convection will develop ahead of a slow-moving cold front that will be dropping south into a very moist (PWs 2+ inches) and unstable (MUCAPE > 2000 J/kg) environment, while some modest right-entrance region upper jet forcing will offer some enhanced ascent. Heavy totals appear likely, with both the HREF and REFS showing high neighborhood probabilities for some 2 to 4 inch totals within the Slight Risk area, mainly between the Hampton Roads area and Morehead City. There was a minor northward adjustment of the Marginal and Slight Risk areas across central Virginia to account for the latest model trends compared to the overnight issuance. Less organized activity is expected back along the front extending across the southern Appalachians, Tennessee Valley, and parts of the lower Ohio, mid Mississippi, and lower Missouri valleys. While widespread heavy totals are not expected, the moisture-rich environment (PWs 1.75-2 inches) is expected to support storms capable of producing localized heavy amounts and isolated runoff concerns. ...Eastern Dakotas into the upper Mississippi Valley... A shortwave moving off of the top of the western U.S. ridge will interact with a frontal system advancing through the northern Plains into the Upper Midwest. An amplifying west-southwesterly low level jet will support increasing PWs (1.75-2 inches) and instability ahead of a frontal boundary. The models have trended the axis of heaviest rainfall farther north into central and northern Minnesota, and therefore the existing Marginal Risk area has been extended to the Minnesota/Canada border. Any new burn scar areas will be more susceptible to potential flood issues. ...Eastern Gulf Coast into the Southeast... Newly formed Tropical Depression Two is idling in place across the northeastern Gulf about 150 miles south of Panama City, Florida. Recent radar imagery indicates the core of convection and heaviest rainfall well offshore, and the latest CAM guidance suite suggests this will remain the case going through the remainder of the afternoon and into tonight. However, some heavier amounts along the west coast of Florida are likely with outer feeder bands and could lead to some localized instances of flooding where training convection develops. Therefore, the Marginal Risk was maintained from the overnight issuance. An axis of enhanced low level convergence and pooling moisture to the north is still expected be a focus for diurnal storms capable of producing heavy rainfall rates. Therefore, a Marginal Risk was maintained from the central Gulf Coast northward into the Tennessee Valley. Recent CAM guidance indicate localized totals of 1 to 3 inches across portions of this region through early evening where the most persistent convection develops. Pereira/Hamrick Day 2 Valid 12Z Mon Jul 20 2026 - 12Z Tue Jul 21 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE DESERT SOUTHWEST AND NORTH CAROLINA... ...Southwest and Great Basin... Mid-level energy moving west of the region, and dry air advection from the south will begin to diminish the heavy rainfall and flash flooding threat over West Texas. However farther west, the monsoonal moisture plume will remain firmly in place, ensuring another day of efficient rainfall production over portions of the Southwest and Great Basin. Models show the upper high originally centered over Utah and Colorado beginning to slide southeast, allowing moisture and energy to spread northwest into the Great Basin and along the western slopes of the Sierra Nevada, raising the potential for increasing storm activity and isolated runoff concerns in those areas. The greater heavy rainfall and flash flooding threat will remain focused from southwestern New Mexico and southeastern Arizona northwestward along the Mogollon Rim into northwestern Arizona. This is expected to be the focus for better synoptic forcing and greater instability, supporting intense short-duration rain rates that will elevate the risk for flash flooding, especially in areas of complex terrain, dry washes, and burn scars. For the 19Z Update, a minor westward extension of the Slight Risk was made across northwestern Arizona to the Lake Mead area. ...Upper Great Lakes... An amplifying upper trough supported by energy diving out of Canada will advance from the upper Mississippi Valley to the upper Great Lakes. Strong southwesterly to west-southwesterly low level inflow will continue to sustain deep moisture ahead of the cold front and across the advancing warm front. This moisture along with strong forcing, produced in part by left-exit region upper jet dynamics, will generate organized convection capable of producing rainfall rates of 1-2 in/hr. Fast storm motions should limit the overall heavy accumulation and flash flooding threat. However, localized short-term training could raise at least some isolated concerns. No changes were needed here for the updated Day 2 outlook. ...North Carolina and Southern Virginia... A lingering boundary and corresponding pool of deep moisture convergence, with PWs generally near or slightly above 2 inches, will support additional thunderstorms capable of producing heavy downpours. There has been a trend for heavier QPF in today's guidance across much of central and eastern North Carolina, and after consultation with the local WFOs, a Slight Risk area has been introduced for this area. Heavy rainfall expected through Sunday night will lead to reduced FFGs and more saturated soils that will be more prone to flooding issues. ...Gulf Coast... The models continue to show the footprint of the heaviest amounts associated with Tropical Depression Two over the northern Gulf remaining mostly offshore. The Marginal Risk has been maintained along the coast from West Florida near Tampa, to southeastern Louisiana, which encompasses areas generally along the Interstate 10 corridor, with the highest totals likely near the Big Bend of Florida. Moisture pooling along an axis of enhanced low level convergence northwest of the circulation may extend the threat for heavy rainfall further inland into the far lower Mississippi Valley. If there are northward trends in later model cycles, it is possible that a Slight Risk could eventually be needed for portions of this outlook area. Pereira/Hamrick Day 3 Valid 12Z Tue Jul 21 2026 - 12Z Wed Jul 22 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHWEST AND EASTERN KENTUCKY TO THE DELMARVA... ...Southwest to the northern Rockies... Models show the upper high continuing to shift east as an upper trough begins to drift into the Pacific Northwest. This will allow the monsoon moisture plume to spread farther north, with moisture anomalies over 3 standard deviations above normal extending as far north as the northern Rockies. This will support increasing convective development with isolated flash flooding concerns as far north as southwestern Montana and southern Idaho. However, the greater heavy rainfall and flash flooding threat is expected to remain centered over western New Mexico, central and northern Arizona, and southern Utah. Guidance shows a fairly well- defined shortwave moving around the western periphery of the upper high, which along with PWs over 1.5 inches in many spots, and highly sensitive soils, will likely generate additional widespread storm coverage and flash flooding concerns. Given the synoptic setup and anomalous moisture, this can be considered a high-end Slight for parts of Arizona and a potential upgrade to Moderate Risk may be required in future outlooks if models trend higher. No major changes were needed for this region in the 20Z update. ...Ohio Valley to the Mid-Atlantic... Upon examination of the 12Z model and CAM guidance suite, there is a general upward trend in expected QPF across more of the region to include the central Appalachians and Blue Ridge Mountains, and therefore the two existing Slight Risk areas were merged into a single larger area extending from eastern Kentucky to the DelMarVa. Moist soils and flood-prone mountain terrain are likely to contribute to the flash flood threat across this region. Deep moisture (PWs around 2 inches) will fuel showers and storms ahead of a strong cold front advancing southeast across the region. These storms will be capable of producing 1-2 in/hr rainfall rates, raising flash flooding concerns. The Marginal Risk area was also extended northeastward to include more of central New England where some of the deterministic guidance supports the idea for some 1-2 inch rainfall maxima. Farther east across the Mid-Atlantic, strengthening southeasterly flow ahead of the system moving through the Ohio Valley will transport an anomalous moisture plume into a region of strong ascent. This combination will support increasing coverage of showers and storms capable of producing heavy rainfall. While the exact spatial coverage of heaviest amounts remains somewhat uncertain, portions of the the more flood-prone urbanized I-95 corridor could be impacted, warranting the continuance of the Slight Risk area. ...Gulf Coast... With the heavy rainfall footprint associated with Tropical Depression Two remaining offshore in most of the guidance, we continued to maintain only a Marginal Risk for the central/eastern Gulf Coast that is mainly confined to the Interstate 10 corridor and to the coast. Any northward trends will need to be monitored in case the heavier core of rainfall reaches the coast, which could necessitate the need for a future Slight Risk. Pereira/Hamrick Day 4 and Day 5 Valid 12Z Wed Jul 22 2026 - 12Z Fri Jul 24 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ALONG PORTIONS OF THE SOUTHEAST US AND CENTRAL/WESTERN GULF COAST... ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE INTERMOUNTAIN WEST AND CENTRAl PLAINS ON WEDNESDAY... 2030Z Discussion... Introduced a Slight Risk area along the central Gulf coast on Tuesday and central to western Gulf coast on Wednesday along the path of Tropical Depression 2. Given the amount of shear across the system...the maximum rainfall amounts be displaced to the south of the system which would place it in very narrow corridor along the coast or placed off-shore. But the on-shore fetch of moisture around the center is enough to warrant a Slight for the time being. Until the degree of ridging to the north is resolved...and how much dry air that feeds into the system or its influences on the track...there is too much uncertainty to highlight any more than a Slight Risk area at this point. Otherwise...introduced a SLight Risk area over portions of the Central US as shortwave energy ejecting from the Rockies interacts with a low level boundary to produce convection in an anomalously moist airmass capable of supporting locally heavy rainfall. No other changes needed elsewhere. Bann Previous Discussion... ...Tidewater Region of Virginia and the Carolinas... A slow-moving cold front pushing southeast out of the Mid-Atlantic on Wednesday is likely to continue slowing down its forward speed as it approaches the Tidewater Region of Virginia and the Carolinas on Wednesday. Meanwhile, plentiful tropical moisture will be drawn northeastward from the tropical system that will likely be meandering somewhere near the Louisiana coast on Wednesday. This moisture will ride northeastward ahead of the front, spiking PWATs above 2.25 inches over this entire region. The result of a strong but slow-moving front, well above normal amounts of moisture, and upper level support in the form of a deep trough over the Northeast supporting the surface front from behind/north will make for a nearly ideal scenario for training and backbuilding storms from the afternoon through the evening. This Day 4/Wednesday period is likely to be the fourth consecutive day that showers and thunderstorms have been dropping locally very heavy rain and multiple-inch rainfall totals somewhere in and around eastern North Carolina. The front will act to greatly expand the footprint of heavy rainfall in this area. Since soils are all but certain to be nearly saturated in this area by Wednesday, flash flooding concerns continue to increase. Thus, a higher-end Slight was introduced with this update from Raleigh east, and from Wilmington north through the Hampton Roads area. It's probable that should the trends continue to increase both with the expected rainfall on Wednesday, and the prior days' rainfall in this same region, that a Moderate Risk upgrade will be needed with future updates. By Day 5/Thursday, the front will sag a hair bit further south, likely sparing the Raleigh and Hampton Roads metros from much additional rainfall, but instead concentrating the heaviest rains from the Outer Banks southwest down the coast through Wilmington and including Charleston, SC in heavy rainfall. The ERO thus was started this morning with a Slight Risk for this area. Of course, even just a small increase in forward speed will push the front up to the coast, which would then concentrate all of the heaviest rains off the coast, making the Slight Risk an over-forecast. However, any slower/westward positioning of the front will make for a 5th consecutive day of heavy rains in eastern North Carolina...meaning the Slight Risk would be an under-forecast. Thus, the Slight represents the "happy medium" of these scenarios and fits best with the current rainfall forecast in the area for Thursday. ...Intermountain West... A Slight Risk upgrade was introduced with this update for a portion of the Intermountain West on Wednesday. The area highlighted includes all of southeastern Idaho, much of western Wyoming outside of Yellowstone, as well as far northern Utah and the northwestern corner of Colorado. Well above normal amounts of atmospheric moisture to the tune of up to 4 sigma above normal, and PWATs locally exceeding 1.25 inches will be in place across this region. An approaching longwave trough will direct a strong shortwave northeastward during the afternoon hours. This will result in widespread shower and thunderstorm activity over this area. Topographic interaction with the storms will locally enhance rainfall rates, while also supporting impactful flash flooding as the rain water races down the slopes of the mountains. Due to the abundant moisture available, the storms will not only be numerous, but capable of 2 inch/hour rainfall rates with the strongest cores, a phenomenon not often seen in this part of the country. Wegman 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 $$