FOUS30 KWBC 110851 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 451 AM EDT Sat Jul 11 2026 Day 1 Valid 12Z Sat Jul 11 2026 - 12Z Sun Jul 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS ARIZONA AND THE SOUTHERN PLAINS TO THE CENTRAL APPALACHIANS... ...OK into the OH and TN valleys... An active convective regime is anticipated ahead of a southeastward moving shortwave trough axis extending from MO to OH. At 12z this morning, an initial round of convection will be ongoing from southern IL into portions of KY and TN. Model guidance supports a transition toward a primarily forward propagating convective mode this morning, which should place the overall flash flood risk on a declining trend, though localized upwind propagation may keep an isolated threat going. By this afternoon, the primary MCV/shortwave will shift over IL and IN, interacting with a southward moving frontal boundary to trigger scattered redevelopment across portions of IL, IN and WV. Within this zone, PW values near or just under 2" will overlap with CAPE of 1000-2000 J/kg. While widespread convective organization is not anticipated, slow cell motions and localized mergers near the frontal zone will support heavy rainfall rates capable of producing localized pockets of 2-3" of rain. This is supported by the 00z HREF and REFS, which both show FFG exceedance probabilities of 15-40%. A more organized, and potentially higher end, flash flood threat is expected to evolve later this afternoon into tonight across portions of KY and TN. Convection should develop to the south- southeast of the main shortwave/MCV, likely focusing along remnant outflow boundaries and instability gradients left behind by the morning activity. Global deterministic and AI models favor a heavy rainfall axis focused primarily from KY into northeast TN, whereas high res models (including the RRFS/REFS) suggest the core threat may track further south into TN. Given the strong westerly low level moisture transport south of the MCV, the environment will be favorable for backbuilding and training convective clusters tonight. This environment, combined with PWs hovering around 2", suggests that many HREF members may be underdoing the afternoon/nocturnal threat. Do expect to see a swath of heavy rainfall materialize somewhere across the KY/TN corridor, where an axis of locally higher end flash flood impacts is possible. A higher end Slight risk is maintained, with a MDT risk upgrade not out of the question if we gain spatial model convergence and more confidence on exact convective mode. Further west, isolated to scattered flash flooding is also expected across portions of central OK into AR. Low level flow will become convergent on the southwestern flank of the broader convective regime. Slow cell motions near a boundary will pose a threat over OK, while enhanced northerly flow on the western periphery of the MCV/shortwave will converge with the broad south-southwesterly inflow to promote some backbuilding/training threat over parts AR. ...Mid-Atlantic... A localized flash flood threat is forecast across portions of the Mid-Atlantic. While low level flow will be northerly, one or two low level convergence axes are projected to setup across the region, potentially acting as a focus for convection. Despite the northerly flow, ample moisture and instability will remain in place. Convective cells will generally track from north to south, but localized repeating cells will be possible along the trough axis. The strongest signal for localized 3" totals with the HREF resides along the coastal plain from NJ southward into southeast VA where convergence is enhanced. Because FFG values are generally higher here compared to inland locations, think the overall flash flood risk should stay isolated, though localized urban and low lying flood impacts are expected. ...AZ and NM... The persistent terrain driven pattern continues across the Southwest, with convection developing over the higher elevations before propagating southwestward into a pooling instability axis over the lower deserts of southern AZ. Instability and moisture profiles should be a bit higher today relative to the past few days, leading to a corresponding increase in the overall flash flood risk. Both the 00z HREF and REFS depict greater convective coverage and higher localized rainfall totals. While fast southwestward storm propagation and cell speeds may act as a limiting factor, the moisture/instability footprint should be sufficient to promote some cell mergers and localized 1-2"/hr rainfall, justifying the maintenance of the Slight risk. A Marginal risk has been added to portions of eastern NM. This area received locally heavy rain yesterday, and the model QPF signal is a bit stronger today within an environment characterized by slightly higher moisture and instability. Convection should remain isolated to scattered, with the primary flash flood threat focused over recent burn scars, particularly across the Sacramento Mountains. ...TX... A Marginal risk was added to portions of the TX Hill Country, where PWs are forecast to climb above 2". Isolated to scattered convection is expected within a broad southerly low level flow regime. While most cells will remain transient and produce only brief downpours, any cells that establish mesoscale organization could briefly train or backbuild into the low level inflow. Guidance suggests a weak MCV currently south of the Rio Grande that may track northward towards the region later today, which could provide an additional focus for ascent. The risk area aligns closely with the HREF and REFS 1" EAS probabilities of 10-20% (signaling organization potential), and 3" neighborhood probabilities exceeding 40%. Global deterministic and AI suites also show a distinct convective focus over this corridor. Chenard Day 2 Valid 12Z Sun Jul 12 2026 - 12Z Mon Jul 13 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF EASTERN KENTUCKY AND TENNESSEE INTO THE CAROLINAS.. ...Southeast Quarter of the Country... A Slight risk has been introduced stretching from KY and TN eastward into southern VA and the Carolinas. A well defined shortwave/low over the KY/TN vicinity will interact with a slow moving backdoor front to focus organized convection. High res guidance, including the RRFS, FV3 and 3km NAM, indicates a concentrated axis of convection capable of producing localized totals exceeding 3". While the global GFS and ECMWF are less pronounced with their QPF swaths the GEM regional and UKMET are more in line with the high res guidance. The AIFS and AIGFS also depict a corridor of enhanced QPF that generally matches the Slight risk placement. Beneath the closed low over KY and TN, convection may be less organized, but slow moving. Given PWs near 2" and the possibility of saturated soils from day 1 rainfall, a flash flood risk should continue. Across the central and eastern Carolinas PWs over 2" combined with low level southerly moisture transport and backdoor frontal convergence should create an environment for high rainfall rate driven flash flood potential. Surrounding the Slight risk, a broad Marginal encompasses eastern NM, TX and much of the Southeast. A southward advancing cold front, the aforementioned mid level shortwave/low, and upper jet support will provide the necessary synoptic forcing for scattered convection. PWs over 2" and CAPE of 2000-3000 J/kg where daytime heating is maximized, will support heavy rainfall rates. Some mesoscale uncertainty exists with the track and strength of the shortwave and frontal positions. An embedded Slight risk or two may be needed on future updates as confidence increases. Increasing low level westerly flow along the central Gulf Coast provides a signature for backbuilding and training, but model divergence on the exact axis remains. Given the higher regional FFG, did not want to go with an overly large Slight risk at this time. ...Southwest... Monsoonal moisture and instability will expand northwestward on Sunday, necessitating a broader Marginal risk across AZ. While an embedded Slight risk may eventually be needed, lingering questions regarding storm coverage and organization keep the risk at Marginal for now. Current indications suggest that while robust convection will initiate over the terrain, it will propagate westward quickly, potentially limiting the threat to isolate instances of flash flooding. Chenard Day 3 Valid 12Z Mon Jul 13 2026 - 12Z Tue Jul 14 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE CENTRAL GULF COAST... ...Central Gulf Coast to the Southeast... The inherited Slight risk across portions of the central Gulf Coast has been maintained and expanded both westward into southeast TX and eastward into the FL Panhandle. A favorable synoptic and mesoscale setup for training and backbuilding is forecast to align with coastal areas. Enhanced west to northwesterly low level flow south of the persistent shortwave/low over the TN/GA vicinity will converge with southwesterly inflow off the Gulf. This configuration is conducive for upwind propagation and some training convection. While some uncertainty remains regarding how far inland the heavier totals will reach, the moist airmass characterized by PWs around 2.25" will support heavy rainfall rates. Further west, increasing low level southerly moisture transport out of the western Gulf will push up the Rio Grande Valley and into central TX, potentially resulting in convective clusters Monday night. Future shifts may need to expand the Slight risk even further into TX depending on how this threat evolves. A broad Marginal risk remains in place from TN into the Southeast and southern Mid-Atlantic, Similar to day 2, a lingering shortwave/low will continue to interact with a backdoor frontal zone. Model divergence exists regarding the exact positioning of these features and the available instability footprint by this time. Given this, and the fact that model QPF signals are a bit more muted compared to Sunday, we will maintain the Marginal risk...although an embedded Slight risk upgrade may still eventually be needed as the mesoscale details clarify. ...Southwest... A Marginal risk is maintained from southern NM into AZ, southeast CA and southern NV. Deep monsoonal moisture will continue to push northwestward with isolated to scattered convection expected TO result in at least a localized flash food threat. Chenard Day 4 and Day 5 Valid 12Z Tue Jul 14 2026 - 12Z Thu Jul 16 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ALONG PARTS OF THE CENTRAL GULF COAST ON MONDAY... ...Southeast U.S. into Texas... Lingering effects from elevated moisture and slowly decaying quasi-stationary front across the Southeast U.S. will lead to one last period of elevated convective enhancements from east TX through the southern half of the Southeastern CONUS. PWAT anomalies will remain generally seasonal to perhaps upwards of +1 standard deviations over the region, enough of a threat for heavy rain prospects in a environment that favors relatively slower cell motions. Considering the fact some of the Southeast will have received a formidable amount of rainfall leading into the D4, some localized flash flood concerns will linger for at least one more day before finally waning into the D5 where the risk over the Southeast is void and we settle into a more benign pattern overall. Further west into the western half of TX, the same story cannot be said as the pattern will begin shaping up into a much more favorable flash flood environment thanks to a shift in the mid and upper level pattern west of the Mississippi. Dominant ridging over the top into the northern tier of the CONUS will give way to a broad inverted trough axis migrating westward into the Southern Plains as we move into the middle of next week leading to weakening flow aloft and a myriad of smaller mid-level perturbations rotating under the dominant cyclonic flow. Lowering heights and regional forcing align to foster a more suitable convective environment across the western half of TX with an emphasis currently on west and southwest TX as noted via the multi-model consensus in both the deterministic and ensemble outputs. Some of the guidance is incredibly aggressive in their presentations with several inches of rain in both the D4 and D5 time frames with a general maxima located over the Lower Trans Pecos over into the neighboring Edwards Plateau where the pattern would allow for greater low-level convergence and prospects for organized convective clusters to sneak out of Mexico (Mexican State of Coahuila). Considering a solid agreement within the model suite this evening, felt confident enough to introduce a SLGT risk across southwest TX over into the Edwards Plateau and portions of the central RGV. This is certainly an area to monitor closely as significant rainfall potential is plausible in the current synoptic evolution being depicted. ...Southwest U.S... The Southwestern U.S. will lie within the western flank of the broad ridge pattern over the Central and Eastern U.S which will provide a dominant southerly flow over the region allowing for continued moisture advection and enhanced surface troughing over AZ up through the Great Basin. This pattern is a continuation of the Monsoonal presence out west with a potential for increasing flash flood prospects as multi-day impacts could spur targeted opportunities for repetition of areas getting hit by convection in consecutive periods. This setup remains very stable in terms of the broad synoptic pattern in place over the western CONUS, however we will see a persistent moisture plume advect more formidable deep layer moisture poleward as we move into early-mid next week leading to PWAT anomalies pushing the 90-99th percentile according to the NAEFS and 00z ECENS outputs. The strongest anomalies will lie within the Great Basin up into the Northern Rockies on D4 with some modification by D5, but still very much entrenched within the upper bounds of the anomalies, especially over the Northern Rockies and Interior Northwest. Increased upper troughing migrating from the west will slide under the ridge across the Northern CONUS leading to an enhancement for convective potential over a broader scope by D5 with widespread thunderstorm prospects aligned from the Canadian border in MT down through the Inter-Mountain West into the Southwestern deserts. This setup can lead to sneaky significant rainfall prospects for those in the interior with a more typical Monsoonal presentation in the convective coverage. Given the above variables, the MRGL was expanded north and northwest for D4 into the Great Basin with another MRGL risk added across the Northern Rockies in the western half of MT and northern ID. D5 is a broad MRGL risk for much of the Southwest and interior west, including areas that were omitted from the previous period(s) MRGL risks. There is potential for targeted SLGT risks to be issued in future updates as we move closer to the event, so please check back over the next several days as the pattern becomes much more active and favorable for flash flood prospects. Kleebauer 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 $$