FOUS30 KWBC 150036 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 836 PM EDT Sun Jun 14 2026 Day 1 Valid 01Z Mon Jun 15 2026 - 12Z Mon Jun 15 2026 ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR THE SOUTHERN PLAINS AS WELL AS FOR NORTHERN NEW ENGLAND... ...Southern Plains... 01Z Update: The general synoptic pattern remains on track with a slow-moving cold front likely to be a focus for heavy convection this evening into the early morning hours of Monday. Current radar and satellite trends indicate scattered heavy thunderstorms over central and east TX with a smattering of heavy cells focused across southwestern TX near the terrain. Instability and PWATs are more than sufficient for significant convective development this evening as PWATs well north of 2" across much of TX east of the 100W longitude marker signal a primed scenario for intense rainfall rates >2" in any storm that can materialize. Much of the previous forecast below remains on track, so changes to the SLGT risk were minor in this update. Kleebauer ..Previous Discussion.. A higher-end Slight Risk is noted across west Texas and the Hill Country where afternoon and evening thunderstorms will impact those areas. For the Hill Country, the main flooding threat will be tonight, as merging storms may yield an axis of heavier rain with potential rates of 2"/hr (20-60% chance from the 12Z HREF neighborhood probs). The storms will run into increasing resistance tonight in the form of a strengthening LLJ, which should slow down the forward speed of the storms as the traverse the Hill Country. Due to the flashy nature of the terrain in the Hill Country, the higher-end Slight was warranted. Back into New Mexico, afternoon and evening storms could interact with both the terrain features in the area, such as the Sacramento Mountains, urban El Paso, and any burn scars in the area. Fracasso ...Northern New England... 01Z Update: Only minor changes made to the SLGT risk across northern New England with the main change affecting a trimming of the SLGT and MRGL risk across western and Upstate NY. The general synoptic pattern remains on track as the shortwave trough axis continues to push through Quebec with precipitation just now entering into the outlined area. Heaviest axis of QPF is forecast across VT into the Hudson Valley, most of which will occur overnight along and just ahead of the cold front. Kleebauer ..Previous Discussion.. A Slight Risk is maintained for northern New England. The same cold front that will be impacting the Southern Plains will have a much easier time pushing eastward in northern areas, as a large upper level low over Canada pushes frequent shortwave disturbances east across the northeastern U.S.. Despite the progressive nature of the front, a surge of moisture will rapidly advect northward into New England ahead of the front, aided by increasing upper level support as a strong shortwave becomes more negatively tilted with time as it rounds the southeastern periphery of the upper level low. The moisture surge will also increase the instability, with MUCAPE values around 1,000 J/kg expected on average, and values up to 2,000 in some areas, including southeastern VT. The plume of moisture and instability will support numerous fast-moving thunderstorms training northeastward along and south of the Canadian border. The training storms will impact recently hard hit areas of northern New England, where soils are wetter than normal going into this event (FFG values around 1-2"/hr). While there's some question as to how strong the storms will get, the likelihood they will train along and south of the plume of greatest rainfall is high. The storms will train over northern New England for several hours before the cold front sweeps across from west to east tonight. The hilly terrain here can exacerbate rainfall rates and lead to flash flooding, especially in narrower river/stream valleys. Fracasso ...Mid-Atlantic... 01Z Update: No changes to the previous forecast with the best risk for flash flooding likely to be more urban based or within the complex terrain of the Appalachians and neighboring Blue Ridge. Kleebauer ..Previous Discussion.. Maintained the Marginal Risk for the Mid-Atlantic due to the continued chance for afternoon and evening storms feeding on the same moisture plume that will advance into New England. This could lead to localized instances of flash flooding, especially in urban areas along the I-95 corridor, though the severe threat appears greater. Fracasso Day 2 Valid 12Z Mon Jun 15 2026 - 12Z Tue Jun 16 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER SOUTH TEXAS... ...Southeastern Texas to the Lower Mississippi Valley... In coordination with the Brownsville and Corpus Cristi offices, we have introduced a Moderate Risk area to South Texas for this Excessive Rainfall Outlook. Though there remains uncertainty in the path/strength of the mid-level system over northeastern Mexico, most of the guidance does bring it to the US/Mexican border by 12Z Tue, acting as a trigger to the moisture-laden atmosphere with PWATs of over 2 inches up to near 2.5 inches (>99th percentile or +4 sigma). As this feature pushes northeastward out of the mountains of Mexico towards south Texas, it will not only increase the low level inflow of tropical moisture, but will provide ample forcing to organize the storms into slow-moving lines of training cells that track northward/northwestward with time up the Rio Grande. Any and all storms will have impressive amounts of moisture to work with to produce heavy rain given the fully saturated lower atmosphere all the way up to the tropopause per some forecast soundings. Instability due to extensive cloud cover commensurate with such amounts of moisture will likely be the only limiting factor for coverage of heavy rain. Focused the Moderate Risk on the highest HREF/REFS probs for heavier rain and some very robust CAM QPF (>5-8"), but with room to maneuver in subsequent issuances based on the rainfall that falls tonight. To the north, the strong cold front over north Texas through southern Arkansas at the start of the day Monday will continue making painfully slow progress south towards the western Gulf Coast. The surge of deep tropical moisture will actually further increase the amount of available moisture the storms will have to work with as they push south across Texas. The MCS from Sunday night along the Rio Grande will continue south into Monday morning along the Rio Grande and the Texas Hill Country. This MCS will weaken by midday, only to be replaced with far more numerous showers and thunderstorms all across southern and eastern Texas. These storms will form as the surge of moisture and plentiful instability from the Gulf advects north and west into southeast Texas. The storms from any morning MCS will quickly evolve into a slow-moving line of storms from east Texas into Mississippi due to the abundant moisture and instability running into the very slow-moving cold front roughly near the AR/LA border. For some areas of east-central Texas, northern Louisiana, and western Mississippi, there may be no stop between any early morning rain from overnight MCS and the afternoon convection that quickly blossoms along the frontal interface. High FFGs and somewhat drier than normal surface soils going in to the Day 2 (depending on what happens today/tonight), should work to preclude Moderate Risk level coverage of flash flooding, but the whole area is in a higher-end Slight and a Moderate Risk upgrade is possible with future updates. ...Eastern Maine... Lingering rainfall early on Day 2 may still cause localized runoff issues over eastern Maine before the rains moves out tomorrow afternoon. Added Marginal Risk in coordination with WFO CAR. Fracasso/Wegman Day 3 Valid 12Z Tue Jun 16 2026 - 12Z Wed Jun 17 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE WESTERN AND CENTRAL GULF COAST... ...South Texas... The entire focus of heavy rainfall across South Texas Tuesday will be the speed of movement of the upper level disturbance near or perhaps offshore the TX coast. The dynamical guidance is generally slower than the AI/ML guidance, which has been the case for at least the past 24-36 hrs. But nearly all guidance shows the potential for >3-6" of rain on day 3. Upper level Pacific moisture will combine with exceptionally deep Gulf moisture along the western periphery of the Gulf and support near record PWATs (2.5-2.75 inches) for this time of year for some areas of deep south Texas, particularly along the coast. With the disturbance in place, and strengthening with time, this abundant moisture will be focused into slow-moving bands of heavy rain- producing thunderstorms. The exact tracks/speed of the slow-moving disturbance will be key as to who sees the most rain, as the storms ride north off the Gulf and into coast to the east of the center of circulation. With rain wrapping all the way back toward the Hill Country, this could lead to another day of heavy rain atop saturated soils (and lower FFG values). Again, uncertainty is high with respect to the westward extension of the heavier rain footprint, but an additional several inches of rain is quite possible in the TX coastal plain. A slower movement of the system would support another Moderate Risk area for South Texas, but will wait for a bit more clarity on timing with future model runs. Regardless, there will likely be urban flooding impacts from Brownsville to Corpus Christi and perhaps northward along the coast. ...Louisiana into the South... Up the coast from South Texas, the plume of abundant Gulf moisture will continue to stream north into the slow-moving front that will remain set up from east Texas through northern Louisiana and into western Mississippi. Combined with a 100-kt RER jet near the Mid- South, broad lift may support an arc of higher QPF north of I-10. Training storms tracking eastward parallel to the front will pose a flash flooding problem over the region ahead of the upstream system somewhere along/near the TX Coast. Maintained the Slight for this region, especially considering the likely much more favorable hydrology as this will be the second or third day (depending on where you are) of heavy rain for this region. A faster forward speed of the upper level disturbance could increase the rainfall forecast for this region which may suggest a Moderate Risk with future updates. Fracasso/Wegman Day 4 and Day 5 Valid 12Z Wed Jun 17 2026 - 12Z Fri Jun 19 2026 ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF MIDDLE MISSISSIPPI VALLEY, OHIO VALLEY, MID-SOUTH, AND GULF COAST ON DAY 4 AND DAY 5... 20Z Update: Only minor changes were necessary for the D4 and D5 periods as guidance remains steadfast on a highly anomalous upper air pattern materializing through the upcoming week. Main discrepancies occur over the Southern U.S. with the handling of a disturbance currently progged through the western Gulf. Ensemble outputs were favored in providing any distinct changes to the MRGL and SLGT risks issues for both days, respectively. Adjustments to SLGT risks for both periods were contributed in part to the updated D4/5 QPF and the ensemble probabilities for >1" and >2" areas during the forecast. There could very well be shifts in the alignment of the SLGT and even prospects of future upgrades across both the Central Gulf coast and the Ohio Valley for either period, however will maintain continuity in the SLGT at these leads to allow for greater consensus and better indication of QPF magnitude as we move closer to the impact time frames. Kleebauer ..Previous Discussion.. An anomalous upper-level pattern will be the catalyst for active days 4-5 timeframe from the Gulf Coast on north to the OH Valley and as far east as the central Appalachians. Southeast TX and portions of the Deep South will also experience widespread thunderstorms. On Day 4 (Wed.) a robust 500mb vorticity maximum will spawn a strong area of low pressure at the nose of a 500mb jet streak. ECMWF SAT percentiles show show MSLP values that are among the lowest in the CFSR database (1979-2009) over the Midwest by 00Z Thursday that continue into early Thursday morning over the Great Lakes. 850mb winds will be roaring to the tune of 50 kts and potentially stronger than that over the OH Valley. The combination of highly anomalous low pressure over the Midwest paired with high pressure south of Bermuda will force Gulf moisture to race northward into the Middle MS Valley and on east into the OH Valley. With PWs also above the 90th climatological percentile, storms may be fast movers, but they will contain efficient warm rain processes. A Slight Risk was introduced from the MS Valley to as far east as central OH to account for the increased flash flood potential. Farther south, the pool of anomalous PWs accompanied by a strengthening southerly IVT over the western Gulf will keep the TX Coast at risk for Excessive Rainfall. While guidance still shows some differing solutions, the region will only continue to see soils grow more sensitive after multiple days of rain prior to Wednesday. A Slight Risk was introduced for the Lower and Central TX Gulf Coast, aligning with where the heaviest WPC QPF is located. For Day 5 (Thurs.), between the NAEFS and ECMWF SATs, the southerly winds within the 1000-500mb layer over the western Gulf are remarkable with the entire layer's southerly wind anomalies averaging at least the 97.5 climatological percentile. This means the Gulf is wide open for business, not just with low-level moisture but into the mid-to-upper levels as well. ECMWF and GEFS ensemble means on Day 5 have PWs above 2.2" over the central Gulf Coast with >90th climatological PWs as far north as the OH Valley. A strong cold front will trigger widespread thunderstorms within this environment that is likely to pose a flash flood threat in portions of the recently more sensitive soils of the OH and TN Valleys, leading to the issuance of a Slight Risk in these areas. Farther south, guidance shows varying solutions of what could transpire in east TX. The 12Z ECMWF EFI has a swath of >1 Shift of Tails (SoT) from east TX to as far north as northern MS, and even a small >2 SoT north of I-10 in east TX, indicating a signal for locally significant rainfall being possible in these areas. The details on the development of low pressure in the Deep South remain unclear. That said, there is no denying the copious amounts of moisture at these thunderstorms disposal and soils throughout the region will have only grown more sensitive after multiple days of Excessive Rainfall. A Slight Risk was introduced over the Upper TX coast on east into southwest LA where it aligns with not only the ECMWF EFI signal but the overlap with the more anomalous moisture content and the heavier WPC QPF within the TX/LA area. Mullinax 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 $$