Subj : HVYRAIN: Excess Rain D1-2 To : All From : Mike Powell Date : Sun Jun 14 2026 08:16:43 FOUS30 KWBC 140803 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 403 AM EDT Sun Jun 14 2026 Day 1 Valid 12Z Sun Jun 14 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... Today will likely be the calmest of the next 3 days across Texas, which isn't saying much as it will still be plenty active. A very slow moving cold front will sink south across Oklahoma and Arkansas today. Ahead of the front, an impressively moisture-laden air mass is in place over not just Texas, but much of the Gulf Coast. Across eastern Texas, an ongoing MCS across Oklahoma and Arkansas delineating the leading edge of the aforementioned cold front will continue to drift south and weaken through the morning hours, which is typical behavior for MCSs once the sun comes up. While the MCS will have some forward speed to it, the availability of plentiful moisture, with PWATs to 2 inches will continue to support heavy rainfall with the strongest cells. The remnants of the MCS will likely impact the Metroplex in the mid-to-late morning. Meanwhile, plentiful southerly flow off the Gulf into southeast Texas will lead to widespread but largely disorganized shower and thunderstorm activity from the Houston and San Antonio metros north. The plentiful moisture will still be available, so anywhere where cell mergers or localized training features develop, localized flash flooding will be possible today. Any urban areas will only increase the flash flooding potential, though there's considerable uncertainty whether any of the biggest cities in Texas will be directly impacted. Across west Texas and the Hill Country, afternoon and evening thunderstorms will impact those areas, with portions of west Texas recently hard hit from heavy rains at a higher threat for additional flash flooding. A higher-end Slight has been issued for this region. For the Hill Country, the main flooding threat will be tonight, as an MCS develops due to plentiful merging thunderstorms and a southward push of the cold front in that region. 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 also introduced for this region as well. 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. ....Northern New England... A Slight Risk upgrade was introduced with this update in coordination with BTV/Burlington, VT and CAR/Caribou, ME forecast offices. The same cold front that will be impacting the Southern Plains will have a much easier time pushing eastward, 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 north 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 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. 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. Topographic effects could locally increase rainfall rates, as well as worsen any possible flash flooding. This further supports the Slight Risk upgrade for the area. ....Elsewhere... The Marginal Risk for the Mid-Atlantic and the east coast of Florida are largely the same. For the Mid-Atlantic afternoon and evening storms feeding on the same moisture plume that will advance into New England could lead to localized instances of flash flooding, especially in urban areas along the I-95 corridor, though the severe threat appears greater. On the east coast of Florida, sea breeze interactions with the abundant moisture over the state should allow for a renewed development of afternoon and evening thunderstorms today. The storms will be nearly stationary, so mergers will pose the greatest threat for more prolonged periods of heavy rain, though all strong cells will be capable of localized heavy rain. Wegman Day 2 Valid 12Z Mon Jun 15 2026 - 12Z Tue Jun 16 2026 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTH TEXAS THROUGH THE LOWER MISSISSIPPI VALLEY... As far as changes to the inherited forecast go, the day 2 forecast is the most similar to the prior forecast. A strong cold front over north Texas through southern Arkansas at the start of the day will continue making painfully slow progress south towards the western Gulf Coast on Monday. Meanwhile a 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), 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. For South Texas, the primary flash flooding threat for the period will occur overnight Monday night. While the abundant moisture will be in place in this region, there will be a lack of forcing, due to the distant cold front over the Hill Country, until the arrival of a potent upper level disturbance. This disturbance is likely at least in part the remnant circulation of former East Pacific tropical storm Cristina. As this feature pushes northeast 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 northwestward with time up the Rio Grande. PWATs will be 4 sigma above normal, exceeding 2.5 inches at times, so any and all storms will have impressive amounts of moisture to work with to produce heavy rain. Instability due to extensive cloud cover commensurate with such amounts of moisture will likely be the only limiting factor for coverage of heavy rain. A Moderate Risk may also need to be considered in south Texas should coverage of storms remain similar with more CAMs coverage and portions of this area get significant rainfall on Day 1/today. Wegman $$ --- SBBSecho 3.28-Linux * Origin: Capitol City Online (618:250/10) .