Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 25 2025 00:54:47 FOUS30 KWBC 250054 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 854 PM EDT Tue Jun 24 2025 Day 1 Valid 01Z Wed Jun 25 2025 - 12Z Wed Jun 25 2025 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF CENTRAL AND SOUTHERN NEW MEXICO... ....New Mexico... A strong warm core ridge centered over the Ohio Valley and Mid-=20 Atlantic with its western extent pushing back west beyond the=20 eastern portions NM. A steady south-north progression within the=20 mid and upper levels will send numerous smaller shortwave=20 perturbations through NM. Anomalous moisture ranking in the 99th=20 percentile via NAEFS and ECENS Climatological percentiles will=20 remain parked over the region. Morning activity left some southern areas out of the mix today, but the 18z HREF probabilities of 0.5"+ suggest that this region remains a threat overnight, possibly from convection moving in from the west. Local topographic effects=20 within this pattern will yield some significant rainfall potential=20 over areas that are prone to flash flooding, especially with the=20 burn scars still present near Ruidoso creating higher runoff=20 capabilities.=20 The difference the past 24 hrs. has been the expected influence of the approaching trough out west providing a reinforcement of the trailing upper jet with the amplitude of the pattern creating more room further west for large scale ascent, and moisture advection back into the western half of NM, even sneaking into Southeast AZ. The entire evolution has spurred scattered to widespread=20 thunderstorm activity over the aforementioned regions with cold=20 pool mergers from storms likely to produce some upscale growth in=20 the evening as the convergence of cold pools will act to spawn more multi-cell modes. The flash flood threat will linger through the=20 overnight time frame before finally settling down closer to=20 Wednesday AM. The various risk levels were barely nudged as recent radar reflectivity trends and 18z HREF probabilities of heavy rainfall at various threshold indicate that local 2-4" totals remain possible=20 into early Wednesday. ....Central Plains to Midwest... Thunderstorms are most numerous near the NE/CO border and northwest MO at this time as a shortwave enhances activity. A ring of fire=20 type of convective pattern remains from NM through portions of the=20 High Plains into the Central Plains and Midwest towards the Great=20 Lakes around the northwest periphery of the warm core ridge.=20 Activity is along and near a quasi- stationary front bisecting the=20 areas above. Areas of northeast KS, southwest IA, and northwest MO=20 are the main focus for flash flood concerns with saturated grounds.=20 Thunderstorms are likely to carry east and northeast into=20 Wednesday morning towards the Great Lakes.=20 A strong 700-900 kg/ms IVT pulse is advecting northeastward into=20 the Central Plains and Midwest, so the heavy rain threat with=20 2-3"/hr rates will certainly have potential for basically anywhere=20 in the Central Plains/Midwest domain. Recent trends suggest that=20 convection moving across southern NE would be a concern over the=20 next several hours. The nocturnal LLJ allows the stationary front=20 to begin lifting north in the form of a warm front tonight, in=20 theory. The mean layer flow orients more parallel to the front=20 creating an environment capable for cells to mature and begin=20 training over areas within proxy to the boundary. Roth/Kleebauer Day 2 Valid 12Z Wed Jun 25 2025 - 12Z Thu Jun 26 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF NEW MEXICO, CENTRAL PLAINS AND MIDWEST... ....2030Z Update... Following a similar trend to the Day 1 update, the main adjustment to New Mexico and Texas includes a Southward extension of the Slight Risk area to the International Border based on HREF and REFS EAS probabilities of 1-2". Coverage of rainfall is still expected to diminish compared to yesterday, although additional significant flash flooding is possible in light of ongoing activity. Depending=20 on overlap of rainfall, a Moderate Risk is still on the table for=20 future updates. In the Upper-Midwest, the Slight Risk was expanded northeastward based on a consensus amongst the HREF and REFS suite. Neighborhood probabilities suggests rainfall amounts of 3-5" are possible as thunderstorms develop and train along an east-west oriented front amid highly anomalous precipitable water values around 2" (in the 99th percentile per the NAEFS). As this moist plume advects eastward, diurnal heating along the front should spur scattered thunderstorm development across the Northeast and Mid-Atlantic. While weak wind profiles should limit overall storm organization compared to further west, brief very heavy rainfall rates could drive isolated flash flooding issues atop saturated soils in the region and sensitive urban areas. A Marginal Risk was also introduced over the eastern Gulf Coast as a retrograding upper-low begins to slow down over the region. Activity should remain fairly disorganized beneath this feature, although isolated flash flooding is possible with saturated soils in the region. Asherman ....Previous Discussion... ....New Mexico... Despite a smaller areal coverage anticipated for convection across New Mexico for Wednesday, scattered thunderstorms will still cause problems during afternoon initiation as ample heating during the prime destabilization window (16-21z) will yield another threat of heavy rainfall across the terrain and adjacent valleys in Central and Southern NM. Current signals are nowhere near as robust as the D1 time frame, but with forecasted significant impacts the period prior, there's a greater threat of truly compromised FFG's leading in, allowing for the bar to be very low for flash flooding over areas that will see significant rainfall in the areas referenced above. Hi-res ensemble blended mean QPF is now solidly within the 1-2" range with locally higher totals across the Sacramento's. Areal average 0.5-1" of rainfall is forecast over much of South-Central NM and over the Sangre de Cristos with totals potentially up to 2" in stronger convective cores. The overlap with the previous period allows for at least a SLGT risk with a higher end SLGT progged over the Sacramento's where convective initiation is likely. A targeted upgrade is plausible within the two main mountain areas in the state, especially when you factor in the antecedent conditions for the period in question. If CAMs come in more robust, or impacts during the D1 are severe enough to fully compromise soils to where any convective threat could be deemed significant. ....Central Plains to Midwest... Convective pattern across the Plains and Midwest at the end of the D1 will translate northward into the Upper Mississippi Valley with organized convection over NE/IA and SD/MN converging along the propagating warm front leading to a swath of heavy rainfall across much of the Southern 1/3rd of MN. All guidance is in agreement on a pretty significant QPF shield moving through the area encompassing Southern MN up through Northwest WI with some back-building potential along the front as it migrates north and begins to slow its momentum. Areal average of 1-2" with locally up to 4" totals are forecast across that portion of the Upper Midwest, reflected well within the NBM 90th percentile QPF signature, as well as within the 12-00z time frame covered by the end of the 00z HREF blended mean. This is just round 1 of what will be yet another secondary convective initiation come Wednesday evening when another strong shortwave and attendant IVT pulse comes pushing back over Eastern NE, Western IA and points north. Additional heavy rainfall will intersect many areas that will have seen significant totals earlier in the period and the second half of the D1. The compounding impacts will lead to scattered to widespread flash flood instances as FFG's will be notably lower comparatively to the before the previous rounds. Ensemble bias corrected mean is now between 3-4" over a large area encompassing Southern MN into Northwest WI with 2-3" positioned just to the southwest of MN. EC AIFS output is in agreement with the positioning of the QPF maxima anticipated, something that has not been the case over the past few days, so we seem to be moving into a greater consensus. As a result, there is a large high-end SLGT risk positioned from Northeast NE up through MN into the western portion of WI. An upgrade within anywhere in that zone is plausible in the coming updates as multi-day impacts could spur some locally significant flash flood prospects. Kleebauer Day 3 Valid 12Z Thu Jun 26 2025 - 12Z Fri Jun 27 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE MIDWEST AND NORTHERN GREAT LAKES... ....2030 Update... A Marginal Risk was also added over parts of the eastern Gulf Coast as the aforementioned upper-low lingers overhead and overlaps with rainfall from the day before. Otherwise, generally minor adjustments overall to the overnight thinking. Could see the need for targeted upgrades in the Midwest and Northeast/Mid-Atlantic depending on overlap from Day 2, so stay tuned as high-resolution guidance comes into range in subsequent updates. Asherman ....Midwest... The final shortwave in the progression bleeding over from the previous D2 time frame will continue pushing northeast before finally vacating the Upper Midwest later on Thursday. Heavy rain threat will continue over parts of MN and WI before eventually impacting the Western U.P. of Michigan before its departure. Instability across the region will be significantly lower than previous days with the warm front becoming stationary prior to reaching the southern shores of Lake Superior. The threat for flash flooding is most notably in the first 6-12 hr window of the forecast with a sharp decline in the threat afterwards as the pattern shifts with the ridge expected to be breaking down. 1-2" with locally higher amounts will allow for flash flooding in any area from IA up through MN/WI, especially in places where significant rainfall has occurred in prior periods. A broad SLGT risk remains in place over the Northern Great Lakes and Upper Midwest with the biggest change being the extension down through Central IA as trailing thunderstorms are forecast within the frontal orientation Thursday afternoon and evening. ....New Mexico... Isolated to scattered thunderstorms across the Sacramento's and adjacent desert will maintain at least some threat for flash flooding given expected wet antecedent conditions following previous multi-day convective impact. Coverage and magnitude will be lower than previous periods, but still enough of a threat and coverage to warrant a MRGL continuation. ....Mid Atlantic... Disturbance rounding the northern periphery of our massive ridge will ultimately slide down through the Mid Atlantic during the mid to late-afternoon hrs. on Thursday. The combination of strong diurnal destabilization during the daytime and prominent moisture lingering over the area will create a very buoyant environment capable of strong thunderstorm genesis anywhere from NY state down through the Central Mid Atlantic including; MD/PA/DE/Northern WV and VA. Current projection of QPF is fairly isolated in the heavier convective outputs with some deterministic depicting totals as high as 2-3" in spots. Initial assessment of the setup leads towards a low end MRGL risk for now, but will assess how models handle the shortwave disturbance and proposed ascent pattern within a fairly unstable environment over the next few days. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7EYm7wSn1BfYrdh2Rvf7BKs9IYsYqewy0n8kpVhUtbzq= Pb0fyqP7kSO0Wz8fcNJJolo0DPBytr4KX_UM5js0B7EMSD0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7EYm7wSn1BfYrdh2Rvf7BKs9IYsYqewy0n8kpVhUtbzq= Pb0fyqP7kSO0Wz8fcNJJolo0DPBytr4KX_UM5js0QBOIj8s$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7EYm7wSn1BfYrdh2Rvf7BKs9IYsYqewy0n8kpVhUtbzq= Pb0fyqP7kSO0Wz8fcNJJolo0DPBytr4KX_UM5js0qrM2bYQ$=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .