Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 06 2025 00:34:17 FOUS30 KWBC 060033 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 833 PM EDT Thu Jun 5 2025 Day 1 Valid 01Z Fri Jun 06 2025 - 12Z Fri Jun 06 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTH-CENTRAL PLAINS... ....Central to Southern Plains... A broad area of convection this evening across the High Plains=20 down into Southwest TX will account for 3 areas of focus for the=20 remainder of the D1 ERO. The most significant of the heavy rain=20 prospects is currently in the initial phase with a strong=20 mesocyclone over Southeast CO likely to propagate downstream and=20 grow upscale with aid from a budding nocturnal LLJ positioned=20 across KS/OK and points south. 50+ kt deep layer shear will help=20 maintain a relevant kinematic environment capable of enhancing and sustaining an eventual MCS moving southeast from Southwestern KS down through Northern OK during the overnight period, mainly following the northern edge of a theta_E gradient situated across the above zone. Despite forward momentum of the eventual MCS, embedded convective cores will be capable of locally enhanced rainfall rates of 1-2"/hr with totals likely reaching 2-3" in the path of the MCS with some 3-5" totals possible over the upwind side of the complex. For more information on this threat, please see MPD #372. Across the Texas Caprock down into Southwest TX, a few supercells will eventually grow upscale and migrate slowly to the east leading a trail of heavy rainfall in their paths over the next 3-6 hrs=20 before waning overnight. The conglomeration over Southwest TX will=20 maintain the greatest footprint in heavy rain coverage with the=20 highest flash flood threat likely over the terrain areas encompassing the Davis and Glass Mtns, and along the I-10 corridor situated in the Stockton Plateau. Multiple flash flood warnings are already in effect for those areas with totals likely breaching 2" in several areas across the above zones by the end of the event. These setups can be tricky and prolonged heavy rain threats beyond current CAMs inference are unfortunately common as cold pool convergence can maintain cell clustering longer than normal.=20 The zone across CO/KS/OK maintained the previous SLGT risk with a minor extension on the western flank of the risk. The MRGL was kept for much of West TX with the best flash flood risks likely over the Caprock of TX into Northwest TX near the Red River, and over Southwest TX within the Davis/Glass Mtn area and adjacent Stockton Plateau.=20 ....Southern Great Basin into the Central Sierras... Elongated surface trough and attendant surface low across the Southern Sierras will maintain a positively buoyant environment within the confines of the Sierras down into the Southern Great Basin (See MPD #373 for details on the setup across the Great Basin). Visible satellite over the West indicates two distinct surface=20 boundaries bisecting Southern NV into Southern UT and across Northern AZ to the Colorado River Basin at the CA/AZ border.=20 Mesoanalysis across the area indicates a relative instability=20 maximum within that portion of the Desert Southwest with SBCAPE=20 ~500-1000 J/kg aligned over Northwestern AZ into Southern NV, a=20 stripe over the Central Sierra's where locally heavy rainfall is=20 already producing some flash flood concerns in the Foothills. The=20 threat for convection lingering between 01-04z is pretty high when=20 assessing hourly CAMs, and projects well considering the=20 environment in place. This is a signature typically seen as one=20 that can prolong heavy rain potential over the region, an area very susceptible to flash flooding concerns with stronger convective=20 cores. A MRGL risk was maintained over the Southern Great Basin=20 with an extension up through the Central Sierra's given the local=20 instability maximum situated over the area with ongoing=20 thunderstorms.=20 ...Ohio Valley into the Northern Mid Atlantic... Area convection continues to fire within the terrain across WV and Western PA with a tongue of instability remaining along and ahead of a cold front analyzed from the Ohio Valley into the Northeast. Shear remains confined over NY State with less deep layer shear as you move south leading to the strongest thunderstorm activity situated across Southern NY state. A quick 1-2" will be plausible within the environment in place this evening with a trend in less coverage anticipated after 03z. A shortwave currently analyzed over the Mid-Mississippi Valley will slide eastward overnight with a better dynamical input positioned across the Eastern Ohio Valley early tomorrow morning as CAMs initiate another round of convection across OH and Western PA after 09z. Despite a weaker surface based instability prog over the area, there's enough of a combination of boundary layer buoyancy and mid-level ascent to enhance area convection capable of isolated flash flood potential during the early morning hours. As a result, the previous MRGL risk was maintained within that zone of Southern OH, extending northeast into Southern NY State with an alignment closely tied to the cold front progression this evening.=20 Kleebauer Day 2 Valid 12Z Fri Jun 06 2025 - 12Z Sat Jun 07 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF OKLAHOMA INTO THE KANSAS, OKLAHOMA, MISSOURI, ARKANSAS BORDER REGION... ....2030Z Update... ....Oklahoma into the OK/KS/MO/Ar border area... Ongoing convection associated with an MCS passing through eastern Oklahoma during the day 1 period may continue into day 2 Friday morning, with a continued risk for locally heavy rainfall and scattered flash flooding. Otherwise, the previous forecast remains on track, and similar to day 1 in both nature and location, with the expectation that afternoon/evening thunderstorms developing ahead of a triple point low located over the central/southern High Plains will grow upscale into an MCS. This system should track east-southeastward through Oklahoma late Friday night/early Saturday with an attendant risk for locally heavy rainfall rates of 1-2" and totals of 2-4" leading to scattered instances of flash flooding. ....Mid MS, Ohio, and Tennessee Valleys... A complex forecast is apparent for this region given the potential for an ongoing and/or influence from an overnight MCS Thursday night/Friday morning. Hi-res guidance suggests that an MCS developing over the central/southern High Plains and passing eastward through the central/southern Plains Thursday night/Friday morning will continue eastward into the Middle Mississippi/Ohio/Tennessee Valleys Friday afternoon. Any sustained convection may also be augmented by redevelopment along associated outflow boundary(s), which would help to focus what would be a more nebulous distribution of storms and lead to more widespread, higher rainfall totals supportive of a greater flash flood threat. Regardless of the influence of this MCS, the prior forecast remains on track. The presence of an anomalously moist, unstable airmass along and ahead of the quasi-stationary frontal boundary will be enough to trigger scattered to widespread thunderstorms capable of locally heavy rainfall and at least isolated flash flooding. ....New England... A frontal wave forming along a cold front draped through southern New England westward through the Lower Great Lakes will help encourage a moist, southerly return flow from the Atlantic northward through New England during the day Friday. Multiple shortwave passages and a warm conveyer belt setup will lead to multiple rounds of thunderstorms producing locally heavy rainfall. An axis with a potentially higher threat was noted from the eastern Catskills/greater Albany northeastward through northwestern Massachusetts, southern Vermont, and central New Hampshire, particularly given the sensitivity of the more complex terrain through the region. However, with the latest hi-res guidance still relatively localized on higher totals, have held at a Marginal Risk for now pending a confirmation/increase in potentially more widespread, higher totals. Putnam ....Previous Forecast... ....Oklahoma into the OK/KS/MO/Ar border area... Another round of shortwave energy forecast to drop east southeastward from the Central Rockies into the Central to Southern Plains Friday into Friday night/early Saturday. This will support potential for another round of organized convection in the vicinity of the west to east oriented frontal zone. PW values along this front will remain above average...2+ standard deviations above the mean, supporting heavy precip potential. There is fairly good model consensus for an axis of heavy rains along this front across much of OK into the OK/KS/MO/AR border region. Only some slight changes to the previous slight risk area to reflect this qpf axis consensus. ....Southern Great Basin into the Central to Southern Rockies... Not a lot of changes expected to the large scale flow from day 1 across the southern Great Basin into the Central Rockies. PW values forecast to remain above average with additional shortwave energy moving across the region in the west south west flow aloft. This should support another day of widespread scattered convection and localized heavy rain and isolated runoff issues. The marginal risk was extended back across these areas to be more similar to the day 1 period given the similar overall conditions day 2. ....Mid MS Valley, OH Valley into New England... Similar to the day 1 period, an axis of above average PW values will stretch along the slow moving front stretching from the Mid MS Valley, OH Valley into New England. There is good model consensus on a broad region of moderate to locally heavy precip amounts along this front. Only some minor changes to reflect the latest model qpf axis consensus made to the previous broad marginal risk area across these regions. Oravec Day 3 Valid 12Z Sat Jun 07 2025 - 12Z Sun Jun 08 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE LOWER ARKANSAS VALLEY, LOWER MISSISSIPPI VALLEY INTO THE LOWER TENNESSEE VALLEY... ....2030Z Update... The prior forecast remains on track with respect to the Southern Plains eastward through the Lower Mississippi and Tennessee Valleys with only minor areal adjustments based on the latest 12Z guidance. Further north, forecast rainfall totals have come down in New England, with guidance now suggestive of only some relatively isolated totals around 1". Have maintained a Marginal Risk for now but given the lower totals and more progressive nature of the cold front Saturday, a threat for even isolated flooding may not ultimately materialize and will be re-evaluatd in subsequent outlooks. Putnam ....Previous Forecast... The second round of height falls moving into the Central to Southern Plains day 2 will continue to push east southeast toward the Mid to Lower MS Valley, OH and TN Valleys. Upper difluence is forecast to be well defined Saturday into Saturday night/early Sunday in an axis of above average PW values that will remain along the west to east oriented frontal boundary across these areas. This should support potential for another round of organized convection along this front. There is some spread with the qpf axes, but consensus that heavy amounts are possible along this front. The previous slight risk area was expanded eastward considerably from eastern OK, across much of AR, western TN and northern MS. ....Northern New England... A sharpening northern stream trof will push surface low pressure across northern New England on Sunday. There is fairly good model consensus for moderate to locally heavy precip totals across northern New England. Only some slight changes to the previous marginal risk area, extending it into all of northern Maine to cover the model qpf spread. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!58PM3lYvXPLgB0VLwWVGUSax1kTudsU1hgPTPAtj7R95= UACbR97VBZkYpeIdEEOo2uOjIplV2bqsafLYo7Z0mZuBLOM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!58PM3lYvXPLgB0VLwWVGUSax1kTudsU1hgPTPAtj7R95= UACbR97VBZkYpeIdEEOo2uOjIplV2bqsafLYo7Z0yNHPe4A$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!58PM3lYvXPLgB0VLwWVGUSax1kTudsU1hgPTPAtj7R95= UACbR97VBZkYpeIdEEOo2uOjIplV2bqsafLYo7Z0KJfFdG0$=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) .