Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 07 2025 08:16:04 FOUS30 KWBC 070815 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 415 AM EDT Mon Jul 7 2025 Day 1 Valid 12Z Mon Jul 07 2025 - 12Z Tue Jul 08 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTH-CENTRAL TEXAS, THE UPPER OH VALLEY INTO THE NORTHEAST, AND THE MID-ATLANTIC... ....South-Central Texas... With the latest CAMs showing a notable signal for an additional round of slow-moving, heavy rain-producing storms, a Slight Risk was introduced across South-Central Texas, including the Hill Country. Recent runs of the RAP show a slow-moving mid level center drifting southwest toward the Rio Grande, with many of the CAMs showing convection redeveloping later this morning and continuing beyond 12Z. The environment remains very moist, with PWs of 1.5-2 inches within the highlighted area. HREF neighborhood probabilities for accumulations over 2 inches are well above 50 percent within much of the Slight Risk, with some embedded high probabilities for accumulations over 3 inches as well. The bulk of these amounts are expected to occur within the first 6-12 hrs of the period, before waning later today. This includes some of the areas which were=20 recently inundated by very rains and where FFGs remain quite low. ....Mid-Atlantic... Influenced by an upstream trough centered over the Ohio Valley, Tropical Depression Chantal is expected to accelerate to the northeast=20 today, moving out of Virginia and across the Delmarva to the=20 northern Mid-Atlantic Coast later today. While the increase in=20 forward speed will provide some limit to the heavy accumulation and flooding threats, the system will remain an efficient rainfall=20 producer, with heavy rates likely to raise some flooding concerns,=20 especially across urbanized and poor drainage areas. Reflecting the HREF higher neighborhood probabilities for 3 inches or more, a=20 Slight Risk extending from southeastern Virginia to eastern=20 Pennsylvania and central New Jersey was introduced. Indicating the potential for this storm to produce heavy amounts quickly, the=20 majority, if not all of these amounts are expected to occur within the first 6-12 hours of the period, before the system moves back=20 offshore later today. ....Northeast back to the Ozarks... The previously noted upper trough will edge slowly east across the Ohio Valley and Great Lakes, with mid level energy and deep moisture lifting northeast ahead of it.=20 While at least some locally heavy amounts and an isolated threat=20 for flash flooding cannot to be ruled out within the deep moisture=20 pool that exists along and ahead of the entire extent of the low=20 level front, that stretches from the Northeast back through the=20 Ohio Valley and into the mid Mississippi Valley and Ozark region, a greater risk for more widespread heavy rains and flooding concerns is expected across some areas. This includes parts of the upper=20 Ohio Valley northeastward to central New York. Slow-moving training cells, fueled by high PW anomalies (2-2.5 std dev above normal),=20 falling across relatively moist soils are expected to contribute to a greater threat for flash flooding. Therefore, a Slight Risk=20 extending from parts of eastern Ohio to central New York was=20 introduced. ....Northern Plains and Upper Midwest to the Central Plains... A mid level trough will move across the northern Plains into the upper Midwest this period. This will help a push a cold front, extending from the northern Plains back into the central High=20 Plains further south and east. Moist southerly low level flow along with increasing ascent will help support showers and=20 thunderstorms, with the models continuing to show a good signal=20 for organized storms developing and moving across portions of=20 Nebraska and South Dakota. While the generally progressive nature=20 of these storms is expected to limit the threat for widespread=20 flooding, intense rainfall rates may produce some areas of flash=20 flooding, especially across portions of eastern South Dakota and=20 Nebraska, southwestern Minnesota, western Iowa, and northwestern=20 Missouri. The HREF is showing some higher probabilities for amounts over 2 inches, which along with relatively lower FFGs, indicates=20 that at least some isolated areas of flooding are possible. ....Southwest and Southern Rockies/High Plains...=20 Another daily round of showers and thunderstorms are expected to=20 develop and move east from the central New Mexico ranges into the=20 High Plains. Some isolated to scattered storms are expected to=20 develop further southwest across southeastern Arizona as well.=20 Isolated areas of flash flooding will remain a concern, especially=20 across burn scar, complex terrain, and poor drainage areas. Pereira Day 2 Valid 12Z Tue Jul 08 2025 - 12Z Wed Jul 09 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE NORTHEAST AND MID ATLANTIC THROUGH THE TENNESSEE VALLEY, AND FROM THE UPPER=20 GREAT LAKES TO THE CENTRAL AND SOUTHERN PLAINS, AND ACROSS PORTIONS OF THE SOUTHWEST, SOUTHERN ROCKIES, AND HIGH PLAINS...=20 ....Northeast through the Tennessee Valley... Deep moisture ahead of a slow-moving front will continue to provide fuel for training storms and potentially heavy amounts as it slips further south across the Northeast and the Mid Atlantic. Further to the west the front is expected to return north ahead of a shortwave moving into the lower Ohio Valley. A broad Marginal Risk was=20 maintained for now, however embedded upgrades to a Slight Risk may be forthcoming in future issuances with the arrival of new guidance. This may include portions of the Mid Atlantic to coastal New England. The airmass will remain quite moist (PWs 1.75-2 inches), with some of the guidance indicating an uptick in southerly low level inflow and moisture across the region.=20=20 Away from the front, the Marginal Risk was extended further south to include portions of the eastern Carolinas. A lot of the guidance shows a low level trough becoming the focus for deeper moisture and afternoon-developing, slow-moving storms. This may include some of the areas impacted by heavy rains associated with Chantal. ....Upper Great Lakes to the Southern and Central Plains... A mid-to-upper level shortwave will move out of the Mississippi Valley and into the Great Lakes and lower Ohio Valley this period. This will drive its associated frontal boundary and preceding plume of deeper moisture further south and east across the region.=20 Similar to areas further east, a broad Marginal Risk was=20 maintained, recognizing that embedded Slight Risk area(s) may be=20 forthcoming if confidence increases as newer guidance arrives. One potential area centers over the Ozark Region into the mid=20 Mississippi Valley, where deeper moisture and the ascent provided=20 by a mid level shortwave moving through the base of the broader=20 scale trough may generate more widespread heavier amounts. .......Southwest and Southern Rockies/High Plains...=20 Similar to the previous day, another daily round of showers and=20 thunderstorms are expected to develop and move east from the=20 central New Mexico ranges into the High Plains. Some isolated to=20 scattered storms are expected to develop further southwest across=20 southeastern Arizona as well. Isolated areas of flash flooding will remain a concern, especially across burn scar, complex terrain,=20 and poor drainage areas. Pereira Day 3 Valid 12Z Wed Jul 09 2025 - 12Z Thu Jul 10 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE MID ATLANTIC BACK THROUGH THE LOWER MISSISSIPPI VALLEY INTO EASTERN TEXAS... An elongated axis of deep moisture will provide the corridor for showers and storms, capable of producing locally heavy rainfall. A well-defined shortwave moving out of Ohio Valley may provide the=20 focus for organized heavier amounts as it moves through the Mid Atlantic on Wednesday. An upgrade beyond a Marginal may be=20 forthcoming if the models begin to show greater agreement and/or=20 back-to-back days of heavy amounts. Pereira=20 Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8UIsceCk3a4wrI2HP-YsnQOBN__dOKyPnW5v7eNb1xsK= 3BHo8DL8nyP6Lf6EWRVx24uXxHkLmyTZGQz8gy1hIaIgWdM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8UIsceCk3a4wrI2HP-YsnQOBN__dOKyPnW5v7eNb1xsK= 3BHo8DL8nyP6Lf6EWRVx24uXxHkLmyTZGQz8gy1hMeDHdjE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8UIsceCk3a4wrI2HP-YsnQOBN__dOKyPnW5v7eNb1xsK= 3BHo8DL8nyP6Lf6EWRVx24uXxHkLmyTZGQz8gy1hySp7HD0$=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) .