Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 09 2025 15:59:21 FOUS30 KWBC 091559 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1159 AM EDT Mon Jun 9 2025 Day 1 Valid 16Z Mon Jun 09 2025 - 12Z Tue Jun 10 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHEAST, SOUTHEAST, GULF COAST, AND SOUTHERN PLAINS... 16Z Update... Expanded Slight in west Texas=20 Added a Slight around the Houston metro. ....Northeast... Occluded low over Wisconsin this morning will track northeast over the U.P. of Michigan tonight. South and east of the low, upper=20 level divergence and forcing will be maximized as a 100 kt jet=20 streak and enhanced divergence from a shortwave rounding the=20 southern side of the low will increase the forcing for thunderstorms in the Slight Risk area of Pennsylvania and western New York. At=20 the surface, a potent cold front will be moving east from the Great Lakes/Midwest and into Pennsylvania and New York. The front will=20 contribute additional forcing for storms. Somewhat limited Gulf=20 moisture will stream northward ahead of the front, raising PWATs up to 1.5 inches (1.5 sigma above normal). Instability will also=20 increase with daytime heating with MUCAPE values between 500 and=20 1,500 J/kg, with the greatest instability into Pennsylvania. 12Z CAMs generally agree that the current activity moving from Ohio intensifies diurnally across PA and NY. Soil moisture is elevated from recent rains, though storms will be quick- moving, which=20 should temper the flash flooding threat somewhat. However,=20 topographic and urbanized concerns warrants maintenance of the Slight Risk with some further trimming out on the eastern side in NY per coordination with WFO BTV.=20 ....Southeast... Multiple rounds of heavy thunderstorms are expected to traverse=20 across the Southeast through. Ample Gulf moisture is being supplied on strong (30kt) low level flow with as PWATs 1.75 to 2 inches=20 over MS/AL/GA where activity should focus/repeat. Meanwhile, a=20 potent shortwave at the base of the trough currently over the=20 lower-mid Miss River and cold pool interactions from ongoing=20 activity will force additional convection. As the shortwave crosses the Southeast this evening, the storms should evolve upscale from=20 random clusters to lines. As the surface cold front begins to=20 stall, backbuilding storms will become increasingly possible in=20 many of the same areas of southern Mississippi to the western=20 Florida Panhandle that saw convective activity this morning. Widely scattered instances of flash flooding can be expected inland from the central Gulf Coast where a Slight Risk is maintained.=20 ....Texas and New Mexico...=20 12Z CAMs continue to ramp up convective activity today developing this afternoon off the southern Rockies with organized thunderstorm clusters shifting southeast over west into central TX overnight. Much of this activity is west/south of heavy precip from recent days, but given Gulf-sourced moisture extending up through west Texas (1.5 sigma above normal) and high instability, the Slight Risk is maintained and expanded a bit more into central Texas for overnight concerns. Furthermore, a boundary around the Houston metro activates this afternoon with a risk for repeating heavy thunderstorms there. A Slight Risk was raised around the greater Houston metro. Wegman/Jackson Day 2 Valid 12Z Tue Jun 10 2025 - 12Z Wed Jun 11 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHEASTERN NEW MEXICO INTO MUCH OF WEST TEXAS... Yet another round of widespread heavy shower and thunderstorm activity will impact much of far southeastern New Mexico and west Texas again Tuesday and Tuesday night. While some lingering storms will be ongoing at the start of the period in parts of the Hill Country of central Texas, the bulk of the activity will be during the late afternoon into the overnight. Maximum daytime heating across the area will increase the instability across much of west Texas as abundant Gulf moisture remains over the area south of a stationary front over northern Texas. Storms will blossom in coverage towards sunset as the LLJ of additional Gulf moisture strengthens. The convection will both interact with the stationary front, a possible dryline in southeastern NM and far west Texas, and some subtle, but still important upper level impulses that eject out of the southern Rockies. There has been little change in the ERO risk areas as the signal remains consistent targeting west Texas for shower and storm activity. The Slight remains quite large in part due to the widespread area of west Texas that has seen heavy rain recently, resulting in wetter than normal soils, especially north towards the Panhandle. The Marginal Risk along the Gulf Coast and eastern seaboard also remains largely unchanged. Storms will be ongoing into New England at the start of the period, with some chance for largely disorganized convection from the Gulf Coast to the Carolinas. While some of these areas have also been hard hit with heavy rains in recent days, the lack of confidence in much organization to the storms favors a continuation of the Marginal Risk. Cell interactions will likely cause localized Slight Risk impacts along the Gulf Coast, but where that will happen remains highly uncertain. Wegman Day 3 Valid 12Z Wed Jun 11 2025 - 12Z Thu Jun 12 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF TEXAS AND OKLAHOMA... Deep Gulf moisture will advect north across much of Texas (and the Southeast for that matter) on Wednesday and Wednesday night. Slow- moving upper level shortwave energy will shift east across Texas through the period. The stationary front that had been across north Texas for much of the prior 2 days will begin to lift north as a warm front, especially Wednesday night as the nocturnal strengthening of the LLJ overcomes what little southward push of drier air north of the front is left. Meanwhile across West Texas, the typical dry line will also advance eastward, which will work to uplift the moisture and cause more widespread shower and thunderstorm activity. While the storms may be around in isolated clusters through the day, the greatest concentration of storms will initiate in the late afternoon and persist through the overnight. Many of the same areas of northern Texas will be hit with multiple rounds of storms once again. A higher-end Slight is in effect from east of Lubbock through the Metroplex, and from southwestern Oklahoma to around the Austin metro. It's very possible that a Moderate Risk upgrade may be needed for a portion of this area with increasing confidence and CAMs analysis of the convective scenario. Once again, the storms alone would not quite get the risk to a Moderate level, but the combination of the storms and antecedent very wet soil conditions. Up north towards the MN/IA border and southern WI, a subtle shortwave in the jet will interact with a weaker portion of the LLJ which will run into a drier air mass to the north. Showers and storms may train eastward across this region. However, instability will be a tremendous limiting factor in the potential for flash flooding. Soils are at or below normal for moisture in the area, which also will not help with flash flooding potential. A Marginal Risk remains in effect with few changes. The Marginal risk in Montana was also maintained with a small eastward expansion towards the border of ND. Areas of convection will cross MT through the period, but will be few and far between. Low FFGs in this area could allow for isolated instances of flash flooding where there are favorable cell interactions. Wegman Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_bIplAvtfOM0MAq78TZQHtQen152_YNENexipo68yigf= Wy6r7fsTuqPZaG6wUmgx_yZNyFYOohHCY1iG5iSVf0VH3eE$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_bIplAvtfOM0MAq78TZQHtQen152_YNENexipo68yigf= Wy6r7fsTuqPZaG6wUmgx_yZNyFYOohHCY1iG5iSVyqwd28g$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_bIplAvtfOM0MAq78TZQHtQen152_YNENexipo68yigf= Wy6r7fsTuqPZaG6wUmgx_yZNyFYOohHCY1iG5iSV_4jHw74$=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) .