Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 09 2025 20:28:59 FOUS30 KWBC 092028 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 428 PM 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 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 level divergence and forcing will be maximized as a 100 kt jet streak and enhanced divergence from a shortwave rounding the southern side of the low will increase the forcing for thunderstorms in the Slight Risk area of Pennsylvania and western New York. At the surface, a potent cold front will be moving east from the Great Lakes/Midwest and into Pennsylvania and New York. The front will contribute additional forcing for storms. Somewhat limited Gulf moisture will stream northward ahead of the front, raising PWATs up to 1.5 inches (1.5 sigma above normal). Instability will also increase with daytime heating with MUCAPE values between 500 and 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 should temper the flash flooding threat somewhat. However, 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. ....Southeast... Multiple rounds of heavy thunderstorms are expected to traverse across the Southeast through. Ample Gulf moisture is being supplied on strong (30kt) low level flow with as PWATs 1.75 to 2 inches over MS/AL/GA where activity should focus/repeat. Meanwhile, a potent shortwave at the base of the trough currently over the lower-mid Miss River and cold pool interactions from ongoing activity will force additional convection. As the shortwave crosses the Southeast this evening, the storms should evolve upscale from random clusters to lines. As the surface cold front begins to stall, backbuilding storms will become increasingly possible in many of the same areas of southern Mississippi to the western 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. ....Texas and New Mexico... 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 AND WEST TEXAS... 21Z Update... ....South-Central U.S./Texas...=20 Yet another round of widespread heavy thunderstorm activity=20 Tuesday over portions of the south- central CONUS. Diurnal activity originating on the Sacramento Mtns in NM will shift southeast over west TX through the evening. Abundant Gulf moisture remains over=20 the area south of a stationary front over northern Texas. Storms=20 will blossom in coverage towards sunset as the LLJ of additional=20 Gulf moisture strengthens. The convection will both interact with=20 the stationary front, a possible dryline in southeastern NM and far west Texas, and some subtle, but still important upper level=20 impulses that eject out of the southern Rockies. The main change with 12Z guidance, particularly with CAMs today has been a focus farther south...south of the TX Panhandle. Therefore the northern portion of the Slight Risk was trimmed south with a bit more of the Rio Grande downstream of the Big Bend included.=20 ....Gulf Coast and Eastern Seaboard... The Marginal Risk along the Gulf Coast and eastern seaboard again=20 remains largely unchanged. Main risks include ongoing storms in=20 New England at the start of the period, with some chance for=20 largely disorganized convection from the Gulf Coast to the=20 Carolinas. While some of these areas have also been hard hit with=20 heavy rains in recent days, the lack of confidence in much=20 organization to the storms favors a continuation of the Marginal=20 Risk. Cell interactions are still likely to cause localized Slight Risk-level impacts along the Gulf Coast, but uncertainty remains at this time. Wegman/Jackson 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... 21Z Update... ....Southern Plains/Texas/Gulf Coast... Deep Gulf moisture will advect north across much of Texas and the=20 Southeast on Wednesday. Slow- moving upper level shortwave energy=20 will shift east across Texas through the period. The stationary=20 front that had been across north-central Texas for much of the=20 prior two days should begin to lift north as a warm front,=20 especially Wednesday night as the nocturnal strengthening of the=20 LLJ overcomes what little southward push of drier air north of the=20 front is left. Meanwhile across West Texas, the typical dry line=20 will also advance eastward, which will work to uplift the moisture=20 and cause more widespread shower and thunderstorm activity. While=20 the storms may be around in isolated clusters through the day, the=20 greatest concentration of storms should initiate in the late=20 afternoon and persist through the overnight. There is potential for some of the same areas of northern Texas will be hit with multiple rounds of storms once again. A higher-end Slight is in effect for portions of North Texas into southern Oklahoma. The main note for this area is guidance has wide variation of the main QPF axis. This includes the experimental RRFS which for 12Z highlights eastern Texas only for higher rainfall. However, global and regional models are farther west/north. Since uncertainty reigns, only small modifications to the Slight Risk were made - generally an east shift. The Marginal Risk was expanded east over the central Gulf Coast based on confidence of higher QPF inland from the coast. ....Upper Midwest... 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 a minor south expansion based on 12Z consensus including the ECMWF and GFS. ....Montana/Northern Rockies... Further south and east expansion of Marginal risk into the northern Plains and northern Rockies. Areas of convection will cross MT=20 through the period, but the main concern at this time is coverage which may be somewhat limited. Low FFGs over this area could allow for isolated instances of flash flooding where there are favorable cell and terrain interactions. Wegman/Jackson Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5HNnjDzsDU3uipbYGHjj-_DDiLg3BMyr5v3qoc_UsRew= 74GxJGT63i9dRemiVXwGIU11618NBR05kYugLVwmpfFhMcc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5HNnjDzsDU3uipbYGHjj-_DDiLg3BMyr5v3qoc_UsRew= 74GxJGT63i9dRemiVXwGIU11618NBR05kYugLVwmzCVzBpE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5HNnjDzsDU3uipbYGHjj-_DDiLg3BMyr5v3qoc_UsRew= 74GxJGT63i9dRemiVXwGIU11618NBR05kYugLVwmtH4HlgU$=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) .