BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 31 May 2026 00:49:09 +0000 ----------------------------------------------------------- FOUS30 KWBC 310048 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 848 PM EDT Sat May 30 2026 Day 1 Valid 01Z Sun May 31 2026 - 12Z Sun May 31 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF MONTANA INTO WESTERN SOUTH DAKOTA... The Slight risk is maintained into tonight across much of central and eastern MT into western SD. Highest rainfall rate potential (1-2" per hour) will be across southeastern MT into western SD and far northwest NE where instability persists along with periodic=20 backbuilding cells. Elsewhere a broad Marginal risk extends from SD into NE/IA and south across portions of KS and MO. Overall should=20 be an active overnight of convection across this corridor as=20 mid/upper level forcing overruns the axis of better=20 moisture/instability and we see a nocturnal increase in the low=20 level jet. Cells should be moving enough to keep the flash flood=20 risk localized in nature, although there could be one or more=20 smaller scale backbuilding clusters that develop and locally=20 enhance the flash flood risk. Confidence in exactly where this=20 occurs remains too low to introduce any additional Slight risk=20 areas. Chenard Day 2 Valid 12Z Sun May 31 2026 - 12Z Mon Jun 01 2026 ...THERE IS A SLIGHT RISK FOR PORTIONS OF THE SOUTHEAST... 20Z Update... ...Southeast... A nearby frontal boundary will become the focus for yet more strong thunderstorms over much of the Southeast on Sunday. Just south of the front in southern SC, southern GA, and northern FL, this region is a reservoir of >2.0" PWs that are available thanks in large part to a southerly IVT that contains moisture originating from the western Caribbean Sea. Area-averaged soundings suggest a sufficiently unstable atmosphere (>1,000 K/kg MLCAPE), well saturated 1000-500mb columns, and warm cloud layers up to 14,000ft deep in some cases. The key in determining the full extent of the flash flooding threat will be how much cloud debris from Saturday and Saturday night's thunderstorm activity lingers into Sunday. That said, weak capping inversions should allow for storms to develop as early as late morning and soils in the area remain rather saturated following such an active week-long stretch of heavy rainfall. In collaboration with several Southeast WFOs, a Slight Risk was added this cycle given the potential for scattered instances of flash flooding. ...West Texas... A Marginal Risk was introduced this cycle given the growing consensus of global models and CAMs that were hinting at thunderstorms firing over the Davis Mountains and along the dryline. PWs surge to >1.0" in these areas as low-level SErly flow introduces additional 850mb moisture flux into the region and a sheared 500mb vort max approaching from northern Mexico. Sufficient instability also appears to be present with MUCAPE up to 1,000 J/kg expected to be available. West Texas continues to have locally sensitive soils in wake of recent rainfall as well. Given these factors, a Marginal Risk was introduced for a localized flash flood threat in West Texas Sunday afternoon and evening. Mullinax ---Previous Discussion--- Any heavy to excessive rainfall should be located in or near a plume of anomalous moisture plume that will extend from Montana into the Southeast United State. Large scale forcing is more subtle outside of the Northern Plains/Rockies...but there should be some weak shortwave energy embedded within the weak flow that will make them difficult or impossible to time. As this shortwave energy encounters a late day atmosphere with MUCAPE values in excess of 3000 J per kg from the Plains into the Mississippi Valley and parts of the Southeast US...storms have the potential to produce very intense rainfall rates that approach or exceed flash flood guidance along this entire corridor. A large and generally unfocused Marginal Risk area still seems to handle the localized nature of flash flood risk that should exist. The Montana portion of the Marginal Risk has the strongest synoptic forcing as a mid- and upper-level system gradually moves north of the border...keeping the western part of the state in lingering wrap-around rainfall before gradually tapering off. Bann Day 3 Valid 12Z Mon Jun 01 2026 - 12Z Tue Jun 02 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. There remain some hints in latest 12Z guidance that the overall risk of excessive rainfall is non-zero over the Plains from Kansas into Colorado. Models show a low level axis of moisture and instability moving northward on Monday afternoon but the placement of the heaviest thunderstorm activity remains unclear. In addition, portions of the Mid-South may also be at-risk for Excessive Rainfall, but guidance remains murky on where storms will initiate. Given these reasons, the Day 3 ERO remains free of risk areas for the time being. Bann/Mullinax Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7z1PV5kibJsw7ioDubbxKV9f0LcD__edHvdTUpu-3RsP= m7eIp4X-trpImGSHuM6M6ZKt6uZFTFGNoTyfs4kED5Vzino$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7z1PV5kibJsw7ioDubbxKV9f0LcD__edHvdTUpu-3RsP= m7eIp4X-trpImGSHuM6M6ZKt6uZFTFGNoTyfs4kEeTraVI8$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7z1PV5kibJsw7ioDubbxKV9f0LcD__edHvdTUpu-3RsP= m7eIp4X-trpImGSHuM6M6ZKt6uZFTFGNoTyfs4kEYy7Pq4w$=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 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]