Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 13 2025 16:00:06 FOUS30 KWBC 131559 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1159 AM EDT Fri Jun 13 2025 Day 1 Valid 16Z Fri Jun 13 2025 - 12Z Sat Jun 14 2025 ....A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE MISSISSIPPI VALLEY, NORTHWEST GULF COAST, & SOUTHERN MID-ATLANTIC STATES... ....Mid-Atlantic... Stalled frontal boundary stretching across the Delmarva Peninsula towards the Upper Ohio Valley will combine with increasing=20 atmospheric moisture content (1.5-2.0" PWs by this evening) to=20 create efficient rainfall rates within thunderstorms. The southerly mid-level flow will be aided by an upper low currently analyzed=20 over southern MO, but with troughing stretching from the Midwest to the western Gulf. Convection is most likely to trigger first=20 across the Carolinas and the elevated terrain of the Blue Ridge up=20 through the central Appalachians. Mean column wind speeds of 20 kts out of the west should promote some propagation of storms,=20 especially once a cold pool is established, but complex terrain and areas right along the frontal boundary could exhibit some training potential along with rainfall rates up to 2"/hr. The inherited=20 Slight Risk was maintained and expanded a bit westward to encompass more of the sensitive Blue Ridge mountains of central/northern VA. 12z HREF guidance depicts 30-50% chances for 3" totals within 6=20 hours this evening across central VA. This along with the available moisture content and nearby frontal boundary support the potential for scattered instances of flash flooding and the potential for=20 localized considerable impacts in the sensitive terrain near the=20 Blue Ridge as well as urban locations between southern MD and=20 northeast NC. However, some guidance (including the 12z HRRR and=20 experimental 06z RRFS) are mostly void of excessive rainfall=20 coverage, which does prompt some uncertainty during the D1 period. ....Mid-Mississippi Valley and Lower Ohio Valley... The inherited Slight risks were consolidated to focus on the eastern and southern flanks of the mid-level low churning over the region. Isolated flash flooding is still possible across parts of central MO/IL underneath and near the low center, but coverage of heavy rain does not seem widespread enough to warrant a Slight Risk. Moisture and effective bulk shear will be plentiful across much of the Mid-Missippi Valley and lower Ohio Valley while ML=20 CAPE will be sufficient for organized convection in a number of=20 areas. PW values of 1.75-2.0" will near the 90th climatological percentile per the 00z ECENS. The risk percentage for AR is in=20 decline as the heavy rain signal appears better elsewhere, but=20 lowish flash flood guidance and the Ozarks should prove sufficient=20 for widely scattered to scattered flash flood concerns, especially given the potential for storms to re-ignite late tonight under the influence of an increasing low-level jet. Flash flood guidance is=20 many ares appears compromised by recent rainfall (during the past=20 week). Overall, the expectation is for isolated to scattered instances of flash flooding and the greatest concern located within urban and poor drainage locations. ....Northwest Gulf Coast... Showers and thunderstorms are forecast to retrograde from southwest LA across sensitive areas of Southeast TX this morning within an=20 area of low- level convergence and retreating/eroding instability. This occurring after extreme rainfall amounts (7"+) impacted south-central LA early this morning. Additional hourly rain=20 amounts to 2.5" with local totals to 5" are probable along the northwest Gulf Coast due to sufficient effective bulk shear,=20 moisture, and instability, which would be most problematic where it rained heavily on Thursday and within urban areas. 12z HREF probabilities for greater than 5" in 6 hrs are 15-20% and scattered throughout the region. ....Texas Panhandle and Caprock Region... Dryline convection this evening is expected along much of the High Plains, but also as far south as the Texas Panhandle and western Texas where 1-1.25" PWs remain. 3-hr FFGs in the region are below=20 3" and have been somewhat wet as of the last month (100-200% of=20 normal for some locations). A Marginal Risk was added given the=20 potential for numerous thunderstorms, while progressing eastward=20 steadily, could merge and lead to brief periods of training.=20 ....Northern WI/Michigan U.P.... Area of low pressure moving eastward through MN helps drive a risk for heavy rainfall within narrow bands from MN across northern WI Friday morning. Instability appears sufficient in spots (500+ J/kg of MU CAPE) for pockets of organized convection capable of heavy rainfall, but isentropic lift/low- to mid-level frontogenesis is expected to aid heavy rainfall production as well. Hourly amounts to 1.5" with local amounts to 3" are possible where cells train. The inherited Marginal Risk was shrunk based on radar and latest CAM trends. ....Northern Rockies/Western High Plains... The Marginal Risk across Montana maintained along the western interface of the deeper moisture and instability over much of the Plains on the leading edge of a quasi-stationary upper level trough. Snell/Roth Day 2 Valid 12Z Sat Jun 14 2025 - 12Z Sun Jun 15 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN AND NEAR VIRGINIA & ACROSS PORTIONS OF THE SOUTHERN PLAINS... ....Southern Plains, Southeast, Tennessee & Ohio Valleys, & the Mid-Atlantic States... A deep layer cyclone drops southeast from IL into KY with time. The system remains quite moist with sufficient effective bulk shear along and near its associated fronts with greater instability, particularly across portions of the Plains as mid-level capping is increasing due to a strengthening 500 hPa ridge across NM, though the cap is breakable. Because of this greater instability, a few pieces of guidance are quite wet somewhere in the neighborhood of OK and KS, where the 00z GFS, 00z NAM, and especially the 00z Canadian are quite wet, showing maxima of 5-13". Hourly rain amounts to 2.5" appear likely in this environment. Cell training due to storms moving south-southeast down the stationary instability gradient would be problematic if it occurs within a long enough band over several hours. An upgrade to a Slight Risk was made here at the expense of AR due to the significant/increased potential to its west. Should guidance converge on wet solutions, further upgrades could occur. Along the system's stationary front to the east, another day of high moisture, sufficient instability and effective bulk shear team up for heavy rainfall in and near Virginia. Hourly rain amounts to 2.5" with local amounts to 5" are most probable within the new Slight Risk area. Urban areas and places with increasing soil saturation due to the previous day of heavy rainfall would be most at risk for issues. ....In and near the Iowa/Minnesota border... A warm advection pattern returns to the region, bringing precipitable water values up to 1.75" and sufficient effective bulk shear and instability for organized convection. After rainfall on Thursday and Friday, soils should be increasingly saturated/ compromised at this point. However, the guidance spread on the heavy rain signal is quite large...best across southeast SD and southern MN. While increasing warmth at 700 hPa is seen across the central High Plains, any mid-level capping should be minimal. However, the broad reservoir of instability to the southwest could keep southward shifts in the guidance minimal between now and when the convection materializes on Saturday. Played it cautious and introduced a Marginal Risk for the heavy rain potential on Saturday. Hourly amounts to 2" and local totals to 4" are possible, given the available ingredients. This could be from a combination of cell training and occasional mesocyclone formation. The degree of the flash flood threat would depend on whether or not urban centers received this heavy rainfall or if/where soils were sufficiently compromised over previous days within impacted areas. Roth Day 3 Valid 12Z Sun Jun 15 2025 - 12Z Mon Jun 16 2025 ....A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS IN AND NEAR THE VIRGINIAS... ....Southern Mid-Atlantic States... Another round of organized convection within a very moist environment with sufficient effective bulk shear and instability is expected near a stationary boundary. Like previous days, hourly rain amounts to 2.5" with local amounts to 5" are possible. A new Slight Risk area was added to account for both the heavy rain potential in urban centers and what should be increasingly saturated soils due to expected rainfall on Friday and Saturday. ....Northern Plains into the Midwest and Lower Mississippi Valley... A "ring of fire" type of setup appears to be in the offing for this region as ridging continues to build across NM, upper troughing remains stagnant across the Pacific Northwest, and the deep layer cyclone moves from KY towards WV. Temperatures at 700 hPa continue to warm somewhat across portions of the Rockies and the central High Plains, strengthening the mid-level capping inversion and increasing the instability available/forward propagation odds for any organized convective complex that forms around the ridge's periphery. The region with the highest heavy rain potential appears to be from the southern Plains/Midwest southeastward near a possible Mesoscale Convective System. There is significant model spread on location, keeping the risk level as Marginal at this time. However, higher end potential exists for any convection that can train along the instability gradient from roughly eastern KS through AR, as seen in different ways on the 00z NAM, 00z UKMET, and 00z Canadian Regional solutions which show local maxima in the 4-7" range. Should the guidance converge, an increased threat level could be prudent. Roth Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7aw02bAUYpnNEauvwAYJse6SK0EC-OnX5KD0cJ0r8Br8= HM4DdQMFZdSz9TQlVYe7Dmm6b0L7kPsX8N1MyPOmrV6GNGI$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7aw02bAUYpnNEauvwAYJse6SK0EC-OnX5KD0cJ0r8Br8= HM4DdQMFZdSz9TQlVYe7Dmm6b0L7kPsX8N1MyPOmPUXBnaU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7aw02bAUYpnNEauvwAYJse6SK0EC-OnX5KD0cJ0r8Br8= HM4DdQMFZdSz9TQlVYe7Dmm6b0L7kPsX8N1MyPOmAzvk62Q$=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) .