Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 30 2023 00:19:26 FOUS30 KWBC 300019 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 817 PM EDT Thu Jun 29 2023 Day 1 Valid 01Z Fri Jun 30 2023 - 12Z Fri Jun 30 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL HIGH PLAINS AND THE LOWER OHIO VALLEY... ....Northeast... A couple more hours of showers and thunderstorms with heavy rainfall are expected before CIN sets in. The Marginal Risk is maintained for the lingering heavy rainfall risk. ....Northern Rockies and Central Plains... A slow-moving trough moving across the Intermountain West into the Rockies has encouraged showers and thunderstorms across portions of of the WY and CO that are moving into the High Plains. Pooling moisture along a lingering boundary draped along the central High Plains, interacting with larger scale ascent afforded by the approaching trough has led to this development. The Slight Risk area was trimmed on its northern side to account for convective movement. HREF neighborhood probabilities indicate accumulations of 1-2 inches are likely across this area. This includes areas that received 2-4" of rain over the past 24 hours. Storms so far haven't been too quick to move. But, as cold pools form, storms are expected to propagate more steadily to the east, moving into less prone areas, including the Nebraska Sandhills.=20 ....Mid-Mississippi to Lower Ohio Valley... Convection is developing in the wake the bow echo/second organized convective complex that moved across the region on Thursday and is showing some backbuilding character as of late. Strong westerly inflow will support PWs surging to at or above 2 inches along the boundary/CAPE gradient from which the storms are forming downwind. There has been indications within radar reflectivity and SPC mesoanalyses of CIN reducing recently, but storms continue to be quite elevated over a thermal boundary located in MO. A series of shortwaves moving over the top of the upper ridge have been the guilty party in the development of these complexes. Confidence in the details of what is expected this evening into tonight remains limited by the mesoscale guidance spread, but the concern is high enough to leave the risk level as Slight. The Slight Risk area has been trimmed on its north side due to convective movement but it continues to highlight southeastern Illinois to western Kentucky, where 3-7" of rain has fallen over the past 24 hours, per radar estimates.=20 Roth Day 2 Valid 12Z Fri Jun 30 2023 - 12Z Sat Jul 01 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL ROCKIES TO THE CENTRAL/SOUTHERN APPALACHIANS AND ACROSS PORTIONS OF THE NORTHEAST... 2030z update Very few changes were made to the current day 2 ERO. The marginal risk area appears to capture the scattered convection that will occur reasonably well with some increased potential for higher amounts over the North Carolina Piedmont. PWs between 1.75 and 2 inches, coupled with CAPE over 1500J/Kg and saturated soils in some places could support a targeted slight risk area over portions of the Middle Mississippi Valley. Kebede ....Central High Plains to the Appalachians/Northeast... Mid-level energy will continue to move across the top of the ridge centered over the lower Mississippi Valley and the Southeast, likely to help initiate additional rounds of showers and storms from the Ohio Valley eastward as they interact with an axis of deeper moisture. Meanwhile, a more defined upper trough moving out of the West is likely to generate additional storms back to the west from the foothills of the central Rockies into the Plains. Given the typical uncertainty and anticipated fast flow aloft, a broad Marginal Risk was maintained for now. However, embedded upgrades to a Slight Risk may be forthcoming, especially if the models begin to agree on successive days of heavy rain across the central Plains or Midwest. A Marginal Risk was maintained to highlight an increasing threat for heavy rains to spread back into portions of the Northeast that were recently impacted by heavy amounts. Mid-level energy and deeper moisture will be directed northeast into the region ahead of a low centered north of the Great Lakes and usher in renewed PWs near 1.75 inches. Although confidence in the details is limited, there is at least some potential for moderate to heavy amounts to begin to develop across some parts of Pennsylvania and New York that were recently impacted with heavy amounts and where FFGs remain relatively low. Pereira/Snell Day 3 Valid 12Z Sat Jul 01 2023 - 12Z Sun Jul 02 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID MISSISSIPPI INTO THE LOWER OHIO VALLEY... 2030z update The slight risk area over the Mid Mississippi and Lower Ohio Valleys was expanded on its eastern flank to account for greater model signal of heavy rain across southern Illinois/Indiana and northern Kentucky. The favorable moisture and dynamic setup for excessive rainfall hasn't changed since the overnight issuance. Kebede ....Central Plains to the Northeast... Models continue to present a good signal for widespread moderate to heavy rainfall developing ahead of a well-defined trough moving from the central Plains into the mid Mississippi Valley. Deep southwesterly flow ahead of the trough is expected to draw ample moisture (Pws 1.5-2 inches) into a region of large-scale ascent.=20 The models suggest an environment favorable for redeveloping storms and west-east training, increasing the threat for heavy accumulations. A Slight Risk was maintained and broadened to include the area where the ensemble guidance indicated a greater chance for heavy amounts. This included some areas that may be impacted by heavy amounts in Days 1 and 2.=20 Meanwhile, downstream energy is likely to contribute to at least locally heavy amounts and isolated flash flooding concerns across the Ohio Valley into the central to southern Appalachians.=20 Farther to the north, southwesterly flow ahead of a slow-moving trough over the Great Lakes will continue to channel deeper moisture into the Northeast, fueling the potential for the recurrence of heavy rains and flooding concerns for portions of the area. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4nGm1zucVuUCBgKAvbDScU0OGIM7fZJhVZQSMCrVLYYD= Q4jt3epw-xpxafT4ItIcnjqIqMXVOsUGptI9Cu89Bxyj6fU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4nGm1zucVuUCBgKAvbDScU0OGIM7fZJhVZQSMCrVLYYD= Q4jt3epw-xpxafT4ItIcnjqIqMXVOsUGptI9Cu89-eVQI7w$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4nGm1zucVuUCBgKAvbDScU0OGIM7fZJhVZQSMCrVLYYD= Q4jt3epw-xpxafT4ItIcnjqIqMXVOsUGptI9Cu89pDxmH6Y$=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .