Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 24 2025 08:17:30 FOUS30 KWBC 240817 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 417 AM EDT Sat May 24 2025 Day 1 Valid 12Z Sat May 24 2025 - 12Z Sun May 25 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA INTO THE OZARKS... ....Southeastern Kansas and Northeastern Oklahoma through the=20 Ozarks into the Tennessee Valley... Recent mesoanalysis shows increasing PWs on the nose of strong low level moisture advection across Oklahoma into southeastern Kansas. Moisture is expected to continue to pool over this area and lift=20 northeast along a slow-moving low level boundary. Elevated=20 convection developing along the boundary has been training=20 northwest to southeast across southwestern Missouri into northern=20 Arkansas over the past several hours, resulting in localized 1-2=20 inch estimated totals. Hi-res guidance indicates these training=20 storms will continue through the remainder of the overnight and=20 beyond daybreak ahead of an upstream system now organizing over=20 Kansas. The general consensus of the hi-res guidance shows this=20 system continuing to grow upscale, with rainfall rates increasing=20 as it drops southeast into the axis of deeper moisture and greater=20 instability. Heavy rainfall will likely be ongoing within the=20 highlighted area as this system moves through the region near the=20 start of the period. Guidance differs on the details, but most=20 indicate a downward trend in rainfall rates as the system moves=20 progressively to the south and east and begins to weaken later this morning. Following this morning's round, attention will then focus to the evening and overnight, when some of the hi-res guidance shows storms redeveloping over the Plains and propagating east into some of the same areas impacted by the morning convection. Models show=20 low level flow amplifying, supporting a deepening moisture pool in=20 much the same area, providing the opportunity for storms to once=20 again produce heavy rainfall rates, with additional heavy=20 accumulations possible. Currently, the greatest area of concern=20 centers over eastern Oklahoma into northwestern Arkansas. HREF=20 neighborhood probabilities for 24-hr accumulations exceeding 3=20 inches are above 50 percent across the region, with some greater=20 than 25 percent probabilities for accumulations over 5 inches=20 centered over the Boston Mountains. ....Southeastern Wyoming, Northeastern Colorado and the western Nebraska Panhandle... Moist easterly flow will support PWs ~0.75-1 inch (1.5-2 standard deviations above normal), which along with mid-level energy and right entrance region jet forcing, will support storm development with locally heavy rainfall possible from the Laramie Mountains=20 and Frontal Range into the High Plains. A Marginal Risk was added,=20 highlighting the area where the HREF indicates that localized=20 amounts exceeding 2 inches are possible. Pereira Day 2 Valid 12Z Sun May 25 2025 - 12Z Mon May 26 2025 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM FAR SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA INTO THE=20 OZARKS... ....Southern and central Plains through the Ozarks into the Tennessee Valley... Storms developing Saturday night and early Sunday may remain ongoing through the early part of the period across the Ozark region. These storms are expected to move east and weaken early in the period. However, there remains a strong signal for=20 redevelopment during the evening and overnight hours along a=20 lingering boundary extending from Oklahoma through the Ozarks.=20 Enhanced low level convergence will support pooling moisture,=20 fueling heavy rainfall rates with some potential for training as=20 this moisture interacts with a series of mid level shortwaves.=20 Meanwhile, strengthening southerly winds ahead of an amplified=20 trough moving across the Southwest will support deepening moisture=20 along the western extent of the front and an increasing threat for=20 heavy rainfall back across southwestern Oklahoma into northwestern=20 Texas. Some of this activity may also reach the Ozark region by the end of the period. With these repeating events expected to push=20 rain totals into the 4-6 inch range in some spots, a Moderate Risk=20 centered over northeastern Oklahoma into the Ozarks was maintained. While the better organized and heaviest amounts are expected to=20 center near the Ozarks, there is the potential for localized heavy amounts, producing isolated flash flooding concerns, to spread=20 further east along the boundary through the Tennessee Valley and=20 into areas as far east as the southern Appalachians. .....Central Rockies/High Plains...=20 Moisture and forcing will remain favorable for additional rounds=20 of showers and thunderstorms, capable of producing heavy rainfall=20 rates. While widespread heavy totals are not expected, models do=20 show a notable signal for locally heavy amounts, which may raise=20 isolated flash flooding concerns over eastern Wyoming into western=20 South Dakota and the Nebraska Panhandle, as well as over portions=20 of northeastern Colorado.=20 Pereira Day 3 Valid 12Z Mon May 26 2025 - 12Z Tue May 27 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF THE SOUTHERN PLAINS TO THE TENNESSEE VALLEY... While some additional heavy rains are possible across the Ozarks, the greater threat is expected to shift further south as an upper trough moves from the Southwest into the Plains. This will push the front and deeper moisture further south and east. Deep, moist southwesterly flow, with energy aloft, will support an axis for storms to develop from eastern Texas and southeastern Oklahoma to the Tennessee Valley. The overnight models showed enough spread to encourage maintaining just a Slight Risk for now. However, some of the guidance, including the GFS, UKMET, and CMCreg, are producing=20 amounts suggesting an upgrade may be required in a future issuance. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_k_5CRRzUsFnydfjJjPMuOYNQB9EJcfdEYkz1-16xHrC= Mc_41gnN_XeLZtM7_2A_DIDRfGg9l55pwj-YpX_C4bDp2IQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_k_5CRRzUsFnydfjJjPMuOYNQB9EJcfdEYkz1-16xHrC= Mc_41gnN_XeLZtM7_2A_DIDRfGg9l55pwj-YpX_CtpZKGtI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_k_5CRRzUsFnydfjJjPMuOYNQB9EJcfdEYkz1-16xHrC= Mc_41gnN_XeLZtM7_2A_DIDRfGg9l55pwj-YpX_CAZm4YB4$=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) .