Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
097 FOUS30 KWBC 182021 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 421 PM EDT Fri Apr 18 2025 Day 1 Valid 16Z Fri Apr 18 2025 - 12Z Sat Apr 19 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR NORTHEASTERN OKLAHOMA THROUGH CENTRAL MISSOURI... 16Z Excessive Rainfall Discussion Update... Few changes needed with respect to the Slight Risk area across portions of the Southern Plains. The area covers the corridor highlighted by the 12Z run of the HREF and the associated HREF neighborhood probabilities. This also aligns where highest equivalent potential temperature was located at the surface and low levels was already in place this morning. Given the persistent low level jet pulling moisture northward from the Gulf pretty much along the same trajectory...felt that no major changes were needed. Did expand the Marginal risk area a bit southward where the HREF started to show potential for one or more periods of rainfall rates above 1 inch in an hour. Any flooding concerns should be isolated there but enough to pull the Marginal southward. Bann Previous Excessive Rainfall Discussion... A persistent southerly low-level jet transporting deep tropical moisture into the Texas Gulf Coast and along a very slow moving frontal zone draped across the Plains to the upper Great Lakes will lead to the development of convection during peak heating. However, the strongest of the storms will likely be during the late evening and overnight hours. The strong cold front to the north will run into opposing flow from the LLJ, causing its progression south and east to slow as it approaches Oklahoma and Missouri from the northwest. This will act as a wall, resulting in the LLJ air mass to ride up and into the front, then track along the frontal interface to the northeast. This setup will be favorable for training of thunderstorms and some of the individual cells may advance quickly to the northeast as the low-level jet intensifies to 50 kt over northwestern Arkansas Friday night. The rain will be somewhat offset from the area of greatest historic rainfall from 2 weeks ago, and the smaller streams and creeks have fully drained from that event, but the bigger rivers, including the Missouri, Arkansas, and Mississippi continue to drain, and this new influx of rainfall could back up as the new rainfall meets already full rivers. The bulk of the event will focus into the Day 2 period. With greater instability available for the storms to produce heavy rainfall during this period, it`s likely that where the storms are most persistent, there will be widely scattered instances of flash flooding, especially near the Tulsa and Joplin metros. A Marginal Risk area spans from the vicinity of the Oklahoma/Texas border northeastward to Illinois/Indiana. The Slight Risk was adjusted a small amount to the west than the previous forecast. Campbell Day 2 Valid 12Z Sat Apr 19 2025 - 12Z Sun Apr 20 2025 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM NORTH- CENTRAL TEXAS THROUGH MUCH OF SOUTHERN MISSOURI... 2030Z Excessive Rainfall Discussion... The 12Z suite of numerical guidance highlights the continuation of rainfall in a corridor from central Texas northeastward into portions of the Mid- South and neighboring portions of the Mid- Mississippi Valley on Saturday. A consistent run to run westward nudge in the placement of the heaviest rainfall was noted yet again in both the model runs and the deterministic WPC QPF...and the current outlook was expanded just a bit to the west and south compared to the previous outlook. The overall synoptic picture largely remained consistent from earlier outlooks. Previous Excessive Rainfall Discussion... A stalled boundary will lead to a stark gradient between two airmasses, on with some adjustments on the day shift cycle to pull it a little more south into the Lower Mississippi Valley along the front where the better instability should be located. e abnormally cool for mid-April and the rich in moisture. On the north side the cold, dry northeasterly flow will be weakening while in the warm sector there will be an ever increasing supply of hot and humid air straight out of the Gulf being advected northward on up to 50 kt winds across Texas and into the frontal interface from north Texas through Oklahoma and Missouri. Meanwhile in the upper levels, a potent shortwave, previously an upper level low will eject eastward out of the mountains and into this warm and humid air mass. This will result in cyclogenesis across Oklahoma by Sunday morning. Until that happens though, the front will be largely stationary, with the warm humid air tracking northeastward on one side, and cool, dry air tracking southwestward on the cold side. The abundance of moisture and cold pools from Friday night`s storms will support continued shower and thunderstorm development south of the front. As the shortwave approaches, additional shower and thunderstorm development will occur, and with stronger storms due to the added forcing as the surface low develops to the west. The westward trend of QPF persisted into this time period, placing the highest amounts over far north-central Texas, southwest and central Oklahoma. A narrow swath of amounts 3 inches or greater are expected in this part of the region. The storms to run into the Ozarks of Oklahoma, Arkansas, and especially southern Missouri on Saturday. The mountains will further uplift the moisture, resulting additional locally heavy rainfall. As the storms track northeastward across Missouri, the front is likely to direct them into the St. Louis metro. In coordination with LSX/St. Louis forecast office, the Moderate Risk`s northeasternmost extent includes the St. Louis metro. While the storms may not be quite as strong as compared with areas further south and west by the time they reach St. Louis, the urban corridor and confluence of major rivers in the area may exacerbate urban flooding concerns as repeated rounds of heavy rain likely move over the city. The Moderate Risk area was expanded west/southwest farther into north-central Texas. The Slight Risk was shifted into central Texas and the Marginal Risk had minor expansions to the west. With the overall western shift of all of the Risk thresholds, the eastern bounds of each were trimmed back to the west as well. Campbell/Wegman Day 3 Valid 12Z Sun Apr 20 2025 - 12Z Mon Apr 21 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL PLAINS AND PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY... 2030Z Excessive Rainfall Discussion... The system responsible for the potential of heavy/excessive rainfall on Saturday will begin to accelerate to the northeast as the upper trough begins to fill. Rainfall amounts should not rival amounts that are expected on Saturday...but additional rainfall on top recently flooded areas remains a potential concern. Bann Previous Excessive Rainfall Discussion... The upper trough and surface low pressure system will continue to spread showers and thunderstorms across the central U.S. Sunday as it lifts northeastward. The amount of moisture and instability may be reduced when compared to Saturday, however it will likely be above normal. The nature of the low track and associated storms are expected to be a little more progressive which should limit rainfall accumulations. Additionally, the bulk of the higher rainfall amounts is forecast to largely fall north of the Saturday footprint. A Marginal Risk is in place for the Middle and Lower Mississippi Valley and eastern portions of the Central Plains. These areas are north and west of the most sensitive areas of the Mississippi/Ohio River Valleys where streamflows remain high after recent flooding. However, some rain atop recently flooded areas, and runoff from other areas into these rivers, could exacerbate ongoing flooding issues in some areas, so continue to monitor. Campbell Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt