Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
084 FOUS30 KWBC 170849 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 449 AM EDT Sun Aug 17 2025 Day 1 Valid 12Z Sun Aug 17 2025 - 12Z Mon Aug 18 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR A PORTION OF THE UPPER MIDWEST... ...Northern Plains, Upper Midwest and Ohio Valley through Northern Mid-Atlantic... Ongoing swath of repeating heavy rain from southern Minnesota through Chicago and northern Indiana should diminish a fair amount by 12Z. However, the remnant boundary should be a focus for convection to fire upon later today over similar areas and downstream over the Ohio Valley. This warrants a corridor of Marginal Risk that connects the previous one over NY State. Yet another MCS is tracking east through South Dakota tonight with this one taking a bit of a northern track compared to the one last night. This organized activity can be expected to be moving east from the central Dakota border by 12Z with further afternoon development over much of eastern Minnesota into Wisconsin with the aid of the boundary lifting/pivoting from southern MN. Then, this evening another round of organized heavy rain works its way across much of MN reaching northern IA and southwest WI overnight. This warrants northward expansion of the Slight Risk up to Duluth and over more of western Wisconsin. Farther east, scattered heavy thunderstorms over southern Ontario are continuing to push east overnight with a cold front. Strong moisture advection overnight ahead of the front is allowing for much above normal moisture to spread over the eastern Great Lakes with potential for 2" PW in the 12Z BUF raob. Morning heavy rain works its way over western NY and much of PA where a Marginal Risk remains. Stronger NWly flow around the central CONUS upper ridge should keep activity fairly progressive, but the NWly flow did warrant some expansion to the Marginal for the western slopes of the central Appalachians. Remnant moisture over Montana from the atmospheric river that pushed into the Northwest a couple days ago could cause repeating heavy enough rain to be excessive, so the Marginal Risk is maintained there. ...New Mexico and Western Texas... Continued east shift in the monsoonal moisture plume places an isolated flash flood risk over eastern NM and far western TX into the TX Panhandle today where the PW anomaly remains 1.5 sigma above normal. ...Florida... Persistent boundary over the northern FL Peninsula maintains high moisture with 2.25" PW (2 sigma above normal). Mainly diurnally driven convective activity may produce locally excessive rainfall even with the high FFG (around 4"/3hr). Jackson Day 2 Valid 12Z Mon Aug 18 2025 - 12Z Tue Aug 19 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN WISCONSIN INTO NORTHERN ILLINOIS... ...Upper Midwest/Great Lakes... Ongoing Monday morning convection is progged by the 06Z HRRR to be over northeastern IA and southern WI to the IL border before diminishing by midday. The remnant boundary then allows further activity to fire over similar areas later that afternoon. Moisture is quite elevated with PW peaking around 2" in the afternoon. The overlap of these repeating rounds of heavy storms over already saturated ground warrants an upgrade to a Slight Risk for much of southern WI into northern IL per coordination with WFOs MKX and ARX. Given the mesoscale processes over the persistent frontal pattern generous coverage of the Marginal Risk is used to cover much of the Midwest. ...Southwest... The upper ridge axis shifts west to NM on Monday suppressing the monsoonal flow and warranting a Marginal Risk over southern NM and far western Texas. ...Southeast... Added Marginal Risks over the southern Appalachians/Piedmont and northern FL Peninsula for pooled moisture anomalies and perhaps some remnant frontal boundary in FL. These areas would see mainly diurnally driven convection. Jackson Day 3 Valid 12Z Tue Aug 19 2025 - 12Z Wed Aug 20 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE SOUTH CENTRAL GREAT PLAINS THROUGH EASTERN MIDWEST AND IN THE SOUTHWEST... ...Central Plains to the Midwest... Westward motion to the upper ridge axis allows the frontal wave pattern over the Upper Midwest to finally eject southeast Monday night. Positive moisture anomaly with PW 1.5 to 2 sigma above normal extend from MI through MO by Tuesday afternoon. Frontal forcing should allow for progressive motion, but activity could be heavy enough to warrant an isolated flash flood risk and a Marginal Risk. The 00Z global model consensus is for rainfall focus farther west than previous runs, particularly for the EC. Therefore, in coordination with WFOs BTV ALY BUF and BGM, the Marginal Risk was trimmed out of the Northeast. ...Southwest... Remnant moisture with PW anomalies around 1 sigma above normal are over eastern AZ/much of NM on Tuesday. An isolated terrain driven flash flood risk is possible in the diurnal convection, so the Marginal Risk is maintained. Jackson 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