Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
889 FOUS30 KWBC 171551 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1151 AM EDT Sun Aug 17 2025 Day 1 Valid 16Z 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, Ohio Valley, Northern Mid- Atlantic and southeast New England... Showers and thunderstorms linger across portions of eastern SD and southwest MN near a front and associated outflow boundaries. Other dying activity is moving into the Northern Mid-Atlantic States and towards the Lower Ohio Valley. Across the Upper Midwest, there should be some boundary return before evening/overnight convective development occurs near southwest MN due to strong southwest flow importing decent instability into the region. The thunderstorms then move into portions of northern IA and southwest WI. With the signal waning in the mesoscale guidance towards the International Border with Canada, trimmed the northern portion of the Slight Risk area. Due to heavy rains overnight and early this morning, shifted the southern extent more southward to account for at least partially saturated/compromised soils near the IA/MN border and in case the mesoscale guidance is still too poleward with its heavy rain footprint. Farther east, renewed scattered thunderstorm activity is expected across the Northeast ahead of a dying precipitation area across PA, which appears to have an MCV in tow. The Appalachians and possible lee trough/sea breeze front closer to the New England coast should also act as foci near and ahead of the incoming front. Stronger NWly flow around the central CONUS upper ridge should keep activity fairly progressive, so the risk level was left as Marginal. Remnant moisture over Montana and near the Black Hills from the atmospheric river that pushed into the Northwest a couple days ago could cause repeating convection to cause heavy rain to be excessive, so reworked the Marginal Risk 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. Few changes were made to continuity in this region. ...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). Roth/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