FOUS30 KWBC 190003 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 803 PM EDT Sat Oct 18 2025 Day 1 Valid 01Z Sun Oct 19 2025 - 12Z Sun Oct 19 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN AND CENTRAL MISSISSIPPI VALLEY... A shortwave trough moving across the Southern Plains will continue to track eastward into the Southern Mississippi Valley. As it does so...it will help to focus and support convection in a region where the best dynamics are aligned with the best low-level thermodynamics and moisture. That environment is better suited to support strong updrafts that can result in 1+ inch per hour rainfall rates that could result in flooding. Very high flash flood guidance in the area suggests that the flooding would tend to be localized in nature outside of instances where multiple cells train over the same spot repeatedly. The track of the shortwave trough has helped to narrow the corridor for excessive rainfall to the north across parts of the Mid- Mississippi Valley...allowing for that portion of the outlook area to be downgraded from a Slight to a Marginal risk of excessive rainfall. Early evening satellite imagery showed warming cloud tops but convection was still active enough that problems with run-off remain possible for a few more hours...especially where showers and thunderstorms earlier in the day may have lowered flash flood guidance. Bann Day 2 Valid 12Z Sun Oct 19 2025 - 12Z Mon Oct 20 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE CENTRAL APPALACHIANS DOWN THROUGH WEST VIRGINIA AND SOUTHEAST OHIO... 20Z Update: Deepening mid and upper trough will move progressively to the northeast with a strengthening surface low and trailing cold front migrating through the Great Lakes and Ohio Valley by Sunday morning, entering into the Northeast and Mid-Atlantic areas by the second half of the forecast period. Current forecast is for modest instability pre-front and strengthening mid and upper forcing will initiate a period of locally heavy rainfall across the eastern Ohio Valley into the Central Appalachian area during the forecast cycle leading to isolated flash flood prospects in its wake. Dry antecedent grounds and faster storm motions should preclude any widespread flash flood prospects, however terrain funneling and drainage concerns in-of the Southern Laurels into the Central Appalachian areas of WV are still cause for concern on a local scale. 12z HREF EAS probs for >1" are incredibly high (60-90%) across both regions with modest 30-50% probs also situated just west of the mountainous terrain. These areas are a bit more suitable in this scenario for flash flooding in the grand scheme, but previously mentioned antecedent conditions and forward speed should curb the threat towards the lower end of the MRGL risk threshold. The MRGL risk from previous forecast was trimmed considering latest trends in guidance, but maintained over those aforementioned terrain areas across southwest PA, southeast OH, and much of WV. Kleebauer Day 3 Valid 12Z Mon Oct 20 2025 - 12Z Tue Oct 21 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHERN NEW YORK STATE INTO WESTERN NEW ENGLAND... 20Z Update: General continuity was maintained for the D3 forecast as guidance remains steadfast on the heaviest rainfall focused over Northern NY state into interior New England. Run off concerns within the terrain are the greatest threat as the areas remains very dry overall. Rainfall rates between 1-1.5"/hr at peak are anticipated considering the environment. Rainfall threat will decay southwest to northeast as the cold front presses quickly through the region. Kleebauer ..Previous Forecast.. The negatively tilted upper trof moving into the Lower Lakes/Central Appalachians/Mid- Atlantic region late day 2 will continue to be very progressive as it swings northeastward into Southern New England day 3. While there will be an axis of above average PW values, 2+ standard deviations above the mean and anomalous 850-700 mb moisture flux anomalies, 2 to 4+ standard deviations above the mean accompanying this upper trof day 3, the expected overall progressive nature of the precipitation area should preclude any widespread runoff issues. There is model consensus for max precip areas of 1.5-2"+ across northern NY State, Vermont, western MA, central NH and western ME. The previous marginal risk area was decreased in size and oriented to fit the above mentioned areas where isolated runoff issues in the higher terrain may occur. Oravec 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