Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
369 FOUS30 KWBC 140059 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 859 PM EDT Wed Aug 13 2025 Day 1 Valid 01Z Thu Aug 14 2025 - 12Z Thu Aug 14 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE SOUTHERN PLAINS TO THE NORTHEAST, PARTS OF THE NORTHERN PLAINS, AND THE SOUTHWEST... 01Z Update... Ample moisture ahead of an upper trough axis extending from the Great Lakes back into the southern Plains continues to fuel isolated to scattered showers and storms from New England back into southern Texas. While pockets of heavier rainfall rates persist, much of the organized, heavier rainfall from earlier in the day has diminished, with the loss of daytime heating contributing to the waning threat for widespread heavy rains. While isolated to scattered showers and storms are expected to continue through the evening into the overnight, the consensus of the hi-res guidance does not indicate additional development of heavy rains that would produce more than isolated flash flooding concerns. Therefore the Slight Risk areas were removed from the southern Plains, Southeast, and Mid Atlantic. Recognizing the potential for isolated concerns to continue, a Marginal Risk was maintained from southern Texas to New England. In the Southwest and the northern Plains, the footprints were reduced, but a Marginal Risk was maintained for portions of both areas. Pereira Day 2 Valid 12Z Thu Aug 14 2025 - 12Z Fri Aug 15 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF COASTAL MID ATLANTIC REGION... The 12Z HREF showed an uptick in convection capable of potentially producing excessive rainfall over southeast Virginia and adjacent portions of northeast North Carolina. Being located in a moisture- rich region between a surface trough of low pressure along/near the coast...storms that form and an approaching cold front to the west should help foster an environment in which storms can produce downpours which lead to scattered instances of flooding. The 12Z HREF neighborhood probabilities peak in the 25 to 40 percent range for 2 inches of rainfall in an hour and 15 to 20 percent for 3 inches of rainfall in an hour. A targeted Slight Risk was issued to cover the risk. Elsewhere...was able to largely maintain continuity in the Upper Midwest and Southwest. Trimmed a portion of the Marginal risk area in parts of Utah where forecast soundings showed a considerable amount of dry air in the sub-cloud region, Bann Previous Excessive Rainfall Discussion ...East Coast to Lower Mississippi Valley... The cold front from Wednesday will continue to advance toward the southeast with lingering high moisture ahead of the boundary from New England into the Mid-Atlantic Coast. Potential for localized excessive rainfall within the anomalous PW axis and with forcing ahead of the front, but cloud cover may limit the potential for higher instability values. There should be at least an isolated flash flood threat with thunderstorms ahead of the front from southern New England to the Mid-Atlantic coast. Farther south, from the Southeast to the Lower Mississippi Valley, there does not appear to be a substantial focus area for excessive rainfall potential, hence the broad Marginal Risk, but high moisture and daytime heating will result in scattered thunderstorms with peak rainfall rates in the 1 to 3 in/hr range. Similar to Wednesday, parts of the Lower Mississippi Valley will have high PWs and slow cell motions given placement between a mid- level ridge center over KS and another over the northeastern Gulf. ...Southwest... The upper trough over California on Wednesday will continue to move east on Thursday with increased moisture advection into Arizona and parts of Utah into the Four Corners region. PW values are forecast to increase to near +1 standardized anomaly for Arizona into southern Utah. While cloud cover is a bit uncertain for Thursday into Friday, ahead of the western trough and from any lingering disturbances from the previous day, A similar sized, perhaps slightly larger, Marginal Risk is drawn for Thursday into Friday following the model QPF consensus and Arizona Regional WRF simulated reflectivity, which showed the potential for more widespread coverage of thunderstorms on Thursday compared to Wednesday. ..Upper Mississippi Valley... A cold front will move into the north-central U.S. on Thursday with a steady enhancement to southerly/southwesterly 850 mb winds ahead of the boundary. Even after diurnal weakening of the nocturnal low level jet, 00Z GFS forecasts show 20-40 kt continuing from the central Plains into the eastern Dakotas and Minnesota through Thursday evening. Locally heavy rain may be ongoing Thursday morning with decent potential for another round Thursday night with favorable jet diffluence/divergence aloft, possible moderate instability and standardized PW anomalies of +1 to +2. Confidence on the exact location remains uncertain however, with hopefully increasing confidence occurring as we move into the hires range. Otto Day 3 Valid 12Z Fri Aug 15 2025 - 12Z Sat Aug 16 2025 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FROM THE LOWER MISSISSIPPI VALLEY TO THE SOUTHEAST COAST...AS WELL AS THE SOUTHWEST/FOUR CORNERS REGION AND THE UPPER MISSISSIPPI VALLEY... 2030Z Excessive Rainfall Discussion Update... Only a few changes made to the on-going Day 3 Excessive Rainfall Outlook. One of the changes was to align the Marginal Risk area in the Southwest with the leading edge of the mid-level height falls. Otherwise the outlook areas still have the support of the overall synoptics in the South/Southeast and the Upper Midwest. Bann Previous Excessive Rainfall Discussion... ...Southeast Coast to Lower Mississippi Valley... Lingering high moisture will be in place on Friday, south of a southward sagging frontal boundary with standardized PW anomalies of +1 to +2 from the Lower Mississippi Valley to the Southeast Coast. With an upper ridge centered over the northeastern Gulf, there will be potential for mesoscale impulses to ridge around the ridge and help focus diurnally driven thunderstorms during peak heating. Similar to previous days, locally high rain rates with 1 to 3 in/hr may occur with localized training. ...Upper Mississippi Valley... A cold front will continue to advance downstream through the Upper Mississippi Valley but slow/stall back toward the west. PWs will remain above average in the vicinity of the front and organized thunderstorm potential will exist within the mean westerly flow aloft. Similar to previous days, nocturnal strengthening of the low level jet at night will have the potential to generate an MCS or loosely-organized convective cluster with localized training potential. Confidence is rather low at 3 days out, but the Marginal Risk was drawn to cover the various model solutions and conceptual thinking for greatest rainfall potential near the front and low level jet axis intersection. ...Southwest... Active southwesterly flow across much of the western U.S. will encourage the further expansion of above average moisture into the Four Corners region and northern Great Basin. While standardized PW anomalies will generally peak in the +1 to +2 range, not everyone within these anomalies will see the same flash flood potential. The focus appears to be best tied to the Mogollon Rim into the Wasatch and central to southern Rockies, ahead of a number of shortwave impulses moving in from southern California. Tied to the relatively stronger belt of westerlies could be jet-induced divergence maxima aloft to help in the production of locally heavy rainfall. Otto 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