FOUS30 KWBC 260055 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 855 PM EDT Thu Jun 25 2026 Day 1 Valid 01Z Fri Jun 26 2026 - 12Z Fri Jun 26 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FOR PORTIONS OF SOUTHEASTERN KANSAS AND SOUTHWESTERN MISSOURI... 01Z Update... Made a few more minor adjustments based on observations and recent HRRR runs. The Slight and Moderate Risk areas centered from the central Plains to the mid Mississippi/lower Ohio valleys remain much the same. There is still a good signal for training storms, resulting in heavy amounts across this region overnight. The heaviest amounts and greater threat for flash flooding remains centered over southeastern Kansas into southwestern Missouri, where a Moderate Risk was maintained. RRFS neighborhood probabilities for amounts over 3 inches are above 50 percent within much of the region highlighted by the Moderate Risk. Within this area are also some higher probabilities for amounts exceeding 5 inches. Both the HRRR and RRFS are also showing a noteworthy signal for localized amounts of a similar magnitude a little farther east over eastern Missouri. Both suggest a narrow axis of 3+ inch amounts centering just south of I-70. 2345Z Special Update... In addition to making some smaller-scale adjustments to the previous outlook areas based on recent hi-res guidance and observations, a Slight Risk was added to southwestern Oklahoma. Developing convection now moving from the Texas Panhandle into western Oklahoma is expected to further organize and drop southeast this evening. Some hi-res guidance, including recent runs of the HRRR, show backbuilding/training cells along the southwestern flank of the developing complex -- contributing to heavy amounts which may result in flash flooding. Refer to WPC MPD #527 for additional information regarding the near-term heavy rainfall and flash flooding threat across this area. Pereira ...Plains to Mid-Mississippi Valley... Shortwave trough drifts east across KS today in a more zonal flow pattern than prior days as the high over west Texas is suppressed. This flow runs parallel to a slow-moving front bisecting KS into MO. Surface cyclogenesis over eastern CO will shift east with the shortwave trough and along the quasi- stationary front. 12Z CAMs generally agree with a farther south solution both for the ongoing convection over south-central KS and the afternoon/evening activity with the shortwave. The 12Z FV3LAM does not have the morning convection and is thus too far north. The 12Z NAMnest is also farther north, but with the evening convection, so this will have to be monitored through the rest of the day. For now, the Moderate Risk is expanded west and south a bit given radar and CAM trends. The thermodynamic posture for this evening will be seen as reputable for heavy convective cores as regional theta_E's remain elevated across the Central and Southern Plains to Mid-Mississippi Valley with the core of greatest SBCAPE positioned along and south of US54 in southeastern KS to southwest MO. It is this area where HREF probabilities for rates >1"/hr are most noteworthy with modest probabilities (20-35%) for upwards to 2"/hr in the stronger cell cores. The strengthening nocturnal LLJ and intensifying isentropic ascent across the area downstream of the surface low will create a period of widespread heavy rainfall over that area of southern KS into southwestern MO. Flow running parallel to the boundary only adds for the potential of back- building until the surface low and attendant shortwave can finally eject eastward into the Mid- Mississippi Valley which can be noted in the hourly composite radar forecasts via various CAMs. Elevated antecedent soil moisture and lingering hydrologic concerns across southeast KS into southern MO only add to the heightened risk of flash flooding as the area will likely struggle to maintain any additional rainfall, especially significant totals over 2". The SLGT risk expands east through the areas above with an elevated SLGT through the St. Louis metro as heavy rain shifts east ahead of the shortwave trough across eastern MO and southern IL overnight. ...Southeast U.S... Gulf moisture converging along a remnant stationary front should trigger diurnal activity over AR/southern MS/AL and GA as best depicted in the 12Z RRFS. A disturbance along this boundary should be a mechanism for targeted low- level convergence in a zone of favorable boundary layer moisture and instability. Signals for locally heavy rainfall of 2+ inches are noted in the deterministic CAMs with the HREF blended mean QPF between 12z Thursday to 00z Friday showing pockets of 1.5-2" located from the MS coastal areas through the I-10 corridor towards Tallahassee, back up into southern GA, as far east as Savannah/Brunswick in this latest cycle. This is coincident with the 500mb vorticity trajectory of our mid- level impulse generated from the previous period of thunderstorms which provides a better target point for heavy rainfall compared to just your standard pulse convection regime we see in the summer. Modest HREF neighborhood probs of 20-40% exist for localized totals >3" across the aforementioned areas, enough to account for potential isolated flash flood concerns, mainly within more urbanized/developed areas across the Southeast. As a result, maintained the previous MRGL risk with an expansion over New Orleans. ...Interior West... Multiple shortwaves and elevated moisture presence across the Interior Mountain West will lead to another afternoon and early evening of scattered convection with localized flash flood concerns today. The threat remains low-end for the time being given the current QPF outputs, however this could still provide some isolated flash flood prospects in those terrain focused zones across UT/CO, as well as any heavy rain encounters in the favored slot canyon areas littered over western CO into UT. The previous MRGL risk was generally maintained. ...Northeast... A potent shortwave trough located over the Northern Great Lakes into the neighboring Ontario Province will allow for a focused area of ascent downstream of the mean trough as the Northeastern U.S. nestles squarely into the left exit region of a modest 110kt jet ejecting eastward across the Great Lakes. Sufficient deep layer moisture and added shear with the incoming disturbance will aid in maintenance of an area of quick-moving convection across NY state through central and northern New England later this afternoon. High probabilities for >1" and low probs for 2" indicates a general pattern of 1-2" with perhaps a few pockets exceeding 2" in the setup over the Hudson Valley into VT/NH, enough to warrant at least a low to modest threat of localized flash flood concerns, especially given some of the more saturated soils located over the region as noted via the latest NASA SPoRT 0-10cm soil moisture percentiles >90%. The previous MRGL risk was generally maintained with only some expansion south and east where FFG is lower. Jackson/Kleebauer Day 2 Valid 12Z Fri Jun 26 2026 - 12Z Sat Jun 27 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT FROM NORTHEAST OKLAHOMA TO CENTRAL WEST VIRGINIA... ...Southern Plains to the Mid-Atlantic... A shortwave trough shifts from Missouri to the central Appalachians along a stationary front through the period. Abundant moisture pools along this boundary from northeastern OK to the Mid-Atlantic with PW anomalies of 1.5 to 2.5. The combination of forcing, moisture, and instability allows for an enhanced slight risk (and probable Moderate eventually) though there remains some uncertainty where the greatest heavy rain focus will be. For now the30 threat areas is expanded west to east with the Slight Risk now over northeast OK and through central West Virginia. Latitudinal differences in the main forcing boundary also warrant expanding the southern border of the Slight Risk into AR/TN and the northern border into central IL/IN. The 12Z NAMnest remains the farthest north solution, but it was also notably north for the Day 1 period (with the same frontal case). There remains a localized threat area for 3-5" rainfall from the St. Louis metro south through the confluence with the OH River and in southern/central IN where a Moderate Risk would be warranted. Sufficiently strong southwesterly flow east of the central Appalachians, along with PW anomalies of 2 sigma Friday night warrants expanding the Marginal Risk over the central Mid-Atlantic. The presence of 70F dew points and maintained instability overnight near a boundary is often sufficient for prolonged overnight activity across this area. ...Montana into North Dakota... Deep low pressure center shifts from the BC coast to Washington through the period with associated shortwave troughing lifting through Montana. Strong steering flow will keep activity progressive, but the environment for organized convection with potential for training. This threat area expands from central MT into central ND, so the Marginal Risk was expanded east. Moisture looks sufficient with PW anomalies of 1.5 sigma. Corridors of 1-2" rainfall, locally 3" are likely. ...Central High Plains... Increased troughing over the Great Basin promotes return flow up the High Plains with evening convective activity off the Sangre de Cristos and Front Range that spills onto the central High Plains through the night. The risk for repeating cells in a moist environment with PW 1.5 sigma above normal warrants a Marginal Risk for the central High Plains. ...Northern New England... Shortwave low moving through Quebec Friday will allow a trough axis to swing through New England. Sufficient instability and mid- level forcing from the disturbance and diurnal heating should lead to enhanced thunderstorms capable of producing 1-3" of rainfall through much of Maine as well as northern NH/VT. Locally repeating activity could allow localized flash flooding despite moisture being rather limited. The Marginal Risk was expanded south into VT/NH and southern ME. Jackson/Kleebauer Day 3 Valid 12Z Sat Jun 27 2026 - 12Z Sun Jun 28 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT FROM THE EASTERN OHIO VALLEY INTO EASTERN TENNESSEE... ...Ohio Valley... A more amplified western trough with ridging over the east-central states. All the while the existing frontal boundary from Friday continues to promote heavy rain. The Slight Risk for central WV and eastern KY is maintained with an expansion south into eastern TN given 12Z consensus. The Marginal Risk back over the mid-MS Valley was broadened a bit as well given wet antecedent conditions there. ...Mid-Atlantic... Ongoing activity Saturday morning looks to settle over eastern VA/the Delmarva by Saturday afternoon with a risk for localized flash flooding. A Marginal Risk is raised for these areas in a similar design to the heavy rain case from Tuesday. ...Northern Plains... Broad trough over the interior Northwest Saturday. Energy shedding from this low along with ample shear and moisture anomalies creeping above the 90th percentile up over the Northern Plains will be sufficient in locally enhanced rainfall rates, especially in any supercell cores and multi-cell mergers that transpire once the LLJ kicks in after 00z. A broad MRGL risk remains in effect for the threat up across eastern MT and ND (for the second day) with a potential for a targeted upgrade in future updates. Jackson/Kleebauer Day 4 and Day 5 ...The probability of rainfall exceeding flash flood guidance values is less than 5 percent... Pereira 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