900 FOUS30 KWBC 041940 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 340 PM EDT Sat Apr 4 2026 Day 1 Valid 16Z Sat Apr 04 2026 - 12Z Sun Apr 05 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE ARKLATEX/LOWER MISSISSIPPI VALLEY AND A PORTION OF THE OHIO VALLEY INTO WESTERN PENNSYLVANIA... ...South-Central Texas into ArkLaTex... Cold front position is currently analyzed just to the east of the DFW metro with heavy rain migrating into northeast TX and the ArkLaTex. Expect this area to be a focal point this afternoon as frontal convergence and a modestly unstable environment will aid in some heavier rainfall coverage with totals between 2-4" expected. Upstream trends in precip magnitude signal this range to be pretty consistent with some localized flash flooding occurring where heavy rain persists for 2+ hours. Right now the best spot is across the area stretching from Texarkana to Tyler where models have been consistent with a band of heavier precip leading to precip totals >3" in areas. Antecedent conditions initially are very dry, so this will curb some of the threat upfront, but persistent heavy rainfall could still spur up some flash flood prospects, especially inside the urban areas along I-30 and I-20. Further southwest into hillier terrain of south-central TX along I-35, consensus has grown for a round of heavy thunderstorms to impact areas from Waco down to just north of San Antonio. PWATs running around the 99th percentile climatologically, as noted by the latest 12z RAOB from KFWD with a similar environment situated across much of east TX should be sufficient for efficient rainfall rates between 2-3"/hr at peak intensity. This is highlighted well within the 12z HREF hourly probs of >2"/hr running between 20-35% within the I-35 corridor extending from Waco, south. This area is notoriously more flashy due to the topographic composition and sprawling urbanization factors lined up across the interstate domain. It will not take much to cause some local issues with flash flooding in any strong cells that materialize. The SLGT risk was expanded south given the above, and in conjunction with coordination from the local WFO's out of Houston and Austin/San Antonio as it encompasses portions of their respective CWA's. ...Lower Mississippi Valley... The SLGT risk over MS/LA was generally maintained with the only viable change being the addition of the risk introduced into the New Orleans metro. This area has a split in CAMs on whether heavy thunderstorm activity encroaches the area from the south as prevailing southerly flow within the confluent pattern between the front to the west and sprawling surface ridge to the east should keep a moist, unstable airmass in place for the entirety of the period. If any convection makes it to the area, it has the potential to pack a punch as the environmental conditions provide the opportunity for a quick 2-4" of rainfall as indicated by moderate to high neighborhood probabilities within the latest HREF (40-70%) for exceeding 2" of rain this period. The region further north along the Mississippi, including the Jackson area are still expected to see the greatest threat for heavy convection later this evening as the axis of confluence and stronger forcing will combine to bring a period of heavy rainfall prior to the frontal passage. Considering the high EAS and neighborhood probabilities for >1" and >2" respectively, there was no reason to deviate from the previous forecast. ...Ohio Valley into Western Pennsylvania... A wavy quasi-stationary front positioned from IL to PA will be a focal point for convective development later today with a cold front approach from the west as a primary surface low lifts northeast through the Great Lakes. The area along I-76 in Ohio and points southeast to Pittsburgh have some of the lower FFG's in the country currently, all of which due to previous days of impact that led to scattered flash flood issuances and moderate river flooding in the vicinity. A well-defined axis of confluent flow across the Mid Atlantic to Ohio Valley will allow for the prospects of scattered convection capable of localized flash flooding, especially in the corridor that has been heavily impacted in recent days. The overall output from the hi-res isn't necessarily impressive, but multiple CAMs do try to drop a quick inch or two within that domain that's more sensitive to any additional rainfall. The setup is conducive for these concerns, so despite the modest probs indicated within the HREF neighborhood prob fields, the antecedent conditions combined with those probabilities was enough to maintain the SLGT risk from previous forecast, and expand a bit further east to include the Pittsburgh metro and surrounds. Kleebauer Day 2 Valid 12Z Sun Apr 05 2026 - 12Z Mon Apr 06 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTH TEXAS ON SUNDAY... Steady progression of a cold front from the north will lead to the first 6hrs of the period being the highlight for any flash flooding concerns across Deep South Texas. The trends have been for the front to clear the Rio Grande in the morning, so some lingering heavy rainfall across the four southernmost counties from Zapata to Cameron will be the most susceptible to localized flash flood concerns in the D2. The NAM Nest continues to be the least progressive with the cold front leading to lingering heavy convection up by Jim Hogg to Kleberg counties, so kept the MRGL risk in a similar alignment to the previous forecast to account for the potential. Much of the rainfall will be beneficial, so the primary threat will be within the more urbanized portions of South TX. Rainfall totals between 1-2" will be most common with prob fields indicating a low-end potential for 3-5" in the strongest storms. Kleebauer Day 3 Valid 12Z Mon Apr 06 2026 - 12Z Tue Apr 07 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann/Kleebauer 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