Subj : HVYRAIN: Excess Rain D3-5 To : All From : Mike Powell Date : Wed Jun 17 2026 10:42:34 FOUS30 KWBC 170822 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 422 AM EDT Wed Jun 17 2026 Day 3 Valid 12Z Fri Jun 19 2026 - 12Z Sat Jun 20 2026 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR MUCH OF SOUTHERN ALABAMA... ....Southeast... Any lull in heavy rainfall across southern Alabama from Thursday night behind the precipitation shield associated with the remnants of Potential Tropical Cyclone 1 will end in a hurry Friday morning as the cold front over the Tennessee Valley continues to press southward and runs into the ongoing southerly flow and low-level jet of deep tropical moisture from off the Gulf. The clash of these air masses looks to maximize over southern Alabama, where storms are likely to continue in some form or fashion for much of the day Friday. Assuming the multiple inches of rain from Thursday occurs in these same areas, the slightly lower storm total rain on Friday will make little difference for the flooding risk, as multiple inches of rain fall over the same areas very hard hit from Thursday. This very good overlap in the storm placement from Thursday to Friday necessitated a risk upgrade across southern Alabama for the Day 3/Friday period. Should this overlap continue to hold and the widespread multiple inches of rain with localized totals to double digits from Thursday occurs as forecast, it's entirely feasible that the hardest hit areas may need further upgrades to the flooding risk. Unfortunately the track record with the CAMs ensembles on maintaining continuity day to day on where the storms will occur is not very good, so any movement breaking the overlap will greatly improve the rather ominous flooding outlook for southern Alabama on Friday. Convective coverage over Alabama should diminish greatly Friday night as heavier rains to the west and the departing system to the east should put the state in a relative ridging pattern, allowing for a much needed break from the rainfall. ....Texas Hill Country... Southeasterly flow of deep moisture from off the Gulf will continue across much of Texas through the Day 3 period. Northwestward moving convection on the leading edge of the deep moisture will collide with storms that form along the dry line and the Mexican mountains Friday evening, resulting in MCS development that turns the storms back towards the best instability to the southeast. This should result in some areas seeing multiple rounds of heavy rain producing storms over the historically flash flood prone region of the Texas Hill Country. Thus, a Slight Risk area remains in effect for the region. Lesser amounts of rain are expected further east into north-central Texas and the Metroplex, so the Slight Risk inherited with downgraded in that area. Wegman Day 4 and Day 5 Valid 12Z Sat Jun 20 2026 - 12Z Mon Jun 22 2026 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE OF CENTRAL PLAINS THROUGH THE MID MISSISSIPPI INTO THE LOWER OHIO VALLEY... Day 4... A well-defined 500mb shortwave trough will move from the Great Basin into the northern Rockies midday Saturday, reaching the northern High Plains by Saturday night. Ahead of a southward advancing Canadian cold front, a northward-lifting warm front across the central Plains will lead an anomalous moisture plume into an increasing unstable environment. While exact convective placement varies, the deterministic models remain in generally good agreement -- depicting a deepening surface low over the central Plains that will help to focus moisture along the leading edge of a strengthening low level jet. A deepening pool of moisture (PWs increasing to 1.5-2 inches) over central Nebraska/Kansas eastward into southwestern Iowa and western to central Missouri will support efficient rainfall rates. This ample moisture along with large- scale ascent afforded by mid-level shortwave and right- entrance region jet forcing will further encourage heavy rainfall and the potential for flash flooding across the region. Therefore, a Slight Risk was maintained across the region. Farther south, a weakening frontal boundary and residual tropical moisture will trigger additional thunderstorms from South Texas across the Gulf Coast. Localized flooding will likely remain a threat given the increasing sensitive soils. Day 5... Forecast confidence lowers notably heading into the latter half of the weekend as guidance begins to diverge on the track of the leading wave forming over the central Plains on Day 4. Notably, the ECMWF offers one of the more northerly solutions compared to other guidance. Beyond the primary wave's track from the Midwest into the East, considerable model spread exists regarding the timing of the trailing front and subsequent wave and storm development. With the continuation of ample moisture, instability, and strong forcing areas of heavy rainfall and flash flooding appear likely. Given the model spread, the outlook area, including a Slight Risk extending from the lower Missouri to the lower Ohio Valley, relied most heavily on a multi-model ensemble mean. Pereira $$ --- SBBSecho 3.28-Linux * Origin: Capitol City Online (618:250/10) .