FOUS30 KWBC 230035 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 835 PM EDT Tue Sep 22 2026 Day 1 Valid 01Z Wed Sep 23 2026 - 12Z Wed Sep 23 2026 ..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHERN NEW MEXICO... ...New Mexico and West Texas... Current radar and satellite composite indicate a turbulent evening on tap for much of New Mexico with an eastern extension into west Texas. Shortwave analyzed over Chihuahua will lift northward through the course of the overnight with increasing ascent and convergence across southern NM and along the Southern Rockies into the Sacramento Mountains as prevailing southeasterly flow allows for focused low-level orographic ascent within the terrain over NM. Heavy rain has plagued the region over the course of the last 6 hours with a continuation expected overnight as multi-model consensus, including all CAMs have targeted a large area from far west TX, including the El Paso metro, to points north and west of the city center as the focus for significant rainfall and flash flood prospects. PWATs remain elevated to a degree that PWAT anomalies based on the recent mesoanalysis and RAOB's from KEPZ and KABQ pushing well over the 90th percentile as of 18z with a likelihood of PWATs come the 00z sounding depicting closer to the upper threshold of the climatological max when assessing the latest RAP mesoanalysis output. This setup is likely to provide several flash flood warnings with a heightened risk of considerable to potentially catastrophic tags due to the propensity of run off in the deserts and complex terrain across NM. 00z HRRR remains very bullish on local totals between 2-4", additional located over south-central NM and the Sacramento Mountain areas, a signal typically coinciding with major flash flood capabilities and increasing hydrologic concerns as we move into Wednesday morning. A high-end MDT risk remains forecast for the area west and northwest of El Paso in NM with a broad MDT encompassing much of the state given the nature of the heavy precip. Little deviation from previous forecast for all risks given the consistency in guidance and ground truth playing out as modeled. ...Ohio Valley and Mid-Atlantic... Heavy rain prospects continue across portions of the Carolina Piedmont into the Midlands of SC with a small ribbon of convection lingering along the slow advancing backdoor front over eastern NC. Models are in flux with the specific location of heavy rainfall, but assessment of the latest radar to CAMs trends signals the HRRR/RRFS are doing the best job at handling the current evolution with weight given more towards these CAMs than other guidance. The positioning and coverage of the convection makes sense synoptically as the airmass along and south of the wedging cold front is much more buoyant and capable of maintaining stronger convective cores that could produce flash flood concerns. Some elevated convection is capable of isolated flash flooding into NC and VA within urbanized zones, but the threat is dwindling as the night progresses. This led to the MRGL and SLGT being cut back over those areas with a maintenance over the Central and Southern Appalachian front into the SC Piedmont and southwestern NC due to the greater instability maxima. Localized amounts of 2-4" are plausible in the SLGT risk area in those more impacted locations, but signal still leans towards isolated to widely scattered flash flooding prospects, a step downward in potential compared to earlier this afternoon. ...South Florida... A Marginal Risk has been maintained for portions of South Florida as PWATs remain elevated supporting heavy rainfall rates and a localized urban flash flood risk lingering into the first part of the evening before waning after midnight. Kleebauer Day 2 Valid 12Z Wed Sep 23 2026 - 12Z Thu Sep 24 2026 ..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF CENTRAL AND EASTERN NEW MEXICO... ...New Mexico and West Texas... The heavy rainfall threat established on day 1 will be ongoing and continue and peak over NM on day 2 as large scale forcing gets even stronger. A well defined mid level shortwave is forecast to lift northward across the state, accompanied by robust upper level divergence and the likely development of a surface low. PW values will remain near record levels for this time of year, with an anomalously deep moisture profile. With such strong forcing and widespread moisture in place, the primary limiting factor for heavy convective rates will be the extent of cloud cover and its impact on destabilization. While widespread clouds are a concern, daytime heating should allow at least the eastern edge of the rainfall shield to sufficiently destabilize, aided by broad easterly upslope flow. Thus while some areas may see predominately stratiform rain, a concentrated swath of intense convective rainfall remains likely. The most recent guidance still points toward totals of 2 to 4 inches during the 24-hr period, potentially higher up to 5 inches. This is likely to result in scattered to numerous instances of flash flooding, some of which could be life-threatening and significant. This would be most likely across sensitive terrain, urban areas, and burn scars. The inherited ERO risk is in good shape given the most recent guidance. ...Mid-Atlantic... A complex synoptic pattern will be present over the eastern U.S. as a mid to upper level low slowly drifts from the Ohio Valley towards the Mid-Atlantic, while a separate coastal low develops offshore. Meanwhile, surface high pressure positioned to the north will advect drier and more stable air into the corridor between these two features. Much of the deepest moisture and instability will remain offshore with the coastal low. The primary threat for heavy rainfall over land should focus closer to the cold core of the upper low from the OH Valley down through western NC and into north GA. While PW values will have lowered across this area, model guidance still indicates CAPE exceeding 1000 J/kg within a trough axis over the region. This localized axis of instability, coupled with a stationary convergence axis, will support the development of slow moving convective cells. Even with the reduction in deep moisture, locally heavy rainfall rates are likely. Given that at least some of this region will have compromised FFG and heightened hydrologic sensitivity from previous rainfall, some flash flood risk is expected to continue. Based on signals from the 00z REFS and HREF members, as well as the GFS and ECMWF, a small Slight risk has been introduced stretching from eastern TN into eastern KY and southern WV, where the focus for slow moving convection is expected to be greatest. ...Florida... A Marginal risk continues across south FL where above normal PWs and instability will continue to pose a localized flash flood risk. Chenard/Taylor Day 3 Valid 12Z Thu Sep 24 2026 - 12Z Fri Sep 25 2026 ..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF NEW MEXICO AND THE TEXAS PANHANDLE... ...Southwest... The stronger mid level forcing and highest PW anomalies will shift northward out of NM and into Colorado and the central PLains on Thursday. Despite the loss of stronger large scale forcing, daytime destabilization over NM is actually forecast to increase in the wake of the exiting system compared to prior days. While PW values decrease some, they will remain above the climatological 75th percentile. With less concentrated forcing and somewhat reduced moisture, the overall areal coverage of heavy rainfall across NM should diminish relative to days 1 and 2. However, the combination of stronger instability and sufficient moisture will still support intense localized convective rainfall rates capable of producing significant rainfall totals. Given the hydrologic sensitivity built up from preceding days of heavy rain, a Slight risk is maintained for NM into the TX Panhandle. Locally significant flash flood impacts will remain possible. Isolated to scattered flash flooding will also be possible across portions of Arizona, southeast Utah, and Colorado as shortwave energy lifts northward across the region. ...Central Plains... The deep moisture plume will maximize over the Central Plains on Thursday, pushing PW values toward late September record levels. The mid to upper pattern coupled with a robust low level moisture transport axis supports a favorable setup for organized convection across portions of KS and NE, with backbuilding/training a possibility. There remains some uncertainty in the placement of the heaviest rainfall and eventually a Slight Risk might be needed. Chenard/Taylor Day 4 and Day 5 Valid 12Z Fri Sep 25 2026 - 12Z Sun Sep 27 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN US/WESTERN PLAINS AS WELL AS EASTERN NEW ENGLAND... ...Southern Rockies to Central and High Plains... Day 4...Multiple areas of interest for the end of the week into the weekend with a broad trough sweeping through the interior northwest with a shortwave ejection out of the Rockies, enhancing regional ascent within the Central High Plains into the Missouri River Valley and adjacent Corn Belt. Model spread continues to be relatively low with the handling of the two features leading to better than normal confidence at range for a period of heavy rain from widespread convection across the above area. Main axis of heavy rainfall will likely be over central and eastern NE into western IA and portions of northern KS and southern SD. Totals are currently between 1-2" on areal average, but signal with instability was sufficient for a broad MRGL risk placement maintained over the area with only minor adjustments from the previous forecast. Further south over the Southern High Plains, a weak shortwave over the Southern Rockies will advance east-northeast within the mean mid-level flow with enough diurnal instability to couple with the focused ascent pattern to cause a period of convective initiation across the Southern High Plains of NM into the TX Panhandle. Signals remains on the weaker side, but some of the areas anticipated to be impacted will still be in recovery from the barrage of heavy rain prospects the day prior, especially into NM. A broad MRGL remains in effect for the above area. Day 5...Main attention over the Midwest as the disturbance over the northern tier of the CONUS migrates eastward and leads to a carryover threat from the prior period. Models are less in agreement on the overall threat, so the MRGL risk in place over the Midwest into northern Missouri is of the lower end variety given some of the model discrepancy. A period to monitor as there's an equal chance of a higher risk and a removal pending the eventual convective evolution. ...Eastern New England... Day 4...Models remain consistent on the potential for a strong synoptic surface low off northern Mid Atlantic coast with heavy rain prospects in-of southeastern New England to perhaps as far south as the northern Mid Atlantic coastal areas. As of the latest ensemble probs and mean QPF distribution, the primary threat is still over southern New England with southeastern MA into RI as the areas of interest with 2+" totals plausible in the setup. The one positive in this evolution is a limited convective footprint leading to mainly heavy stratiform type precipitation coincident with a Nor'Easter that tends to offer some flash flood threat, but primarily leans more hydrological in terms of long term heavy rain leading to swollen rivers and streams with urban flooding due to poor drainage and consistent run off from prolonged rainfall. The MRGL risk inherited was only adjusted a bit from the previous issuance but maintaining the foothold over eastern MA into RI. Day 5...There's some discrepancy in the southward push of heavy rainfall (ML vs NWP outputs) as the upper pattern shows an occluding low with a drift to the west or southwest over the course of Saturday. Pending the upper level evolution, heavy rain prospects could be felt as far south as the NJ coast, perhaps leaking into portions of the Delmarva while still dealing more rainfall into LI and portions of southern New England. At this juncture, went with persistence in the forecast as higher probs remains situated over southern New England, but will have to monitor any trends backing more west to southwest with the occluding low which would bring heavier rain and perhaps a shift of the risk area further in that direction. Given the lack of relevant instability with the setup, a MRGL risk is still the most likely excessive outcome in the forecast, but positioning is where there could be some changes in the coming days, pending trends in guidance. 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 $$