760 FOUS30 KWBC 182030 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 430 PM EDT Thu Jun 18 2026 Day 1 Valid 16Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026 ...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL GULF COAST... ...WIDESPREAD AND LIFE THREATENING FLASH FLOODING LIKELY TODAY FOR THE CENTRAL GULF COAST... ...1600 UTC Update... A widespread and life-threatening flash flood event is underway across the central Gulf Coast and will continue to expand northeastward deeper into the Southeast throughout the day. Flash flood emergencies have already been issued both in southeastern and central LA as well as southern Mississippi where bands of backbuilding, training thunderstorms have already lead to MRMS estimated rainfall totals of 9-11" (see WPC MPD #450 for more details). Torrential rainfall is expected to continue throughout the day with these ongoing storms as well as additional bands of thunderstorms supported by a surface low associated with the remnants of Tropical Storm Arthur, an impressive ~40-50 kt low level jet off the Gulf, and daily-record level PWATS over 2". Some modest adjustments were made to the inherited outlook based on ongoing thunderstorms and the latest 12Z hi-res guidance including a westward expansion of the High Risk to central Louisiana where ongoing life-threatening flash flooding is occurring. A slight northeastward expansion was also included across southern Mississippi and Alabama given moderate to high probabilities from the HREF of 5-8"+ of rainfall. Guidance in general has suggested a northeastward expansion of the flash flood risk bringing heightened concern to southwestern to central Georgia as well as further north into the southern Appalachians. Elsewhere, the Slight Risk over portions of the southern Plains/Texas was also expanded based on the latest 12Z hi-res guidance. Thunderstorms are expected to develop later this evening and into the overnight hours in vicinity of a wave of low pressure along an approaching cold front and southward along the dryline. Sporadic/slow storm motions and clustering of storms will support locally heavy rainfall, especially if the collective clustering/merging of cold pools can result in more organized complexes as suggested by some of the hi-res guidance. This includes both along the Red River Valley, where a Slight Risk is already in place, as well as further south along the dryline into the Texas Hill Country where the Slight Risk has been expanded. Some of the latest hi-res guidance (including the RRFS) is more bullish on the potential for heavier rainfall spreading southward given expected storm motions and potential for a more organized complex to develop. Another round of thunderstorms is expected today over portions of Arizona and New Mexico where some locally heavy rainfall/isolated flash flooding will be possible given heightened moisture in place. Most storms will likely be diurnally driven along the more complex terrain. Increased moist southerly flow off the Atlantic into interior New England/Upstate New York ahead of an approaching low pressure system will also bring the threat for some locally heavy rainfall (1-3" totals) and isolated flash flooding. Putnam ...Previous Discussion... ...Southeast... The remnants of Post Tropical Cyclone Arthur are moving into the Central Gulf Coast this morning. While the cyclone center may have dissipated, the moisture plume and associated rainfall shield most certainly have not. Rainfall moving into southeastern Louisiana right now are producing rates to 3 inches per hour. These kinds of rainfall rates are expected to continue with the strongest cells for much of the day today across the central Gulf Coast. An impressive 50 kt low level jet at 850 is advecting very deep tropical moisture into the coast. This is pushing PWATs to over 2.6 inches. Meanwhile instability over the Gulf is up to 4,000 J/kg. This is supporting very efficient cells capable of multiple inch per hour rates to the east of the remnant circulation center. Multiple waves of storms will track south to north across eastern Louisiana into southern Mississippi this morning. The area has been hard hit with heavy rain in recent days, so larger rivers are already flooding, and soils are nearly saturated, so nearly all of the heavy rainfall is expected to convert to runoff, resulting in more significant river, stream, and creek rises though the morning. The eastern side of the plume of moisture will spawn additional numerous thunderstorms into southern Alabama and the Florida Panhandle through midday. The storm organization is expected to change a bit into the afternoon with peak heating. To the west across Mississippi and Louisiana, backbuilding and training convection is expected to form into 1 or 2 nearly stationary lines, as the individual cells embedded within train towards the east along the line. Meanwhile, over Alabama, multiple lines of eastward moving lines of storms will get the flooding and heavy rainfall started as early as mid-morning. The western end of the line in LA/MS will become the trailing storms on the southwest end of the MCS associated with post tropical cyclone Arthur. This line will very slowly drift southeastward towards the Gulf Coast, likely impacting Mobile and eventually the Pensacola area, as well as points north. This will result in multiple hours from mid-afternoon into the evening where training storms track over the same areas. The eastward moving convection is expected to move faster towards the east than the storms can backbuild, so the trailing line responsible for the worst flooding should gradually shift east as well. The storms could persist as long as until midnight in the Florida Panhandle, but most guidance has it moving on and dissipating earlier in the evening. Regardless, with potential for multiple inch per hour rainfall rates with numerous storms through the day tracking over the same areas, the storm total rainfall in these areas is likely to pile up very quickly. Guidance suggests rainfall totals in many areas of the High Risk could exceed 12 inches, though local amounts could approach 20 inches. Widespread and potentially life threatening flash flooding is likely as a result of these double-digit rainfall numbers. Urban areas that could be impacted from New Orleans (in a higher-end Moderate Risk), Mobile, and Pensacola could see life-threatening flash flooding occur as a result. Everyone should heed the advice of local authorities as warnings are issued. Across central Alabama into northern Georgia, storm coverage and intensity of the strongest cells are expected to be a bit lower, but antecedent soil conditions remain nearly saturated. Multiple hours of moderate to at times heavy rain are expected up as far north as Birmingham and northeast as Atlanta. The Moderate Risk for these areas remains in place with few changes. An eastward expansion of the Moderate Risk in west-central Georgia was also made. ...Ohio/Tennessee Valleys... A cold front pushing south across the Ohio Valley today will run into the northern extent of the deep plume of tropical moisture associated with the remnants of Arthur. With daytime heating, the clashing of air masses along the front will result in numerous showers and thunderstorms developing along the front, which will likely be along the KY/TN border, extending ENE into eastern Kentucky and southern West Virginia. The storms will be in a favorable environment for training as the plume of moisture tracks parallel to the front as well. A shortwave trough will help the front advance south and east across the area more quickly this evening through tonight, which should end any backbuilding and training from the afternoon and allow everything to progress eastward, ending the flooding threat. ...Southwestern Oklahoma into North Texas... Overnight tonight, an MCS is expected to develop across southwestern Oklahoma and north Texas in response to both proximity to the dry line, deep tropical moisture with PWATs approaching 2 inches, and a developing low over West Texas, encouraging the formation of a low level jet into the storms. Given this is a smaller feature than the remnants of Arthur to the east, the CAMs are struggling much more with where and how long the storms in the area will form, and where they will track. Most likely the storms will remain along the Red River/OK-TX border. The inherited Slight covering most of the rest of Oklahoma into Arkansas was dropped to a Marginal as this MCS should remain well separated from the rains with Arthur to the east, with little rain in between. Wegman Day 2 Valid 12Z Fri Jun 19 2026 - 12Z Sat Jun 20 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL GULF COAST... ...2030 UTC Update... The prior forecast reasoning remains on track with the greatest concern focused on where additional rainfall Friday may overlap some of the torrential totals seen across the central Gulf Coast into the Southeast on Thursday. Some instances of flash flooding may remain ongoing as well. The now available 12Z hi-res guidance supports the greatest risk of additional rainfall of 1-3", locally 4-6", across much of the inherited Moderate Risk area. Some minor areal expansions where made to the northern extent of the moderate across southern Alabama and Mississippi based on the latest guidance, as well as to the southwest from coastal Mississippi into southeastern Louisiana where some of the heaviest 24 hour totals (MRMS estimated 6-10") had occurred through Thursday afternoon. There was also a signal in the guidance for some similar heavier totals further west across portions of western Louisiana. However, most of this region did not see rainfall over the past day and thus feel comfortable retaining the risk as a higher-end Slight for now. Another more isolated but significant area of concern will be if any rainfall overlaps portions of east-central Louisiana where extreme rainfall of over 24" in the past 24 hours has been estimated by MRMS. Putnam ...Previous Discussion... ...Southeast... While the plume of extreme moisture associated with the remnants of Arthur will be exiting the Carolina coast at the start of the period, deep tropical moisture will remain entrenched over much of the Southeast on Friday. A cold front that tracked over the Ohio Valley on Day 1/Thursday will continue edging southward into the Southeast, bringing much drier air and relief to areas behind it. Unfortunately ahead of it, the air mass will remain soupy. The moisture off the Gulf will have turned eastward along the front on Friday, which will do a couple things: 1) It will not prevent the front from making more southward progress, as opposed to a southerly low level jet which would actively work against a southward moving front. 2) It will create a more unidirectional wind flow through the depth of the atmosphere, which will support faster-moving, but training storms along the front. In addition to any MCSs which could form in the soupy air mass early in the morning, potentially multiple lines of storms will track southeastward along the front into the area that just was hit with Arthur's remnants the previous day. Thus, the Moderate Risk for this area remains in effect. Expected rainfall for most areas will generally stay between 1-3 inches on average, so the rainfall amounts expected on Friday will pale in comparison to today. However, given the expected flooding that will very much still be ongoing on Friday, the addition of 1-3 inches of rain with locally higher amounts where storm training persists longest over these same areas still raised the flooding threat in the area to the Moderate Risk category. Changes in where the heaviest rains today/Day 1 occur may result in shifts of the Moderate Risk, particularly if the heaviest expected rains occur further south and west into Mississippi and eastern Louisiana. A few of the CAMs models are hinting at that possibility. ...Southern Plains... Across a large swath of Texas on Friday, multiple MCSs may impact much of the state. On Friday morning, lingering MCSs from Oklahoma and the Slight Risk on Day 1 may be ongoing into north-central Texas Friday morning, including into the Metroplex. Widely scattered instances of flash flooding will be possible with that. More coverage of storms are expected Friday night. The typical strengthening MCS will advect extreme instability and moisture over all of the eastern half of the state. As storms form and organize into MCSs, the potential for additional instances of flash flooding will increase. There is considerable uncertainty as to where they form and how they track, so a large swath of eastern Texas was included in a Slight Risk, especially down towards San Antonio and Houston, which have been impacted with heavy rains in recent days, and soils remain wetter than normal. Wegman Day 3 Valid 12Z Sat Jun 20 2026 - 12Z Sun Jun 21 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL PLAINS AND MISSOURI VALLEY... ...Central Plains and Missouri Valley... A large area of heavy rain associated with a developing MCS starting Saturday afternoon and continuing into Saturday night is expected to bring widespread heavy rainfall across portions of the central Plains into the Missouri Valley with the greatest threat currently expected across southeastern Nebraska, northeastern Kansas, and far northwestern Missouri/southwestern Iowa. Storms are expected to initiate Saturday afternoon with peak heating. An LLJ of southeasterly flow will pump deep Gulf moisture up the Plains through the day. A developing surface low and upper level shortwave strengthening the low over Colorado will eject into the Plains. This will force the dryline to race eastward in response. The warm front associated with the low and the dry line will uplift the deep moisture, resulting in widespread shower and thunderstorm development. These storms are expected to grow upscale into an expansive, organized convective system into the evening and overnight hours that will then track southeasterly across the risk area. The latest deterministic guidance shows areal average rainfall totals along the expected path of the MCS in the 2-3" range with locally higher amounts of 4-6", more than sufficient to lead to scattered and potentially widespread flash flooding, which has prompted an upgrade to a Moderate Risk. As is usually the case with convective systems the exact path and duration will be determined by more mesoscale details than the guidance can typically pin down at this time frame, so some areal modification and possible expansion of the Moderate Risk will be likely over the next couple of days. The most likely area for expansion would be further to southeast into more of western Missouri and east- central/southeastern Kansans. However, given the noted uncertainty with the evolution of these types of systems at this timeframe, have limited the extent of the risk area to also overlap where the greatest support/confidence is shown by the ensemble mean/probabilistic guidance. ...Southeast... An MCS tracking from the Ozarks following the same front that entered interior portions of the Southeast as a cold front on Friday will help that same front now retreat as a warm front on Saturday. Heavy rains are expected Saturday morning over the Slight Risk area from northern Mississippi to southern Alabama as storms track southeastward along the retreating front. Daytime heating will likely support additional clusters of storms into the afternoon in these areas. The heaviest rains over the most widespread area will be Saturday morning in northern Mississippi. They will be less organized as they move into southern Alabama Saturday afternoon, but given the prior day's expected rains in these same areas, the Slight Risk includes southern Alabama as well. Rainfall totals will likely be more limited than they have compared to the prior days but the region will remain more susceptible to additional instances of flash flooding given the heavy rainfall received from precipitation associated with the remnants of T.S. Arthur. Putnam/Wegman Day 4 and Day 5 Valid 12Z Sun Jun 21 2026 - 12Z Tue Jun 23 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE OZARKS THROUGH THE MIDWEST AND INTO THE UPPER OHIO VALLEY... 2030Z Update... Maintained the Slight risk in the Day 4 period and the Marginal risk on Day 5 with few changes. The wave coming out of the Plains and crossing into the Midwest remains the primary focus for heavy to excessive rainfall on Sunday into early Monday. Some differences linger in latitude of the axis of heaviest rainfall...but probabilities were comparable with the overnight guidance. Likewise...the previously issued outlook was still generally captured the axis of heavier rainfall that could result in heavy to potentially excessive rainfall on Monday. So changes tended to be few. Bann Previous Discussion... Day 4... By the start of the day 4 forecast period a potent shortwave and related surface low are expected to eject eastward out of the central Plains into the Midwest. There will also be a trailing frontal boundary extending into the southern Plains to add a focus for additional thunderstorms. There remains some uncertainty regarding the speed and latitude of these features, but PWs above the 90th climatological percentile (per the 00z GEFS) overlapping with soils likely still recovering from recent heavy rain in the Midwest will lead to at least scattered flash flooding concerns. NBM probabilities for at least 2" are between 30-55% and cover much of the SLGT risk area. Locally higher totals are likely given the convective environment. The progressive nature of these storms may end up limiting the severity of flash flood impacts, but a MDT risk upgrade is possible should training/back-building elements become more obvious in the short range updates. This is especially the case given the sensitivity of the affected regions to additional rainfall. Day 5... The shortwave and low pressure on day 4 is forecast to continue east towards the Mid-Atlantic and Northeast, with additional uncertainties in latitude and speed. Additionally, thunderstorms should reform along the attached frontal boundary extending westward across the Tennessee Valley and into the southern Plains. At the moment most convection appears scattered in nature and low confidence in placement of heavier QPF. Therefore, a MRGL risk is highlighted and will be refined in future updates. Additional thunderstorm activity is likely into the High Plains, with uncertainty surrounding the impact of a nearby southern Canada upper low on thunderstorm activity in the northern High Plains. Snell 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 $$