National Hydromet Discussion
— National
Update
The Texas selection continues to be refined as the significant flooding event winds down. The Limited extent was removed and all that remains now is a Days 1-7 Considerable flooding selection to account for the moderate and major river flooding that continues to route through the basins. Fortunately, there are several days of dry weather to allow for all of these rivers to recede unimpeded.
The next section that required changes was the Central Appalachian and Upper Ohio Valley where the Limited was reduced on the southern portions as current rainfall forecasts and model guidance has backed off the small stream flooding responses. As is typical with convective patterns, there still may be a threat for localized flooding impacts so this area will continue to be monitored for changes. Further north, however, there was a need to expand on some of the selection into portions of eastern Ohio. Additionally, another round of rainfall is forecast to repeat over this area which may remain primed from the rainfall today. As such, this area was converted to a Days 1-7 threat to account for potentially heavy rainfall timing.
Minor adjustments were necessary for the Desert Southwest and Mid-Atlantic into the Northeast for overnight changes in the forecast as well as to update the text to account for changes in timing.
Previous Discussion as Follows
...Considerable flash, urban, and river flooding to continue across portions of Texas through today... Isolated flash flooding possible in eastern New Mexico and southeast Utah, with flooding impacts possible for the broader region through the weekend... Limited flooding impacts possible this weekend across portions of the Mid-Atlantic and Northeast as well as the southern Appalachians into the Upper Ohio Valley...
Texas
The threat of considerable flash flooding in central Texas continues through today for parts of central/west-central Texas, although the trend of a diminishing flood threat continues and additional significant rainfall is not expected after today. Moderate to major river flooding is ongoing or forecast across the region, with most of the gage locations in Hill Country forecast to crest by this weekend, while locations along the Rio Grande, Frio, Neuces, and San Antonio rivers that are well downstream of where the rain fell are forecast to begin cresting early next week. Preliminary data shows 12 gages have gone into major flood status during this event, including 1 that exceeded its flood of record, and additional 6 more forecast to exceed major threshold. In addition, 13 locations went into moderate flood, with another 4 expected to crest in major over the coming week. The only notable change to the Flood Hazard Outlook (FHO) selections for this issuance was the trimming back of the Limited extent in far western Texas.
Desert Southwest
The threat of isolated flash and urban flooding continues today, especially in southwest Utah and parts of eastern New Mexico. The overall flood threat has diminished somewhat from yesterday, especially in Arizona. Areas that have received recent rainfall are more likely to see efficient runoff, but anywhere heavy rainfall sets up could see flooding issues. More significant flooding potential exists over the weekend and into next week, but confidence is low as to the exact timing or where they will appear. Only changes to the afternoon FHO selection were to buffer out some of the northwest corner in New Mexico slightly.
Southern Appalachians through the Upper Ohio Valley
Isolated flash and urban flooding is possible across the region in response to convective rainfall through this weekend. Antecedent conditions are marginally conducive for hydrologic responses following some drying after recent rainfall. Given the potential for training convection and locally robust rainfall rates, flash flooding may quickly occur in urban areas and along steep/hilly terrain.
Mid-Atlantic and Northeast
Heavy rainfall is expected across the region over the weekend, leading to potential flash, urban, and small stream flooding impacts. Antecedent conditions are not conducive to rapid formation of runoff processes, but nonetheless locally heavy rainfall could overwhelm the infiltration rate of soils and lead to flooding issues, especially in heavily urbanized areas. The medium range NWM versions have not started picking up on this potential yet, so corresponding signals remain sparse.
Northern Rockies
Isolated flash flooding remains possible through tonight across northern Wyoming and into Montana due to heavy rainfall. Locally intense rainfall rates will be the primary driver for flash flooding, especially along small creeks/streams draining complex terrain and areas of poor-drainage in more urban locations. Anywhere that has already seen heavy rainfall in the last several days is of course more susceptible to flooding. Flash flooding and debris flows are also possible near recently burned areas.
000 AGUS74 KWCO 181159 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 700 AM CDT SAT JUL 18 2026 .Update... The Texas selection continues to be refined as the significant flooding event winds down. The Limited extent was removed and all that remains now is a Days 1-7 Considerable flooding selection to account for the moderate and major river flooding that continues to route through the basins. Fortunately, there are several days of dry weather to allow for all of these rivers to recede unimpeded. The next section that required changes was the Central Appalachian and Upper Ohio Valley where the Limited was reduced on the southern portions as current rainfall forecasts and model guidance has backed off the small stream flooding responses. As is typical with convective patterns, there still may be a threat for localized flooding impacts so this area will continue to be monitored for changes. Further north, however, there was a need to expand on some of the selection into portions of eastern Ohio. Additionally, another round of rainfall is forecast to repeat over this area which may remain primed from the rainfall today. As such, this area was converted to a Days 1-7 threat to account for potentially heavy rainfall timing. Minor adjustments were necessary for the Desert Southwest and Mid-Atlantic into the Northeast for overnight changes in the forecast as well as to update the text to account for changes in timing. //JAC .Previous Discussion as Follows... ...Considerable flash, urban, and river flooding to continue across portions of Texas through today... Isolated flash flooding possible in eastern New Mexico and southeast Utah, with flooding impacts possible for the broader region through the weekend... Limited flooding impacts possible this weekend across portions of the Mid-Atlantic and Northeast as well as the southern Appalachians into the Upper Ohio Valley... .Texas... The threat of considerable flash flooding in central Texas continues through today for parts of central/west-central Texas, although the trend of a diminishing flood threat continues and additional significant rainfall is not expected after today. Moderate to major river flooding is ongoing or forecast across the region, with most of the gage locations in Hill Country forecast to crest by this weekend, while locations along the Rio Grande, Frio, Neuces, and San Antonio rivers that are well downstream of where the rain fell are forecast to begin cresting early next week. Preliminary data shows 12 gages have gone into major flood status during this event, including 1 that exceeded its flood of record, and additional 6 more forecast to exceed major threshold. In addition, 13 locations went into moderate flood, with another 4 expected to crest in major over the coming week. The only notable change to the Flood Hazard Outlook (FHO) selections for this issuance was the trimming back of the Limited extent in far western Texas. .Desert Southwest... The threat of isolated flash and urban flooding continues today, especially in southwest Utah and parts of eastern New Mexico. The overall flood threat has diminished somewhat from yesterday, especially in Arizona. Areas that have received recent rainfall are more likely to see efficient runoff, but anywhere heavy rainfall sets up could see flooding issues. More significant flooding potential exists over the weekend and into next week, but confidence is low as to the exact timing or where they will appear. Only changes to the afternoon FHO selection were to buffer out some of the northwest corner in New Mexico slightly. .Southern Appalachians through the Upper Ohio Valley... Isolated flash and urban flooding is possible across the region in response to convective rainfall through this weekend. Antecedent conditions are marginally conducive for hydrologic responses following some drying after recent rainfall. Given the potential for training convection and locally robust rainfall rates, flash flooding may quickly occur in urban areas and along steep/hilly terrain. .Mid-Atlantic and Northeast... Heavy rainfall is expected across the region over the weekend, leading to potential flash, urban, and small stream flooding impacts. Antecedent conditions are not conducive to rapid formation of runoff processes, but nonetheless locally heavy rainfall could overwhelm the infiltration rate of soils and lead to flooding issues, especially in heavily urbanized areas. The medium range NWM versions have not started picking up on this potential yet, so corresponding signals remain sparse. .Northern Rockies... Isolated flash flooding remains possible through tonight across northern Wyoming and into Montana due to heavy rainfall. Locally intense rainfall rates will be the primary driver for flash flooding, especially along small creeks/streams draining complex terrain and areas of poor-drainage in more urban locations. Anywhere that has already seen heavy rainfall in the last several days is of course more susceptible to flooding. Flash flooding and debris flows are also possible near recently burned areas. //Bliss Additional National Water Center products are available at www.weather.gov/owp/operations $$