Air Quality Concerns; Fire Weather in the West; Flash Flooding in the Southeast

Wildfire smoke continues to result in poor air quality from the Upper Midwest into the Northeast. Multiple days of hot, dry and windy conditions are expected to bring fire weather concerns for portions of the Four Corners region into the central Great Basin and Rockies. Heavy rainfall and a flash flooding threat continues in the Southeast. Severe thunderstorms continue across the Northern Plains Read More >

Rises on Major Rivers (if applicable)

Biggest takeaway:
This type of flooding of major rivers is typically only a threat for those along major fresh water rivers such as the Potomac, Shenandoah, and Rappahannock – and their tributaries. The threat is categorized as minor, moderate, major, & record to help define the level of risk.

Warning/Trigger for Plan:
NWS Flood Warning for Rivers

Advance Notice/Time to Activate & Accomplish Your Planned Response:
20-60 minutes to as much as 4 days. The further downstream you are, the longer the advance notice.

Frequency:
~0-2/year for minor flooding of the lowest lying properties along the river.
Major flooding of a river is a rare event, but for those along large rivers one that needs to be planned for, given its catastrophic potential.

How Accurate Warnings?
NWS river flood warnings are very accurate, although a certain amount of leeway has to be given for the uncertainty of the exact height of the crest of a flooding river. The crest forecast accuracy is greatest once the bulk of the rain has already fallen, while the water is collecting in the headwaters. Note that rapid snowmelt upstream can also cause river flooding (Jan ‘96).

Determine if you are in an affected area
- The white shaded areas on this map define areas for which Flood Warnings for rivers are issued:
If your location is along the rivers in these highlighted areas:
- Use this webpage to find the nearest point to monitor your river height.
- Receive River Flood Warnings from the NWS.
- Know what river levels (height in feet read by the gauge) it would take to threaten your location to various degrees of severity.
- Have a plan for actions you will take if these various levels are expected/reached.
- Use USGS Water Alert service (or similar) to set up an alert for when critical levels are forecast or reached for your location.
- Know the various calibers of river flooding that will be included in the warning:
  - Minor: Nuisance flooding (non-structural, no significant roads)
  - Moderate: Starts to inundate the lowest homes/businesses and roads along the river.
  - Major: Significant flooding of riverside structures, roads, life & property
  - Record: Higher than ever recorded.
Safety References:
- Flood...The Awesome Power