Winter forecasts often include winter storm or blizzard warnings. Lately, the National Weather Service (NWS) weather forecasts have included a different type of warning: Red Flag Warnings and Fire Weather Watches.
A Red Flag Warning is issued for critical fire danger, and signifies that those weather conditions are occurring, or will occur shortly. These critical weather conditions consist of a combination of strong winds, low relative humidity, and warm temperatures – all which make fire suppression very challenging. Thresholds for these warnings vary by your local associated NWS forecast office (see Table 1).
A Fire Weather Watch is issued in advance of critical fire danger. These Watches signify the forecasted possibility of critical fire weather occurring in the next 24-48 hours. Some offices issue these more than others. These Watches are meant to provide you advance notice so that you can take proper precautions and/or make better decisions based upon these forecasts.
Table 1. Red Flag thresholds by National Weather Service Forecast Office
|
Red Flag Warning Thresholds |
||
|
Forecast Office |
Relative Humidity |
Wind Speeds/Gusts |
|
Goodland |
15% |
Gusts 25 mph or greater |
|
Dodge City |
15% |
Gusts 25 mph or greater |
|
Hastings, NE |
20% |
Sustained winds 20mph/gusts 25 mph |
|
Wichita |
Extreme Grassland Fire Danger Index |
|
|
Topeka |
20% |
Sustained winds 20mph/gusts 25 mph |
|
Pleasant Hill, MO |
25% |
Gusts 25 mph or greater |
|
Springfield, MO |
25% |
Gusts 25 mph or greater |
Generally, these weather conditions create an atmosphere with explosive fire growth potential. Any spark has the potential to create a large fire that will resist typical suppression efforts. Use appropriate caution, such as avoiding outdoor burning, watching for hot exhaust systems over grass, and extra care with welding or anything that might create sparks.
Note that these Warnings/Watches only occur when fuels (material that burns such as grass, leaves, cedars, etc.) are able to efficiently carry fire. During the winter, our grasses are dormant and dead. This provides an ample fuel for fire to easily carry. Therefore, most often these alerts occur between the months of October – May (Figure 1), until the spring rains arrive to drive grass growth again. This doesn’t mean that the fire weather potential isn’t there the remaining months. During periods of drought, grasses can become dormant and carry fire. These particular situations are more difficult to forecast in advance. Reports of fire carrying exceptionally well and being difficult to suppress are critical to the forecast process. If you feel these conditions are occurring, don’t hesitate to contact your local office and spread that information.
Figure 1. Red flag warnings (bright pink) on February 5, 2020. Source: National Weather Service
Mary Knapp, Weather Data Library
Mknapp@ksu.edu
Christopher Redmond, Kansas Mesonet
Christopherredmond@ksu.edu
Jason Hartman, State Forester - Kansas Forest Service
hartmanj@ksu.edu
Tags: fire red flag warnings