National Weather Service United States Department of Commerce

Abundant moisture will result in increasing cloud cover and a chance for scattered showers and thunderstorms across Central Texas. Highs will be in the upper 80s to low 90s and winds will be out of the south around 10 to 15 mph.
Showers and thunderstorms will be on the increase Friday and will continue over the weekend. The primary concern will be heavy rain and the possibility of flooding. At this time it looks like areas along and north of I-20 will have the highest potential to receive heavy rain and possible flooding. Also, a few strong to severe storms will be possible, mainly south of the I-20 corridor.
Astronomical Fall starts this Saturday September 22nd. On this day, both hemispheres receive the same amount of radiation. Day and night are nearly equal in length (approximately 12 hours). Days will slowly become shorter and nights will be longer.

 
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What is the WFO FWD Fire Weather Threat Index?

 

The National Weather Service (identifier FWD) in Fort Worth has developed an index to assess the fire weather threat across north Texas. The FWD Fire Weather Threat Index that you see on the WFO Fort Worth fire weather pages is a locally-developed scaled value derived from relative humidity, wind speed, and fuel factor.

The values of the index range from 1 (minimal threat) to 100 (highest threat). Theoretically, values should be near  1 when winds are light, relative humidities are over 90%, and fine fuels (typically grasses) are either green or moist from recent rains. 

On the other extreme, values should be near 100 (highest threat) during dry periods in the fall and winter when sustained winds are at least 20 mph and relative humidity values are less than 35%. Recent rainfall and/or substantial green vegetation could make the FWD Fire Threat Index much lower, even with low humidities and strong winds.

Fire Weather Threat Values of FWD Fire Weather Threat Index

LOW
 0-20

MODERATE
 21-40

HIGH 
41-60

VERY HIGH
 61-80

EXTREME
 81-100

Graphic showing Fire Index as a function of wind speed and humidity.