Heat Advisory question...

[Shoshana]

I've noticed this before ... right now there are heat advisories out for three counties in N Texas...

THE NATIONAL WEATHER SERVICE IN FORT WORTH TX HAS EXTENDED THE HEAT ADVISORY FOR DALLAS...TARRANT...AND MCLENNAN COUNTIES THROUGH 600 PM CDT SATURDAY. RESIDENTS OF FORT WORTH...DALLAS...AND WACO CAN EXPECT AFTERNOON INDEX VALUES BETWEEN 105 AND 107 DEGREES...WITH LOWS TONIGHT BETWEEN 78 AND 81 DEGREES ACROSS THESE URBAN AREAS AND THEIR IMMEDIATE SUBURBS.

A HEAT ADVISORY IS ISSUED WHEN HIGH HUMIDITIES ARE EXPECTED TO COMBINE WITH HOT TEMPERATURES TO MAKE IT FEEL LIKE IT IS 105 DEGREES OR GREATER. PERSONS IN THE ADVISORY AREA ARE ADVISED TO AVOID PROLONGED WORK IN SUN...OR IN POORLY VENTILATED AREAS. ALSO...KEEP PLENTY OF LIQUIDS ON HAND AND TRY TO STAY IN OR FIND AN AIR CONDITIONED ENVIRONMENT WHEN POSSIBLE

I added the emphasis ... because I just checked the Austin area forecast ...

This Afternoon: Partly cloudy and hot, with a high around 101. Heat index values as high as 109. South southeast wind around 5 mph.

Saturday: Mostly sunny and hot, with a high near 101. Heat index values as high as 110. Calm wind becoming northeast between 5 and 10 mph.

So why isn't the NWS Austin/San Antonio, TX issuing heat advisories?

Is it up to the local NWS office to decide? (ie NWS Dallas/Fort Worth, TX thinks there should be an advisory, NWS Austin/San Antonio, TX doesn't?)

Y'all have any ideas?

'shana

[WindRunner]

Apparently, the criteria for heat advisories/excessive heat warnings very from county to county. I know that down here around DC they never issue excessive heat warnings, however metro Phili gets them about five times a summer. Upon further examination, the criteria of "excessive heat warning" in the three/four counties that comprise downtown Phili have a warning value that would equate to an advisory for the rest of the area and all of the Sterling area. And since I believe that D-FW is considerably larger than San Antonio/Austin, then a similar situation could be the issue, just one level lower.

[wall_cloud]

Its not that it varies from county to county, but each NWS office has different criteria for the heat advisory criteria. Most of that will depend on climo obviously. 105 degree heat index along the gulf coast is quite common in the summer and is no big deal to residents whereas a 105 HI on the west coast IS a big deal.