Tuesday, June 23, 2009

Excessive Heat Warning until 7pm Tuesday

The National Weather Service has upgraded the Heat Advisory to an Excessive Heat Warning for the metro area. Temps at noon are already in the mid 90s with heat index values near 110. Highs will top out near 100 this afternoon, though heat index values have likely peaked and will remain steady. The dewpoint (amount of moisture in the air) is very high ahead of a "cool front" moving into the region tonight (from the east - which is called a "back door" cold front). The temperature and dewpoint combine to produce the heat index. I expect dewpoints to slowly drop this afternoon, so as temps rise a few more degrees, the heat index should remain steady in the 108-113 F range. Mid-Southerners should take all precautions necessary today if they must be outdoors, or if at all possible to remain out of the heat entirely. Click here for heat safety information from the National Weather Service.

As the front passes through, dewpoints will be somewhat lower tomorrow and for a few days. So, though temps will not necessarily drop any behind the front, lower humidity values will mean lower heat indices and possibly the end of Heat Advisories after today.

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