Baltimore Sun

More of the same, plus thunder

More heat, more humidity, more polluted air ... But wait! There's even more!

Forecasters out at Sterling say the rising moisture levels in the atmosphere, coupled with a passing low-pressure trough and solar heating should kick off a few scattered thunderstorms by late Tuesday afternoon and evening. The chance of precipitation is put at 30 percent today, rising to 40 percent this evening.


A nice shower might green up the lawns and gardens a bit for those spots lucky enough to be under them. And they would provide at least some temporary relief from the 90-plus temperatures we're expecting this afternoon and pretty much every afternoon right through the weekend.

"The risk of severe weather will be area-wide ...beginning mid to late afternoon across the Potomac highlands, then working eastward toward the urban corridor by evening," forecasters said in this morning's forecast discussion. "Damaging winds [will be] the biggest threat as relatively warm temperatures aloft will limit hail formation... "


The forecast high for BWI-Marshall Airport Tuesday is still 91 degrees. That's what it was yesterday, too, but it managed to reach 94. The forecast for Wednesday and Thursday calls for highs of 95 and 96 degrees, respectively, the highest of the week and up a couple of degrees from yesterday's outlook. Humidity levels will be higher, too, as the offshore Bermuda High pumps more Gulf and Atlantic moisture northward into our region.

These temperatures are all 5 to 10 degrees above the averages for this time of year.

Washington's Reagan National Airport set a new record high minimum temperature this morning. The overnight low was 76 degrees, breaking the old record high minimum for a June 22 of 75 degrees, set in 1893 and matched in 1931.

Central Maryland remains under a Code Orange Air Pollution Alert on Tuesday. Heat, sunshine and vehicle exhaust are combining to create a nasty ozone soup around us. That is deemed unhealthy for sensitive groups. Health authorities urge those with heart or respiratory problems, the very young and the elderly to avoid strenuous outdoor activities.

The forecast calls for only moderate air pollution in the region on Wednesday.

(SUN PHOTO: Jed Kirschbaum, 2009)

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