Unpleasantly hot weather is the story for the next few days as a broad high pressure system sits south of the city. Today is shaping up to be the hottest, most humid day of the week with a high in the upper 90s and dew points in the lower 70s. Both the temperature and humidity are expected to drop slightly tomorrow, but a high in the mid 90s is still pretty stinking hot. A heat advisory is in effect for the city and surrounding suburbs through midnight tomorrow and cooling centers are open across the city.
Hot weather is usually associated with unstable air. The sun beats down, warms up the ground and the hot air starts rising and forming clouds. That's not the case this week as the surface high pressure system is overlain with an upper level ridge. That's a whole lot of stable, sinking air, and sinking air warms by compression, which only adds to the heat. On Wednesday, however, there's a slight chance of a sea breeze, which should keep the heat/humidity combination just below the advisory level. We're still looking at a hot day with a high in the mid 90s. The heat and humidity are expected to return later in the week, with highs in the mid to upper 90s on Thursday and Friday.
Saturday's high is expected to reach the lower 90s before clouds and showers from an approaching cold front turn down the thermostat. If the temperature does reach 90 on Saturday it will make this the fourth straight year that July has had at least ten days of 90-degree weather. That's only happened twice before, from 1952-1955 and 1980-1983.