As we suspected yesterday, the NWS re-issued the regional HEAT ADVISORY for today and has already extended the advisory through Wednesday evening. Those working outdoors need to take special precautions as hourly Heat Index (‘feels like’ temperatures) values climb above 105° in the shade again on Wednesday (and possibly Thursday).
Our forecast stays mainly dry through Wednesday, with only a slight chance of rain for Thursday and Friday. Temperatures through much of the night will remain at or above 80° again, with lows only easing into the upper 70°s briefly for metro Baton Rouge before the morning warm-up begins. And the highs on Wednesday will once again return to the mid 90°s for many neighborhoods. We’ll keep it just about as hot-and-humid for Thursday as well, so don’t be surprised to see the HEAT ADVISORY extended yet another day. The one difference for Thursday is that we may see a couple of showers by the afternoon, but don’t bank on it.
The upper-level ridge we’ve been watching since the weekend remained locked over the Southern Plains today and we expect only a very minor contraction of that ridge and limited westward shift by late Wednesday into Thursday. A look at national radar today shows rains riding around the northern and eastern edge of that ridge, but those cooling showers and storms are a good 150-200 miles east and northeast of metro BR. No chance we’ll see those any time soon.
So the upper ridge is putting the clamps on vertical development of clouds, while surface high pressure over the Gulf keeps a steady SW flow of low-level moisture inbound over the viewing area. The result: humid conditions persist but the clouds are getting “pancaked” from above, limiting the extent of cloud cover and allowing the sun to shine throughout much of the day. In fact, Tuesday might have been even a little hotter had it not been for the haze resulting from the very moist Gulf air mass.
Expect very similar conditions on Wednesday and possible Thursday as well. Even Friday looks mainly-dry for the viewing area.
By the weekend, however, we think that the core of the upper-level ridge will have eased a little farther to the west and will have weakened enough to allow a return of scattered afternoon showers and a few t-storms. The scattered rains and additional cloud cover should keep weekend afternoon highs in the low 90°s: we’re thinking a 30% to 40% rain chance for Saturday with a return of scattered t-showers on Sunday.
And in the tropics? We can’t really say that the tropics are “coming alive,” but there are two tropical waves worth mentioning. The first is located (this afternoon) over the northern Caribbean and along the islands of Hispaniola and Puerto Rico. But satellite trends show that this Caribbean wave is being impacted by fairly persistent shear -- development any time soon seems unlikely.
The second wave looks more interesting, and the NHC is giving it a 30% chance of developing into something tropical in the next two days. Located over the central tropical Atlantic, midway between the Lesser Antilles and Africa, this easterly wave is too far out to sea to be of any immediate concern, but early forecast guidance suggests that the disturbance should reach the Lesser Antilles in the next three to four days. Additionally, the guidance indicates slow-but-steady development as it tracks to the west and WNW at about 15 mph. It’s almost August -- and it fits the August climatology.
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