Tropical Storm Isaac has been slow to strengthen, however, an gradual intensification trend is underway this evening. Recon aircraft investigating the storm is finding dropping central pressure throughout the day. Lower pressure leads to higher maximum winds, but the large size of the circulation makes for a slower response of increasing winds as the pressure drops. As of 7 PM CDT Maximum winds have remain at  70 MPH, slightly short of the 74 MPH threshold for a hurricane. Isaac will likely become a hurricane later today or tonight, and it is becoming more likely that Isaac will make landfall as a category 1 hurricane or at worst category 2. The nightmarish scenario of this becoming category 3 or higher before landfall continues to become even more of a remote possibility. Although Isaac is over warm waters, it struggles with dry mid level air becoming entrained into the center. The latest forecast track shows Isaac most likely moving into Southeast Louisiana  late Tuesday night and Wednesday, then moving into Arkansas by late Thursday into Friday.

Confidence is increasing in the forecast track of Isaac, but there is still considerable spread of model solutions. Below are the early afternoon model runs showing possible landfall scenarios anywhere from Southwest Louisiana to Alabama. The forecast spread should begin to narrow more quickly now that landfall is less than 36 hours away.

The model consensus, as well as the most tightly grouped models both align well with the forecast track, so I would not expect any significant changes to the forecast track throughout the day. This leaves Southeast Louisiana as the primary target for landfall. The saving grace for Louisiana is that Isaac will likely not turn out to be a particularly powerful hurricane. The main threat from Isaac will turn out to be inland flooding. Heavy rains will continue as a relatively slow moving Isaac continues to move Northwest and North into Arkansas. Notice how many of the computer models show the center of Isaac going through or just West of Central Arkansas. This scenario would bring heavy, potentially flooding rains to parts of Arkansas by late Thursday into Friday. Inland tropical systems can also produce severe weather, mainly in the form of weak, short lived tornadoes. Several inches of rain will be possible with Isaac over parts of Arkansas later this week. Below is the HPC rainfall for forecast for Isaac over the next 5 days.

Notice the heaviest rains along and to the east of the forecast center, with a fairly tight gradient on the west side. Under this scenario, very heavy rain would fall across the Eastern half of Arkansas with widespread 3 to 6 inches likely and locally heavier amounts. Rainfall amounts would rapidly diminish heading toward the Oklahoma border. Rainfall amounts will be highly dependent upon the exact track of the center, so this forecast can easily change over the next couple of days. The most likely timing of the heaviest rain for Central Arkansas is late Thursday into Friday morning.