Monday 8/27 Update

Good Monday!  A weak cold front/trough is crossing the region this afternoon, sparking numerous showers and thunderstorms. 

 
Highest concentration of showers and storms will be along and southeast of the Ohio River through early evening, when this activity should begin to taper off.  By tomorrow morning, with a cold front off to our east, we'll notice a modest drop in humidity levels, but temperatures will still be running in the lower 90's tomorrow and Wednesday.

The forecast for the end of the week and weekend is highly dependent upon what Isaac ends up doing.  There is still quite a bit of uncertainty in the forecast models, so at this point in time we still can't commit to fully biting on the rain chances being dangled in front of us.  Here's what some of the models are showing us:

Above is the 12Z run of the European model showing conditions at 7AM Saturday.  Notice the black ring labeled "1012" over SEMO and NE AR....that is the center of the remnant low leftover from Isaac, with the shades of green and yellow showing precipitation in our area Friday & Saturday.

Meanwhile, above is the 12Z run of the GFS model, showing conditions at 1AM Saturday.  Same story here, with the remnant low centered very close to St. Louis, and a pretty good swath of rain over our region.  This certainly looks promising....but take this with a grain of salt.  Other runs of the GFS are indicating the leftovers of Isaac could stay farther west:

Something else we have to consider with Isaac is a strong upper level ridge that will be in place over the middle of the nation:

There is a chance that if that ridge holds strong enough, it could keep Isaac over the southern states for a longer period of time, and could prevent it from making progress northward and into our area.  Again, nothing certain with that...we'll have to see how models handle this over the next couple of days.  I think we'll have a better handle on things tomorrow as Isaac gets closer to landfall. Bottom line...while we're growing more optimistic about getting some rain from Isaac, we are keeping rain chances at 40% for Friday & Saturday.  This is a very challenging forecast, and we'll be working hard to keep it updated over the next few days.  The latest HPC forecast seems to be buying in:

As I type, the 5PM EDT advisory from the National Hurricane Center just came out, and Isaac has still not strengthened to a hurricane.  The storm continues to struggle with some drier air being wrapped into the southeast segment of the storm, limiting its ability to undergo more rapid intensification.  Such has been the story with this storm for a few days now.  Here is the latest forecast track from NHC:

No changes to the track today, as it still looks like landfall will occur very close to New Orleans or the Biloxi/Gulfport area.  The forward speed of Isaac is slowing down, which would put landfall sometime during the wee hours of Wednesday morning.  This slowing trend also means a longer period of torrential rain, wind, and storm surge for the areas affected.

Isaac is a very large storm, with tropical storm force winds extending out 205 miles from the center.  Storm surge estimates continue to run 6-12 feet for southeast LA & MS, and 6-9 feet for AL.  Rainfall totals of 6-12 inches are possible, with localized totals as high as 15-20 inches.  A hurricane warning continues for areas near Morgan City, LA, eastward to the AL/FL border.  Areas such as Pensacola and Destin were dropped from the hurricane warning, but are still under a tropical storm warning.