Thursday, August 30, 2012

Effects of Isaac on Mid-South metro heading into the holiday weekend

Many questions are being asked about the impacts that the remnants of Hurricane Isaac will have on Mid-South weather as we head into a holiday weekend with plenty of outdoor activities planned. The forecast track of Isaac's leftovers are shown below. As the storm exits Louisiana this evening, it will move north across west-central AR into southwest Missouri by Friday night. This places the entire Mid-South in the favorable region for showers and thunderstorms and the possibility of a few severe storms on Friday.

Forecast track of what's left of Isaac.  The Mid-South will be in a favorable region for showers and storms Friday.

Tonight

The northern edge of Isaac's rain shield moved into the metro this afternoon and scattered showers are expected through the evening, tapering off after dark.  (After landfall, much of the precipitation that is well-removed from the center of former tropical systems tends to wane during the evening hours and re-generate by late morning, aided by the sun's heat from above.) A few showers are still possible overnight. The main effect overnight will be continuous southeast wind at 15-30 mph.  No severe weather is anticipated overnight.

Friday

On Friday, showers will expand again across the region and by afternoon some bands of heavier tropical rains and embedded thunderstorms could form to the east of the center (over the Mid-South). Due to the wind shear present east of the center of the storm, some thunderstorms could produce tornadoes, thus there is a slight risk of severe weather posted for most of AR and western TN and MS in the most favorable region.  A note on tornadoes associated with land-fallen tropical systems: they tend to be brief, quick spin-ups, and relatively weak by tornado standards. We're not talking major EF-4/5 tornadoes, but certainly any tornado can produce localized damage. The chances of tornadoes is LOW, but is worth mentioning. We believe the threat to be higher over east AR than east of the Mississippi River.  As mentioned above, weakening of the precipitation occurs by dusk, so for Friday night, the thunderstorm threat should be very low. We'll be close enough to the center of the storm to still have a good chance of rain overnight. Wind tomorrow will be out of the south at 15-25 mph.  Friday night football and the Delta Fair will have to deal with scattered showers.

A slight risk of severe weather is in place for Friday due to the possibility of strong wind and isolated tornadoes

Saturday-Monday

For Saturday, the storm moves well to our north to alleviate any severe weather concerns, however we'll be in a moist tropical-like environment that could produce scattered showers and perhaps some thunderstorms, mainly across west TN and east AR in the afternoon hours.  A similar situation will unfold Sunday and labor Day Monday with a few less showers and thunderstorms each day.  It will remain humid and very warm throughout the Labor Day weekend - perhaps reaching into the mid 90s by Monday again.  A good chance to get in one last summer swim!  Overall, the heaviest rainfall will be found to our west, where it is desperately needed to alleviate extreme drought conditions.  However, 1-3" is possible in the metro area (see map below).

Total forecast rainfall from Isaac through the Labor Day weekend.
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