1. Gusty winds, heavy rainfall, and lingering coastal flooding areexpected from Marco along portions of the Gulf Coast through thisevening. For information on these hazards see products from yourlocal National Weather Service office.

2. Tropical Storm Laura could bring dangerous storm surge, rainfall, and wind impacts to portions of the U.S. Gulf Coast by the middle of the week, and tropical cyclone wind and surge watches have been issued for portions of the U.S. Gulf Coast.

CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

There are no coastal watches or warnings in effect.

Gusty winds, heavy rainfall, and lingering coastal flooding are expected from Marco along portions of the Gulf Coast through this evening. For information on these hazards see products from your local National Weather Service office.

Tropical cyclone wind and surge watches have been issued for portions of the U.S. Gulf Coast for Tropical Storm Laura.

For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

WIND: Wind gusts to tropical storm force are possible over the coastal sections of southeastern Louisiana and Mississippi through this evening.

RAINFALL: Marco is expected to produce additional rainfall accumulations of 2 to 4 inches with additional isolated totals of 7 inches across portions of the northcentral Gulf coast and southeastern United States through Wednesday. Rain totals related to Marco near Apalachicola, Florida reached as high as 11.81 inches on Sunday per a CoCoRaHS report. The additional rainfall may result in areas of flash, urban and small stream flooding along the same area.

SURF: Swells generated by Marco are likely to affect portions of the northern Gulf Coast for the next day or so. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

TORNADOES: A couple of tornadoes are possible late this afternoon through tonight across the Florida Panhandle, southern Georgia, far southern Alabama, and far southern Mississippi.

At 400 PM CDT (2100 UTC), the center of Tropical Storm Marco was located near latitude 29.0 North, longitude 88.9 West. Marco is moving toward the northwest near 7 mph (11 km/h), a turn to the westnorthwest and a slight increase in forward speed is expected to occur tonight. On the forecast track, Marco will move inland over southeastern Louisiana tonight, and across southern Louisiana on Tuesday.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Weakening is expected, and Marco is forecast to become a tropical depression tonight and degenerate to a remnant low on Tuesday.

Tropicalstormforce winds extend outward up to 80 miles (130 km) from the center. A National Ocean Service weather station located on Petit Bois Island, Mississippi recently reported a wind gust to 38 mph (61 km/h).

The estimated minimum central pressure is 1008 mb (29.77 inches).

There has been little change to the structure of Marco over the pastfew hours, with the deep convection and associated heavy rainfallbeing sheared well to the northeast of the exposed center ofcirculation. Based on earlier Hurricane Hunter aircraft andscatterometer data, there was a small area of tropical-storm-force winds in the strongest convection located about 50-75 nmi offshore of the northern Gulf coast. Since the shower and thunderstorm activity is persisting, it is assumed that these windsare still occurring in that offshore area and the initial intensityis being held at 35 kt.

The exposed vortex should continue to spin down as the center of the cyclone reaches the southeastern Louisiana coast late this evening, which would result in the coastal areas being spared from experiencing sustained tropical-storm-force winds. The official NHC forecast shows Marco weakening to a tropical depression tonight, which is in agreement with the model guidance. Strong vertical wind shear should strip away any remaining convection associated with Marco at some point tonight, as indicated by GFS and ECMWF simulated satellite imagery. When the convection does diminish, most of the model guidance does not show any significant new convection developing thereafter. So it is anticipated that Marco will degenerate to a remnant low by Tuesday.

Marco's initial motion is northwest at 6 kt. As the cyclone continues to weaken and degenerate to a remnant low, a turn to the west-northwest is expected as the system becomes steered in the low-level flow. The latest NHC track forecast is little changed from the previous one, and is near the TVCN consensus track guidance.