1. There is the danger of life-threatening storm surge inundation along portions of the immediate coastline and adjacent waterways of northeastern South Carolina and the North Carolina coast, including portions of Pamlico and Albemarle Sounds. Residents in these areas should follow advice given by local emergency officials.

2. Isaias is expected to be at or near hurricane strength when it reaches the coast of northeastern South Carolina and southern North Carolina in a few hours, and hurricane conditions are expected in the Hurricane Warning area this evening.

3. Isaias is expected to bring widespread sustained tropical storm force winds and wind gusts to hurricane force to the mid-Atlantic coast, including portions of the Chesapeake Bay region, on Tuesday, which could cause tree damage and power outages. Tropical storm conditions are expected to spread across New England late Tuesday into early Wednesday.

4. Heavy rainfall along the East Coast near the path of Isaias will result in flash and urban flooding, some of which may be significant in the eastern Carolinas, mid-Atlantic and northeast through Wednesday. Widespread minor to moderate river flooding is possible across portions of the Carolinas and the Mid-Atlantic. Quick- responding rivers in the northeast will also be susceptible to minor river flooding.

CHANGES WITH THIS ADVISORY:

The Tropical Storm Warning has been extended northward to Stonington Maine.

The Tropical Storm Warning south of Savannah River has been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...
- Edisto Beach South Carolina to Cape Fear North Carolina
- Pamlico and Albemarle Sounds, including the Neuse and Pamlico Rivers
- Oregon Inlet North Carolina to the North Carolina/Virginia border

A Storm Surge Watch is in effect for...
- Cape Fear to Oregon Inlet North Carolina

A Hurricane Warning is in effect for...
- South Santee River South Carolina to Surf City North Carolina

A Tropical Storm Warning is in effect for...
- Savannah River to South Santee River South Carolina
- North of Surf City North Carolina to Stonington Maine
- Pamlico and Albemarle Sounds
- Chesapeake Bay
- Tidal Potomac River
- Delaware Bay
- Long Island and Long Island Sound
- Martha's Vineyard, Nantucket, and Block Island

A Tropical Storm Watch is in effect for...
- North of Stonington to Eastport Maine

A Storm Surge Warning means there is a danger of lifethreatening inundation, from rising water moving inland from the coastline, in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic at hurricanes.gov. This is a lifethreatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch means there is a possibility of life threatening inundation, from rising water moving inland from the coastline.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, generally within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

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.

Key messages for Isaias can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml.

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide...

South Santee River SC to Cape Fear NC...35 ft

Edisto Beach SC to South Santee River SC...24 ft

Cape Fear NC to the North Carolina/Virginia border including Pamlico Sound, Albemarle Sound, Neuse and Pamlico Rivers...24 ft

Savannah River to Edisto Beach SC...13 ft

North of the North Carolina/Virginia border to Martha's Vineyard including the Chesapeake Bay, the Tidal Potomac River, Delaware Bay, Long Island Sound, Block Island Sound, Narragansett Bay, Buzzards Bay, and Vineyard Sound...13 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large waves. Surgerelated flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

WIND: Hurricane conditions are expected within the hurricane warning area in South and North Carolina this evening and tonight, with tropical storm conditions spreading onshore in the next few hours.

Widespread tropicalstormconditions are expected in the tropical storm warning area from coastal North Carolina to the midAtlantic states, including portions of the Chesapeake Bay region, tonight and Tuesday, with wind gusts to hurricane force possible. These winds could cause tree damage and power outages.

Tropical storm conditions are expected to reach southern New England Tuesday afternoon and northern New England Tuesday night and early Wednesday.

RAINFALL: The following rainfall accumulations are expected along and near the track of Isaias:

Carolinas and the MidAtlantic: 3 to 6 inches, isolated maximum totals 8 inches.

Eastern New York and western New England from Connecticut to New Hampshire: 2 to 4 inches, isolated maximum totals 6 inches.

Western and northern Maine: 1 to 3 inches.

Heavy rainfall along the East Coast, near the path of Isaias, will result in flash and urban flooding, some of which may be significant in the eastern Carolinas, MidAtlantic and Northeast through Wednesday. Widespread minor to moderate river flooding is possible across portions of the Carolinas and the MidAtlantic. Quickresponding rivers in Northeast will also be susceptible to minor river flooding. TORNADOES: A few tornadoes will be possible near northeastern South Carolina coastal areas by early this evening, before spreading across eastern North Carolina tonight into Tuesday morning. A couple of tornadoes will be possible on Tuesday from eastern Virginia northeastward into southern New England. SURF: Swells generated by Isaias are affecting portions of the Bahamas and the southeast coast of the United States and will spread northward along the U.S. east coast during the next couple of days. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 500 PM EDT (2100 UTC), the center of Tropical Storm Isaias was located by NOAA Doppler weather radars near latitude 32.0 North, longitude 79.4 West. Isaias is moving toward the northnortheast near 16 mph (26 km/h), and this general motion accompanied by a gradual increase in forward speed is expected through tonight followed by a further increase in the forward speed on Tuesday. On the forecast track, the center of Isaias will approach the coasts of northeastern South Carolina and southern North Carolina within the hurricane warning area this evening. The center will then move inland across eastern North Carolina early Tuesday morning, move along the coast of the midAtlantic states on Tuesday, and continue across the northeastern United States Tuesday night.

Data from NOAA Doppler weather radars indicate that maximum sustained winds are near 70 mph (110 km/h) with higher gusts. Some strengthening is forecast later this afternoon or early evening, and Isaias is expected to make landfall tonight at or near hurricane strength along the coast of northeastern South Carolina or southern North Carolina. Only gradual weakening is anticipated after Isaias makes landfall in the Carolinas and moves across the U.S. midAtlantic region tonight and Tuesday.

Tropicalstormforce winds extend outward up to 125 miles (205 km) from the center. During the past couple of hours, a sustained wind of 45 mph (72 km/h) and a gust to 52 mph (83 km/h) were measured by a Weatherflow site at Folly Beach Pier, South Carolina. The estimated minimum central pressure is 993 mb (29.33 inches).

Isaias is undergoing its daily reorganization phase, with a ragged eye-like feature now showing up in NOAA Doppler weather radars from Charleston, Wilmington, and Jacksonville. The last Air Force Reserve reconnaissance flight reported a peak SFMR-derived surface wind speed of 62 kt in the southwest quadrant around 1630Z while Isaias was experiencing a center reformation further to the east. Since then, Doppler velocities of 70-75 kt have been observed between 10,000-15,000 ft in the northern semicircle, but within reflectivity regions less than 35 dBZ, which suggests that a the reduction factor is likely less than the 90-percent value typically used. Thus the intensity is being held at 60 kt, which means that Isaias is very near hurricane status. Another Air Force Reserve reconnaissance will be investigating the cyclone around 0000Z this evening.Isaias is now moving north-northeastward 015/14 kt. The new NHC model guidance remains in excellent agreement on Isaias continuing to gradually accelerate north-northeastward to northeastward for the next 36 hours ahead of a powerful deep-layer trough and associated cold front. The cyclone should make landfall later this evening near the South Carolina-North Carolina border, and then accelerate north-northeastward at 25-30 kt across eastern North Carolina early Tuesday, eastern Virginia and the Delmarva peninsula Tuesday afternoon, and into New England Tuesday night into early Wednesday. The new NHC track forecast is just an update and extension of the previous advisory track, and lies very close to a blend of the tightly packed multi-model consensus aids TVCA, GFEX, TVCX, and NOAA-HCCA.

Satellite animation and special 1800Z upper-air soundings indicate that the vertical shear across Isaias has weakened and has also become more southwesterly, which better aligns with the forecast track. Given this and the improved structure of the system, Isaias is still expected to strengthen and regain hurricane status before making landfall, and most of the intensity guidance shows a 60-65 kt system at that time. It should be emphasized that there is little difference between a strong tropical storm or a category 1 hurricane in terms of impacts.After landfall, Isaias is forecast to only slowly weaken due to interaction with an unusually strong 100-120 kt jetstream. The expected strong baroclinic forcing will keep Isaias' circulation intact and also produce very strong wind gusts along the mid-Atlantic coast tomorrow. As a result, the gust factors at 24-48 h have been increased above the standard 20 percent in the Forecast/Advisory (TCMAT4). The cyclone is forecast to be absorbed by a larger extratropical low over Canada in 3-4 days.