1. Widespread sustained tropical storm force winds and gusts to hurricane force are expected along the mid-Atlantic coast, including portions of the Chesapeake Bay region, through this afternoon, which could cause tree damage and power outages. Tropical storm conditions are expected to spread across New England tonight.

2. Heavy rainfall along the East Coast, near the path of Isaias, will result in flash flooding, some of which may be significant in the mid-Atlantic and Northeast through tonight. Potentially life-threatening urban flooding remains possible in Philadelphia and elsewhere along and just west of the I-95 corridor today. Scattered minor to moderate river flooding is likely across portions of the and the Mid-Atlantic. Quick-responding rivers in Northeast will also be susceptible to minor river flooding.

3. Numerous tornadoes have already occurred over portions of the mid-Atlantic coast this morning. The threat of tornadoes will continue along the mid-Atlantic coast spread into New England this afternoon.

CHANGES WITH THIS ADVISORY:

The Tropical Storm Warning has been discontinued south of Chincoteague, Virginia, and south of Smith Point in the Chesapeake Bay.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- North of Chincoteague Virginia to Eastport Maine
- Chesapeake Bay north of Smith Point
- Tidal Potomac River
- Delaware Bay
- Long Island and Long Island Sound
- Martha's Vineyard, Nantucket, and Block Island

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within the next 12 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.

WIND: Widespread tropicalstorm conditions are expected in the tropical storm warning area in the midAtlantic states and southern New England, including portions of the Chesapeake Bay region today, with wind gusts to hurricane force possible. These winds could cause significant tree damage and power outages.

Tropical storm conditions are expected to reach southern New England this afternoon and northern New England tonight.

Galeforce winds are expected to spread into southeastern Quebec tonight and Wednesday. See products issued by Environment Canada for more information.

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

Central and Northern MidAtlantic: Additional 2 to 4 inches, isolated maximum storm totals of 8 inches.

Eastern New York into Vermont: 2 to 4 inches, isolated maximum totals 6 inches.

Western Connecticut, western Massachusetts, New Hampshire and western 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 midAtlantic and Northeast through tonight. Potentially lifethreatening urban flooding remains possible Philadelphia, and elsewhere along and just west of the I95 corridor today. Scattered minor to moderate river flooding is likely across portions of the MidAtlantic. Quickresponding rivers in the Northeast will also be susceptible to minor river flooding.

TORNADOES: A few tornadoes are possible across northern New Jersey and southeastern New York, through southern New England, by late afternoon. A risk for tornadoes may continue across northern New England through this evening.

SURF: Swells generated by Isaias will spread northward along the midAtlantic and Northeast coasts of the United States today. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 200 PM EDT (1800 UTC), the center of Tropical Storm Isaias was located by NOAA Doppler weather radars and surface observations near latitude 40.9 North, longitude 75.1 West. Isaias is moving toward the northnortheast near 40 mph (65 km/h), and this general motion accompanied by some increase in forward speed is expected through tonight. On the forecast track, the center of Isaias will continue to move near or along the coast of the midAtlantic states today, and move across the northeastern United States into southern Canada tonight.

Data from Doppler weather radars along with surface observations indicate that maximum sustained winds have decreased to near 65 mph (100 km/h) with higher gusts. Only slow weakening is expected this afternoon, followed by a faster rate of weakening tonight. Isaias is forecast to become posttropical tonight or early Wednesday.

Tropicalstormforce winds extend outward up to 140 miles (220 km) from the center. The New York Harbor Entrance buoy (44065) recently reported a sustained wind of 56 mph (91 km/h) and a gust to 72 mph (117 km/h).

The estimated minimum central pressure based on surface observations is 994 mb (29.35 inches).

Doppler radar data from Dover, Delaware (KDOX), and Ft. Dix, New Jersey (KDIX) this morning continue to indicate 70-80 kt winds between 4000-7000 ft over the ocean just offshore the Delmarva peninsula and the southeastern coast of New Jersey, which would normally correspond to 65-70 kt surface winds. However, these velocity values have been collocated with only 15-25 dBZ reflectivity echoes, so the typical 80-85 percent reduction factors likely don't apply. Sustained observed surface winds of 50-55 kt have been reported, so the initial intensity will be held at 60 kt, but that is only for winds over the ocean and near the coast.Isaias is moving north-northeastward or 020/30 kt. The cyclone will continue to accelerate north-northeastward today and tonight within strong southwesterly flow ahead of a deep-layer trough and associated cold front approaching the mid-Atlantic and New England areas from the west. By 24 h, the Isaias is expected to slow down and degenerate into a post-tropical cyclone over Maine before it is absorbed by a larger extratropical low located over southeastern Canada. The new NHC track forecast is just an extension of the previous advisory, and lies very close to the tightly clustered consensus track models.

As Isaias moves north-northeastward through the Mid-Atlantic coast,interaction with a strong upper-level jet maximum is forecast tomaintain the tropical storm's intensity longer than what typically would be expected for inland decaying tropical cyclone. The global models continue to indicate that Isaias is likely to produce widespread tropical-storm conditions, with hurricane-force wind gusts possible along the mid-Atlantic coast through this afternoon. As a result, the gust factor at 12 h remains above the standard 20-percent value in the Forecast/Advisory Product (TCMAT4).

In addition to the wind threat, Isaias is expected to produce heavy rainfall along and just west of the I-95 corridor today, and the Weather Prediction Center has placed a portion of this area in a high risk for life-threatening flash flooding.There also remains a significant risk of tornadoes across the mid-Atlantic coast and southeastern New York this afternoon, possibly spreading into southern New England tonight.