Hurricane Isaias remnants could drop 1 to 2 inches of rain on Montgomery County starting Sunday. Whitemarsh, Plymouth and Whitpain townships face a risk of flash flooding as the weakened storm passes through.
The National Weather Service's Mount Holly office issued a zone forecast Thursday, Oct. 8, putting the chance of rain at 60 percent for Sunday afternoon across eastern Montgomery County and 90 percent Sunday night. Temperatures Sunday night will hold in the lower 60s, with showers continuing into Columbus Day at a 50 percent chance.
Isaias strengthened into a hurricane late Wednesday, Oct. 7, with maximum sustained winds of 80 mph, according to the National Hurricane Center's Thursday morning advisory. The storm is expected to make landfall along the northern Gulf Coast late Friday or early Saturday as a strong Category 2 storm. AccuWeather said there is a chance it could peak as a Category 3 major hurricane before striking land.
It is the season's first Atlantic hurricane. The Oct. 8 formation tied a record set in 1905 for the latest first hurricane in over a century, CBS News reported. A strong El Niño has kept the Atlantic unusually quiet this year, according to an Associated Press report carried by WFMZ.
National Hurricane Center Director Michael Brennan said in a Wednesday video briefing, "We're expecting multiple dangerous, life-threatening impacts along portions of the northern Gulf Coast beginning Friday and continuing into the weekend."
After landfall, AccuWeather forecasts the storm to track northeastward across the Southeast, then turn eastward over the Appalachians and off the mid-Atlantic coast by early next week. By the time remnants reach the Philadelphia region, the system will have weakened into a tropical rainstorm.
AccuWeather said the heaviest local impact will come from rainfall that can lead to flooding, particularly where the ground remains saturated from rain earlier in the week. CBS Philadelphia meteorologist Kate Bilo forecast that remnants could bring 1 to 2 inches of rain, localized ponding and flash flooding along with scattered thunderstorms from Sunday into Monday.
The National Weather Service noted that precipitable water values from the remnants could approach 2 inches, meaning bursts of heavy rain are possible even if total accumulation stays moderate. Forecast models still differ on the storm's exact timing after landfall, and the agency said more certainty will come in the days ahead.
Through Saturday, the forecast for the townships is dry and sunny with highs near 70 degrees. Clouds will build Saturday night ahead of Sunday's rain.
No flood watch or warning had been issued for Montgomery County as of Thursday morning. Residents should monitor the National Weather Service's Mount Holly office for updates as the storm approaches Sunday and avoid driving through flooded roadways.
