Hudson Valley Hazardous Outlook: Drenching Rain Could Cause Flooding

HUDSON VALLEY, NY — Given the amount of precipitation the region has received in the past 30 days, forecasters are concerned that the heavy rainfall predicted in waves Monday could lead to flash flooding.

Widespread 1 to 2 inches with localized higher amounts up to around 3 inches are possible.

"I briefly observed rainfall rates at 2" per hour," Bruce Furbeck of First Due Weather posted at 6:50 a.m. on Facebook. "Our area, Orange County, continues to be concerned with the heaviest potential rainfall moving over the same areas, repeatedly."

In addition to the overnight rain, scattered thunderstorms and showers are expected in the morning and strong to severe thunderstorms will be possible late Monday afternoon into tonight with gusty winds and even an isolated tornado.

"The atmosphere was stable this morning, but as the sun peaks out and things heat up, it becomes unstable, creating conditions for severe showers and thunderstorms, damaging thunderstorm wind gusts, hail, and locally heavy rain," said Todd Snow on the Hudson Valley Weather Facebook page.

For Orange, Putnam, Rockland and Westchester counties, multiple rounds of showers and thunderstorms through early Tuesday may result in isolated to scattered flash flooding if heaviest rainfall moves across the same area, the National Weather Service said in a hazardous outlook issued at 5:43 a.m. Damaging winds will be the main threat. In addition, a brief tornado will be possible.

For Dutchess and Ulster, the storm system will bring rounds of showers and thunderstorms, according to the NWS hazardous outlook. There is a slight risk of severe thunderstorms west of the Hudson River and a marginal risk elsewhere. Isolated to scattered damaging winds are the primary threat and an isolated tornado cannot be ruled out. Locally heavy rainfall is possible. This could lead to a few instances of flash flooding.

"There is potential for a Trace to 4" of rainfall, today," Furbeck said on Facebook. "Raising the hair of my neck is the potential that someone in the area may measure as much as 6" or even as much as almost 10" of rainfall. Yes, something similar that occurred to the West Point area in July could occur somewhere in Orange County or close proximity, again."

Just how much rain has the Hudson Valley gotten in the past 30 days?

Look at the map from NYS Mesonet, which is the centerpiece of the state's Early Warning Weather Detection System, set up in collaboration with the Division of Homeland Security and Emergency Services with a network of 126 weather stations across the state, including at least one site in every county and borough.

The Hudson Valley got 5 inches of rain — more than a month's worth for July — just during the storm July 9-10, explained Junhong Wang, Program Manager, New York State Mesonet and a research associate professor in the Department of Atmospheric & Environmental Sciences at University at Albany, SUNY. That round of rain caused hundreds of millions of dollars in flood damage.

SEE:

• Biden OKs Disaster Declaration For Hudson Valley
• Flood Damage To West Point To Exceed $100 Million

For this week, it'll be rainy Monday and Tuesday, and then we'll get a couple of days to dry out before the next round of showers and thunderstorms.

"The pattern this week will feature frequent showers and thunderstorms, typically every other day or so, across much of the East," AccuWeather Senior Meteorologist Alex Sosnowski said. "Even though it may not rain as much or as often as it did in July, conditions may again pose daily challenges for outdoor plans and travel."

Here's the five-day forecast based on Northern Westchester:

• Monday - Showers with a slight chance of thunderstorms this morning, then showers likely with a chance of thunderstorms this afternoon. Locally heavy rainfall possible this morning. Highs in the upper 70s. Southeast winds 5 to 10 mph. Chance of rain near 100 percent.
• Tonight - Showers likely with thunderstorms in the evening, then showers likely with a slight chance of thunderstorms after midnight. Some thunderstorms may produce gusty winds and heavy rainfall, then some thunderstorms may produce heavy rainfall after midnight. Locally heavy rainfall possible in the evening. Humid with lows around 70. South winds 5 to 10 mph. Chance of rain 80 percent.
• Tuesday - Mostly cloudy with a chance of showers with a slight chance of thunderstorms in the morning, then partly sunny with a chance of showers and thunderstorms in the afternoon. Some thunderstorms may produce heavy rainfall in the morning. Humid with highs around 80. Southwest winds 5 to 10 mph. Gusts up to 25 mph in the afternoon. Chance of rain 50 percent.
• Tuesday Night - Mostly cloudy with a chance of showers and thunderstorms in the evening, then partly cloudy after midnight. Lows in the lower 60s. West winds around 10 mph with gusts up to 25 mph. Chance of rain 30 percent.
• Wednesday - Sunny. Highs in the mid 80s. West winds around 10 mph with gusts up to 20 mph.
• Wednesday Night - Mostly clear. Lows in the lower 60s.
• Thursday - Mostly sunny. Highs in the mid 80s.
• Thursday Night - Mostly cloudy in the evening, then becoming partly cloudy. A 40 percent chance of showers. Lows in the mid 60s.
• Friday - Partly sunny. A chance of showers in the morning. Highs in the lower 80s. Chance of rain 30 percent.
• Friday Night - Partly cloudy. Lows in the mid 60s.

Here's the next 48 hours at a glance, based on Highland Falls: