Strong cold front to bring rain, thunderstorms, late tonight and Saturday

The persistent cloud-cover over much of the region during the past several days finally broke today, leading to a beautiful fall day. However, as the evening progresses, clouds will be on the increase due to a strong low pressure system in Ontario, Canada, and its associated strong cold frontal boundary dragging to its south. These features will be moving eastward throughout the night and approach our area during the day tomorrow.

Today’s NAM Model valid for 2:00pm tomorrow afternoon shows the strong cold front crossing our area, with much colder 850mb temperatures about to move in.

Fortunately, for people going out tonight, any rain should hold off until midnight or slightly later for western sections, and after 2:00am for NYC and east. Plus, given that we are still on the warm side of the cold front, temperatures will not be all that chilly tonight, with lows around 60.

7:00pm: Mostly cloudy skies, temperatures in the low to mid 60s.

10:00pm: Cloudy skies, temperatures in the low 60s.

Midnight: Cloudy skies, temperatures in the low 60s. A 30% chance of showers for western zones, with only about a 10% chance of showers for NYC and east.

2:00am: A 60% chance of rain for western zones, with a 30% chance of rain for NYC and east, and temperatures around 60.

4:00am: An 80% chance of rain for western zones with a rumble of thunder possible, and a 60% chance of rain for NYC and east, with temperatures around 60.

As we move forward towards daybreak tomorrow, the strong dynamics of the cold front will be closer to our area, which may help to increase instability and lift. This leads to the possibility for heavy downpours and even some thunderstorms; the best chance for any thunderstorms will be to the west of NYC.

Today’s NAM Model valid for 11:00am tomorrow shows a potent jet streak (peak of a jet stream) moving into the Ohio Valley and Appalachians, helping to provide the dynamics necessary for periods of heavy rain.

While rainfall amounts will not be extremely prolific over a widespread area, the prospects of steady rain with some heavy downpours for some areas may be particularly high between 6:00am and 10:00am. Northern zones may get more rain due to their closer proximity to the strongest dynamics. After 10:00am, the slight risk for scattered embedded thunderstorms is there for the entire area — though none should be severe. A few strong wind gusts are possible, however.

Once the cold front moves through tomorrow evening, temperatures will drop quickly, and clouds will rapidly clear.

Today’s NAM Model valid for 8:00pm tomorrow evening shows the clouds clearing the area.

This means that for people going out tomorrow night, the weather should also be fine. It may be a bit chilly and windy, however, with temperatures falling through the 50s and into the upper 40s, but sky-conditions after dinner-time will be good.

Today’s NAM Model valid for early Sunday morning shows temperatures dropping into the upper 30s in much of the interior, with 40s elsewhere.

Sunday will have mostly cloudy skies, but have that classic Autumn “nippy” feel to the air, with highs in the low 60s and breezy conditions. Sunday night should be similarly chilly to Saturday night. Temperatures will gradually moderate next week.