It has been quite some time since our area experienced an area-wide moderate rainfall event. That looks to change during the middle of this coming week, as the remnants of Hurricane Patricia interact with another atmospheric dsiturbance over the Central United States. The resulting low pressure system will develop through the Great Lakes and into Canada, allowing the northward surge of moisture along the East Coast and toward our area on Wednesday.
Interestingly enough, the indirect impacts from Patricia will be enough to bust a pattern which had been continuously dry in our area. Moderate drought conditions continued in much of Northern New Jersey, NYC, Long Island and Connecticut to start this week, still lingering from the very dry summer months. New York City is still running 8″ behind the average seasonal rainfall total. This weeks rainfall event, then, may be “welcomed”.
Still, the dynamics behind the event are likely to produce a stinker of a day on Wednesday. Forecast models are in good agreement that the remnant moisture associated with Hurricane Patricia and a large upper level trough over the Central United States will begin to interact on Tuesday. While this interaction doesn’t directly affect us, the resulting atmospheric evolution certainly will.
As the remnants of Patricia are tugged northward, through the Ohio Valley, by the larger trough to its west, a southerly flow will develop in the low levels of the atmosphere along the east coast. This will help advect more moist air northward, as the system develops. Meanwhile, forcing for precipitation will shift northeastward as well, and rainfall will develop on Wednesday. This will bring periods of rain throughout the morning and afternoon on Wednesday — with some intermittent breaks.
As the system evolves, a cold frontal boundary will swing eastward through Pennsylvania either late Wednesday night or Thursday. With this cold front will come another bout of steadier and heavier rain, but behind it will come drier air — which always lingers around these stronger, more powerful systems. So while a widespread rain event is likely on Wednesday, it won’t linger enough to wash out the entire second half of the week. By later Thursday into Friday, the atmosphere will become much more stable — and cooler — allowing for pleasant weather to return.
Rainfall totals, while “moderate” on all forecast models throughout the area, will be generally low compared to our surroundings. Much more prolific rainfall is expected in the Southern US, and Central United States into the Great Lakes. Still, up to 1″ of rain through Wednesday and Thursday will suffice to aid in recovering from our yearly rainfall deficit, and hopefully put at least a bit of dent in the drought conditions which still persist in the area as of Monday morning.