For the second week in a row, the Triangle is expecting rain and cooler than average temperatures to settle in for the weekend. It might not be the way we'd like to enjoy our weekends, but on the bright side, if the calendar said "January," we'd be expecting a wintry mix. At least it's summer!
So, what will cause our unusually cool weekend? High pressure will be sitting over the New England states through at least Monday while an area of weak low pressure will drift into the area on the other side of the Appalachian mountains over Kentucky, Ohio, and Indiana. Both systems will stall in their places, and the high pressure will win out in affecting North Carolina's weather.
The winds move around high pressure out from the center and curve to the right (clockwise), so when a strong area of high pressure sits over New England, our winds come from the northeast. From that direction, the air flow is cooler, moist, and is pushed up against the mountains in the western side of our state, where it becomes stuck until something in the atmosphere spurs a change.
With the added moisture in the air, we see cool, rainy weather for an extended period of time. Little pulses of energy that move through the atmosphere can cause the rain showers to become thunderstorms, so there is a chance we could at least have the excitement of thunder Saturday evening with one of those pulses. Otherwise, just expect a lot of rain.
In fact, some areas of the state could receive up to three inches of rain, and flooding will be a distinct possibility. By Monday, the high over New England will begin to move again, allowing the low on the other side of the mountains to move as well. The winds will shift, but a chance of rain will remain in the forecast as the low passes. Our temperatures will start to climb back toward normal by the middle of next week.