Decent amounts of rain occurred over significant parts of North and South Carolina, as well as South Georgia, last week. This axis of heavier rainfall (black dashed line) occurred along a slow-moving and weak frontal boundary.
Here is the percent of normal rainfall from last week. Fortunately, for a couple of weeks now, the Southeast U.S. has experienced daily scattered thunderstorms. While some spots have received minimal amounts of rain – others spots have received significant rainfall. In the following image, areas in blue and purple received above-normal amounts of rain for the week.
Taking a look at the big picture for this week, we find low pressure dropping south across the Great Lakes, Northeast, and much of the Ohio Valley. This dip in the jet stream will result in several cold fronts droping into the region, each bringing in a reinforcement of drier air and scattered showers and storms.
Most of the atmospheric energy will remain to our north, and low-level moisture will be limited. Thus, I expect thunderstorm activity to be less than the past few weeks. There will be several days with scattered storms, but just as many, if not more, will be dry.
With weak forcings, it will be a bit difficult to pin-point areas of heavier rain; however the best changes for more significant rain will be over Mississippi and Alabama, as well as Florida. Lighter amounts of rain can be expected over North Georgia, the Carolinas, and Virginia.
Taking a quick look at the topics – while there has been a pickup in activity recently – a strong ridge of high pressure off the east coast will block any systems from making an Atlantic landfall. The most likely track will continue to be from east to west across the southern Gulf of Mexico. There is an outside change for a system that would move into the central Gulf to curve northeast. In any event – there are no signs of any tropical activity over the Southeast U.S. this week.
Rainfall and Runoff Forecast
I want to introduce a product that you will see each week. This is my forecast for rainfall and runoff for Week 1, Week 2, and next month. The horizontal bars (color-coded) indicate the rainfall potential. The arrows indicate runoff potential and the thin black line indicates the runoff trend. Keep in mind that this is for the entire Southeast U.S. and will be general in nature. If your group would like information specific to your area/projects, please let me know (firstname.lastname@example.org). I think it is important to show both rainfall and runoff. For example, for most of the region, while rainfall might be below normal for the next few weeks, the arrow point down shows that runoff potential will be even less. I’ll discuss this more in future issuances of Blue Water Outlook products.
Weekly Take Away Points
- Less rain this week than last – especially over the Carolinas
- Possibility of 1- to 3-inch Rains over parts of Mississippi and Alabama
- More soil moisture decreases than increases
- No sign of tropical activity
The national Weekly Water Outlook can be seen here…