A major pattern change is on the way starting tomorrow and lasting through at least Wednesday of next week, in fact, we may not see a completely dry day until next Thursday. Models continue to illustrate a very wet period over the next few days, widespread rainfall and Flash Flooding expected.
WHAT: Two areas of low pressure (one over the Gulf of Mexico and another off the NC coast) will bring a flow of moist air across central NC, resulting in rain through early next week. The combination of Tropical moisture and a stalled cold front will create for major rainfall, especially from Greensboro and points west. Precipitable Water near 2" will bring a high chance for slow-moving storms. High Pressure north will create a blocking situation, this will result of days of clouds and on off thunderstorms and rain.
Weak high pressure nosing down east of the Appalachians will provide weak cold air damming settling somewhere between I-85 and I-20 Saturday before gradually eroding late Sunday. Southeasterly riding up and over the cool dome near the surface will provide areas of enhanced rainfall rates near the cold air damming boundary as well as near the escarpment, including the North Carolina foothills and southwest mountains due to decent upslope enhancement. Model guidance suggests there will be enough breaks in the clouds south and east of the cold air damming boundary at times to allow for at least some destabilization, raising the risk for thunderstorms for these areas in the mountains and foothills. Over Central and Eastern NC training showers and thunderstorms will be likely at any-point over the weekend
RAINFALL/FLOODING: Rainfall amounts over the weekend are expected to be fairly impressive, on the order of two to four inches for areas East of Greensboro to the coast. 4-6 inches of rain west of Greensboro, and 7-8" of rain where the training of thunderstorms occur near the wedge boundary or near the escarpment in the Foothills and Mountains (Hickory west) . The risk of flooding is particularly concerning late Saturday into Sunday as rounds of heavier rainfall leading up to this time will prime the area for the potential for flash flooding and debris flows (mountains) as well as flooding and even potentially some flooding for prone rivers, despite recent dry conditions. In fact, the Weather Prediction Center day three forecast now has most of the western part of the state (see below) in a Moderate Risk for excessive rainfall Saturday into Saturday night.
Above is a look at my predictions of rainfall based on a verity of models, this was hard, the GFS and EURO are not on the same track at all. While the Euro is forecasting upwards of 10-12" in the mountains and Foothills, the GFS has haft that amount and less east. My forecast is right in the middle of both.
Above is the forecasted area of Moderate and Slight risk of Flash Flooding Saturday through Sunday from the Weather Prediction Center, moderate risks are rather uncommon for North Carolina. Flash flood forecasting is still one of the most difficult aspects of meteorology. If you live near a creek or river, or in a low line area, now is the time to make sure you are prepared for rapid raises of water and Flash Flooding.
While the weekend will not be a complete washout, it will be very wet with on and off showers and thunderstorms likely everywhere. Unfortunately, we can not pinpoint exactly where and when the rain will fall over the weekend so I would have alternative plans in place. Please stay tuned for updates over the next few days. Bottom line is be ready for a very wet period through at least Wednesday, there will be breaks and sunshine. However, Flash Flooding is real concern as we head toward the end of the weekend.