FLASH FLOODING POSSIBLE; SOME AREAS COULD SEE TWO MONTHS WORTH OF RAIN THIS WEEK
Well, if you missed the rain, don't worry it is coming back in full force this week. Arthur will be nothing compared to the amount of rain expected this week across the state. Flash Flooding possible for everyone, but looking more likely in the Mountains and Foothills. Mudslides possible as well in the mountains and River Flooding too. A major pattern change is on the way starting tonight and lasting through at least Friday; in fact, we may not see a completely dry day until next Saturday. Models continue to illustrate a very wet period over the next few days, widespread rainfall and Flash Flooding expected. WHAT: A stalled upper level low over North Carolina will bring days of cloudiness and rain. 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 Wednesday before gradually eroding late Thursday. 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 next few days.
RAINFALL/FLOODING: Rainfall amounts from this are expected to be fairly impressive, on the order of 2-3 inches for areas East of Raleigh to the coast. 3-6 inches of rain west of Raleigh, and 6-8" 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 Tuesday into Thursday 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 two forecast now has most of the western part of the state (see below) in a Moderate Risk for excessive rainfall Tuesday into Tuesday night.
This means there's a 20-50% chance of Flash FLooding within a 25 mile point in the red and a 10-20% chance in the yellow. A level 3/5 risk is rare and more common during major flooding events.
Wednesday Flooding Outlook:
WILL IT RAIN EVERYDAY ALL DAY LONG: The short answer is no, the rain will be on and off throughout the state Tonight through Friday. The most substantial periods of rain will be tonight-Tuesday and Wednesday night. Please be prepared for Flash Flooding, especially in areas that normally flood first; I expect a Flood Watch to be posted for a portion of the state later this afternoon and evening. While the week 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 week, so I would have alternative plans in place. Please stay tuned for updates over the next few days. The bottom line is be ready for a very wet period through at least Friday; there will be breaks and sunshine. However, Flash Flooding is a real concern as we head toward Tuesday into Wednesday.