|2.15mph from the S
... Above normal temperatures and an active weather pattern will persist through the week. A frontal system will bring showers and possibly a few thunderstorms to the area on Wednesday, while another system impacts the area later in the week.
NEAR TERM /THROUGH TONIGHT/... As of 315 AM EST Sunday: Widespread low stratus and fog continue to overlay the CFWA, mainly east of the mountains. Very tight dewpoint depressions and a shallow moisture layer underneath a weak nocturnal inversion will support continued low clouds and fog through daybreak. With elevated dewpoints and low cloud deck, overnight lows are still on track to remain ~10 degrees above normal. With light winds, patchy dense fog can't be ruled out and the only hindrance to widespread fog development will be the low stratus deck that's currently overhead. Spotty dense fog has been observed in the Upper Savannah Valley and in portions of the foothills near the Blue Ridge Escarpment.
Without a clear-cut mechanism to help scatter out the low cloud deck, expect the deck to remain stubborn through mid-morning before insolation gets the best of it and allows for the deck to scour. As that is happening, a southern stream shortwave and associated DPVA will aid in activating the stalled frontal boundary to the south. With continued moist southerly flow, don't be surprised if clouds stick around and light precip sneaks into our southeastern zones. Model guidance are in good agreement with a surface wave deepening along the frontal boundary and becoming a coastal low pressure just offshore the Carolinas by Sunday evening. If this shifts further west, areas like the I-77 corridor could pick up a few light showers by then. Right now, the forecast is for the coastal low to remain far enough to the east that we end up on the subsidence side of the low. Despite the low cloud deck, the warm start and warmer air aloft supports max temperatures to rise up to 6-12 degrees above normal for most locations.
Forecast becomes tricky Sunday night as the aforementioned surface low gets its act together and moves just offshore the North Carolina Coast by daybreak Monday. This should shift low-level winds to a northeasterly component and advect drier air into the region. Model guidance still support another nocturnal inversion overnight Sunday with lingering moisture trapped underneath and thus, another round of low clouds and fog will be possible. The deck low stratus won't have as low of cloud bases due to a slightly deeper sub cloud layer and low-level subsidence filtering in. Will be interesting to see the extent of the associated low clouds and how it affects the forecast as the edge of the deck may only reach the eastern half of the CFWA. Overnight lows will remain ~10 degrees above normal.
SHORT TERM /MONDAY THROUGH WEDNESDAY/... As of 230 AM Sunday: An upper low moves from the SC coast north into the NC Coastal Plain on Monday. A surface low follows a similar track as the upper low. Surface flow will turn northerly as the low moves by to our east. However, low level moisture remains quite high in easterly then southeasterly flow. There is little in the way of synoptic forcing, but the weak upslope flow and isentropic lift will lead to isolated very light showers or sprinkles Monday and Monday night. The air mass continues to warm, so even with a mix of clouds and sun and some very light showers, highs will rise to 10 to 15 degrees above normal. Lows will be around 15 degrees above normal.
The upper low opens up and moves north into the Mid-Atlantic on Tuesday. Short wave energy consolidates as it moves east near the Gulf Coast. This short wave moves east across the area Tuesday night. A frontal system associated with this wave approaches the area from the west Tuesday and into the area late Tuesday night. Deepening moisture and increasing forcing will lead to increasing precip chances late Tuesday into Tuesday night. High PW values and strong forcing creates the potential for some heavy rain Tuesday night, especially east of the I-77 corridor. Highs will be nearly steady Tuesday, with lows rising a few degrees Tuesday night.
The cold front crosses the are Wednesday with good shower coverage across the area. The guidance shows a low pressure along the front moving over or near the area. The ECMWF is farther south with little to no instability for our area and weak shear. The GFS and Canadian show the low tracking along or near the I-85 corridor. The more northern track would bring the potential for weak instability and strong shear to the southern portions of the area. Still too early and too much uncertainty to be sure about any severe potential, but it bears watching. Moderate to heavy rainfall would also be possible. Highs drop a few degrees on Wednesday.
LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 245 AM Sunday: Precip chance quickly drops off Wednesday night as the short wave and cold front move east of the area. A short wave ridge and dry high pressure returns for Thursday and Thursday night. Lows 10 to 15 degrees above normal Wednesday night drop a few degrees Thursday night. Highs Thursday will be around 10 degrees above normal.
A series of short waves dig a trough over the central CONUS Friday. This trough moves into the area late Saturday. A complex frontal system associated this trough moves into the area on Saturday with the main surface low moving west of the Appalachians, while a secondary low forms and moves over or near the area. Once again, the ECMWF is farther south with the secondary low than than the GFS. The Canadian this time is farther south as well. Just like the Wednesday front, a farther north low would bring the possibility of more instability and shear than the farther south low. Either way, the guidance does agree on high PW values and strong forcing, so heavy rainfall is possible even if thunderstorms are isolated and non- severe. Highs near to slightly above normal Friday rise a few degrees on Saturday. Lows Friday night will be around 10 degrees above normal.