Key MESSAGE 1, Light southerly flow has redeveloped areawide this morning, and dewpoints are starting out in the mid to upper 70s which is higher than the low to mid 70s yesterday morning. Meanwhile, ensemble and EFI guidance point towards another day of above normal highs. This combination should support a larger footprint of heat indices in excess of 105 degrees compared to yesterday. As such, the Heat Advisory covers a larger area today. Additionally, the advisory has been expanded further north in the coastal plain, and now includes Greene, Pitt, and Beaufort Counties. Heat indices may once again flirt with 105 degrees on Friday. However, increased cloudcover and an increased risk of thunderstorms should temper this risk some. A smaller Heat Advisory may be needed on Friday, especially if thunderstorm activity is delayed later into the day.
KEY MESSAGE 2, Light southerly flow has help boost dewpoints into the mid to upper 70s this morning. Even with some mixing this afternoon, heating of the more moist boundary layer should support strong instability developing by this afternoon with MLCAPE forecast to reach 2000-3000j/kg. Deep layer shear will be weak (10-20kt), favoring poorly organized multicells. During the day, the primary forcing mechanisms look to be the seabreeze and an inland trough. Convergence doesn't look great with either, and this may tend to keep convective coverage isolated to widely scattered during the daylight hours. The primary risk with the strongest cells should be gusty outflow winds of 40-50 mph.
Later this evening (ie. After 10pm), a broken line of thunderstorms is forecast to be approaching the area from the NW. This convection will be tied to a cold front that will be moving SE out of Virginia. Most short-term guidance insist that this convection will be on a weakening trend as it approaches ENC. However, given the increased forcing along the front, the convection may last longer than some guidance suggests, even if elevated/weak in nature. Prior to more substantial weakening, a risk of strong to marginally severe outflow winds may accompany the thunderstorms as they reach the far northern reaches of ENC.
On Friday, the cold front is forecast to stall across the central and eastern Carolinas, and will interact with a very moist and strongly unstable airmass, favoring the development of numerous thunderstorms. Deep layer shear should get a bump up in the vicinity of the front, and synoptically this appears to be a decent setup for several instances of severe weather. The primary risk should once again be strong to damaging wind gusts. However, given the slightly better shear and a signal for rotating updrafts, a hail risk may develop in some of the strongest/tallest cores.
In addition to the severe weather potential, there will also be a risk of intense rainfall rates and hydro concerns. Strong instability, 2"+ PWATs, increased large-scale and mesoscale forcing, and the potential for training convection all point towards a risk of flooding, including at least a few instances of flash flooding. It's possible that a Flood Watch may be needed for a portion of the area. The potential for scattered to numerous thunderstorms looks to continue into Saturday. However, instability will be lower, and this may lead to a lowered risk of severe weather. Heavy rain and flooding concerns may continue, though.
12z Thursday through Monday Satellite imagery this morning reveals an area of low stratus and FG from near KILM north through KDPL and then on north into central NC. This area has mostly remained west of the ENC TAF sites, and this is expected to continue to be the case based on the current, and forecast, low-level flow. On the edge, though, there will continue to be a risk of brief reductions to VIS through about 13z this morning.
This afternoon, another round of isolated to scattered TSRA is expected along the seabreeze. A TSRA risk may also develop further inland along a weak inland trough. Guidance appears to be backing off some on the risk during the daylight hours, but we'll continue to maintain a PROB30 mention for most TAF sites for now. After sunset, an elevated risk of TSRA may develop for at least the northern half of ENC as a broken line of weakening SHRA and TSRA approaches from the north.
Outlook: A heightened risk of TSRA is expected Friday into Saturday thanks to a stalled front and various waves of low pressure interacting with a very moist and unstable airmass. During this time, widespread sub-VFR conditions can be expected, including a risk of LIFR conditions at times during the strongest TSRA and heaviest RA. Additionally, TSRA will carry a heightened risk of gusty/erratic winds of 40kt+, especially on Friday. A risk of hail up to 0.75" may accompany the strongest cores as well. Drier conditions begin to move in Sunday and Monday with a reduced risk of TSRA.
Southeast to south winds of 5-15kt are expected through early this evening, with seas of 2-3ft. The thunderstorm risk should mainly be confined to the inland rivers and sounds through this afternoon. The risk should then expand to all waters later this evening and tonight as a cold front drop south into the area. The strongest thunderstorms this evening and tonight could produce gusty winds of 30-40kt. Behind the front, light north winds are expected, especially for the waters north of Cape Hatteras.
Outlook: A front will stall across the area Friday and Saturday, with one or two areas of low pressure lifting northeast along it. This will lead to a varying wind pattern that will hinge on where the front stalls and how strong each low is. By later Saturday into Sunday, a more dominant southwesterly flow is expected.
The front and surface lows will support an increased risk of thunderstorms Friday and Saturday for most waters. The strongest thunderstorms will be capable of gusty winds of 40-50kt+ and perhaps some hail. The thunderstorm risk is expected to lower by Sunday and Monday.
Nc, heat advisory from 11 am this morning to 8 pm EDT this evening for ncz044-079-080-090>092-094-193>196-198-199. Marine, none.
