Key MESSAGE 1, Light southerly flow continues this afternoon well ahead of a cold front that is situated from West Virginia to Pennsylvania. Heat indices are around or just above 105F with temps of ~90F and dew points in the upper 70s. A Heat Advisory remains in effect until 8 PM for the western half of the FA. A few showers have developed. While MLCAPE has risen to 2000+ J/kg, deep layer shear is weak and there really isn't a forcing mechanism for convection outside of the seabreeze. Coverage should be isolated with a risk of gusty outflow winds of 40-50 mph in the strongest storms. Heat indices may once again flirt with 105 degrees on Friday. However, increased cloud cover 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. Will hold off on additional headlines at this time, but will reevaluate this evening/tonight.
KEY MESSAGE 2, Later this evening into the overnight (likely after midnight), a broken line of thunderstorms is forecast to be approaching the area from the NW. This convection will be tied to the above mentioned 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 during the early morning hours. Storms will likely dissipate by 4-7 AM.
On Friday, the cold front will continue to slowly move south toward the area before stalling in the vicinity of central/eastern NC. It 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. Combined with strong surface heating/plenty of instability, a few strong to severe storms are possible with the main threat being damaging to severe (50 kt/58 mph) winds. 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. While no watches have been issued with the afternoon package, a Flood Watch may eventually be needed for a portion of the area. While the greatest coverage of storms (and highest flood threat) may be more towards central NC, any storm will be capable of producing localized rainfall amounts of 2-3+" in a short time. The 12z/20 HREF has a ~30% neighborhood probability of 3" of rain in 3 hours across west and northwest portions of the CWA. 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. Precipitation chances will be lower on Sunday and Monday as the low-level flow becomes NW then SW and the upper trough axis pushes well to our northeast. It will be seasonably hot and humid but well short of Heat Advisory criteria.
18z Thursday through Tuesday Mainly VFR through the period outside of showers/storms. Isolated convection has developed early this afternoon and we'll continue to maintain a PROB30 mention for most TAF sites but will amend as needed. After sunset (but mainly overnight/early Friday AM), 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.
Benign conditions are expected outside thunderstorms for at least the next few days. S-SW winds of 10-15kt are expected through tonight. A few thunderstorms are possible over the waters this afternoon and evening, with the risk increasing tonight. The strongest storms this evening and tonight could produce gusty winds of 30-40kt. A cold front stalls over the area on Friday with light north winds expected across NE NC with S-SW winds south of the front over the SE NC waters.
Outlook: The front will move back north as a warm front Friday night and will be to our north on Saturday, with one or two areas of low pressure lifting northeast along it. This will lead to a varying wind pattern Friday evening/night but S-SW winds return on Saturday. A more dominant southwesterly continues Sat night/Sunday.
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 until 8 pm EDT this evening for ncz044-079-080- 090>092-094-193>196-198-199. Marine, none.
