Key MESSAGE 1, An anomalously strong upper level trough amplifies over the eastern US today, with a potent shortwave diving southeast through VA and the Carolinas. A strong LLJ ahead of this feature should lead to increasing moisture advection, with PWATs once again climbing back above 2". Meanwhile, heating of a moist boundary layer should support moderate instability, with MLCAPE rising into the 1500-2500 j/kg range. Mhx 18Z sounding shows MUCAPE in excess of 5kJ/kg, but we've been relatively clear from the debris clouds . Aloft, a notable upper jet max is forecast to overspread the instability axis, supporting deep layer shear of 30-45kt. While instability will be moderate, the shear/instability/forcing combo is notable for this time of year. This combination supports the threat for severe weather, with modest support from ensemble, analog, and machine learning guidance. The main potential limiting factors are timing and potential subsidence, with area remaining capped through much of today. Most guidance continues to show that the stronger convection will not reach ENC until, or after, sunset. Despite the potential for a gradually stabilizing boundary layer, if strong large-scale forcing is realized, it should help support deep convection well past the typical diurnal max in convective intensity this time of year. Thus the reason the watch is in effect until 1am. The watch may need to be extended eastward through portions of ENC later this evening, as TS probs for the OBX zones have increased a bit. Will see how upstream development occurs in VA before any watch extention attm. Storm mode could be a bit messy, with combination of supercells early ahead of more organized multicell line segments later. Given the potential amount of forcing present, it appears likely that a MCS will move through the eastern Carolinas and VA during the evening and early overnight hours posing a risk of damaging winds. Low- level SRH around 100-200m2/s2 may support a few rotating updrafts capable of hail and tornados. However, those latter 2 hazards should be lower compared to the wind risk. Given the trend in the track of the low further away from the FA and the later arrival of convection, SPC has removed the FA from the 5% tor threat, limiting the potential to 2% across all of ENC. While convection looks to be fairly progressive, heavy rain in a high PWAT airmass could pose a localized flood threat, esp for areas that have received heavy rain over the last few days (Hyde county east through the Outer Banks), where WPC is suggesting 6hr rainfall amounts in excess of one inch.
KEY MESSAGE 2, Cold front will push offshore early Wed morning, with sfc high pressure building in from the west while troughing continues aloft. This will keep temps seasonable and mostly dry through late week. The next frontal system will impact the area this weekend into early next week, with increasing precip chances.
00z Wednesday through Sunday VFR flight cats across all terminals this afternoon with SW breeze in place. Area will remain mostly dry through this afternoon, though decaying showers approaching from the NW may skirt inland terminals through ~20Z. Shower and thunderstorm chances increasing this evening and into the first part of tonight. Strong to severe thunderstorms possible, with the main threat of damaging wind gusts 45-65 mph. Have included TEMPO IFR groups to try to time out the tstorm potential tonight, generally 00-05Z. Storms will grad push offshore late tonight. Ssw winds will gusts 15-20 kt this evening and into the first part of tonight. Widespread, long lasting fog seems unlikely with at least a breeze persisting through the overnight, but there may be brief drops in VIS due to patchy fog behind the storms tonight. Usual offenders with the pessimistic outlooks that don't pan out for the most part suggest low level stratus. Not enough confidence in this happening to include prevailing CIGs for any TAF sites, so continue mention of SCT sub FL020 MVFR stratus. Best chance for MVFR CIGs from stratus across the Nern tier, making PGV the only TAF site with higher potential. Mostly clear skies save for some diurnal CU in the afternoon WED with NW breeze becoming more WNW through the day.
Outlook (Wednesday through Saturday): Much drier behind the fropa for Wed into the end of the week as high pres rebuilds. Periods of early morning fog and/or stratus possible each night.
Latest obs show SW winds 10-15kt across coastal waters and PamSound with less than 10 kt across inside waters, with seas 2-3 ft. Ssw winds will increase through the afternoon and evening, becoming 10-20 kt by early this evening with seas building to 2-4 ft. Ssw winds will peak at 15-25 kt gusting 20-30 kt tonight, with seas building to 4-7 ft. Expanded existing SCAs to include all inside waters save for Pamlico Pungo Rivers. Scattered strong to severe thunderstorms will be possible late this afternoon into tonight. These storms will be capable of 40-50 kt winds, small hail, waterspouts, and frequent lightning.
Outlook: Modest NW wind surge 10-20 kt behind the front Wed with seas grad subsiding. Light to moderate NW winds continue Thu with 2-4 ft seas. Flow becomes more southerly late Fri and Fri night.
Nc, none. Marine, small craft advisory until 5 am EDT Wednesday for amz131-137- 230-231. Small craft advisory until 5 am EDT Wednesday for amz135. Small craft advisory until 8 am EDT Wednesday for amz152-154. Small craft advisory until 8 am EDT Wednesday for amz156-158.
