Key MESSAGE 1, A hot and muggy afternoon across ENC today with widespread temps in the mid 80s to 90s and heat indices around 100-109F inland. A diurnal Cu field along and out ahead of the seabreeze has developed this afternoon with widely scattered showers and thunderstorms already developing along the seabreeze today. Latest RAP mesoanalysis shows widespread MLCAPE values around 2000-3000 J/kg, low level lapse rates of 8-9C/km, and deep layer shear values around 20-25 kts across ENC as of this update. With the seabreeze providing the focus for lift, expect ongoing showers and thunderstorms to increase in coverage and intensity as the afternoon wears on under this favorable environment for thunderstorm development. With ample CAPE, and enough lift a few of these storms could become strong to severe in nature bringing a threat for wet microbursts (up to 60 mph gusts), frequent lightning, and heavy rain. Given the expected scattered nature of this activity have capped PoPs at Chance as not everyone will see rain and thunderstorms today.
Seabreeze thunderstorms gradually push inland through the afternoon and begin to dissipate after sunset. However, as this occurs deep layer shear will be on the increase with the approach of an upper level trough, peaking at 25-35 kts out ahead of an approaching cold front with the highest shear values noted along our northern periphery. This will lead into our next potential thunderstorm threat from the west. Latest guidance suggests broken linear segments of thunderstorms will develop along a surface trough to our west this afternoon across central NC/VA and push E'wards this evening and overnight, likely reaching the area after sunset. While instability is forecast to be waning, with enough shear these segments could hold together long enough to promote a second strong to severe thunderstorm threat into tonight. Greatest risk for this second round of storms looks to occur across our northern zones tonight with this activity pushing off the coast by about 2AM Monday. This activity would once again bring a threat for strong and damaging wind gusts (40-60 mph) to the area. Spc has noted much of the area under a slight risk (level 2/5) for severe thunderstorms today mainly west of the coast and OBX with a marginal risk (level 1/5) for severe thunderstorms noted elsewhere across the coast and OBX.
Beyond tonight, overall pattern through the week remains at least marginally conducive for shower and thunderstorm threats each afternoon and evening. The next best chance for stronger storms appears to be Thursday into Friday ahead of a stronger front where deeper shear will likely be present with equally strong instability.
KEY MESSAGE 2, Afternoon convection has allowed heat indices to drop below heat advisory criteria and have cancelled the Heat Advisory for the remainder of the day.
Once the first front passes on Monday, a relatively cooler couple of days are likely. Heat and humidity will likely return again on Thursday and Friday ahead of the late-week front with more widespread heat index values of 105-110 forecast.
00z Monday through Friday VFR conditions across the terminals early this evening with afternoon convection winding down. There is an additional line of showers and thunderstorms across the piedmont that may bring another round of convection and sub-VFR conditions and gusty winds this evening, mainly to across western rtes through approx 03z. Guidance shows the storms weakening as they progress eastward and expect little impacts from them at OAJ and EWN but will continue to monitor. Behind the convection, another pre- dawn bank of MVFR to IFT stratus could develop inland. Fog appears less likely overnight with winds unlikely to decouple. Latest guidance shows coastal sections have the better probs for stratus, in the area where stronger storms occured this afternoon. Mvfr cigs may linger through mid morning as LCL rise. Scattered afternoon showers and thunderstorms mainly along the sea breeze Monday afternoon with better chances for storms at EWN and OAJ.
Outlook: Front clears area later Monday although iso to sct shower and thunderstorm risk will extend into Tuesday and Wednesday. More widespread convective threat returns Thursday into Friday with stronger front. Overnight fog and stratus threat possible each morning.
Once again little in the way of changes to the marine forecast as we do expect conditions to worsen this afternoon as the pressure gradient tightens between a surface trough and cold front to our west and a ridge of high pressure to the east. Sw winds are already about 10-20 kts with a few gusts up to 25 kts noted across our coastal waters already. With the aforementioned cold front not forecast to cross our waters until Mon morning expect widespread 15-25kt SW winds with gusts up around 25-30 kts across our coastal waters, Pamlico, Croatan/Roanoke Sounds and Neuse River this afternoon and tonight. This coincides with ongoing small craft advisories. Elsewhere slightly lighter winds will be in place and dont plan on expanding ongoing SCA's. These elevated winds continue into Mon morning, but as a cold front tracks across our waters winds will ease as the pressure gradient relaxes with winds lowering to 5-15 kts with a few gusts up towards 20 kts across all waters. Winds will also become NE'rly behind the front. 2-4 ft seas this afternoon will increase to 4-6 ft across our coastal waters this evening and remain elevated into Monday morning before lowering down to 3-5 ft by 11AM Mon. This will bring an end to our small craft advisories. Lighter winds and lower seas are then forecast through the rest of the period with the front hanging around the area. Outside of SCA conditions, there will be a renewed risk of showers and thunderstorms especially after nightfall as more organized convection inland migrates over area waters after 00z. Environment will be favorable for a few stronger storms with gusts in excess of 40 kt.
Outlook (Mon night through Sat): Periodic nocturnal and early morning risk of showers and thunderstorms is possible each weeknight, although most likely odds will be Thursday night into Friday ahead of stronger front approaching area waters. This front will also be the next focus of widespread SCA conditions with a low risk of Gales across the outer waters.
Nc, beach hazards statement until 8 pm EDT this evening for ncz195- 196-199-204-205. Marine, small craft advisory until 8 am EDT Monday for amz135. Small craft advisory until 3 am EDT Monday for amz137-231. Small craft advisory until 5 am EDT Monday for amz150. Small craft advisory until 11 am EDT Monday for amz152-154-156- 158.
