Key MESSAGE 1, Yet another warm and muggy morning today with temps in the 70s to low 80s and debris clouds from dissipating showers to the north and west of the area filtering into ENC. As far as today goes, do expect any leftover debris clouds to dissipate later this morning with yet another hot day on tap. 1000-850 MB thicknesses will be slightly higher today (1435-1440 m) as compared to previous days which should result in highs in the 90s. Latest guidance suggests we at least near record high temperatures today, though whether we reach record highs today will be dependent on if morning cloud cover dissipates early enough. See CLIMATE section for more information.
With a front to the north slowly encroaching, moisture is forecast to pool out ahead of the front allowing dewpoints to potentially increase into the mid to upper 70s, resulting in widespread "feels like" temperatures of 105-110F this afternoon across ENC. While we toyed with the idea for an Extreme Heat Warning across our SW'rn zones, think the morning debris clouds plus afternoon shower and thunderstorm activity should preclude us from reaching criteria. As a result have kept the heat advisory in place across all of ENC. We continue to encourage anyone planning on spending time outdoors to stay hydrated and to limit exposure to the heat, if able.
While we "cool down" as compared to today this weekend, with frontal progression slow to occur, temps still get into the mid 80s along the OBX to low to mid 90s inland. With dewpoints remaining in the mid to upper 70s this weekend could see continued heat indices around 105 F. While the footprint will likely be smaller, this could result in additional heat headlines this weekend with the greatest chance to see additional heat headlines across our SW'rn zones which will be the last to be impacted by the aforementioned front. Front will lift north as a warm front Sun into Mon and Mon would be our next best chance at more widespread heat headlines across ENC.
KEY MESSAGE 2, Best chance to see more widespread shower and thunderstorm activity occurs today and over this weekend with the approach of a frontal boundary and associated mid level shortwave. At the outset, have a mid level ridge centered over the Southeast. While initially this morning we will not have much upper level support with a mid level shortwave still in the Ohio River Valley riding along the periphery of this ridging, we should see a more active seabreeze that pushes inland later this morning and afternoon as winds are more S'rly as compared to previous days. So the seabreeze wont be pinned along the coast. This should result in a more active seabreeze with better moisture and more interactions with local sound and river breezes as well, aiding in surface convergence. Then as we get into tonight a combination of the aforementioned front and mid level shortwave should provide additional lift for another round of showers and thunderstorms coming in from the north and west. This front then likely stalls across the area on Sat bringing continued rounds of shower and thunderstorm activity before the front finally lifts north as a warm front on Sun. Overall this should result in continued chances for scattered precip over the next few days so have kept high end chance PoPs in the forecast.
Pre-storm environment today and tomorrow is marginally conducive for strong to severe storms as well as isolated flooding potential, supported by both NWP and AI guidance. Latest guidance suggests while deep layer shear will be weak (generally around 20-25 kts), instability will be more than sufficient (MLCAPE around 2000-3000 J/kg) for strong updrafts along the seabreeze and aforementioned front. With moisture also pooling ahead of the front, PWATs increase to 2-2.25" today as well. Activity should be mainly diurnal, although there is a risk of some overnight convection as upstream activity migrates along the sub-tropical ridge. Thunderstorm activity is forecast to wane in intensity and coverage as we get later into tonight, though with the front hanging around the area tomorrow as well yet another potential round for strong to severe thunderstorms will be possible mainly south and west of where the aforementioned front stalls. Strongest storms could produce wet microbursts, frequent lightning, and torrential rainfall given this environment. While not likely there is also a non-zero tornado threat within the strongest storms. As a result SPC has portions of the area under a marginal risk (level 1/5) for severe weather today and tomorrow.
In addition to this, slow storm motions, upper level winds parallel to the surface front, and ample moisture will bring a threat for isolated instances of flash flooding and WPC also has the areas under a marginal risk (level 1/4) for excessive rainfall today and tomorrow as well.
KEY MESSAGE 3, A second frontal boundary looks to approach early next week after a brief lull Sunday. Still plenty of details to hammer out, but medium- range AI NWP guidance points once again to at least a marginal risk of stronger storms for portions of the Carolinas, along with a heavy rainfall risk as humid airmass remains unyielding.
12z Friday through Tuesday Primarily VFR conditions are noted across ENC this morning with the lone exception being across the OBX where some patchy fog is noted resulting in MVFR to IFR vis at times. Vfr conditions across all of ENC should return within the next hour or so as the Sun rises and leftover high cirrus overspread the region. As we get into the afternoon, the risk of TSRA is forecast to increase due to the combination of a moist and unstable airmass, an upper level wave, a surface cold front, and the seabreeze. Have added TEMPO groups for TSRA at EWN/OAJ when activity is currently forecast to start the earliest this afternoon with PROB30 groups across ISO/PGV still given the later start of shower and tstm activity. Timings for these groups is generally during the highest confidence timeframe of precipitation potential. Where TSRA occur, the environment appears supportive of LIFR/IFR conditions, along with gusty/erratic winds of 40kt+. As we get into tonight shower and thunderstorm chances will gradually decrease from west to east, but behind this activity low stratus and sub-VFR conditions may develop especially near the aforementioned front which is forecast to stall over ENC. Timing for low stratus development appears to be after 06Z tonight and have put in SCT MVFR cloud decks in at all TAF sites to account for this.
Outlook (Saturday through Tuesday): Continued chances for sub- VFR conditions will persist into Sat afternoon with a stalled front draped over ENC bringing additional rounds of shower and thunderstorm activity. However, VFR conditions return Sat evening/Sun as high pressure briefly builds into the area. Yet another potential round of sub-VFR conditions are possible Mon/Tue with the passage of yet another front.
Ongoing 5-10 kt S-SW'rly winds and 1-3 ft seas are noted across all waters this morning out ahead of an approaching cold front. As this front begins to approach from the north later today we see the pressure gradient tighten. This will result in near SCA conditions this afternoon into tonight. Winds increase to 10-20 kt when coupled with typical thermal gradient. An infrequent gust to 25 kt is not entirely out of the question, mainly for soundside waters and coastal zones north of Hatteras, but probabilities are too low to warrant SCA headlines. With winds increasing seas will also build to 2-4 ft this evening. These elevated conditions will continue into Sat morning before gradually weakening as the front stalls and the pressure gradient relaxes some with winds falling to 5-15 kts and seas back down to 1-3 ft. Front will also bring an increased risk of showers and thunderstorms Fri afternoon into the late evening hours, a few storms could be strong and produce gusts over 35-40 kt.
A return to more benign boating conditions are then forecast Sat night into Sun as high pressure ridging builds into the area. Yet another front nears the area Mon into Tue bringing yet another low-end chance at SCA conditions and more widespread shower and thunderstorm activity.
Nc, heat advisory from 11 am this morning to 8 pm EDT this evening for ncz029-044>047-079>081-090>092-094-193>196-198-199- 203>205. Marine, none.
