Key MESSAGE 1, Latest surface analysis this hour shows stalled frontal boundary draped from roughly Wilmington northward to along the I-95 corridor with high pressure centered off the coast of New England extending along the mid- Atlantic coast. The boundary is forecast to gradually lift north and eastward later this afternoon in response to a mid-level shortwave forecast to track across the mid-Atlantic. Ongoing convection has likely abated peak heating and will keep highs at or slightly below 90, capping heat indices at 100-105.
Tomorrow is a different story with the frontal boundary fully lifted into the mid-Atlantic and thicknesses soaring back to 1435-1440+ m, setting the stage for highs in the mid to upper 90s inland assuming relatively clear skies to start the day. The level of humidity is the main point of uncertainty as surface winds will be WNW to NW, suggesting downsloping and Tds trending lower than model consensus. If this does occur, HI values will almost certainly still reach between 105-110 F. For that reason, issued a Heat Advisory for tomorrow across all inland zones. A short-fused upgrade to Extreme Heat Warnings, however is not out of the question overnight mainly along the southern coast where the sea breeze will boost dew points.
Another frontal boundary quickly pushes across NC tomorrow evening before stalling along the coast. Like this weekend, southern counties will likely remain hot and humid while Albemarle and vicinity see some modest relief. A more widespread cooldown, however, is on the horizon late week as a stronger cold front dives out of Canada and across the eastern CONUS.
KEY MESSAGE 2, Regional radar this evening shows clusters of strong to severe thunderstorms ongoing from West Virginia into Virginia. The airmass downstream of these clusters still appears at least modestly supportive of severe thunderstorms. However, as we move further into the night, a stabilizing boundary layer should lead to a lowering severe risk as the convection approaches SE Virginia and NE North Carolina. The forecast will remain unchanged through the night, but the key message for the rest of the night is a reduced risk of severe weather.
A cold front then approaches from the north and west tomorrow evening. Aforementioned heat and humidity will easily boost instability with a forecast 1500-2500 J/kg of MLCAPE, but shear will once again be lacking at generally 20 kt or less. However, with PWATs remaining at or above 2" conditions will once again be favorable for a stronger storm or two to impact the area bringing a damaging wind, frequent lightning, and torrential rain threat. Convective evolution will not be terribly different from the past couple of days, with an afternoon focus along sea and sound breezes and then upstream convection along remnant differential heating boundaries inland, and then an evening focus as a potentially more organized complex pushes across the state through the evening hours - this, like tonight, would pose the higher severe threat with damaging winds. Ai NWP guidance has elevated probabilities, which are plausible since northwest flow events tend to overperform across eastern NC.
KEY MESSAGE 3, A brief return to more climo PoPs is forecast Tue and Wed with the seabreeze and stalled front offshore being the main focus for showers and thunderstorms. Stronger front is likely to approach the region and stall late week, serving to both offer a reprieve from oppressive heat and humidity, and a chance of strong to severe thunderstorms as shear increases alongside the boundary with stronger troughing. Given how far out this is, there are still several details to hammer out but will be monitoring trends in the forecast for any adjustments in timing and strength of this front in the coming days.
00z Monday through Friday SHRA and TSRA from earlier in the evening have weakened considerably, with only a few LTG strikes noted between KISO and KPGV. Given this trend, TSRA have been removed from all TAF sites for the remainder of the night. Overnight into early Monday morning, guidance suggests MVFR CIGs may develop. However, the probability of this occurring is only around 20-40%. Therefore, the TAFs will only show a SCT015 layer to highlight the potential.
During the day on Monday, a southwest to west-southwest wind will develop. Slightly drier air and weak lift should keep the TSRA risk low for much of the day. The risk then looks to increase during the evening hours as a cold front approaches from the west.
Outlook (Monday night through Friday): A more widespread threat of sub-VFR conditions is possible Monday night into Tuesday ahead of the next front before VFR conditions return Tue into Wed. Yet another front begins to approach from the west later in the week once again bringing increased shower and thunderstorm risks as well as increasing risks for sub-VFR conditions.
Benign boating conditions expected the rest of evening. Southwest flow will strengthen with tightening thermal gradient in the afternoon Monday, and we may see some infrequent gusts to 25 kt across sounds and near-shore waters. Seas likely climb up to 4 feet briefly tomorrow aft and evening. Additional showers and thunderstorms likely overnight Mon as front approaches waters.
Outlook (Monday night through Friday): Benign boating conditions continue Tues and Wed with eyes to next potential SCA late next week with a stronger frontal boundary. Each day will bring a low to moderate risk (20-40%) of showers and thunderstorms to area waters.
Nc, heat advisory from 11 am to 8 pm EDT Monday for ncz029-044>047- 079>081-090>092-094-193>196-198-199-203>205. Marine, none.
