Key MESSAGE 1, Notably warm low-level thicknesses amid westerly low- level flow should support another day of hot temperatures with highs topping out in the mid 90s inland and near 90 along the coast. The westerly flow will probably lead to a slightly drier airmass today, with dewpoints potentially mixing out into the upper 60s to lower 70s across parts of the coastal plain. Should this occur, the heat indices would tend to be capped a bit lower compared to areas closer to the coast where the inland-advancing seabreeze will keep dewpoints elevated. In light of this, a Heat Advisory remains in effect for a smaller portion of ENC where the risk of 105+ heat indices is the highest.
A southerly return flow develops tonight and then continues into Thursday. This should lead to rising dewpoints amid notably warm low- level thicknesses and anomalously warm highs (mid to upper 90s inland and low 90s along the coast). The combination of hot temperatures and rising dewpoints is expected to support a more expansive area of heat indices of 105+, and heat headlines are likely again on Thursday.
By the weekend, increased cloudcover and thunderstorm activity should help to hold temperatures and heat indices down. It will still be very humid, but the risk of 105+ heat indices looks lower.
KEY MESSAGE 2, A slightly drier airmass aloft, and perhaps a bit of subsidence, in the wake of the shortwave moving offshore this morning should help to limit convective coverage today. Late tonight, and especially on Thursday, moisture is forecast to begin to return to the area in earnest, with PWATs climbing back above 2". Deep southerly flow then continues into at least the first half of the weekend, keeping a deep layer of moisture in place across the eastern Carolinas.
At the surface, inland troughing and the seabreeze should initially be the focus for isolated to scattered convection on Thursday. By Thursday evening or Thursday night, a notable cold front will begin to encroach on the area from the NW. This may lead to an uptick in convective coverage during the evening hours, and potentially even lasting into Thursday night. Moderate to strong instability and steep low-level lapse rates should support a risk of strong to marginally severe thunderstorms with this initial activity. The risk of strong thunderstorms may last into Thursday evening, especially if a line of thunderstorms manages to make it to the coast.
On Friday, a shortwave and an associated SFC low are forecast to lift NE across the Carolinas and interact with the above- mentioned cold front amid a moderately unstable and moisture- rich environment. Synoptically, this is a favorable setup for widespread convection. Perhaps one important caveat is where the front stalls as this is where forcing and rainfall rates should be the strongest. Of note, southwesterly flow parallel to the stalled front adds increased confidence in training thunderstorms capable of flooding and the potential for a few instances of flash flooding. Forecast aids and ensemble guidance support the potential for heavy rain and flooding. Wpc has highlighted portions of the area in a Slight Risk of excessive rainfall. Additionally, with the front in the area, deep layer shear should get a boost, with a continued risk of strong to severe thunderstorms. Of note, machine learning and AI guidance favor Thursday over Friday for severe potential. Regardless, stay tuned as we continue to fine-tune where/when the greatest risk of severe weather and flooding will be.
Scattered to numerous thunderstorms may linger into Saturday depending on where the front is located and how much instability remains.
07z Wednesday through Sunday A weak area of low pressure is moving offshore at this time, with a light north to northeast flow ongoing in its wake. While the airmass is drying out some, there may be enough residual low-level moisture to support areas of low stratus or reduced VIS (BR/MIFG). It's possible that the drier air plus a slightly mixed airmass may limit how widespread of an aviation impact occurs with any stratus or reduced VIS. Stay tuned for updates/amendments through the night.
On Wednesday, the risk of TSRA looks lower (10-30%), and should be confined to the typical seabreeze favored areas.
Outlook: The risk of TSRA is expected to increase on Thursday, and remain elevated through at least Saturday. Periods of sub- VFR conditions in TSRA and low CIGs can be expected through the weekend.
A weak area of low pressure will continue to move through the central waters early this morning. Light northerly winds of 5-10kt will develop in the wake of the low. A relaxed gradient will then continue to support light winds and good boating conditions today. Southerly flow returns tonight for all waters. Seas of around 2 ft are expected through tonight.
Outlook: Building southerly flow is expected on Thursday, with winds of 10-20kt expected. Seas will respond and build to 2-3ft during this time. A cold front will then approach the waters Thursday night with an increased risk of thunderstorms and winds becoming northerly. The front is forecast to stall over the area, though, leading to southerly flow south of Cape Hatteras and northerly flow to the north. An increased risk of thunderstorms is expected to continue into Friday thanks to the front over the area. This risk may last into Saturday as well. Eventually, the front should move north out of the area with southerly flow dominating for all waters by Sunday.
Nc, heat advisory from 11 am this morning to 8 pm EDT this evening for ncz090-092-094-193>196-198-199. Marine, none.
