Key MESSAGE 1, A notable upper level ridge, currently centered over the Midwest, will shift east this week with anomalous heights overspreading the Mid-Atlantic and Carolinas. Beneath the ridge, an expansive area of anomalously warm low-level thicknesses are forecast to reside across the Southeast U.S., with 850mb temperatures reaching around 20C. Meanwhile, southerly flow will help hold dewpoints in the 70s most days, especially Wednesday through Friday. The combination of highs in the 90s and dewpoints in the 70s will make it feel like 100 to 110 degrees during that time. Forecast aids like the ECMWF's EFI show an impressive signal for anomalous heat mid to late-week, adding confidence to the impact. Lastly, the NWS' experimental Heat Risk puts most of ENC in the "Major" impact category. Bottom line, it will be dangerously hot and humid for much of the upcoming week, with impacts expected to peak Wednesday- Friday.
Assuming the forecast holds, heat headlines will likely be needed for portions of the area. To give some context to the anomaly of this incoming heat wave, heat headlines a fairly rare this late in the season. Since 2005, heat headlines have been issued in September only once (2020). If dewpoints mix out some, then heat indices may not get as high, despite the anomalous temps. Based on the latest guidance, though, headlines appear likely.
KEY MESSAGE 2, A strong cold front is forecast to move through the Carolinas Friday night or Saturday. At minimum, this will knock down the heat, bringing a refreshing break from the anomalous heat and humidity. Additionally, guidance show a decent signal for convection with the front. Synoptically, the setup appears favorable for strong to severe thunderstorms depending on the timing of the passage of the front. Machine learning guidance shows a decent signal for this potential as well. From a probabilistic standpoint, the risk appears to be the highest on Saturday.
Behind the front, highs are forecast to drop back down into the 80s, with lows in the 60s. Adding to this will be dewpoints falling back into the 50s and 60s making it feel more comfortable.
18z Monday through Saturday Forecast confidence is moderate to high over the next 24 hours.
The seabreeze is expected to be more muted today, with a much lower risk of TSRA compared to yesterday. For this reason, I kept TSRA out of all TAF sites for the remainder of the afternoon. Vfr conditions are expected to prevail through this evening. Then, later tonight into early Tuesday morning, guidance shows a moderate signal for sub- VFR VIS due to BR/MIFG. In light of this, I added MVFR conditions for KOAJ and KEWN where confidence in highest. All TAF sites may see reduced VIS, but the signal in guidance isn't quite as strong inland as it is closer to the coast. Dry conditions and a continued reduction in TSRA is expected on Tuesday.
NOTE: AMD NOT SKED has been appended to the EWN TAFs as the site is not transmitting through normal channels. The site is still reporting via telephone so it will be monitored, but not as frequently as when it is completely operational. The next closest ASOS is at Cherry Point (KNKT).
Outlook: Mostly VFR conditions are expected through the end of the week along with a reduced risk of TSRA. Occasional sub-VFR conditions may occur during the early morning hours in BR/MIFG each day.
Good boating conditions are ongoing at this time with winds around 5- 10kt and seas of 1-2ft. These conditions are expected to continue through Tuesday morning. By Tuesday afternoon, a strengthening thermal gradient should lead to southwesterly winds building to 10- 15kt, with seas building to 2-3ft.
The risk of thunderstorms looks very low (<10% chance) through Tuesday afternoon for most waters. The one exception is the far outer central and southern waters along the Gulf Stream, where scattered thunderstorms will continue to be a risk.
Outlook: Generally good boating conditions are expected through Friday. It will be breezy each afternoon and evening with the diurnal max of the thermal gradient, and some waters may come close to 25kt at times, especially Thursday and Friday. Over the weekend, a strong cold front is forecast to move through with a chance of thunderstorms and winds flipping around to northeasterly.
Nc, none. Marine, none.
