Key MESSAGE 1, A plume of tropical moisture characterized by 2"+ PWATs and dewpoints in the 70s is forecast to get pulled north through the southeastern CONUS over the weekend to the east of the northward-advancing remnants of TC Isaias. At the surface, a warm front/coastal trough will trudge north along the southeastern coastline, likely with a weak, non-tropical area of low pressure developing along it. Along and ahead of the warm front, a strong southeasterly LLJ will develop, supporting increasing WAA and moisture transport into the area with a shield of moderate to heavy rain developing across the coastal Carolinas. Along and just behind the warm front, the precip will likely become more banded and contain some embedded convective elements with very heavy rain. It's these bands that will pose the greatest risk of flooding. The time period of most concern for these heavy rates and flooding potential are overnight tonight into early Sun morning. Convective guidance suggests rainfall amounts as high as 4-6"+ are possible if those bands manage to reach the coast. As is often the case with convection nearing the coast, whether some of the moisture transport will be cutoff by strong convection over the Gulf Stream is in question. If this happens, amounts would be quite a bit less for areas outside of the coastal waters. 10/00z REFS LPPM continues to show amounts in the 3-6+" range possible for the immediate coast and OBX zones. Will continue Flood Watch for areas along the coast, effective later this afternoon through early Sun afternoon.
KEY MESSAGE 2, Possibility of convective elements reaching the coast would warrant a tornado risk later this evening as the aforementioned warm front lifts through ENC. Plenty of low level helicity in place with the inc serly flow in place and strong veering wind profile downstairs. The greatest tor threat would likely be focused near the srn/sern coast where better instability advects onshore. For Sunday, flow becomes more unidirectional with swrly low level winds ensuing during the afternoon. While helicity wanes, better instability will be in place due to daytime highs expected in the low 80s and TD's in the 70s. Will have to watch for continued severe threat Sunday afternoon ahead of the cold front, esp if there are some breaks in the cloud cover.
The remnants of Isaias are forecast to round the upper level ridge and move off the Northern Mid-Atlantic Coast early next week. Drier air then moves in behind it with drying conditions developing Sun night into Mon.
KEY MESSAGE 3, Strengthening onshore winds, building seas, and higher than normal astronomical tides may support some coastal impacts this weekend. There remains uncertainty on the magnitude of impacts, especially given the shorter-duration of the stronger winds, as well as what should be a weaker swell compared to the recent Nor'easter. With that in mind, there will be an increased risk of rip currents and large waves, at a minimum. High Surf Advisory remains in effect between Ocracoke and Oregon Inlets focused overnight into Sunday. Additionally, some of the most vulnerable locations along the Outer Banks may see at least some minor issues, especially with Sunday morning's high tide (7-9am). There may also be some minor coastal flooding around sounds and tidal waterways around the Crystal Coast due to the higher astronomical tides.
06z Saturday through Wednesday Forecast confidence is moderate to high over the next 24 hours.
VFR conditions currently across the terminals early this morning, with widespread mid clouds blanketing the area. Clouds will steadily lower through the day as low- mid level moisture advection increases. Expect MVFR to develop mid morning to afternoon, then IFR late afternoon and evening. Guidance continues to differ quite a bit regarding the timing of lower cigs. Light rain this morning, becoming more widespread, heavy at times expected this afternoon into tonight, with potential for embedded storms esp along the coast tonight. The gradient will begin to strengthen as a frontal zone strengthens to the south of ENC. It's expected that this will lead to increasing east winds, with gusts of 20-30kt likely today.
Outlook (Sun through Wed): Widespread rain, heavy at times, and gusty nerly to erly winds along with likely IFR conditions will continue through the first part of Sunday, with potential for embedded TSRA. Clearing conditions expected Sunday night into Monday but with gusty wrly to nwerly winds behind it.
Latest obs show NE-E winds 5-15 kt with seas 2-4 ft. Conditions will quickly deteriorate this morning and through the day. Nerly gradient strengthens through the day, with winds ramping up to gales 20-30 kt gusting 30-35 kt later in the afternoon from S to N across the coastal waters. For the sounds and rivers, SCA winds develop with these nerly pinched gradient winds. Seas will peak at 7-11 ft tonight. East winds will grad weaken from south to north overnight and early Sun, grad veering. Gales remain for the outer waters with this swrly flow on Sunday. For the rivers and sounds, winds should remain in the strong SCA range with speeds of 20-30 kt expected.
Outlook (Sun through Wed): Strong winds will turn further to the s and SW Sun. Gales remain for the outer waters with this swrly flow on Sunday. For the rivers and sounds, winds should remain in the strong SCA range with speeds of 20-30 kt expected. In addition to the winds, nearshore seas are expected to peak in the 6-10ft range at 7-8s. For the outer coastal waters, seas may reach 8-11ft.
Thunderstorms capable of strong winds and waterspouts will be possible as well, mainly overnight into Sunday. Conditions gradually improve by Sun evening with clearing returning by Monday morning as high pressure begins to build in.
Nc, flood watch from 2 pm EDT this afternoon through Sunday afternoon for ncz047-081-092-094-194>196-198-199-203>205. Beach hazards statement from 8 am EDT this morning through this evening for ncz195-196-199-203>205. High surf advisory from 8 pm this evening to 8 pm EDT Sunday for ncz204-205. Marine, small craft advisory from 2 pm this afternoon to midnight EDT Sunday night for amz135. Small craft advisory from 2 pm this afternoon to 2 am EDT Sunday for amz136-137. Gale warning from midnight tonight to noon EDT Sunday for amz150-180. Gale warning from 6 pm this evening to 2 am EDT Sunday for amz152-154. Gale warning from 2 pm this afternoon to midnight EDT tonight for amz156-158-186-188. Gale warning from 6 pm this evening to 2 pm EDT Sunday for amz182-184. Small craft advisory from 5 pm this afternoon to 8 pm EDT Sunday for amz230-231.
