Key MESSAGE 1, While a warming trend is still expected through this weekend, elevated smoke from Canadian wildfires continues to complicate the temperature forecast. Available smoke guidance suggests this smoke layer mainly over Virginia, will sink back south into North Carolina on Friday. In fact, guidance suggests the layer of smoke may lower closer to the surface and lead to some reductions to visibility, especially across northern sections of ENC. Yesterday we saw a sharp gradient in temperatures for areas underneath the smoke compared to areas with full sunshine. It appears that gradient will be over ENC today, with temperatures most impacted across Virginia. If the smoke does, indeed, fill back in from the north on Friday, then temperatures would likely be impacted. For now, we have also gone below blended guidance for highs on Friday.
The uncertainties with temperatures also complicates the decision to issue heat headlines or not.The potential impact from smoke plus afternoon mixing out of lower dewpoints could be enough of a limiting factor to keep the risk of 105+ heat indices lower Friday. If the smoke ends up having less of an impact, then heat indices would likely be higher. Moistening southerly flow should lead to higher dewpoints Friday. Even with muted afternoon heating, the temp/dewpoint combo appears more supportive of heat headlines compared to today. Will hold off for now, but a Heat Advisory may be needed for Friday and again Saturday.
KEY MESSAGE 2, There are several factors expected to support an increasingly active pattern from the weekend into next week, but also with some important considerations.
Upper level troughing is forecast to develop across the Eastern U.S. With ridging shifting away from the area. The lack of subsidence, alone, can help support a more active pattern. Additionally, persistent southerly flow east of the trough, potentially with a subtropical connection, should act to enhance low-mid level moisture across the area. Meanwhile, heating of a moistening boundary layer should lead to sufficient instability and reduced inhibition in support of periods of convection.
At the surface, lee-side troughing and, eventually, a frontal boundary should provide areas of enhanced low-level forcing. Additionally, while guidance remains mixed, there is a modest signal for low pressure development across the northeastern Gulf. Whether this obtains tropical characteristics or not, it could act to enhance rainfall along the Southeast U.S. Coast if it ends up getting pulled north ahead of the above-mentioned upper trough. Not all guidance show this, though, as some ensemble members take the low west across the northern Gulf Coast. The National Hurricane Center has maintained a 20% probability of development over the next 7 days, and it is something we will be monitoring through the weekend and into next week.
Tropics aside, deterministic and machine learning guidance continue to show a good signal for some strong to marginally severe thunderstorm potential during this period of active weather. Right now the signal is the strongest on Sunday. Given increased forcing and the potential tap of subtropical moisture, heavy rain and some hydro impacts may eventually be realized.
18z Thursday through Tuesday VFR conditions are expected to prevail through the period. There remains an elevated layer of smoke from Canadian wildfires that is meandering around the region. Guidance suggests this should remain elevated and not impact VIS through Friday.
Outlook (Friday night through Tuesday): Guidance suggests smoke from Canadian wildfires may try to work down to the surface Friday night with reductions to VIS possible. It's unclear whether or not smoke impacts will last into the weekend. Otherwise, the risk of TSRA is expected to slowly increase Saturday night, becoming more likely from Sunday into early next week. Sub-VFR conditions can be expected along with the TSRA impacts.
Latest obs show light to moderate SW winds 5-15 kt with seas around 2 ft. Winds will pick up to 10-15 kt this afternoon and evening with seas building to 2-3 ft. Similar conditions are expected on Friday. The one difference is for the northern waters. A slowing front is forecast to move into those waters Friday afternoon with winds becoming southeast or east for several hours. Eventually, southerly flow will return for all waters Friday night as that front lifts back north.
Outlook (Friday night through Tuesday): Southwesterly winds are seas are expected to build to 20-30kt over the weekend as the gradient sharpens in advance of another front approaching the region. Over the outer coastal waters, frequent gale-force gusts appear possible for several hours Saturday night into Sunday morning. It may not quite reach the threshold for a Gale Warning there, but the increased winds are notable. Seas will quickly respond to the winds, building to 4-7ft by Saturday night. Elevated winds and seas are expected to last into early next week for the nearshore coastal waters. For the outer waters, elevated winds and seas may last for much of the week.
Nc, none. Marine, none.
