Key MESSAGE 1, While a warming trend is still expected through this weekend, elevated smoke from Canadian wildfires has complicated the temperature forecast. The smoke, while elevated, was thick enough to reduce daytime heating and keep temperatures lower than originally anticipated. Available smoke guidance suggests this smoke layer will shift north into Virginia today, then 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. Even so, given some uncertainty on where the smoke will be, we opted to go below blended guidance for highs today to reflect the potential for temps to be muted some. If the smoke does, indeed, fill back in from the north on Friday, then temperatures would likely be even more impacted then compared to today. 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. For today, the potential impact from smoke plus afternoon mixing out of lower dewpoints should be enough of a limiting factor to keep the risk of 105+ heat indices lower. For this reason, no heat headlines have been issued for today. If the smoke ends up having less of an impact today, then heat indices would likely be higher. It looks marginal for heat headlines today either way. On Friday, a moistening southerly flow should lead to higher dewpoints. Even with muted afternoon heating, the temp/dewpoint combo appears more supportive of heat headlines compared to today. This is something we'll continue to monitor in the coming days. It could be that the risk of dangerous heat is delayed until Saturday, assuming the layer of smoke moves out by then.
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.
07z Thursday through Monday VFR conditions are expected to prevail for much, of not all, of the next 24 hours. It's possible there will be some BR/MIFG overnight, but temp/dewpoint depressions aren't as low, and the overall airmass is notably dry for this time of year. We'll continue to monitor trends overnight, but the risk of VIS reductions appears to be lower than this time 24 hours ago.
During the day Thursday, TSRA are not expected, but the seabreeze will move through KOAJ and KEWN with a bump up in winds (perhaps gusting to 20kt at times). Additionally, there is an elevated layer of smoke from Canadian wildfires that is meandering around the region. Guidance suggests this should remain elevated and not work down to the surface through Thursday night.
Outlook (Friday through Monday): Guidance suggests smoke from Canadian wildfires may try to work down to the surface Friday or Friday night with reductions to VIS possible. It's unclear whether or not smoke impacts will last beyond Friday. Otherwise, the risk of TSRA is expected to slowly increase Friday and Saturday, becoming more likely from Sunday into early next week. Sub-VFR conditions can be expected along with the TSRA impacts.
Modest southwesterly winds of 10-15kt are expected later today through tonight along with 2-3ft seas. 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 through Monday): 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.
