Key MESSAGE 1, High pressure continues to keep enough dry air in place and subsidence aloft to preclude a rain threat through Saturday outside maybe a stray, short lived seabreeze shower. In fact, the 7/31 00Z KMHX sounding had PWATs of around 1", which is climatologically near the 10th percentile for the time of the year. Light winds and seasonable temps again today, with light westerly winds become southerly behind the sea breeze. Temps near 90s inland, mid 80s along the coast. High gradually shifts offshore tonight, with the return of synoptically southerly flow Saturday. With the onshore flow, atmospheric profile gradually moistens, but given how dry we are the moisture will not rebound fast enough for an appreciable rain chance Saturday. Despite the low chances for rain Saturday, we should see an increase in cloud cover, which will keep temps Saturday similar to today (near 90 inland, mid 80s along the coast) despite the southerly flow.
Despite the calm winds and mostly clear skies paired with recent rainfall, the subsidence should be strong enough to prevent impactful fog formation this morning and Saturday morning.
KEY MESSAGE 2, Sunday morning an upper trough will be deepening over the Ohio Valley as it moves towards the eastern seaboard, while at the surface an associated closed low is expected to traverse the Great Lakes region. As these features move east, they will encounter the Bermuda high and the upper trough over the Ohio Valley is expected to stall before reaching the eastern seaboard. While the main trough stalls, embedded shortwaves rounding the base of the trough may advect into the region Sunday through at least Monday. These features, in addition to the sea breeze each afternoon/evening, will be the main forcing present for a notable increase in precip chances.
Sunday morning the warm front will be moving through, with maybe some more stratiform along it and dewpoints increasing behind it. As the day progresses and the profile moistens, the environment becomes more favorable for more robust convection to occur. In the afternoon/evening hours, we could see enough recovery paired with forcing aloft for showers and thunderstorms. Cloud cover will play a big role in how large CAPEs can truly get, but with the dewpoints rising there should be enough instability entering the region for CAPE values of 1000-2000 J/kg Sunday. While shear is not too impressive with the unidirectional SE flow, the combination of long, skinny CAPEs, PWATs over 2", and slow storm motions could result in heavy rainfall rates. Where storms develop. Precip coverage Sunday is expected to be more scattered in nature with two foci for convection. First is along the coast where showers can tap into Gulf Stream instability throughout the day along and behind the warm front, and second is in the afternoon/evening hours along the Coastal Plain west of hwy 17 where forcing is a bit better thanks to closer proximity to the trough.
Monday the trough is still stalled to our west, but is just a little bit closer allowing for weak height falls and weak embedded shortwaves to move through aloft. This better forcing, paired with another day of long skinny CAPEs and PWATs north of 2" brings high precip chances with heavy rainfall rates and slow storm motion vectors. The better forcing likely brings with it better coverage of precip. All this brings flash flooding concerns to mind, especially with how much rain has been observed in many locations in the past 1-2 weeks. We are currently in a Marginal (level 1/5) Excessive Rain Outlook for Sunday. What prevents it from being higher is likely the uncertainty on instability with antecedent cloud cover and the lack of substantial ground-level forcing. With high temps forecast to only be in the low to mid 80s Sunday, the sea breeze may be weak in nature.
Beyond Monday, the trough/low is still expected to linger to our west until eventually it gets picked up and shifted to our north by another trough moving through the Great Lakes region. As a result, daily elevated precip chances continue through mid-week.
06z Friday through Tuesday Pred VFR conditions expected through the TAF period with mainly diurnal Cu through peak heating. Given calm winds and clear skies overnight, cannot completely rule out patchy shallow ground fog but given a very dry airmass just above the surface, any impacts will be minimal. Href and REFS probs are less than 15 percent for vsbys less than 5SM. Winds remain light today, less than 10 kt, with the sea breeze pushing inland during the afternoon.
Outlook (Friday night through Tuesday): It remains dry with primarily VFR conditions forecast tonight through Sat as high pres builds overhead and eventually pushes offshore. Periods of shallow early morning fog and/or stratus possible Friday and Saturday nights. Periods of sub- VFR may develop Sun into early next week with with a warm front moving through.
Benign boating conditions are noted across our area waters early this morning as high pressure continues to build in from the north and west bringing widespread 5-10 kt winds coming from the west and 2-3 ft seas to ENC. Expect winds to remain light through today remaining around 5-10 kts while seas across our offshore waters remain around 2-3 ft with dry conditions forecast. Flow becomes more southerly tonight and remains around 5-10 kts as high shifts offshore.
Outlook (Saturday through Tue): Southerly flow continues through Sat with seas persisting at 2-3 ft as high pressure pushes offshore. Southerly winds will strengthen Sunday to 15-25 kts with gusts up to 25-30 kts across ahead of an approaching front. Seas will also respond building closer to 4-7 ft across the coastal waters bringing an increasing chance of SCA conditions to much of our waters (outside maybe inland rivers) Sun into Mon. In addition to this, increasing chances for showers and thunderstorms will be possible as well starting Sun. Winds/seas begin to ease later Mon into Tue with weak high pressure building overhead and aforementioned front dissipating to the west.
Nc, none. Marine, none.
