Key MESSAGE 1..Southerly onshore flow and a mix of high clouds and diurnal Cu will be the name of the game this afternoon as high pressure continues to shift further offshore. This mornings upper air sounding still shows pretty widespread dry air across ENC today so outside of some increasing cloud cover as moisture continues to advect in moistening up the atm profile, not expecting much in the way of rain this afternoon. Highs get into the low 90s to upper 80s inland and mid 80s along the coast and OBX today.
KEY MESSAGE 2, We enter into an unsettled pattern once again starting tonight into Sunday with daily chances for showers and thunderstorms into at least mid week. Upper level trough currently in the Midwest will dive SE'wards into the Tennessee River Valley Sun into Mon eventually stalling as an upper level ridge blocks this troughs forward progress. At the mid levels, will see multiple shortwaves round the base of this trough promoting periods of lift across ENC and the offshore waters with the first weak mid level shortwave tracking along the coast starting tonight into Sun morning with additional shortwaves coming in from the west Sun afternoon and again on Mon/Tue. At the surface, closed low in the Midwest will gradually shift E'wards into the Ohio River Valley with its associated surface front stalling just to the west. These features, in addition to the sea breeze each afternoon/evening, will be the main forcing present for a notable increase in precip chances.
Starting later tonight into Sun there will be two areas of focus for shower and thunderstorm activity. The first will be overnight into Sun morning along and behind a N'ward moving warm front/coastal trough with much of the activity occuring near and east of Hwy 17. We should still be too dry aloft inland as the boundary moves through, so thunder chances remain low inland Sun morning. Proximity to the gulf stream could allow isolated to scattered showers and thunderstorms to reach coastal communities south of Oregon Inlet. The second will be in the afternoon/evening with shower and thunderstorm activity coming in from the west associated with the stalling upper trough. Cloud cover will play a big role in how high instability can truly get, but with the dewpoints rising there should be enough instability entering the region for 1000-2000 J/kg of MLCAPE 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 and wet microbursts where storms develop. The best coverage is expected to be to our west closer to I-95, with more isolated to scattered coverage across the Coastal Plain but will continue to monitor trends in the CAM guidance and adjust PoPs accordingly.
Monday the trough will remain stalled to our west and gradually weaken. This reduces the potential for height falls over the region despite the trough creeping a bit closer. Still, we should see embedded shortwaves moving through aloft. Slightly better forcing, paired with another day of long skinny CAPEs and PWATs north of 2" brings higher precip chances compared to Sunday with heavy rainfall rates, a low end wet microburst threat, and slow storm motion vectors. 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 and Monday with best chances at seeing flash flooding likely along Hwy 17 and points east. What prevents it from being higher is 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 Monday, 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 with a low end risk for flash flooding. By the end of the week it looks like we return back to climo or below climo PoPs as a lack of mid level shortwaves or significant forcing will be noted across ENC though we do begin to warm back up with temps returning to the upper 80s to low 90s inland and mid 80s along the OBX.
00z Sunday through Thursday VFR conditions will prevail through much of the TAF period, however there will be opportunities for sub-VFR conditions at times. A wetter pattern will begin to develop late tonight into Sunday bringing an increased chance showers that could bring occasional sub-VFR conditions to the terminals. Initially, coastal sections will have the better chance for showers with onshore flow, then will expand inland through the day Sunday. May also see a period of MVFR cigs as the LCL's rise from around daybreak through the morning hours with highest probs across western rtes. Southerly flow will also increase Sunday with gusts around 20-25 kt during the afternoon.
Outlook (Sunday night through Thursday): Periods of sub-VFR ceilings/vis are possible Sun night into early next week as ENC enters into a more unsettled period of weather with daily chances for showers and thunderstorms with a stalled upper trough off to the west. Precip chances and thus the threat for sub-VFR conditions look to decrease beyond Wed.
Biggest chance on this update was the inclusion of small craft advisories starting on Sunday across all near shore coastal waters and inland waters. Ongoing 5-10 kt S-SE'rly winds with gusts up to 15 kts will continue into tonight with winds becoming more S-SW'rly and increasing to 15-25 kts with gusts up to 25-30 kts late Sun morning into Sun afternoon. In response to the strengthening winds Sun, expect ongoing 1-3 ft seas across our coastal waters to build late Sun morning to 4-8 ft by Sun evening, thus resulting in widespread SCA conditions. In addition to this as a weak warm front/ coastal trough lifts north across the area increasing shower and thunderstorm chances are likely starting from south to north Sun morning and persisting into the end of the period.
Outlook (Sunday night through Thursday): Southerly winds remain elevated into Monday before gradually decreasing Mon afternoon and evening keeping SCA in place. Winds will ease first across the inland waters and N'rn sounds thus ending SCA's by Mon morning here with SCA's ending across the coastal waters south of Oregon Inlet by Mon evening. Expect more benign winds and seas from Tue onwards as weak high pressure builds over the area. In addition to the above, elevated chances for showers and thunderstorms will remain possible into midweek.
Nc, beach hazards statement through Sunday evening for ncz195-196- 199-204-205. Marine, small craft advisory from 2 pm Sunday to 8 pm EDT Monday for amz131-150-230-231. Small craft advisory from noon Sunday to 8 pm EDT Monday for amz135. Small craft advisory from 2 pm to 8 pm EDT Sunday for amz136- 137. Small craft advisory from 11 am Sunday to 11 pm EDT Monday for amz152-154-156-158.
