Key MESSAGE 1, Thunderstorm activity has greatly diminished over the past 1-2 hours, with the last remaining activity pushing through Pitt and Martin Counties. Despite some decent cores recently, weakening low-level lapse rates and increasing CIN should support a reduced risk of severe weather the remainder of the evening. Additionally, given how much the airmass has been worked over by previous convection, the risk of thunderstorms now appears lower overnight that previously thought, and the forecast has been updated to reflect this expectation.
PREVIOUS DISCUSSION: An active precip pattern persists into Wed as a series of shortwaves, inland troughing, and a very slow moving backdoor front will converge to produce higher than climo coverage of showers and storms each afternoon to early evening. Guidance continues to suggest PoPs remain around the 50-80% range each afternoon and evening. While PoP's will be higher than they have been the past several days, precip will certainly be very hit or miss across ENC, but much welcome none the less.
Have seen PWATS jump to 2+ inches across ENC today with this very moist airmass remaining in place over the next few days. Combined with ample heating across ENC, instability will rapidly build each day with MLCAPE values generally expected to be between 2000-3000+ J/kg each afternoon. While instability will certainly be plentiful, deep layer shear will not be, as wind shear struggles to get above 25 kts. This will likely limit any significant storm organization over the next few days but cannot rule out some wet microbursts or stronger winds (40-60 mph) within the strongest storms along the aforementioned seabreeze and surface trough. Because of this, SPC has outlined a good portion of ENC in a Marginal Risk (1/5) of severe tstorms tomorrow. Another round of decent covg of afternoon showers/storms possible Wed as the aforementioned boundaries may still be in place. In addition to the severe threat today and tomorrow, there will also be a heavy rain threat with any thunderstorm that develops as well given the high PWAT's (2" +) and slow storm motions which could lead to some localized flooding mainly in poor drainage and urban areas. As a result WPC also has much of the area under a marginal risk for excessive rainfall over the next two days as well.
Beyond mid week, PoPs return back to climo (20-40%) as more typical seabreeze showers/storms return. Hts/thicknesses slowly build in the process as ridging begins to build once again, with heat indices 100-105 in the forecast.
KEY MESSAGE 2, Aforementioned ridging builds mid to late week into the weekend, as ensemble mean heights rise back to above normal, and forecast temps reach well into the 90s, pushing heat indices to potentially at or above 105F again as a very humid atmosphere will be in place as well. Efi for both Min/MaxTs are pushing into the 80th percentile esp late in the week.
KEY MESSAGE 3, With the aforementioned high heat and humidity expected, a very unstable atmosphere develops per med range guidance hinting at ML CAPES aoa 3.5k J/KG, and SFC based instability between 4-5k J/KG. As is typical this time of year, deep layer shear will not be too strong, but any storms that can develop with some upper level support could produce strong downdraft/microburst winds and very heavy rain characterized by PW's exceeding 2".
00z Tuesday through Saturday TSRA activity is finally winding down across ENC, with the last remaining activity focused around KPGV. Given how widespread the TSRA were earlier today, it now appears the airmass will be less supportive of TSRA overnight. The risk of TSRA is then expected to increase again on Tuesday, especially after 16z. Any TSRA that develop on Tuesday will be capable of 30-45kt winds and significant reductions to VIS.
With much of the area receiving rain earlier today, the ground will be very moist. Light winds plus the moist ground/near surface layer may support a period of reduced VIS due to BR/MIFG/FG. Given the expected conditions, the potential exists for a deeper, more impactful FG to develop with IFR/LIFR conditions. For now, the TAFs reflect the most likely scenario (MVFR VIS), but just be aware of a reasonable worst case scenario of lower conditions.
Outlook (Tue through Fri): Shortwave energy tracking cross the region into midweek brings good chances for showers and thunderstorms and potential for sub-VFR conditions into Tue, possibly into Wed as well. Beyond mid week, more typical iso to widely sct activity expected as ridging rebuilds into ENC.
Steady 10-15 kt SW'rly winds with gusts up around 15-20 kts is noted across our waters this afternoon while seas along the coastal waters remain around 2-4 ft. These conditions should continue to persist today as Bermuda high remains offshore and a front slowly begins to approach. As this front begins to get a little closer tonight winds especially across the Pamlico Sound and coastal waters south of Oregon inlet should increase slightly with gusts up to 25 kts possible across the aforementioned waters. As a result have kept the SCA's up across these waters starting around 10PM tonight and persisting into Tue morning. Seas will also build to about 3-5 ft during this timeframe with some 6 ft seas possible 20+ NM away from shore.
Outlook (Tue through Fri): The gradient relaxes Tue morning with winds returning to 5-15 kt. Weakening front moves into the waters on Wed, though as is typical in July, the front appears to wash out, with any N'rly flow behind it short lived with return flow developing as early as Wed evening. Sw'rly winds look to strengthen some on Fri as a thermal trough strengthens across the area bringing our next potential threat for SCA's to the waters.
Nc, none. Marine, small craft advisory until 8 am EDT Tuesday for amz135-156-158. Small craft advisory from midnight tonight to 8 am EDT Tuesday for amz152-154.
