Marine Weather and Tide Forecast for Nags Head, NC

KEY MESSAGES
1) Thunderstorm risk remain today with marginal severe threat this afternoon and again on Sunday. Rainfall chances linger through the week.

2) Heat Advisory remains in effect south of Highway 70 this afternoon. Potential for hazardous heat remains late next week.

DISCUSSION
KEY MESSAGE 1...Another hot day today with temps ranging from the mid 80s to the mid 90s, with the warmest temps noted along and south of Hwy 70 as a stalled front front is located from W-E along the Hwy 70 corridor this afternoon. This front is forecast to gradually lift N as a warm front later tonight.

Otherwise latest surface analysis depicts agitated Cu field developing along the seabreeze today with much of the area under a moist and unstable environment. The seabreeze will continue to push further into the coastal plain as the day wears on and be the focus for shower and thunderstorm activity this afternoon, with a few storms potentially becoming strong to severe in nature. With MLCAPE values around 1000-1500 J/kg, DCAPE values above 1000 J/kg, and decent mid level lapse rates (around 5.5-6.5 C/km) quickly developing updrafts are forecast today. Combined with PWATS generally around 2" today, this environment would promote a threat for strong and damaging downburst winds (40-60 mph), frequent lightning, and heavy rain within the strongest storms. SPC has also highlighted the seabreeze corridor (SW of mainland Hyde/Dare Counties) with a marginal risk (level 1/5) for severe weather today. This thunderstorm risk continues into this evening before waning with the loss of daytime heating. Do expect a quieter night tonight thunderstorm wise with the potential for some mid and low level stratus to develop depending on the exact evolution of the seabreeze activity today. Lows get into the mid 70s tonight not providing much relief from the heat.

Synoptic pattern will remain rather active over the next few days with daily chances for convection across ENC Sunday and into early next week with multiple fronts crossing the FA into midweek. This occurs in conjunction when troughing aloft develops, opening moisture transport from the Gulf. However, this shouldn't be read as a high coverage of thunderstorms each day. On Sunday, prefrontal trough develops around the coastal plain providing the necessary focus for shower and thunderstorm development Sun afternoon and evening. Activity likely starts off to the north and west and progresses E'wards as the afternoon wears on. With strong instability forecast to be in place (MLCAPE 1500-2500 J/kg) and increase shear with values closer to 25-35 kts a few of these storms could become strong to severe in nature with the strongest activity likely noted along our northern tier. Damaging wind gusts would be the primary hazard within the strongest storms. SPC has the far northern section of our FA in a Slight (Level 2/5) risk of severe thunderstorms. This strong to severe thunderstorm risk then looks to continue into Sun night and Mon morning as a cold front approaches from the west and may reinvigorate thunderstorm activity especially near the coast and offshore where highest instability will be noted.

Early next week, higher than climo shower and storm chances are in the forecast with the greater moisture content through the column leading to PWATs in excess of 2". Additionally, deep layer shear of around 30-35kt with weak cyclogenesis along another front set to approach and stall over the area Mon may support a modest increase in the potential for organized convection, some of which could be on the strong side. The last of a series of fronts finally pushes off the coast by midweek allowing for lower precip chances outside of a daily seabreeze. We will be monitoring the approach of yet another front late next week as well.

KEY MESSAGE 2... No real change to the long term as more climo high and low temps mainly due to cloud cover/tstm activity will persist into midweek. However, as we get into Thurs/Fri next week heat and humidity look to increase once again which could bring the potential for hazardous heat indices and related health impacts.
Probabilistic heat risk guidance suggests a 50-70% chance at reaching major level heat risk thresholds on Thurs/Fri which is a slight increase in the threat as compared to yesterday. Those that are sensitive to heat should continue to monitor the forecast over the next few days to see how things continue to trend and take proper precautions if needed. In addition to this, guidance continues to suggest an abnormally strong low, (with a surface pressure currently forecast to be about 2-3 standard deviations below the mean for the time of year), will develop in the Plains around midweek and push NE'wards on Thurs/Fri into the Great Lakes vicinity with its associated front approaching from the west at the same time late next week.
Combined with high pressure ridge centered across the Atlantic the pressure gradient will tighten quite a bit resulting in the potential for anonymously windy conditions as well if current trends hold. ECMWF EFI for wind gusts on Thursday are closer to the 80th to 90th percentile for Thursday lending some credence to the potential for higher winds during that timeframe.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
Showers and thunderstorms are weakening early this evening with loss of sfc heating but could see a few showers or isolated thunderstorm through about 02z bringing brief sub-VFR conditions. Greater low level moisture in place overnight is bringing higher probability for stratus with HRRR probs around 40-60% developing after 07z through around 14z. A moist and unstable airmass remains in place and expect scattered showers and thunderstorms to develop Sunday afternoon bringing occasional sub-VFR conditions. With increasing shear developing, much of the region is in a marginal risk for severe storms with far NW rtes in a slight risk. Winds will become SW Sunday with gradients tightening and could see gusts around 15-20 kt inland and to around 25 kt along the coast.

Outlook: Another front approaches and stalls over the area Mon leading to a wet period early next week with greater chances for sub VFR flight cats until the front clears through mid-week.

MARINE
Stalled frontal boundary remains draped across our area waters extending from the Neuse River NE'wards to Rodanthe and points north. This has resulting in light winds (generally 5-15 kts with a few gusts up to 20 kts), but a chaotic wind field ranging from SW'rly winds S of the front to NE-E winds north of the front. Seas have generally remained around 2-4 ft this afternoon and should continue to persist at these heights through tonight with light winds continuing as well through tonight eventually becoming S'rly across all waters as the stalled front lifts N as a warm front. Could see some nocturnal convection develop later this evening across our coastal waters which would result in a locally enhanced winds and seas across the region where thunderstorms developed. Then as we get into Sun afternoon and evening a thermal trough develops inland and a cold front approaches from the west tightening the pressure gradient and allowing S-SW winds across the mouth of the Neuse RIver, Pamlico/Roanoke/Croatan Sound, and all coastal waters to increase to 15-25 kts with gusts up to 30 kts starting Sun afternoon and persisting into Mon morning resulting in Small Craft Advisory issuance across these waters. Occasional gale force gusts will also be possible across the outer coastal waters (20+ NM offshore), but confidence is not high enough to preclude gale issuance. Lighter winds will be found across the northern Sounds and adjacent rivers so SCA's are not planned here. Seas will also build to 4-6 ft across the coastal waters SUn evening as well given the strong winds. On top of all of this shower and thunderstorm activity is once again forecast to increase in coverage later Sunday with the approach of the aforementioned front.

Outlook (Sun night through Wed): The risk of thunderstorms will continue to increase into early next week, with best chances in the late afternoon to evening hours. The last in a series of fronts clear the area by midweek with high pressure briefly returning thereafter. A chance at SCA to potentially gale force winds is possible late Thursday with the approach of a stronger front but trends will need to be monitored for more clarity on the wind forecast.

MHX WATCHES/WARNINGS/ADVISORIES
NC...Beach Hazards Statement through Sunday evening for NCZ195-196- 199-204-205.
MARINE...Small Craft Advisory from 2 PM Sunday to 8 AM EDT Monday for AMZ135-152-154-156-158.
Small Craft Advisory from 4 PM Sunday to 3 AM EDT Monday for AMZ137-231.
Small Craft Advisory from 6 PM Sunday to 3 AM EDT Monday for AMZ150.