textproduct: NWS Wilmington

WHAT HAS CHANGED

Discussions updated. Heat Advisory in effect for eastern portions of the area. Guidance is generally coming into agreement on at least northern portions of the forecast area seeing showers and thunderstorms ahead of the incoming cold front arrive on Thursday afternoon or evening, with heavy showers and storms developing across the rest of the area on Friday.

KEY MESSAGES

1) Hot weather continues today with the highest heat indices in eastern portions of the forecast area.

2) Slow-moving cold front will bring periods of heavy showers and thunderstorms mainly between Thursday and Saturday night, with an attendant risk for localized flash flooding.

DISCUSSION

KEY MESSAGE 1...Hot weather continues today with the highest heat indices in eastern portions of the forecast area.

Similar to yesterday, a ribbon of enhanced low to mid-level moisture is expected to pass over the area which should help encourage the development of isolated to scattered showers and thunderstorms along the sea breeze during the morning. However, the timing of this moisture plume's passage is earlier in the day, with the highest precipitable water values expected to move offshore by midday while a tongue of drier air slides in from the southwest. While this drier air will reduce the chances for showers and storms during the afternoon, isolated activity cannot be ruled out as the sea breeze shifts inland and troughing aloft makes for a slightly less hostile environment.

The aforementioned moisture should help eastern portions of the area keep their dew points higher for longer this morning, and with a warm start in the 80-84F range and dew points in the mid-upper 70s, reaching or exceeding a 105F heat index appears likely within the advisory area, even if a brief shower or storm passes overhead.

KEY MESSAGE 2...Slow-moving cold front will bring periods of heavy showers and thunderstorms mainly between Thursday and Saturday night, with an attendant risk for localized flash flooding.

Although the trend has been for a slower arrival of this cold front, various guidance tools and cluster analysis appear to be coming to a consensus that at least northern portions of the forecast area will see showers and storms associated with this front arrive Thursday afternoon or evening and continue gradually southeastward overnight. There is also some signal for a more active sea breeze or confluence zone to form near the coast and produce a separate area of showers and storms ahead of the main frontal band of precip on Thursday, but this carries low confidence. Unsettled conditions featuring scattered to numerous showers and thunderstorms appear likely on Friday through Saturday night as the front stalls near the coast. Guidance tools now suggest an amplification of the jetstream pattern will force the cold front offshore on Sunday, although the shortwave helping to do this may be well-timed to produce additional isolated to scattered showers and storms on Sunday as the air behind the front is not much drier or cooler.

Although drought conditions across the area have made for very thirsty soils, the presence of precipitable water values in the 2.1- 2.4" range, which is about 120-140% of normal for this time of year and supportive of rain rates in excess of 2"/hr, and the fact that very dry soils often become less receptive to rainfall both point towards a risk for localized flash flooding where heavy showers and storms track over the same areas.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

MVFR stratus expected at coastal terminals possibly moving towards inland terminals towards dawn. Have accounted for CIGs becoming more scattered through 14z. Into Wed afternoon coastal terminals will again have the threat of periodic restrictions with storms on the sea breeze but confidence is low at this time on coverage. Otherwise, winds will continue gusting 20-25 kts tonight with speeds diminishing slightly ~8-9Z but not by much. Wind speeds pick up again after dawn with 30kt gusts again possible at coastal terminals through the afternoon. Gustiness may diminish towards 00Z but there's uncertainty as a cold front approaches which could bring more predominant MVFR/IFR CIGs.

Extended Forecast...Potential for periodic MVFR/IFR conditions from storms beginning Thu and remaining possible through late Sat, most numerous in the afternoon and evening.

MARINE

Wednesday through Monday...Breezy southwest winds will continue through today ahead of an approaching cold front, resulting in Small Craft Advisory conditions with the strongest winds close to shore. Wind gusts around 25 kts may linger beyond the current SCA end time in the waters between Surf City and Cape Fear, but will allow a future forecast update to make the final call on extending the advisory. Otherwise, winds weaken tonight into Thursday as the cold front drifts in from the north and stalls along or inland of the coast by early Friday. Guidance now suggests the front should be pushed offshore by early Sunday, resulting a short period of northwesterly winds on Sunday before the flow weakens to 10 kts or less from Sunday afternoon through Monday.

Elevated seas in the 4-6 ft range this morning are expected to fall slightly to 3-5 ft this afternoon, then diminish to 2 to 4 ft on Thursday as winds weaken. Periods of scattered to numerous heavy showers and storms are anticipated due to the front, mainly between Friday and early Sunday, creating hazardous conditions for small craft in and near thunderstorms.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for NCZ096-099-105>110. Beach Hazards Statement from 6 AM EDT this morning through this evening for NCZ106-108. SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for SCZ054-058-059. Beach Hazards Statement from 6 AM EDT this morning through this evening for SCZ054-056. MARINE...Small Craft Advisory until 10 PM EDT this evening for AMZ250- 252-254-256.