Area Forecast Discussion

WHAT HAS CHANGED

Discussions updated. Heat Advisory has been issued for Friday for heat index values up to 106F.

KEY MESSAGES

1) Temperatures well above normal through Sunday with heat indices over 100 degrees possible each day.

2) Limited rain chances until the arrival of a cold front this weekend, with elevated rain chances continuing into next week.

DISCUSSION

KEY MESSAGE 1... Temperatures well above normal through Sunday with heat indices over 100 degrees possible each day.

KEY MESSAGE 1 DESCRIPTION... Mid-upper ridging will shift across the area over this weekend as a cold front settles in from the northwest and stalls. Compressional warming and westerly downslope flow will help to boost max temps to well-above normal levels on Friday, with record highs possible inland and highs into the low 90s even at the coast due to a pinned sea breeze. Heat indices should easily reach into the low 100s across much of the area on Friday, but whether dew points stay high enough to support 105F remains the biggest question. However, given this is the first significant heat wave of meteorological summer and expected HeatRisk values in the major to locally extreme range, a Heat Advisory has been issued with this package for areas away from the immediate coastline.

Over the weekend, the proximity of the front nearby or over the area should help spark greater cloud cover and precip coverage each day, leading to slightly lower max temps, but areas which end up avoiding any prolonged cloud cover or precip should see similarly well-above normal max temperatures in the mid-upper 90s inland and low 90s along the coast. Heat index values into the low 100s appear likely, with additional Heat Advisories possible due to the accumulating effects of the heat wave as overnight mins in the mid-upper 70s do not offer much relief in the morning and forecast HeatRisk continues to be in the major to extreme range.

KEY MESSAGE 2... Limited rain chances until the arrival of a cold front this weekend, with elevated rain chances continuing into next week.

KEY MESSAGE 2 DESCRIPTION... With a mid-upper ridge axis crossing the area Friday night into Saturday, the daytime coverage of showers and storms should remain very isolated through the end of the week. Although increasing amounts of instability will be present for thunderstorms as temperatures rise, forecast soundings depict a considerable amount of subsidence and dry air in the mid-upper troposphere, which will inhibit development and keep coverage limited. One exception may be forward-propagating storms from the Piedmont dropping in during the late afternoon or evening, which could bring a gusty wind threat if they reach this far south before falling apart.

Over the weekend, the mid-upper ridge axis will shift just offshore as a surface cold front pushes southeast and stalls nearby or over the area. This is likely to increase the coverage of showers and storms on Saturday to scattered due to convergence along the front and along the sea breeze, although continued dry air in the mid- upper troposphere will be a limiting factor for the duration and coverage of storms. The front will linger nearby on Sunday, keeping at least isolated afternoon/evening showers and storms in place. Guidance tools have recently trended towards a sharper shortwave trough moving through the Ohio Valley, which could increase convective coverage along and near the front. However, it appears this may focus north of the area initially during the day before decaying convection moves in primarily over Sunday night into early Monday. Thereafter, guidance tools generally suggest additional shortwave troughs will rotate around broader troughing over the eastern half of the US, bringing periods of enhanced chances for showers and storms, although specifics on when and where this occurs remain murky.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

High confidence in prevailing VFR conditions persisting through the TAF period as steady southwest flow holds firmly in place. Gusty winds are anticipated at coastal terminals this afternoon behind the sea breeze before slackening this evening. An isolated brief shower or storm cannot be ruled out, mainly at inland terminals near I-95 late this afternoon into early evening. Otherwise, the steady winds will keep fog out of the picture overnight.

Extended Forecast...Brief MVFR/IFR possible in isolated afternoon/evening storms on Friday. Increased coverage of storms this weekend into early next week will increase potential for transient restrictions at all sites. Otherwise, VFR.

MARINE

High pressure will shift into the central Atlantic this weekend. As a result, expect south to southwest winds to continue at 10-20 kts through Friday night as a Piedmont trough tightens the pressure gradient against the high. With very warm temperatures on land, expect a healthy sea breeze to develop as well, and result in gusty south to SSE winds near the coast, which can top out around 20-25 kts during the afternoon. As a cold front shifts in from the northwest and stalls on land while the high moves further away, south to southwest winds slacken on Saturday, but a healthy sea breeze will continue to bring enhanced winds near the coast. The approach of a stronger front on Sunday and Monday should enhance winds again as the gradient tightens, but this also looks to stall on land.

Seas will run generally 1-3 ft in the 0-20nmi zone and 2-4 ft in the 20-60nmi zone through Sunday morning. An easterly 1-2 ft swell with a period around 8 sec will decay through Friday to 1 ft or less. Enhanced winds on Friday will lead to wind waves contributing 2-3 ft (3-4 ft) waves in the 0-20nmi (20-60nmi) zones during those days. Lingering southerly wind waves of 1-3 ft will continue into Sunday morning. For Sunday afternoon through Monday, stronger winds ahead of a cold front should help bring 2-4 ft seas into the 0-20nmi zones, with 5-6 ft seas possible in the 20-60nmi waters on Sunday night into Monday.

CLIMATE

Hot temperatures are expected this weekend which may reach record highs. The hottest day is expected to be Friday, but Sunday may reach similar levels. The high temp records for each climate site are provided below for these dates (June 12 and 14).

Location Jun 12 Jun 14 Wilmington, NC: 98 (1920) 99 (1958) Lumberton, NC: 103 (1911) 101 (2015) N. Myrtle Beach, SC: 96 (2016) 98 (2010) Florence, SC: 97 (2022) 102 (1958)

ILM WATCHES / WARNINGS / ADVISORIES

NC...Heat Advisory from 11 AM to 8 PM EDT Friday for NCZ087-096-099- 105-107-109. Beach Hazards Statement until 8 PM EDT this evening for NCZ106- 108. SC...Heat Advisory from 11 AM to 8 PM EDT Friday for SCZ017-023-024- 032-033-039-055-058-059. Beach Hazards Statement until 8 PM EDT this evening for SCZ054- 056. MARINE...None.